Amaranthus as a potential dietary supplement in sports nutrition

ABSTRACT

Amaranthus is considered a superfood with high nutraceutical value. It is a functional food composed of bioactive compounds crucial for sports nutrition including secondary metabolites, tocopherols, sterols, squalene, trace elements, polyphenols, peptides, polyunsaturated fatty acids, antioxidants, proteins, fat, carbohydrates, fibers, minerals, and vitamins making it a versatile supplement source. Notably, it is rich in amino acids, including branched-chain amino acids (BCAAs), natural enhancer of nitric oxide levels for improved circulation, endurance, strength, and stamina in athletes. It has been found to improve aerobic capacity, muscle recovery, and improved body composition. It is rich in fiber making it a beneficial prebiotic for athletes to maintain gastrointestinal health after intense training. Being rich in antioxidants and gluten-free, it’s ideal for special diets to reduce fat and increase muscle mass. A comprehensive overview of the ergogenic potential of Amaranthus and further research promises insights into developing Amaranthus-based dietary supplements for enhancing sports performance..

KEYWORDS:

• Amaranthus
• sports performance
• antioxidants
• functional food
• BCAAs
• prebiotic

1. Introduction

The genus Amaranthus L. belongs to the Amaranthaceae family; it is commonly known as amaranth and consists of approximately 80 species worldwide, consumed as grain and vegetable amaranth (Riggins & Mumm, 2021). The grain amaranths (mainly Amaranthus cruentus and Amaranthus hypochondriacus) were distributed from central Mexico and Guatemala to different places of North Mexico and other regions of the U.S.A. In South America (mainly Amaranthus caudatus), they are found in a band stretching from southern Ecuador through Peru and Bolivia into northern Argentina (Council, 1984). Their distribution with great diversity is extended from warm temperatures to tropical zones. Amaranths are amazingly attractive plants with pigmentation patterns ranging from yellow, orange, and crimson. It was an important food crop historically in the Aztec, Inca, and Mayan societies and was a part of the regular diet, in addition to other grains or crops such as corn and beans (X. Wu & Blair, 2017). It was mainly cultivated in Mexico, and according to an estimate, more than 20,000 tons per year of amaranth were harvested for food around 1400, but its production declined particularly after the collapse of Central American cultures and revived after the 1990s, gaining interest at the beginning of the 21st century. Apparently, the United States, Canada, Mexico, Guatemala, China, and Argentina are important amaranth production countries for consumption and fodder use. Amaranth is one of the few crops providing multiple applications from different parts of the plant, in which leaves are consumed as vegetables, grains as cereals, and flowers are used to color clothes (Hoidal et al., 2019). However, amaranth grains have been most commonly used as human food in many forms, such as flour-based products like bread, pancakes, cereals, cakes, or other snacks. It can be consumed as porridge and as a gluten-free, nutritious cereal.

Pseudocereal grains are becoming popular among people, particularly athletes nowadays, for their high nutraceutical value, health benefits, and demand for gluten-free foods. And for such reasons, it has gained more comprehensive cultivation and commercial interest recently (Martínez-Villaluenga et al., 2020; Nandan et al., 2024). Moreover, for athletes on a vegetarian diet, plants constitute an alternative source of proteins with the advantage of the absence of cholesterol and low saturated fats compared to animal proteins. Since both the leaf and seeds of Amaranth have high nutritive value, dual-use amaranth production systems have also been developed where farmers can harvest both leaves and seeds while maintaining seed yield (Hoidal et al., 2020). Recently, sportspersons’ knowledge has changed substantially regarding the awareness of the relationship between health and diet. Athletes now have an understanding that nutrition not only provides essential nutrients it also helps them to improve their well-being and reduce health risk (Coelho et al., 2018). Amaranth does not contain gluten, which has made it popular over the last few years because of the increased sensitivity of people in consuming cereals or food containing gluten. Amaranth grains are a rich source of bioactive compounds with antioxidant, antithrombotic, hypocholesterolemic, antidepressant, and anticancer effects (Skwaryło-Bednarz et al., 2020). The rich amino acid profile of amaranth grain, particularly rich lysine content, is of special importance to athletes. It can provide optimum nutrition supplement to athletes focusing on improving body composition, muscle building, and performance enhancement. As compared to other grains, amaranth has higher lysine content and other essential amino acids. It is also an excellent source of starch, fiber, minerals, and vitamins (Coelho et al., 2018). It can be used as a whole food or as an additive with other cereals in food products to increase the nutritional value of the food. Amaranth has been shown to have high acceptability, high biological value proteins, hypocholesterolemic effect, and high bioavailability. All these attributes can be of great nutritional significance in the diet of a sportsperson. The antioxidant activity of Amaranth makes it a desirable part of an athlete’s nutrition or diet plan since antioxidant supplementation has become a usual practice among athletes to decrease oxidative stress, assist in recovery, and improve performance (Neubauer et al., 2015). Amaranthus is also being explored for its potential applications, such as gluten-free food development, additives and emulsifiers, fat replacers, and encapsulated bioactive compounds. The protein fraction of amaranthus consists of 65% albumin, 17% globulin, 11% prolamin, and 7% of glutelin (Coelho et al., 2018).

2. Approach

In the current review, a literature search for publications related to the role of Amaranthus spp in sports nutrition was performed using PubMed, Google Scholar, semantic scholar, and Google. The keywords used in the search were “Amaranthus”, “amaranth”, “antioxidant activity”, “free radical scavenging”, “amaranth in sports nutrition”, “amaranth as functional food”, “Amaranth gluten-free snacks”, “aerobic capacity amaranth consumption”, “randomized controlled trial Amaranth”, “Amaranth in Sports”, “Amaranth supplement for endurance”, and “Nutritional profile of amaranth”. This review presents a comprehensive overview of the published literature and elaborates on the sports nutrition potential of Amaranthus spp.

3. Amaranth: superfood of the third-millennium

3.1. Revival of the ancient crop and growing commercial interest

Amaranths originally held prominent roles in pre-Columbian civilizations’ religious, agricultural, and economic activities, including the Aztec, Maya, and Inca. Amaranth is one of the underutilized or “orphan” traditional crops, provided the general shortage of research and partial breeding efforts compared with significant crops. Amaranth has been ignored as an underused crop despite the high nutrient content of its grain and leaves (Riggins & Mumm, 2021). This ancient food crop is now experiencing a revival in acceptance as a highly nutritious and resilient “ancient grain” for modern diets worldwide in addition to its native region. Amaranth, a highly nutritional pseudocereal and traditional American crop, has good food potential value (Paredes-Lopez, 2018). Amaranth grain does not contain gluten. The high content of quality protein and unsaturated fatty acids is one of its advantages. It is also a carrier of precious fiber and a good source of squalene (Pavlik, 2012). Amaranth grain (Amaranthus cruentus) is a nutritious pseudo-cereal consumed as a potential dietary supplement. Revival of amaranth is taking place as third-millennium food and a possible dietary supplement. Most amaranth species are edible, and some wild or weedy species are harvested as leafy greens. However, three species A. caudatus, A. cruentus, and A. hypochondriacus are commercially cultivated worldwide as pseudocereal or grain crops. A. tricolor and A. blitum, are cultivated as a leafy vegetable crop, mainly in Africa and Asia. In addition, some species are commonly grown as colorful ornamental plants. Cultivated amaranths are remarkable for their high nutritional value, versatility, and palatability, and as a nutritious alternative for an expanding market of food, snacks, and cosmetic products. They also possess favorable agronomic characteristics, such as rapid growth rates, efficient photosynthesis, high resistance to drought, biotic stress, heat, abiotic stress, and salinity (Estrada et al., 2021). These traits make amaranths likable crops for agriculturally less favorable marginal lands. Accordingly, amaranths are endorsed as promising crops for the future by various organizations focused on conserving agricultural biodiversity, optimizing nutrition, and food security. For example, A. blitum, A. cruentus, and A. tricolor are identified by the African Orphan Crop Consortium as having enormous potential for addressing nutritional security and removing stunting in African children (Riggins & Mumm, 2021).

The amaranth grain has the edge over other significant cereals as food sources – rice, wheat, and maize in terms of protein content and essential nutrients. Considering the vulnerability of modern crops to predicted climate change and extreme weather conditions, the integration of underutilized, easy-to-grow, nutritious crops will help expand our food sources and will help to reduce the effect of climate change and improve food quality and food security. Amaranth received little attention in the last century with limited breeding efforts. However, it has gained interest in recent years because of its amino acid and micronutrient profile. It also has a very high climate resilience to environmental stress like heat and drought and can be quickly grown in places and conditions where it is not easy to grow other crops. The high genetic variability of amaranth is advantageous for them to be adapted in most of the world’s arable regions, from tropical to temperate climates, under different environmental conditions. Amaranth seeds are gluten-free and have received much attention in recent years because of their remarkable nutritional value and potential health benefits. For this reason, promoting the planting, development, and research on amaranth and their related products has increased recently. Amaranth (Amaranthus spp.) is considered to have the potential to alleviate malnutrition in many developing countries and parts of the world (Caselato-Sousa & Amaya-Farfán, 2012). Amaranth is gluten free and rich in protein content, which increases its demand in the flourishing sports nutrition supplements industry. The rising demand of vegetarian and vegan supplements and growing awareness about health benefits of amaranth have boosted the global amaranth market. Amaranth is a good source of nitrate for athletes and helps increase performance in endurance exercises. Based on this beneficial effect, an Indian Firm Arjuna Natural launched Oxystorm branded amaranth extract to the European sports nutrition market. Similarly, there are multiple brands in market for different amaranth-based products and the commercial interest in pseudocereal-based products in sports nutrition market is growing continuously around the globe (Aderibigbe et al., 2022; Morales et al., 2021; Searby, 2016).

Nutritional profile, ingredients of amaranth, phytoconstituents, and possible effect

Amaranth grains are a tremendous source of protein and essential minerals such as calcium, phosphorus, iron, and branched chain amino acids. The nutritional profile of amaranth is ideal for meeting athletic training nutritional demands (Correa et al., 1986). A detailed overview of nutritional profile and phytoconstituents of Amaranth is described in Tables 1–5 with values expressed per 100 g edible portion.

Table 1. Proximate principles and dietary fibre (All values are expressed per 100 g edible portion, ND in the table represents below detectable limit).

Species	Plant part	Water g	Protein content g	Ash g	Total fat g	Total fiber g	Carbohydrates g	Energy KJ	References
Amaranthus cruentus	Seeds	9.20 ± 0.40	13.27 ± 0.34	3.05 ± 0.30	5.56 ± 0.33	7.47 ± 0.09	61.46 ± 0.60	1489 ± 1	(Bressani et al., 1987; Longvah et al., 2017)
Amaranthus caudatus	Seeds	11.62–11.72	12.50–14.77	2.94–3.02	10.6–16.7	13.8–16.4	62.41	1547	NIN (Bressani et al., 1987; Kraujalis & Venskutonis, 2013; Longvah et al., 2017; Martinez-Lopez et al., 2020; Repo-Carrasco-Valencia et al., 2009)
Amaranthus hibridus	Seeds	13.25	15.60	5.01	7.7–12.8	6.3	50.77	289.92	NIN, (Longvah et al., 2017; Oyelola et al., 2014)
Amaranthus hypochondriacus	Seeds	11.90–13.55	13.70–15.60	2.94–3.99	6.1	5.0	50.52  ±  1.15	56.60  ±  1.56	(Bressani et al., 1987; Council, 1984; Longvah et al., 2017)
Amaranthus gangeticus	Leaves (Green)	86.85 ± 1.21	3.29 ± 0.57	2.52 ± 0.32	0.65 ± 0.07	4.41 ± 0.10	2.28 ± 0.62	128 ± 17	(Longvah et al., 2017)
Amaranthus gangeticus	Leaves (Red)	85.56	3.93	2.61	0.63	4.91	2.37	140	(Longvah et al., 2017)
Amaranthus gangeticus	Leaves (Red and Green mix)	86.37 ± 0.38	3.09 ± 0.14	2.55 ± 0.20	0.53 ± 0.03	4.60 ± 0.36	2.87 ± 0.35	132 ± 6	(Longvah et al., 2017)
Amaranth spinosus	Leaves (Green)	86.46 ± 0.48	3.54 ± 0.31	2.94 ± 0.21	0.36 ± 0.02	5.10 ± 0.32	1.61 ± 0.40	110 ± 5	(Opute, 1979; R. Singhal & Kulkarni, 1988)
Amaranth spinosus	Leaves (Red and Green mix)	86.64	2.80	3.20	0.34	5.57	1.45	99	(Opute, 1979; R. Singhal & Kulkarni, 1988)

Table 2. Water soluble vitamins (All values are expressed per 100 g edible portion, ND in the table represents below detectable limit).

Species	Plant part	Thiamine (B1) mg	Riboflavin (B2) mg	Niacin (B3) mg	Pantothenic acid (B5) mg	Pyridoxine (B6) mg	Biotin (B7) чg	Total folates (B9) mg	Total ascorbic acid mg	References
Amaranthus cruentus	Seeds	0.04 ± 0.007	0.04 ± 0.007	0.52 ± 0.05	0.28  ± 0.03	0.33  ± 0.023	1.87  ± 0.24	24.65  ± 3.21	23.0	(Gamel et al., 2006a; Longvah et al., 2017; Oboh et al., 2008)
Amaranthus cruentus	Leaves	ND	4.1	15.6	ND	ND	ND	ND	445  ± 0.21	(Gamel et al., 2006a; Oboh et al., 2008)
Amaranthus caudatus	Seeds	ND	2.4	28.0	ND	4.5	ND	52.8–73	29.8	(Gamel et al., 2006a; Prakash et al., 2009)
Amaranthus caudatus	Leaves	ND	ND	ND	ND	ND	ND	ND	3.86  ± 0.20	(Gamel et al., 2006a; Prakash et al., 2009)
Amaranthus hybridus	Leaves	ND	ND	ND	ND	ND	ND	ND	321.4  ± 1.0	(Adefegha & Oboh, 2011; Jagannath et al., 2012)
Amaranthus gangeticus	Leaves (Green)	0.01 ± 0.000	0.19 ± 0.028	0.71 ± 0.06	0.41 ± 0.09	0.21 ± 0.010	2.46 ± 0.25	70.33 ± 8.10	83.54 ± 10.54	(Longvah et al., 2017) NIN
Amaranthus gangeticus	Leaves (Red)	0.010	0.269	0.62	0.37	0.22	2.95	81.95	86.20	(Longvah et al., 2017)
Amaranthus gangeticus	Leaves (Red and Green mix)	0.01 ± 0.000	0.22 ± 0.030	0.69 ± 0.04	0.37 ± 0.03	0.19 ± 0.015	2.41 ± 0.24	69.08 ± 6.27	77.24 ± 7.57	(Longvah et al., 2017)
Amaranth spinosus	Leaves (Green)	0.01 ± 0.000	0.13 ± 0.011	0.63 ± 0.02	0.33 ± 0.02	0.22 ± 0.051	3.07 ± 0.09	41.44 ± 3.48	82.56 ± 8.24	(Longvah et al., 2017)
Amaranth spinosus	Leaves (Red and Green mix)	0.01	0.15	0.72	0.31	0.20	2.91	44.23	77.30	(Longvah et al., 2017)

Table 3. Fat soluble vitamins (All values are expressed per 100 g edible portion, ND in the table represents below detectable limit).

Species	Plant part	Ergocalciferol (D2) μg	Alpha tocopherols mg	Beta tocopherols mg	Gama tocopherols mg	α-Tocopherol equivalent mg	Phylloquinones (K1) μg	References
Amaranthus cruentus	Seeds	53.98 ± 3.38	0.06 ± 0.00	0.22 ± 0.10	0.03 ± 0.01	0.15 ± 0.03	2.50 ± 0.87	(Lehmann et al., 1994; Longvah et al., 2017; Tang et al., 2016)
Amaranthus caudatus	Seeds	.04	7.88 ± 0.93	33.72 ± 1.11	0.37 ± 0.01	1.32 ± 0.08	ND	(Antognoni et al., 2009)
Amaranthus caudatus	Leaves	ND	27.3 ± 1.83	4.65 ± 0.85	1.27 ± 0.09	ND	ND	(Antognoni et al., 2009)
Amaranthus gangeticus	Leaves (Green)	16.01 ± 2.74	0.41 ± 0.05	ND	0.26 ± 0.10	0.44 ± 0.05	280 ± 15.0	(Longvah et al., 2017; Tang et al., 2016)
Amaranthus gangeticus	Leaves (Red)	15.10	0.44	ND	0.21	0.46	312	(Longvah et al., 2017; Tang et al., 2016)
Amaranthus gangeticus	Leaves (Red and Green mix)	15.25 ± 1.37	0.42 ± 0.10	ND	0.25 ± 0.05	0.45 ± 0.10	284 ± 9.4	(Longvah et al., 2017; Tang et al., 2016)
Amaranth spinosus	Leaves (Green)	15.23 ± 0.28	0.28 ± 0.02	ND	0.03 ± 0.01	0.28 ± 0.02	443 ± 3.6	(Longvah et al., 2017; Tang et al., 2016)
Amaranth spinosus	Leaves (Red and Green mix)	15.04	0.28	ND	0.04	0.28	448	(Longvah et al., 2017; Tang et al., 2016)

Table 4. Carotenoids (All values are expressed per 100 g edible portion; ND in the table represents below detectable limit).

Species	Plant part	Lutein μg	Zeaxanthin μg	β- Carotene μg	Total carotenoids μg	References
Amaranthus cruentus	leaves	10.25	ND	ND	132	(Adebooye et al., 2008; Longvah et al., 2017; Musa & Oladiran, 2011; Oboh et al., 2008)
Amaranthus cruentus	Seeds	4.11 ± 1.16	ND	ND	59.68 ± 3.09	(Adebooye et al., 2008; Longvah et al., 2017; Musa & Oladiran, 2011; Oboh et al., 2008)
Amaranthus caudatus	Leaves	ND	ND	ND	15.33	(Prakash et al., 2009)
Amaranthus gangeticus	Leaves (Green)	8397 ± 1005	164 ± 32.3	8553 ± 1813	20473 ± 1060	(Adebooye et al., 2008; Longvah et al., 2017)
Amaranthus gangeticus	Leaves (Red)	7439	118	8457	21449	(Adebooye et al., 2008; Longvah et al., 2017)
Amaranthus gangeticus	Leaves (Red and Green mix)	7390 ± 1361	148 ± 30.0	8464 ± 1753	20181 ± 1961	(Adebooye et al., 2008; Longvah et al., 2017)
Amaranth spinosus	Leaves (Green)	1861 ± 203	126 ± 16.3	1594 ± 315	4174±815	(Longvah et al., 2017)
Amaranth spinosus	Leaves (Red and Green mix)	1748	160	1487	4540	(Longvah et al., 2017)

Table 5. Bioactive compounds and possible effect of different species of Amaranthus.

Amaranth species	Bioactive compounds present/main biological activity reported	References
Leaves
A.spinosus	Alkaloids, tannins, saponins, steroids, flavonoids, terpenoids and glycosides were present with high content of total phenolics. Cardiac glycosides and tannins were present. A total of 24 essential oils from leaf were identified. Oxygenated monoterpenes, sesquiterpenes were the most abundant. Strong antioxidant and antimicrobial activity, antihemolytic activities, Potency for use in producing pharmaceutical bioactive compounds for therapeutic drugs.	(Gebregiorgis Ambaye, 2015); (Rjeibi et al., 2017; Sable, 2017)
A. hybridus	Rich in polyphenols (total phenolic contents: 2181.2 mg/100 g dm, total carotenoids (113.6 mg/100 g dm) and β-carotene (18.4 g/100 g dm). Lipid profile showed significant amounts of the fatty acids, linolenic, linoleic and palmitic with moderate concentrations of palmitoleic, stearic, and lignoceric acid. It was rich in folic acid (72 mg/100 g dm), Ca, Mg, Fe, Zn, Se. Improvement in cell viability accompanied with a significant decrease in DNA damage and genotoxic effects against two potent mycotoxins.	(Ibrahim et al., 2015; Nsamou et al., 2022)
A.viridis	Rich in tannins, saponins, general glycosides, and alkaloids. Flavonoids were conspicuously absent Aqueous and butanolic extracts had tannins whereas flavonoids and saponins were present only in aqueous extract. Acetonic extract showed the presence of saponins and cardiac glycosides while chloroform extract additionally had alkaloids, tannins. Aqueous and benzene extract had flavonoids and alkaloids. Antioxidant and anticancer, Analgesic & antipyretic activity, Free radical inhibition was high, source can be used as raw ingredient in the preparation of herbal-based drugs.	(Sivagnanam & Chandra, 2016); (Sobha et al., 2018)
A. blitum, A. caudatus A. tricolor, A. blitoides A. cruentus A. albus A. retroflexus A. hybridus	All examined taxa had flavonoid sulphate, flavon C & C-/O glycosides in all of their examined organs with the exception of A. tricolor. Leaves had isorhamnetin, kaempferol and rutin. Quercetin was found in all of the studied species with the exception of A. blitum and A. caudatus species. Antioxidant activities	(Adegbola et al., 2020; Akin-Idowu et al., 2017; Balasubramanian et al., 2017; Jimoh et al., 2019; Noori et al., 2015)
A. tristis A. hybridus	Presence of carbohydrates, alkaloids, flavonoids, tannins, steroidal glycosides, and phenols was detected which was the maximum in ethanolic extract. Potent hypoglycemic activity	(Balasubramanian et al., 2017; Rajan et al., 2017)
A.tricolor	Pigments, β-carotene, vitamin C, Total phenolic content (TPC), Total Flavonoid content (TFC), Total antioxidant capacity (TAC), phenolic acids and flavonoids were detected in leaves. Trans-cinnamic acid was the newly identified phenolic acid. Salicylic acid, vanillic acid, trans-cinnamic acid, gallic acid, chlorogenic acid, rutin, isoquercetin and m-coumaric acid were the most abundant phenolic compounds increased with the severity of salinity stress. Good antioxidant and anti-aging source	(Adegbola et al., 2020; Akin-Idowu et al., 2017)
Seeds
A. cruentus A. hybridus A. caudatus A. hypochondriacus	Highest tannin content (0.14 g/100g) and Iron chelating (66.72%) capability was documented in A. caudatus. A. cruentushad highest total flavonoid (9.93 mg CE/100g) content. A. hybridus had the maximum phytate (1.58 g/100g) & total polyphenols (30.79 mg GAE/100g). Food biofortification, Free radical scavenging activity	(Mala et al., 2017; Manyelo et al., 2022; Riggins et al., 2021)
A.cruentus A. caudatus	Three major peptides under 3 kDa were detected which exhibited HMG-CoA reductase inhibition. Hypocholesterolemic effect	(Escudero et al., 2006; Plate & ArêArêAs, 2002; R. A. Soares et al., 2015)
A. hypochondriacus A. cruentus	The crude oil content in seed ranged from 7.5% to 6.0%, with linoleic, palmitic, and oleic acids as the major fatty acids of the oil in both genotypes. The unsaponifiable fraction was rich in sterols (campesterol, stigmasterol, and β-sitosterol), and significant levels of squalene were found. Unique nutraceutical properties	(Bhat et al., 2015; El Gendy et al., 2017; Gandhi et al., 2021; Martinez-Lopez et al., 2020; Soriano-García & Aguirre-Díaz, 2019)

Some scientific studies have investigated and established that phytochemicals and some bioactive compounds from amaranth exhibit antiobesity and antioxidant activities. The results from such studies suggested that incorporation of amaranth in diet can help in regulation of oxidative stress and lipid metabolism more efficiently. Therefore, inclusion of amaranth in athletes’ diet can help in achieving nutrition requirements and fitness goals together (Chaturvedi & Gupta, 2021; Miguel, 2018; Mroczek, 2015). The nutrients and phytoconstituents present in Amaranth described in detail in Tables 1–5 include presence of proteins, fibers, vitamins, minerals, carotenoids, and other bioactive compounds which are further discussed individually in upcoming sections of the Review for elaborating their significance in athlete’s nutritional needs and performance based on an optimal diet. For example, high levels of carotenoids in blood are associated with antioxidant activity and better physical performance (Jeong et al., 2020). Fiber rich diet such as amaranth can help improve digestion and gut health in athletes. Proteins in Amaranth are mainly found in amaranth seeds with approximately 14% protein content, and the main ingredients of amaranth seed protein are albumin and globulin (Zhang et al., 2023). The nutritional quality of protein of amaranth seed is of high quality and has high protein digestibility, lysine availability, net protein utilization, and protein efficiency (Schmidt et al., 2021). The protein content of amaranth seeds is high in lysine and methionine and the bioavailability of amino acids is also higher compared to other grains (Rivero Meza et al., 2023). The proportion of essential amino acids in the protein content in amaranth seeds is similar to the World Health Organization (WHO) recommendations and is close to the animal protein quality. Amaranth protein also contains amino acids lysine, tryptophan, threonine, leucine, valine and isoleucine (Rivero Meza et al., 2023). Adequate intake of protein and micronutrients in diet is important for athletes for faster recovery and optimal performance (Beck et al., 2015, 2021; López-Martínez et al., 2022; Williams, 2004).

4. Amaranthus as functional food for exercise and sports

Amaranth (Amaranthus cruentus L.) is a pseudocereal grain rich in macronutrients and micronutrients, including vitamins and minerals, rich in proteins with high nutritional quality. Strategies to improve its intake, digestibility, and bioavailability are being explored in multiple studies (Pirzadah & Malik, 2020). Considering the health benefits and functional food value of Amaranth, crucial food applications of Amaranth are being tested and developed for the growing market (Coelho et al., 2018). The antioxidant and anti-inflammatory activities of components or phytochemicals of amaranth are well known, and their contribution to numerous health benefits is well studied (Baraniak & Kania-Dobrowolska, 2022a). It is known to lower oxidative stress in various diseases (Tang & Tsao, 2017). The functional food value of Amaranth is described here under the subheadings: as an antioxidant, anti-inflammatory, anti-obesity activities, nutraceutical properties, and health benefits.

4.1. Antioxidant anti-inflammatory and anti-obesity activities

Antioxidants are essential for athletes to get rid of reactive oxygen species produced during physical activity, sports, and during metabolic reactions in the body. Amaranth has an antioxidant effect due to its content of flavonoids and phenolic acids. Amaranth is rich in antioxidants such as gallic acid and vanillic acid which attributes to its defensive behavior. The antioxidant activity of plants, generally, is accredited to their phytochemical compounds. However, hydrolysates and bioactive peptides also have numerous biological functions, including antioxidant effect (Park et al., 2020). Research studies have addressed in vitro, in vivo, and chemical assays-based antioxidant activity of different amaranth species. Multiple studies concerning free radical scavenging activity and metal chelation capacity of amaranth protein hydrolysates and bioactive peptides have been conducted recently (Park et al., 2020). Amaranth is one of the leading suppliers of bioactive compounds, essential vitamins, and minerals that are important for the health of athletes. It has gained much interest recently because of its nutritional value and potential health benefits. It is also famous as an essential antioxidant, scavenging Reactive Oxygen Species, thus preventing oxidative stress-mediated chronic diseases. Antioxidant activity of different parts of the Amaranthus plant has been shown based on multiple chemical assays (Gebregiorgis Ambaye, 2015; Inglett et al., 2015; Jo et al., 2015; Park et al., 2020). Some in vitro studies have also shown the antioxidant capacity of Amaranth (Chandrappa et al., 2020; Odongo et al., 2018; Sasikumar et al., 2015). Moreover, multiple studies have also confirmed the antioxidant activity of amaranth in vivo (Ayoka et al., 2016; Lado et al., 2015; Velarde Salcedo et al., 2017; Yilmaz-Ozden et al., 2016). The antioxidant activity of Amaranth has been demonstrated in its protein hydrolysates and peptides (Orsini Delgado et al., 2016; Sabbione et al., 2016; Sandoval-Sicairos et al., 2020).

Amaranth offers superior antioxidant activity compared to cereals. Compared to staple cereal sources, amaranth provides optimal nutrition per the recommended daily allowance of all nutrients (Shahbaz et al., 2022). The antioxidant effect of amaranth is attributed to the presence of bioactive phytochemicals such as phenolics, betanins, and carotenoids. Amaranth has two morphological types described as red and green morphs. A study by Sarker et al. evaluated the composition, antioxidant activity, antioxidant pigments, minerals, and phytochemicals of the green morphs and found abundant carbohydrates, dietary fiber, and protein, minerals including potassium, calcium, magnesium, iron, manganese, copper, and zinc. Antioxidant capacity was quantified as free radical quenching capacity, as antioxidants including total phenolics, total flavonoid equivalents, vitamin C, as well as antioxidant pigments carotenoids, chlorophylls, and betalains. The research concluded that the green morph amaranth could be a potential source of nutritional components and antioxidants in the human diet providing nutrients and an antioxidant-rich food (Sarker et al., 2020). The same research group studied red morph amaranths and other species and identified them as a potential source of nutrients, antioxidant pigments, minerals, and phytochemicals. These compounds scavenged ROS and served as potential antioxidants in our daily diet to attain nutritional and antioxidant sufficiency. Silva et al. investigated the bioaccessibility of proteins, phenolics, flavonoids, and antioxidant activity of A. viridis and found that 90% of the protein was bioaccessible and identified it as a rich source of bioactive compounds and antioxidants (Silva et al., 2021). Multiple studies and abundant scientific evidence have established the antioxidant activity of Amaranthus (Park et al., 2020).

Therefore, Amaranth can prove to be a beneficial addition to an athlete’s diet and will help in overcoming oxidative stress and fatigue. It will also help in promoting recovery, boosting the immune system, reducing muscle damage, and enhancing performance. The inclusion of Amaranth in an athlete’s diet can help prevent detrimental effects of reactive oxygen species produced during and after strenuous exercises (Neubauer et al., 2015). Selenium and betacyanins in edible amaranth seed sprouts were found to avoid NFκB translocation to the cell nucleus. They showed an anti-inflammatory effect by significantly decreasing the pro-inflammatory cytokine IL6 in RAW 264.7 macrophages (Tyszka-Czochara et al., 2016). The hydromethanolic extract of amaranth seeds was found to decrease nitric oxide production in mouse macrophage-like cell line RAW264.7 and increase the nitrates and nitrite levels in the mouse body 8 hours after one oral dose of amaranth extract (Liberal et al., 2016; Subramanian & Gupta, 2016). Increases in nitrate and nitrite levels are indications of the scope of improvement of overall performance of people involved in brisk physical activities or sports (Bloomer et al., 2020; Sweazea et al., 2018). Early studies show that amaranth can reduce inflammation by slowing down the body’s production of immunoglobulin E. Antioxidants in Amaranth also help strengthen the immune system.

4.2. Nutraceutical properties and health benefits of the new millennium crop: Amaranth

The word amaranth means “unfading” or “immortal” in Greek. This genus’s origin comes from the production of Amaranth’s tiny flowers in dense inflorescences at the end of branches that can stay for a very long time. The bright crimson flowers of the plant make a striking sight all summer long. The nutritional content of Amaranthus leaves changes substantially throughout development, with high levels of iron in the middle of vegetative growth and high ranges of magnesium, vitamin A, and copper at the end of the vegetative development stage (Hoidal et al., 2020). After harvesting, the seeds are used similarly to grains like rice and oats. Amaranth can offer substantial health benefits as a part of a healthy diet. It is a source of vitamin C, which is central to the body’s healing process and repair because it helps process iron, form blood vessels, repair muscle tissue, increase bone density, and maintain collagen. More people have become conscious of its impressive nutritional profile. Amaranth’s adaptability and pleasant nutty, sweet flavor make it a more popular snack or food product. Amaranth has been recognized as a complete food with multiple nutraceutical properties advantageous for sportspersons.

Amaranth is one of the alternative food crops with tremendous yield potential and nutraceutical value to fulfill the nutritional demand of current times for sportspersons. It is an economical source of all required macronutrients and micronutrients. It has gained worldwide attention not just because of its nutritional profile but also its adaptability to adverse heat, stress, and drought conditions. It is easy to grow in agriculturally marginal lands (Rastogi & Shukla, 2013). Amaranth is considered to be revived as a third-millennium food with multiple advantages, such as the presence of high-quality proteins, unsaturated fatty acids, valuable fiber, and a very rich source of squalene (Bressani & Garcia-Vela, 1990). Squalene is an essential antioxidant for athletes. It is a natural triterpene with active oxygen scavenging activities and preventing oxidative damage. Therefore, including amaranth in an athlete’s diet can help protect the body from free radicals and strengthen the immune system. It is an excellent source of protein compared to meat and milk. It is a rich source of folic acid, calcium, iron, phosphorus, vitamins, and minerals. It is rich in lysine, an essential amino acid that helps absorb calcium, produce antibodies and collagen, stimulate growth hormone, and regulate blood nitrogen levels in adults. It is a good source of fiber, ideal for weight loss. The leaves of amaranth are also a good source of calcium, iron, magnesium, phosphorus, vitamin C and K (Pavlik, 2012). For athletes to perform at their best, significantly higher energy expenditure is required. And to supply that energy and meet the demands of the athletes, a balanced diet with optimal nutrition is a must. It can also help athletes avoid sports injuries, oxidative stress, diseases, and decreased physical performance during competition. Vitamin supplementation is common among athletes during physical activity to prevent muscle injuries and cardiovascular diseases and to regulate their microbiome and gut health (Brancaccio et al., 2022).

There are multiple health benefits attributed to Amaranth grain consumption. It has been shown to promote the immune system, lower cholesterol levels, reduce glucose levels, exhibit anticancer activity, and exert anti-allergic and antioxidant properties (Caselato-Sousa & Amaya-Farfán, 2012). Athletes are particular in choosing a diet with low fat intake to manage their serum cholesterol levels and LDL levels and prevent an increase in body fat percentage. In addition to the hypocholesterolemic effect of Amaranth grains, Amaranthus spinosus leaves have also been shown to regulate obesity and obesity-induced metabolic disorders (M. R. U. Prince, Zihad, et al., 2021). It has enormous potential for the overall health and fitness improvement of athletes. It helps improve liver and kidney function as well as management of body weight, reduction in abdominal fat deposition, developing of glucose tolerance, and regulating lipid profile (M. R. U. Prince, Zihad, et al., 2021).

Amaranth seed oil is an unexplored novel raw material with multiple applications. Remarkably, amaranth oil is apparently the richest plant-based source of squalene, a valuable compound to cosmetic and pharmaceutical industries (Moszak et al., 2020a). In the context of human health, some studies have identified amaranth oil as a source of bioactive seed peptides, flavonoids, and other components that may help improve hypertension and cardiovascular diseases (Añón et al., 2022; Martirosyan et al., 2007).

Amaranthus is considered a natural resource of dietary fibers and proteins along with several bioactive agents such as vitamins, minerals, essential amino acids, unsaturated fatty acids, and flavonoids (Park et al., 2020; Soriano-García et al., 2018). It also contains important pigments like chlorophyll, anthocyanin, carotenoids, betalain, cyanin, xanthin, and amaranthine, which constitute a powerful source of antioxidants due to their free radical scavenging activity (Cai et al., 2003). Other vital phytochemicals that act as antioxidants include flavonoids, phenolics, beta carotene, and vitamin C. Amaranthus is considered a crop possessing significant potential for beneficial health effects and economic importance (Soriano-García et al., 2018). Due to its unique qualities, such as safe use and cost-effectiveness, it has an advantage over synthetic dietary supplements for direct use as popular nutraceuticals; leaves are used as vegetables and grain in the form of flour. Figure 1 depicts the potential of amaranth in performance enhancement and also illustrates the nutritive value of amaranth for athletes. Amaranth is a versatile supplement for athletes with multiple health benefits such as Amaranth can be taken as pre-workout nitric oxide supplement (Liubertas et al., 2020; Subramanian & Gupta, 2016); it is protein-rich and has high nutritive value (Malik & Singh, 2022; Pareek & Singh, 2021; Torregrosa-García et al., 2019); it is rich in BCAAs and antioxidants (Kim et al., 2006; Martinez-Lopez et al., 2020; Tang & Tsao, 2017); it has high content of vitamin C, E, K1, and manganese (Martinez-Lopez et al., 2020; Niro et al., 2019; Rastogi & Shukla, 2013); it has been shown to improve heart and eye health (Chmelík et al., 2019; Haskell et al., 2005; Martirosyan et al., 2007; Suri et al., 2017); it can be a good alternative for athletes in Gluten free diet (Caeiro et al., 2022; de la Barca et al., 2010; Niro et al., 2019; Rai et al., 2018; Woomer & Adedeji, 2021); it is rich in fibers and improves digestion (Baraniak & Kania-Dobrowolska, 2022b; Repo-Carrasco-Valencia et al., 2009); it has been shown to have prebiotic and hemoglobin increasing effect (Gullón et al., 2016; Orsango et al., 2020); it is an important component of diets of vegetarian and vegan athletes (Balakrishnan & Schneider, 2022; Rogerson, 2017; Schoenfeld, 2020); it has been shown to increase bone strength (Baraniak & Kania-Dobrowolska, 2022b; Martinez-Lopez et al., 2020); it has anti-inflammatory properties and boosts immune system (Martinez-Lopez et al., 2020; Tang & Tsao, 2017); it is hypocholesterolemic and can help in weight loss (Morales et al., 2021; Moszak et al., 2020b; M. R. U. Prince, S. N. K. Zihad, et al., 2021; Shahbaz et al., 2022; T. Wu et al., 2019); it has been demonstrated to improve aerobic capacity and metabolism on ingestion (Liubertas et al., 2020; Yelisyeyeva et al.,2009, 2012); it stimulates muscle growth because of its amino acid profile and high protein content (Bull et al., 2022; López et al., 2019; Malik & Singh, 2022); it increases endurance and stamina (E. Espino-González, M. J. Muñoz-Daw, et al., 2018; B. Olawoye et al., 2021); it can be included in athlete’s diet as protein-rich instant beverage and some research groups have developed amaranth-based protein-rich beverages for athletes (Arcila & Mendoza, 2006; Manassero et al., 2020)

Figure 1. Performance enhancing and nutritive value of Amaranth for athletes.

5. Amaranth: an important nutraceutical for sports nutrition

Amaranth is a pseudo-cereal crop containing an uncommon type of starch, high-quality oil, and proteins, and it represents a good alternative for athletes with gluten intolerance (Ballabio et al., 2011). Amaranth is considered a “natural biopharmaceutical” plant because it contains potential health-promoting compounds such as rutin and nicotiflorin, capable of boosting human health (Peter & Gandhi, 2017). Amaranthus is crucial for dietary supplements overall and for athletes (Goncharov et al., 2021). Its grains, leaves, and seeds are rich in protein, fiber, vitamins, minerals, nutrients, and energy compared to other regularly consumed leafy vegetables or cereals. It is a pseudocereal with healthy nutritional ingredients for improving the nutritional quality as a healthy alternative to frequently used nutraceuticals (Jan et al., 2023; Martinez-Lopez et al., 2020). As a leafy vegetable, Weedy Amaranthus has remarkable protein, dietary fiber, carbohydrates, minerals, and bioactive compounds like beta carotene, which are highly beneficial for athletes (Huerta-Ocampo & Barba de la Rosa, 2011).

Among the multiple constituents in Amaranth that are relevant in sports nutrition, one is its rich content of amino acids, including branched-chain amino acid content (BCAAs). Sarker et al. demonstrated the nutraceutical value, presence of antioxidants, high protein and fiber content, vitamins, phenolics, pigments, nutrients, and flavonoids in the leafy vegetable weedy species of Amaranthus (Sarker & Oba, 2019). With such a nutritional profile, as a part of dietary intake, it can be vital to provide athletes with a nourishing and antioxidant-rich diet. In addition to the protein-rich profile, amaranth is a natural blood nitric oxide enhancer that helps improve circulation, endurance, strength, and stamina. It has been found to improve aerobic capacity, muscle recovery, and improved body composition in physically active young people. A study by Liubertas et al. elucidated the use of dietary nitrate from amaranth to improve aerobic capacity during increasing cycling exercise in young, physically active male persons (Liubertas et al., 2020). It is rich in fiber and thus can also be beneficial as a probiotic for athletes to maintain gastrointestinal health after intense training. It is rich in antioxidants, and since it is gluten-free, it can be employed in special diets to reduce fat and increase muscle mass.

5.1. Significance of gluten-free amaranth in athlete’s health and performance

Fortified foods are becoming very popular recently to fulfill the nutritional requirements of all age groups. The availability of natural food fortificants for athletes is an advantage and can provide multiple health benefits and improve performance. Amaranth is one such natural food fortificant with a rich profile of macro and micronutrients, including iron, folate, zinc, protein, β-carotene, calcium, potassium, and fiber. It can be added to the diet or commonly used products by using the latest processing technology for fortifying foods like biscuits, pasta, bread, snacks, flakes, porridge, ladoo, dhokla, and many more (Vishwakarma et al., 2022).

Amaranthus seeds have multiple bioactive compounds and phytoconstituents beneficial for human health. In amaranth seeds, unsaturated fatty acids, carotenoids, and tocopherols have shown a high correlation to antioxidant activity. Free radicals formed in the body during physical activity can cause damage to the DNA, cells, proteins, and tissues of the body. They can also affect sports performance and recovery from sports injuries. The antioxidants in amaranth can help protect the athlete’s body and help improve performance (Tang et al., 2016). The carotenoids in amaranth can also help maintain and enhance visual abilities vital for sports performance. Multiple studies have shown the predominant role of carotenoid supplementation in improving visual abilities, including contrast sensitivity, glare reduction, photo stress recovery, and visual reaction time. These are all critical tasks for optimal sports performance (Eisenhauer et al., 2017; Nolan et al., 2011).

Amaranth is an indispensable food for vegetarians and vegans because of its protein content. It is an excellent alternative for those who have gluten intolerance or have celiac disease (Alvarez-Jubete et al., 2010). It can be added to their daily diets by adding nutritional value without any adverse effects. It is an excellent option for athletes with special dietary needs. It offers a high-quality nutrition option for vegan and gluten-intolerant athletes (Torregrosa-García et al., 2019). Amaranth is a seed that often gets included in the “super grain” family and has a much superior protein profile than most grains (Arendt et al., 2013). Amaranth is also a complete protein rare in non-animal protein sources, making it a vital ingredient for vegans and vegetarians (Castro-Martínez et al., 2012). Amaranth can be puffed into a gluten-free cereal form – handy for those trying to reduce their gluten intake. For some specific physical activities requiring iron-rich food, such as running, the amaranth seeds can provide up to 82% of the recommended daily intake of iron in one meal (Rabecca & Vigasini, 2014).

5.2. Amaranth’s ergogenic potential in enhancing sports performance, weight loss, and boosting recovery

Amaranth is a great recovery superfood post-workout, training, or exercise. Investigation of the role of Amaranth as a supplement for sports and workouts is an emerging field of research. It is a complete protein in seed form and is rich in calcium and other minerals, which play an active role in postworkout recovery and the strengthening and growth of muscles in athletes. Its nutritional content and bioactive compounds can also lower cholesterol and ward off multiple diseases such as cancer, diabetes, heart disease, osteoporosis, and stroke (Medina-Godoy et al., 2013; Orona-Tamayo et al., 2019a). The macro and micronutrients present in amaranth help preserve bone mass and help the body to increase the efficiency of muscle tissue recovery. The calcium in the content also helps in weight loss by releasing the intestine and quenching hunger.

Amaranth consumption helps in improving cardiovascular performance. It has been shown to lower total cholesterol, LDL, VLDL cholesterol, and triglycerides. Its high squalene content is primarily responsible for cardiovascular benefits, including blood pressure regulation (Orona-Tamayo & Paredes-Lopez, 2017). Its content of polyunsaturated fatty acids influences a better heart rate recovery after exercise. It also helps in improving heart rate variability by activating aerobic metabolism (Añón et al., 2022). It is also capable of improving cognitive abilities and intellectual activity. Its content of complex carbohydrates, amino acids, and fiber helps supply energy to neurons or brain cells in the form of glucose. It improves muscle recovery with the presence of its unique amino acid profile. For use as a post-workout drink, it can be easily dissolved in water. It helps restore glycogen, which is an important fuel reserve that needs to be replenished after a workout or training session.

Amaranth can help lose weight if added to the diet; its rich protein and fiber content can help reduce weight. If added to the breakfast meal, it can help decrease the ghrelin hormone levels known to stimulate hunger. The resulting high protein diet can help reduce appetite and calorie intake. Increased fiber intake helps lower the risk of gaining weight and body fat (Moszak et al., 2020a). Amaranth can boost metabolism without adding to the overall weight. Amaranth grain is rich in squalene, a strong antioxidant that helps detoxify the body and thus helps keep a check on body weight. Its high protein and fiber content helps give a feeling of being full for long and helps control the frequent snacking behavior while providing complete nutrition.

5.3. Amaranth: superfood for muscle gain, BCAAs in Amaranth

Athletic performance improvement depends on successive incremental training sessions and proper fueling with a balanced diet consisting of carbohydrates, proteins, electrolytes, fluids, antioxidants, and many factors affecting recovery after training. With our focus on nutrition and supplementation with amaranth, it is important to understand that exercise or sports creates physiological stress and depletes our body of nutrients and fluids. It is during recovery that the body rebuilds itself. Balanced diet with essential nutrients plays a significant role in recovery, resulting in increased performance ability and improved overall health. Amaranth grain is considered a complete protein and contains all the essential amino acids. Amino acids play an important role in boosting the overall performance of athletes. Several amino acids stimulate metabolism and activate skeletal muscle function. Amino acids increase hormone secretions, modify fuel during activity, prevent muscle fatigue, and overcome overtraining effects (Kamei et al., 2020). Skeletal muscle function and maintenance are of utmost importance for athletes since it plays an important role in exercise, energy expenditure, and metabolism.

Muscle strength and muscle gain are one of the most important targets of athletes in specific sports, as well as for generalized fitness goals. Muscle synthesis and muscle gain largely depend on the protein-rich diet, with optimal essential amino acids content and stimulus for growth such as resistance training or concurrent training. Based on their goals, athletes monitor and supplement their diet to include all essential amino acids and optimal protein content in their regular diet. Athletes are aware of the side effects of synthetic supplements that are popular for their fast and effective results on muscle gain. Therefore, there is an increasing trend to include herbal supplements or whole foods rich in protein and essential amino acids as per the requirement of the individual goals of athletes. Including natural alternatives in the form of supplements, additives, or as part of regular diet helps athletes avoid the harmful side effects of synthetic supplements. Amaranth is one of the most popular and trending superfood among athletes aiming to gain muscle mass and muscle strength to fulfill such targets. It is gluten-free and anti-allergic, making it even more desirable for the needs of sportspersons. Amaranth has a high content of branched-chain amino acids. Amaranth seeds leucine content is 731 mg/100 g of dry weight basis, Isoleucine content is 406 mg/100 g of dry weight basis and valine content is 453 mg/100 g of dry weight basis (Malik & Singh, 2022; Motta et al., 2019).

Amaranth seeds also have methionine, an essential amino acid, which is known to improve the body’s muscle-to-fat ratio and athletic performance. It positively impacts bone mass and energy metabolism of the body. Another essential amino acid present in amaranth seed, Lysine, is necessary for maintaining optimal strength and performance for athletes (Malik & Singh, 2022). Lysine performs multiple bodily functions, including calcium absorption, building collagen, hormone production, carnitine production, and regulating the immune system. Lysine is important for athletes because it helps build protein, promote growth, restore muscle strength and energy, and also helps strengthen joints and reduce pain. Amaranth grain has a comparatively higher content of essential amino acids such as tryptophan and lysine than other cereals. Therefore, amino acid profile, including lysine and tryptophan content in amaranth, can compete with animal protein food source (Písaříková et al., 2005). BCAAs are essential for muscle protein synthesis to build muscles. Leucine in amaranth is one of the key starters for muscle protein synthesis, which helps increase muscle growth. Elite athletes who train for extended periods and cannot access whole food or complete protein during training or workouts include BCAAs in their diet through animal or plant-based proteins for vegetarian or vegan athletes. Amaranth provides a natural source of BCAAs if added to the diet of athletes and helps in muscle building and recovery without any side effects.

5.4. Amaranth as a prebiotic, endurance enhancer, and stamina booster for athletes, and its role in body composition improvement

The insoluble and soluble fibers in amaranth can act as prebiotic and help improve and maintain healthy gut bacteria populations (Gullón et al., 2016). Amaranth consumption has been found to increase the population of Bifidobacterium and Lactobacillus species. Amaranth seed oil is remarkably high in polyunsaturated fatty acids, and it is best to consume polyunsaturated fat from whole foods like amaranth in place of processed foods (Procopet & Oroian, 2022). Amaranth oil is also found beneficial in sports activities. Athletes who took amaranth oil as supplements experienced increased heart rate variability along with improved employment of oxidation waste products (Yelisyeyeva et al., 2012). These effects are speculated to improve physical performance by supporting nitric oxide production. Amaranth has been consumed since ancient times and has cultural significance. Its grains alone or mixed with other grains in meals can be used as cereals for breakfast, and their health-enhancing effects have been acknowledged and explored more in recent times. Amaranth grain’s nutrient profiles are enriched with sprouting and fermentation and their suitability to different processing techniques and the rapid increase in microbiota highlighted pseudocereals’ probiotic and prebiotic effects. Using cultures or naturally fermented amaranth showed good substrate properties for probiotic bacteria, especially for Lactobacillus strains. Studies have found that they increase the synthesis of short-chain fatty acids due to their prebiotic effects and reduce the number of pathogenic microorganisms. Taking into account these effects, they are considered good sources for symbiotic formulations to be established for treating dysbiosis, obesity, celiac disease, lactose intolerance, inflammatory bowel diseases, and inflammation-mediated chronic disorders (Ugural & Akyol, 2022). In a study by Arslan-Tontul et al., amaranth was found to have the highest stimulation effect on the growth of probiotics (Arslan-Tontul et al., 2022). Amaranth grains have been widely used in food formulations because of their balanced nutritional properties and presence of bioactive peptides (Orona-Tamayo et al., 2019b). In another study by Hernandez Garcia et al., some bioactive peptides were identified from Amaranthus hypochondriacus L. and developed a non-dairy germinated amaranth-based functional beverage. It was found that by using amaranth, it is possible to develop functional drinks with potential antioxidant and hypoglycemic activities (Hernández-García et al., 2022).

Amaranth has an antioxidant effect, and its nutrient profile is impressive with prebiotic and health-improving effects. In another study by Lucia et al., supplementation with a nutraceutical consisting of amaranth and micronutrients was found to augment mucosal immunoglobulin A (IgA) production and responses to oral vaccination with cholera toxin (CT) in a mice model colonized with microbiota from undernourished Bangladeshi children. This study provided a preclinical proof-of-concept supporting the information that diet ingredients and microbiota regulate mucosal immune response to CT vaccination (DiLuccia et al., 2020). Zoblkova et., investigated the influence of an antisclerotic diet with a probiotic sour-milk product enriched with an extract of leaves of amaranth in patients with ischemic heart disease and hypertension and found the positive dynamic of clinical manifestation, lipid spectrum of blood, coagulograms, and antioxigen status (Zoblkova et al., 2004). In a study by Moszak et al., the effect of functional food amaranth seed oil was studied on weight loss, body composition, and metabolic parameters. It was found that edible amaranth oil is highly nutritious and potentially improves metabolic measurements during the 3-week body mass reduction program in the obese population (Moszak et al., 2020a). This suggests that edible amaranth seed oil can be an important dietary supplement for athletes undergoing weight reduction programs. Another study by Yelisyeyeva et al. studied the effect of amaranth oil supplementation on aerobic metabolism and heart rate variability in athletes. Supplementation with Amaranth oil caused improved uptake of oxidative products, modulation of catalase, and SOD activity with ensuing development of an antioxidant effect. The findings were very distinct in athletes (Yelisyeyeva et al., 2012). As observed in both study groups, improvement in HRV by daily consumption of Amaranth oil suggested enhanced production of endogenous oxygen and enhancement of the cardio-respiratory function. The fiber of amaranth works as a prebiotic and improves the intestinal microbiota that helps maintain good athletic performance.

The studies discussed above give a compelling insight into amaranth’s vital role and scope in sports nutrition. It is an indispensable revived gluten-free ancient crop with ergogenic potential, superior nutritional profile, and functional food properties compared to other cereals and supplements.

6. Development of food products, protein bars, and other supplements with amaranth ingredients

Snacks are an indispensable part of the human diet providing satisfaction and a supply of necessary nutrients. Snack foods may be eaten at every mealtime or in-between from breakfast to midnight and are popular in all age groups. Innovation in the snack market is a trending phenomenon nowadays with increasing demand for functional foods and the introduction of plenty of healthy snacks fulfilling nutritional, energy as well as immunity-enhancing needs. The snack bar’s demand in the market is expected to grow at a faster growth rate and is expected to further upsurge in the coming years due to the rising awareness for fitness and healthy eating behaviors (Pinto et al., 2017). Realizing the benefits of eating smaller meals contributes to increased snack intake, which is expected to fuel demand for snack bars among athletes who are conscious of their fitness and body composition. Amaranth has enticed a great deal of interest in recent decades due to its valuable agricultural, nutritional, and functional characteristics. Grain amaranth is being advanced as an energy food combined with traditional cereal grains in breakfast foods, bread, multigrain crackers, pasta, pancake mixes, or popped as a snack food product (Bassore & Desalegn, 2017; Bender & Schönlechner, 2021; Manikandaselvi & Nithya, 2011; Ssepuuya et al., 2018). Amaranth has also been used to develop ready-to-eat snacks or food products alone or in combination with other pseudocereals, legumes, or grains (Espinoza-Moreno et al., 2016). Athletes regularly update their diets with healthier snacks ready to eat and fulfill their nutritional requirements. One such effort to develop a ready-to-eat expanded snack was made by Espinoza-Moreno et al. by combining amarantin transgenic maize and common black bean (Espinoza-Moreno et al., 2016). The optimized expanded snack consisted of high dietary fiber, protein, phenolics, and high antioxidant activity. Such ready-to-eat nutritious snacks can be added to an athlete’s diet to maintain optimal performance and prevent chronic fatigue and diseases. Products like this can provide an alternative to athletes compared to the widely available commercial food products or snacks with low nutritional value and high caloric content. Another study by Beswa et al. found that adding Amaranth leaf powder to provitamin A biofortified maize snacks enhanced the nutritive value of the snack (Beswa et al., 2016). Amaranth grains, leaves, and isolated proteins can all be excellent addition to any healthy food snack. They can be optimized as per the need of athletes or specific sports nutrition needs. One more study by Singh et al. attempted to develop good quality, healthy, functional snack bar with a combination of amaranth grain, banana peel powder, and oats, with the highest percentage of amaranth grain in the combination (Singh et al., 2022). Increased protein, mineral, β-glucan, dietary fiber, essential amino acid, phenolic, and antioxidant activity of functional snack bars are highly beneficial for sportspersons for their training and performance.

As a consequence of growing consumer demand for products with better quality and health benefits, research efforts intend to incorporate multigrain flours into snack products which could significantly improve the nutritional composition while harnessing their health-promoting properties (Olagunju et al., 2022). Some studies established that the developed multigrain snack products from the optimized blend of indigenous cereals, including amaranth, exhibit nutritional efficacy to supply more than 25% recommended daily allowance (RDA) of protein and a significant amount of essential mineral elements. Also, the developed snack exhibited potent radical scavenging, metal-chelating properties, and low glycemic index. It showed superior nutritional composition, antioxidant potential, and low glycemic response; hence, it may serve as a healthy product with nutraceutical potential. It can be concluded that adopting indigenous cereals in the optimized blend for snacks may help reduce risk factors of cardiovascular diseases that are among the significant causes of death in today’s globalized world (Olagunju et al., 2022). In India, many homemade recipes include multigrain formulations, and amaranth is also included in some recipes for snacks like laddoos and chikkis. In traditional knowledge, Indian food recipes included amaranth as a source of boosting immunity, improving health, fighting inflammation, and improving bone density and vision. To increase the amino acid content and protein fraction of the diet, everyday bread or rotis are also made from a combination of flours of different grains, and amaranth is one of the crucial ingredients. Such addition of amaranth in snacks and daily diet can help athletes improve their immune system, recovery from training or after physical activity, and improve their performance (Arendt et al., 2013).

Gluten-free snacks are one of the most trending and in-demand food products in the market for individuals and sportspersons. Gluten intolerance is a huge hindrance for athletes since they have to maintain a balanced diet and fulfill their nutritional requirements. To meet this challenge of consumer or athlete’s needs, several research groups have been putting efforts into launching nutritious gluten-free products. For example, Miranda et al. presented a gluten-free formulation of amaranth, brown rice, and cactus pear peel to be considered low fat, high protein, and fiber-rich gluten-free snack (Miranda et al., 2018). In a similar study by Paul et al., it is concluded that amaranth seeds, watermelon seeds, and their flour can be successfully incorporated into “Biscuits”, “Mathri,” and “Laddoo”. Incorporating different proportions of amaranth seed flour and watermelon seed flour for value addition in traditional recipes can be encouraged and popularized to improve the intake of protein, fat, calcium, carbohydrate, and iron. The amaranth seed flour and watermelon seed flour can also be used out of season (Virginia et al., 2014). Gebreil et al. have also investigated the utilization of amaranth flour in the preparation of high nutritional value bakery products, crackers, and tortillas produced using amaranth flour. In their study, they found that amaranth is a rich source of bioactive compounds, and due to its nutritional benefits, it can be used in developing and enhancing functional foods. Also, results indicated that crackers and tortillas prepared with amaranth flour exhibited higher antioxidant activity than control formulas (Gebreil et al., 2020). There are multiple breakfast recipes like zucchini amaranth patties, blueberries amaranth porridge, toasted coconut amaranth porridge, banana pecan amaranth porridge, amaranth peanut butter cups, plum and walnut amaranth bars, spinach almond amaranth muffins, upma, laddoo, kheer, khichri and many more which can be incorporated in daily diet of athletes. These products can also provide variety in the daily dietaries in addition to their nutritional benefits (Bello-Pérez & Paredes-López, 2009; Bello-Pérez et al., 2022).

Amaranth seeds are used as whole grain or flour for consumption, and they can be cooked, popped, roasted, fermented, germinated, flaked, toasted, or extruded. It is directly cooked and eaten as soup or as sprouts (Ofelia et al., 2019). Cooking can lead to losses of nutrients such as minerals, amino acids, and phenolic compounds. Popping or puffing of amaranth seeds is found to decrease iron and calcium content and phenolic content too (Gamel et al., 2006b; Lara & Ruales, 2002). Extrusion of amaranth grain did not show any effect on amino acid composition, whereas a decrease in levels of phenolic compounds was observed (Chávez-Jáuregui et al., 2000; Repo-Carrasco-Valencia et al., 2009). Germination and sprouting have been found to increase the antioxidant activity of amaranth grains. It also increased the phenolic and flavonoid content. Fermentation has been shown to increase the copper and magnesium content and antioxidant activity. It has also been shown to increase the content of all amino acids except tyrosine, glutamic acid, and proline and a decrease in arginine (Paśko et al., 2009). Germination is one of the traditional and effective methods to increase the nutraceutical value of food grains. It has been observed that germination of amaranth resulted in high protein and available lysine content. In addition, protein digestibility was also found to be relatively higher (Paredes-Lopez & Mora-Escobedo, 2008; Valadez-Vega et al., 2022). It is also observed that germination of amaranth seeds leads to reduce the anti-nutritional component and increase the antioxidant activity, bioactive potential, and nutritional value (Thakur et al., 2021). Toasting has also been shown to increase the phenolic and flavonoid content of amaranth grain. In addition, increased antioxidant activity and decrease in iron content as well as partial inactivation of lysine have been observed. Processing results in changes in minerals, amino acids, and phenolic content of amaranth seeds (Bressani et al., 1992). However, more research is needed to understand the effects of food processing in amaranth grain and development of amaranth-based products.

Manufacturing and processing of amaranth to develop edible products or dietary supplements plays a vital role in its nutritional properties for sports nutrition. The protein composition of amaranth is mostly affected since the protein is present in the pericarp of the seed and in processing methods mostly the pericarp is removed. Different culinary and technological processes also negatively affect the protein composition of amaranth grain (Muyonga et al., 2014). Popping and roasting are the heat processing methods that lead to a reduction in protein digestibility of grain amaranth. Roasting also has a negative impact on antioxidant activity of amaranth grain (Muyonga et al., 2014). Extrusion process has also been observed to affect the functionality of albumin and globulin fractions of the amaranth grain (Cárdenas-Torres et al., 2019). Popping enhances sensorial attributes of amaranth but heat labile amino acids are lost in this process resulting in reduced protein quality (Amare et al., 2015). Antioxidant capacity is affected in cooked, popped, toasted, or extruded amaranth grain for consumption, and this should be considered while including amaranth as a whole grain or processed form in diet of an athlete (Queiroz et al., 2009). PUFAs, mainly linoleic acid, another crucial nutrient for athletes, are also affected by processing methods like puffing which is usually applied to make popped amaranth as a breakfast product (Caselato-Sousa & Amaya-Farfán, 2012; R. S. Singhal & Kulkarni, 1990; Torregrosa-García et al., 2019). Extraction technologies can also affect amaranth bioactive compounds and their functionality. Despite the adverse effects seen in processing of amaranth as cited above, there are some amaranth supplementation studies in physically active people where amaranth is taken in the form of amaranth-based beverage, amaranth oil with positive impact on sports performance and improved aerobic metabolism in athletes (E. Espino-González, Muñoz-Daw, et al., 2018). Based on available literature, whole grain amaranth has the best nutritional properties for athletes. Germinated and fermented amaranth flour can be used to develop gluten free products for athletes. Germination or sprouting of amaranth grain can also be suggested to be of value addition in terms of nutraceutical potential for sports nutrition (B. Olawoye & Gbadamosi, 2020). Jet cooking process does not influence protein or amino acid content of amaranth; therefore, products from steam jet cooked amaranth flour can also be recommended for athletes and their protein requirement fulfilment will not be compromised (Liu et al., 2022). Fermentation is another recommended process that can be adopted in amaranth consumption by athletes since it maintains amino acid profile of amaranth with an added advantage of increased protein digestibility (Amare et al., 2015). Further research is needed considering the limited studies available in literature regarding changes in nutritional properties of amaranth after processing in context of sports nutrition.

Processing of amaranth grain through different methods impacts its chemical composition, protein content, starch and fat content, protein and lipid digestion (Grundy et al., 2020; Stankevich et al., 2021). Objectives to increase the cultivation and consumption of grain amaranth need to be supported by learning about effective processing and preparation techniques for optimal nutritional application in sports nutrition (Aderibigbe et al., 2022; Alencar et al., 2019). Not all processing methods have the same effect on the macronutrients structure and organisation. In particular, proteins can denature, be hydrolysed, or form aggregates as a result of processing and leading to altered functional properties and digestibility (Capuano et al., 2018; Coelho et al., 2018; Foegeding & Davis, 2011). It is, therefore, possible that the proteins get entrapped into the network of starch granules formed during the popping process and build-up of internal moisture (Grundy et al., 2020). Thermal treatment, such as toasting, may denature the protein and make it less soluble, reducing their digestibility (Foegeding & Davis, 2011). Popping conditions such as temperature, moisture content, and heating/treatment time may influence the physio-chemical properties of puffed amaranth and may have caused these differences in digestibility (Grundy et al., 2020). Some amaranth species are known to enter dormancy in response to stressful climate conditions, which may impact the seed coat and processability. Although processing affects nutritional composition and functionality of amaranth grains, processing methods like heat treatment, germination, fermentation, defatting, autoclaving, and blanching are also useful in reducing antinutrient composition (tannin and oxalate) of amaranth grains which have a dietary effect (B. T. Olawoye et al., 2017). The antinutrients tannins reduce absorption of nutrients and inhibit digestion and absorption of proteins, and therefore heat treatment helps improving bioavailability of minerals such as calcium, iron, sodium, and zinc (Gamel et al., 2006b; B. T. Olawoye et al., 2017). Many processing methods, such as the extrusion cooking process, are also being optimized to produce highly acceptable amaranth-based products with maximum retained nutritional and functional properties (Chávez-Jáuregui et al., 2000). It has also been observed that wet processing techniques are better than dry processing techniques to retain nutrient bioavailability, which is crucial in sports nutrition (Jw et al., 2014). Amaranth production, handling, and consumption face several constraints, including manual harvesting, soil preparation, nitrogen levels, post-harvest handling, limited cultivation, lack of improved varieties, disease and pest issues, limited market linkages, and limited commercialization (D’Amico & Schoenlechner, 2017). The primary challenges in post-harvest handling of amaranth are its high perishability, inadequate storage technologies, insufficient processing, inefficient handling procedures, and poor temperature control (Perez‐Rea & Antezana-Gomez, 2018). These issues underscore the need for comprehensive post-harvest management strategies tailored to amaranth’s specific needs to maintain its quality and nutritional value throughout the supply chain. Additionally, developing improved varieties, enhancing cultivation practices, and strengthening market linkages are essential to fully realize amaranth’s potential. Harvesting and handling amaranth seeds are particularly challenging due to their small size and susceptibility to shattering and lodging, making the harvest and post-harvest processing of grain amaranth quite difficult (Aderibigbe et al., 2022; Sattar et al., 2024).

7. Rationale for amaranth consumption by athletes

Recently, many studies have been conducted on human consumption of Amaranth. Scientific evidence elaborating the rationale for amaranth consumption by athletes is discussed here. To explore the beneficial effects of amaranth supplementation in athletes, Liubertas et al. studied the effect of amaranth (Amaranthus hypochondriacus) dietary nitrates on the aerobic capacity of physically active young persons. It is known that elevating plasma nitrites through dietary nitrates supplementation, such as beetroot consumption, is related to enhanced muscle efficiency, fatigue resistance, and performance. This research group identified amaranth (Amaranthus hypochondriacus) as an alternative source rich in dietary nitrate. It was found that long-term (6 days) use of dietary nitrate from amaranth may improve the aerobic capacity in young, physically active male persons. It can be endorsed as a nutritional supplement during the last week of preparation for competition in endurance events (Liubertas et al., 2020). In another randomized trial by Subramanian et al., assessment of oral intake of a nitrate-rich dietary supplement (amaranth extract) resulting in increased nitrate and nitrite levels in blood plasma and saliva of healthy adults was done. Nitric oxide generation is essential for the integrity of the cardiovascular system. These outcomes clearly indicate that a single oral dose of amaranth extract can increase the nitrate and nitrite levels and can help to improve the overall performance of people involved in vigorous physical activities or sports (Subramanian & Gupta, 2016). In another study by Fejer et al., new mutant Slovak amaranth varieties “Pribina” and “Zobor” were studied as a potential source of biologically active substances. Amaranth species denote a diverse group of plants and are a rich source of secondary metabolites with many positive biological effects. Antioxidant activities of both extracts showed high positive correlations to the content of total phenolic substances, total flavonoids, and rutin (Fejér et al., 2021). Ramirez Torres et al. found that using amaranth protein hydrolysates efficiently reduces systolic blood pressure. It was concluded that using amaranth-optimized hydrolysates as hypotensive supplements or ingredients for functional foods seems feasible (Ramírez-Torres et al., 2017). Konyole et al. conducted a randomized controlled trial on the effect of locally produced complementary foods on fat-free mass, linear growth, and iron status among Kenyan infants. The WinFoods was found to have the same effect on fat-free mass and linear growth (Konyole et al., 2019). Chmelik et al. summarized Amaranth as a potential dietary adjunct of lifestyle modification to improve cardiovascular risk by altering cardiovascular risk factors such as cholesterol, diabetes, and hypertension. It is speculated that squalene can play a part in hypocholesterolemic effect (Chmelík et al., 2019). Concerning the antidiabetic (Valenzuela Zamudio et al., 2022), antihypertensive (Nardo et al., 2020), and antioxidant activities, maximum studies were done in vitro and exhibited good potential for all three biological effects. The antidiabetic, antihypertensive, and antioxidant activities found in vitro should be confirmed further in animal or human models. Another study by Jamka et al. worked on a comparison of the effect of Amaranth Oil on selected atherosclerosis biomarkers in overweight and obese subjects. Amaranth oil has recently gained attention due to its possible health benefits. Amaranth oil was found to have a beneficial effect on atherosclerosis markers but not greater than rapeseed oil. Nonetheless, further studies with a longer intervention period are needed (Jamka et al., 2021). Moszak et al. studied the effect of amaranth seed oil supplementation on weight loss, body composition, and metabolic profile of obese patients following a 3-week body mass reduction program in a randomized clinical trial. It was concluded in the study that therapies involving edible amaranth seed oil with high nutritional value demonstrate potential for refining metabolic measurements through body mass reduction programs. Therefore, obese patients undertaking weight reduction programs may benefit from amaranth seed oil supplementation (Moszak et al., 2020a). It also indicated that amaranth oil consumption can be useful for athletes on weight reduction programs. Yelisyeyeva et al. conducted a trial and found activation of aerobic metabolism and improved heart rate variability by Amaranth oil in athletes (Yelisyeyeva et al., 2012). Macharia-Mutie et al. worked on a simulation of the effect of maize porridge fortified with grain amaranth on iron intake and status in children in Kenya. It was found that adding grain amaranth to maize-based porridge could improve Fe intake and status in pre-school children (Macharia-Mutie et al., 2013). In nutshell, there is sufficient scientific evidence to support the positive beneficial effects of amaranth consumption in humans including some studies on athletes. It has been clearly demonstrated in multiple studies that amaranth supplementation can boost sports or physical performance, improve body composition, and can help in improving muscle growth and strength.

8. Conclusions and prospects

In light of the information and literature discussed in this review, future studies should focus on identifying bioactive compounds, bioactive peptides, and nutrients from Amaranthus spp. with multivariate applications. In addition to the above, in vivo and ex vivo experimental validation of bioactive compounds and phytochemicals to test their potential as bioactive molecules of pharmaceutical significance should be performed. Main components of amaranth protein include globulins, albumins, and prolamins and can be hydrolysed by different methods to release different bioactive peptides. These peptides confer positive physiological functions such as diminishing arterial pressure, antithrombotic, antimicrobial, improving cholesterol and antioxidant activity (Silva-Sánchez et al., 2008). In amaranth grain protein, peptides GGV, IVG, and VGVL showed inhibition of the HMG-CoA reductase, indicating hypocholesterolemic effect. Lunasin-like peptide which is an anticancer bioactive compound has also been found in amaranth grains. Most frequent peptides in amaranth, especially globulin 11S, are antihypertensive and can regulate blood pressure (Silva-Sánchez et al., 2008; R. A. M. Soares et al., 2015). Amaranth seed can be a potential source of bioactive peptides with diverse bioactivities and functions relevant to sports nutrition, although more research is needed in this area to further evaluate the role of these peptides and functional molecules in sports nutrition. In commercial products, the safety of peptides, nutraceuticals, food products, beverages, and sports drinks is essential. Moreover, computational approaches could be used for initial screening and prediction of the potential composition of food products and precursors of bioactive peptides. Hydrolysates, proteins, and bioactive peptides derived from Amaranthus spp. could be substituted for synthetic antioxidants in nutraceuticals, sports drinks, snacks, and functional food industries. However, intense and continuous research efforts are still necessary for several areas, such as amaranth breeding and field cultivation, relevant food and feed processing technologies, product development, product commercialization, and marketing. New and improved amaranth cultivars are needed with advantageous traits such as increased height, improved functional properties and nutraceutical value. Continuous research efforts and agro-techniques have been adopted and future breeding strategies are being developed to improve quality, nutritional quality traits, and quantity of amaranth grain production (AnuradhaKumari et al., 2023; Ochieng et al., 2019; Wanyama et al., 2023). Various species of Amaranthus should be studied separately for their bioactives and by using these data and plant breeding techniques work should be done to develop high yielding as well as desired nutrition profile new varieties. Further value-added products may be developed to popularize this nutritious plant.

Disclosure statement

No potential conflict of interest was reported by the author(s).