Nuts of Fibrous Hemp Cannabis sativa L. - Concentrated Power of Nutrients

ABSTRACT

The fibrous hemp Cannabis sativa L. called also: industrial hemp and cannabis, is a plant widespread all over the world, grown mainly for its fiber, used for various purposes. Hemp fruits (also known as seeds or nuts) are mainly used to produce of oil for food, cosmetic and as bird feed. The nuts contain about 30–35% of oil with 80 to 90% of essential fatty acids (EFA), of which 55–56% is linoleic acid (LA) from the omega-6 group and 22–25% α-linolenic acid (ALA) from the omega-3 group, as well as amino acids, participating in the formation of albumin and globulin (edestin), vitamins, and minerals. The article describes in detail: the nutritional value of hemp nuts, the possibilities for the use of hemp nuts, discussion about the cannabinoid content of fibrous hemp nuts, and legislative issues concerning the cultivation of industrial hemp. The paper reviews the literature on the most important nutritional properties of the seeds and products made from the processing of hemp seeds, making it a very versatile raw material used among others in the food industry.

摘要

大麻纤维也称为: 工业大麻和大麻，是一种广泛分布于世界各地的植物，主要为其纤维而种植，用于各种用途. 大麻果实（也称为种子或坚果）主要用于生产食用油、化妆品和鸟类饲料. 坚果含有约30-35%的油和80-90%的必需脂肪酸（EFA），其中55-56%是欧米伽-6组的亚油酸（LA），22-25%是欧米加-3组的α-亚麻酸（ALA），还有氨基酸，参与白蛋白和球蛋白（edestin）、维生素和矿物质的形成. 本文详细介绍了大麻坚果的营养价值、使用大麻坚果的可能性、纤维大麻坚果中大麻素含量的讨论以及有关工业大麻种植的立法问题. 本文综述了有关大麻籽及其加工产品最重要营养特性的文献，大麻籽是食品工业中用途广泛的原料之一.

KEYWORDS:

• Hemp seeds (nuts)
• essential fatty acids
• use of hemp nuts
• nutrition value
• hemp protein
• plant - based food

关键词:

• 大麻籽（坚果）
• 必需脂肪酸
• 使用大麻坚果
• 营养价值
• 植物性食品

Introduction

Hemp (Cannabis sativa L. var. sativa) is a plant belonging to the family Cannabaceae and the genus Cannabis. This species is characterized by its ability to adapt to changing environmental conditions, and the spread of hemp has been correlated with commercial sea and land routes. The plant is relatively easy to grow, requiring good soil, fertilizer and water, but no pesticides or herbicides. Fibrous hemp is one of the few plant materials with such versatile uses. Today, hemp is experiencing a renaissance as a food product, a medicinal product, as a raw material for textiles and many other applications. Interest in this plant is directed mainly toward the production of seeds for human and animal nutrition, shives for eco-logical construction (Strzelczyk, Lochynska, and Chudy 2021) and animal bedding, and fiber for the textile and paper industries. Seeds and their products – oil, cake and fibrous hemp meal can be used as feed additives in animal nutrition, mainly as a source of essential fatty acids and essential amino acids (Citti et al. 2019).

The abundance of vital substances and antioxidant potential stored in the nuts (commonly known as seeds) of hemp makes the plant count as a superfood. While ordinary foodstuffs provide us with basic nutritional value, superfoods provide a range of easily digestible protein, important fatty acids, enzymes, amino acids, antioxidants vitamins, inorganic substances,, and bioflavonoids. It is in all these substances that fibrous hemp is rich (Cerino et al. 2021).

Flour extracted from grinding hemp seeds, compared to wheat flour, has more valuable properties and can be used interchangeably as an additive in the production of functional foods. One of these directions could be the baking industry, which is one of the primary food industries of the industry, and can be used in a wide variety of food technologies, such as beer, sugar and baking industries (Manaia, Ana, and Rodriges 2019; Rusu et al. 2021).

Hemp foods strengthen the immune system, prevent diabetes, cardiovascular disease, fight inflammation, and provide energy and a sense of wellbeing. Hempseed and hempseed oil are among the few natural plant products considered to be the healthiest, and the additional presence of high-quality fats makes them a staple for people eating a healthy diet (Cerino et al. 2021).

Hemp nuts are also a rich source of protein with a complete profile of amino acids and contain all saturated and unsaturated fatty acids in nutritionally perfect proportions. Hemp seeds are a source of essential unsaturated fatty acids with a favorable ratio (3:1) of omega-3 (α-linolenic, stearidonic) and omega-6 (linoleic, γ-linolenic-GLA) acids (Farinon et al. 2020). Polyunsaturated fatty acids are beneficial for the cardiovascular system, reducing the risk of sudden cardiac arrest and cardiac arrhythmias, and lowering blood cholesterol levels. GLA acid and vitamin D3 prevent osteoporosis and are beneficial in its treatment. Oils rich in essential fatty acids are also used in cosmetic and hygienic industry for production of preparations used in atopic dermatitis, psoriasis, soothing inflammation, preventing excessive water loss from epidermis, antiseptic, anti-aging; they are also ingredients of hair dyes, shampoos and soaps (Cerino et al. 2021).

In addition, hemp contains vitamins such as E, D3, C, B (B1, B2, B3, B6), magnesium, insoluble fiber, carotenoids, micro (iron and zinc) and macro elements (phosphorus, potassium, magnesium, sulfur, calcium), which have a health-protective effect on the human body by protecting it from oxidative stress caused by free radicals (Cerino et al. 2021).

All varieties of hemp, both Polish and foreign permitted for cultivation, contain traces of the psychoactive substance Δ⁹-THC, and the limit for these compounds in the EU is 0.3% (from 2023) but in Poland from 2022, in Canada 0.3% (Moran 2015).

Hemp seed (Cannabis sativa L.) contains large amounts of nutrients, including protein, dietary fiber, minerals and unsaturated fatty acids, making it an excellent high-protein and high-fiber food enrichment component. The purpose of this paper was to present the most important nutritional properties of the seeds and products made from processing hemp seeds, making it a very versatile raw material used in the food industry, among others.

Nutritional value of hemp nuts

Protein

The protein that is found in nuts of fibrous hemp belongs to the complete, easily digestible ones. Proteins have several functions in the body as building blocks, providing a kind of scaffolding; carriers of information. Proteins renew and repair our cells. The body needs a balanced amount of non-produced amino acids: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Fibrous hemp nuts are rich in all these valuable and essential amino acids (Teleszko, Zając, and Rusak 2022).

Hemp seeds (nuts) contain 20–25% (Teleszko, Zając, and Rusak 2022) and even 28% of this organic compound, and its content is higher compared to flax seeds, which usually contain about18% (Manaia et al., 2019; Rupasinghe et al. 2020).

The protein of fibrous hemp seeds consists mainly of the easily digestible proteins edestin and albumin, rich in essential amino acids (Dąbrowski and Skrajda-Brdak 2016; Rupasinghe, Vasantha et al. 2020). Hemp seeds consist mainly of storage proteins, including albumin (25–37%) and globulins (67–75%). They do not contain protease inhibitors, resulting in improved protein digestibility. The essential amino acid content of hemp seed is higher than that of soy protein and is sufficient for people 10 years of age and older. The amino acid profile of the proteins found in the seeds of the Henola and Bialobrzeskie varieties was presented by the authors (Teleszko, Zając, and Rusak 2022). They showed that, according to the Institute of Medicine (IOM; Washington, DC, USA), the amino acid composition of hemp protein draws special attention due to the excellent concordance of Thr and Leu contents. According to IOM experts, the reference (theoretical) protein with an essential amino acid composition optimal for humans contains 2.7 g Thr (threonine) and 5.5 g Leu (leucine)/100 g protein, which is exactly the amount calculated for the seed protein of the Henola variety. For the cultivar Białobrzeskie the content of Thr was slightly higher and amounted to 3.05 g/100 g. The limiting amino acid in hemp protein is Lys (lysine). In terms of the content of Tyr (tyrosine) + Phe (phenylalanine) – (average content for both varieties 6.21 g/100 g) and His (histidine) (2.33 g/100 g), the hemp protein showed a high degree of similarity to that of hen’s egg and other plant products rich in protein, such as broad beans, lupine, flax and rapeseed. Hemp seeds are characterized by high contents of Glu (glutamic acid); Arg (arginine) and Asp (aspartic acid) (Cerino et al. 2021).

Protein content can vary depending on the variety and environmental factors as well as seed processing methods. Protein is also found in the pomace after pressing and in post-extraction meal. The greatest amount of protein is found in the endosperm of the seeds, small amounts of protein were determined in the fruit and seed husks, the removal of which (in which most of the fiber is found), leads to a 1.5-fold increase in both the amount of protein and fat (Farinon et al. 2020; Mattila et al. 2018).

Hemp nuts contain amino acids that participate in the formation of albumin and globulins, as well as edestin (a simple protein belonging to the globulin group), and are an excellent substitute for dairy in the diet. Hemp protein contains all the essential amino acids (EAA) that ensure the smooth functioning of the entire body. The amino acid found in the highest amount is glutamic acid (3.74–4.58% of whole seeds), followed by arginine (2.28–3.10% of whole nuts)(Rodriguez-Leyva and Pierce 2010).

Fatty acids

Fats are the second most important building material in the body, after proteins. The common feature of fat storage materials is their difficult solubility in water and easy solubility in organic solvents. Fat accumulates in the seeds, especially of oil plants, which include fibrous hemp (Teleszko, Zając, and Rusak 2022).

Fibrous hemp nuts contain 25–38% fat (average 30.9% on a dry weight basis) (Bailoni et al. 2021; Rupasinghe et al. 2020; Teleszko, Zając, and Rusak 2022). Seed fat is the most abundant energy storage material, as it yields more energy in the burning process than carbohydrates or proteins. (Rodriguez-Leyva and Pierce 2010) report that 100 g of fibrous hemp seeds provide 567 kcal; 2,200 kJ (25), according to Mattila et al. (2018) the energy value of whole seeds is 2,301 kJ/100 g and 1,890 kJ/100 g. On the other hand, Teleszko, Zając, and Rusak (2022) showed that comparing two Polish hemp varieties Białobrzeskie and Henola, the energy value of these two varieties was at a similar level, i.e. 1860–1905 kJ/100 g; which gives 451–461 kcal/100 g in the tested seeds. Slightly higher values are reported by the authors Cerino et al. (2021), who showed that 100 hemp seeds provide 500–600 kcal. Oilseeds, provide not only a highly valued nutritional product for humans and animals, but also a raw material for many industries, especially soap industry (detergents, soaps). Hempseed oil is used to make body oils and creams which penetrate deeply into the skin. Due to its high content of polyunsaturated fatty acids, fibrous hemp seeds are suitable for the production of printing ink and wood preservatives (Teleszko, Zając, and Rusak 2022).

Hemp seeds are used to produce high-quality edible and industrial oils. The former is produced by cold-pressing selected seeds and then filtering to remove solid impurities, while retaining the EFA (essential unsaturated fatty acids) and taste. The health benefits of fibrous hemp seed oil are related to the presence of polyunsaturated fatty acids, which stimulate the immune system of the human body (della Rocca and Di Salvo 2020; Elena, Stefania Surdu, and Asaftei 2009).

Essential fats are those which are not synthesized in the human body and must be supplied with food, including EFAs from the Omega-3 and Omega-6 groups. The proportion of EFAs in hemp oil is very high and amounts to 90%. The main fatty acids are linoleic acid (18:2 n-6) and α-linolenic acid (18:3 n-3), which belong to the EFAs. The nutritional value is additionally increased by the presence of γ-linolenic acid (18:3 n-6, GLA) and stearidonic acid (18:4 n-3, SDA), which are biological metabolites of linoleic and α-linolenic acid (Dąbrowski and Skrajda-Brdak 2016). A study by the authors (Teleszko, Zając, and Rusak 2022) confirmed that lipids from hemp seeds are characterized by a high content of unsaturated acids (UFAs). In the oil fraction extracted from the seeds of “Henola” and Białobrzeskie cultivars, the share of these acids constituted on average 88% of the total FA content. The UFA profile was dominated by polyunsaturated fatty acids (PUFA).

α-linolenic acid is metabolized in the body, performing many important functions.

In the process of combustion, it provides the body with energy necessary for work. It is recommended for athletes before competitions. It is a component of body cell membranes, which should be flexible and ensure proper transport of nutrients and communication with other cells. Alpha-linolenic acid contributes to maintaining normal blood cholesterol levels (Elena, Stefania Surdu, and Asaftei 2009).

The ratio of LA (from the omega 6 group)/ALA (from the omega 3 group) acids in hemp seeds is 2: 1 (Spano et al. 2020) or 3: 1 (Deferne and David 1996; Rupasinghe et al. 2020). In addition, the presence of omega 9 fatty acids and the rare gamma-linolenic acid, GLA, make hemp seeds undoubtedly fibrous and extremely healthy and nutritious.

The proportion in which omega acids are present is important because omega-6 acids have pro-inflammatory effects and omega-3 acids have anti-inflammatory effects. Omega acids are very desirable in our diet, but they should be consumed in proper proportions. Too much presence of omega-6 acids may contribute to the formation of inflammation in the body. The negative effect of LA acids, in turn, neutralize ALA acids. So if we suffer from omega acids deficiency or consume excessive amounts of products rich in omega-6 fatty acids, hemp seeds will be an excellent choice for us, because they will allow the body to restore the natural balance in the content of these fatty acids. This is particularly important in the prevention of cardiovascular disease, including the prevention of arrhythmia, heart attack, atherosclerosis and ischemic heart disease (Rupasinghe et al. 2020).

Hemp nuts consumed whole or ground, as well as the oil pressed from them, provide EFAs that must be supplied to the human body from the outside, as we cannot synthesize them ourselves (Deferne and David 1996). Polyunsaturated fatty acids stimulate the immune system. The dietary and medicinal effects of polyunsaturated fatty acids are effective provided that the hemp oil is protected from oxidation processes. When hemp seed oil is subjected to heat, light, air, or improper storage, the fatty acids in the oil are rapidly degraded and lose their healthful properties. In the case of unsaturated fats, oxidation processes proceed rapidly, which can result in the formation of free radicals that strongly inhibit normal lipid metabolism in the body. The oil is obtained by cold-pressing methods (at temperatures below 40-50°C), carefully packaged in an inert gas atmosphere, protected from light by using appropriate packaging, and stored at 8-15°C (Rupasinghe et al. 2020).

Gamma linolenic acid

Fibrous hemp nuts contain the very rare GLA gamma linolenic acid, which belongs to the highly unsaturated fatty acids, of the omega-3 group. Depending on the type of acid and their proportion in the diet, influence, among others: cardiovascular function; blood pressure regulation; proper vision; skin health; optimal brain function (Teleszko, Zając, and Rusak 2022). Hemp seeds are a rich source of nutrients and contain γ-linolenic acid (GLA, 18:3, n-6), which is the healthiest most prominent fatty acid, ranging from 0.5% to 4.5% in unshelled hemp nuts (Alonso-Esteban et al. 2020).

Vitamins and minerals

Authors Cerino et al. (2021) report that 50 mg of hemp seeds provides over 100% of the daily recommended intake of vitamins A, D, and E. Hemp nuts are an excellent source of vitamin E, dubbed the “vitamin of youth” helps protect cells from oxidative stress. It also supports energy metabolism and keeps red blood cells healthy. It is essential for storing sugar and supports the production of vitamin A. The vitamin content in hemp seeds is about 7.20 mg/100 g, in hemp oil − 79.0 mg/100 g. About 15 g of hemp oil is enough to cover the daily requirement of this vitamin in an adult (Cerino et al. 2021).

Vitamin E is used in the prevention of diabetes, reducing blood sugar levels, slows down the aging process. The supply of this vitamin is important for maintaining firmness of the skin, as it supports collagen production, protects the inner walls of blood vessels and thus prevents strokes and heart attacks. Vitamin E is fat-soluble. During heat treatment, the vitamin is deactivated, so hemp oil should not be used for frying and cooking. The proper functioning of vitamin E depends, among other things, on the presence of vitamin C (Cerino et al. 2021).

Hemp also contains many B vitamins. These vitamins have an anti-stress effect and benefit our nervous system. Vitamin B1 (thiamine), known as the good mood and well-being vitamin, is present in quantities of around 1.3 mg/100 g. Skin energy vitamin is called riboflavin (B2), additionally it supports kidney function and red blood cell production.

In hemp we can also find vitamin B3 (niacin), which is necessary for the metabolism of proteins, fats and carbohydrates; B6 (pyridoxine), the so-called digestion vitamin, is found in hemp in an amount of 0.5 mg/100 g, reduces too high cholesterol levels in the blood, supports the production of antibodies in the body. In addition, in hemp nuts we can find folic acid, or vitamin B9 in an amount of about 18 mg/100 g. The presence of this vitamin is essential for protein production, but especially for DNA production and fetal development.

Fine hemp nuts are a rich source of minerals, which are very important for maintaining the acid-base balance and for many processes occurring in the body (Teleszko, Zając, and Rusak 2022). When found in their natural form, they are more bioavailable, so their effects are much better. Hemp owes its abundance of these substances to its taproot system, which reaches the deepest layers of soil through its extensive and deeply penetrating roots, carrying and storing non-essential substances and minerals in its leaves and seeds. Calcium, which is the building block of bones, is present in amounts of about 150 mg/100 g. In addition, it has an anti-stress effect and regulates blood clotting, activates enzymes. The consumption of about 30 g of hemp nuts covers the daily requirement of an adult for this element. Potassium is present in hemp in an amount of about 900 mg/100 g. Potassium is called “the element of life” because it takes part in almost all processes in the human body. Its main role is to control kidney function and the body’s water balance. Equally important is how potassium affects blood pressure (helping to keep it at a normal level), supports the muscular and nervous systems and oxygenates the brain. Consumption of about 30 g of hemp nuts covers 15% of an adult’s daily requirement of this element. Magnesium is an element necessary for the proper functioning of the human cardiovascular system. However, its role in the body is much broader – the properties of magnesium also include: affecting muscle contractility, stabilizing the nervous system, supporting memory and the work of gray cells, participating in the regulation of blood pressure, supporting electrolyte balance. Hemp contains about 450 mg/100 g of this element. Authors Cerino et al. (2021) report that 50 mg of hemp seeds can cover 50–100% of the recommended daily intake of minerals, including copper, magnesium, and zinc. Iron, on the other hand, is an element with a wide variety of properties. It affects the functioning of the circulatory, nervous, and immune systems, has antioxidant properties, and builds numerous proteins and enzymes. The most important roles played by iron in the human body are: supporting the production of red blood cells and hemoglobin, enabling the proper transport of oxygen in the body, influencing the proper physical and intellectual functioning, participating in the activation of immune cells. It is found in hemp in an amount of about 12 mg/100 g. Manganese, found in about 10 mg/100 g in fibrous hemp, activates enzymes necessary for healthy bone growth. A supply of about 30 g of hemp nuts covers as much as 50% of the daily requirement. Content of copper in hemp nuts is about 7 mg/100 g. This element is a trace element, but it is essential for life, strengthening the immune system and controlling metabolic processes in the liver, gall bladder, guts and heart. A supply of about 30 g of hemp nuts covers about 15% of the daily requirement. The proper functioning of over 200 enzymes in the human body depends on an adequate supply of zinc. Zinc plays an important role in building blood cells and the immune system. The amount of approximately 30 g of hemp nuts covers approximately 14% of the daily requirement for this element (Mattila et al. 2018).

Some minerals, such as magnesium, vitamins E, B and fatty acids contained in fibrous hemp nuts act as antioxidants, that is, they are involved in the fight against free radicals. These in turn are responsible for damaging cell membranes and cells leading to premature aging and cell apoptosis.

Other authors give the content of macroelements on the example of Finola variety (in g kg⁻¹): K (8.59), P (11.6), Ca (1.45), Mg (4.83) and Na (0.12) and microelements (in mg kg⁻¹): Mn (70), Zn (70), Cu (20), and Fe (0.14) (Zuk-Golaszewska, Golaszewski, and Gołaszewski 2018). The mineral contents of whole seeds and fiber hemp hulls alone are (in g/100 g, respectively): macronutrients Ca (0.127; 0.166); Mg (0.496; 0, 221), P (1.17; 0.40), K (0.921; 0.529); micronutrients (in mg/100 g): Fe (4.38; 3.06); Mn (10.5; 12.1), Zn (6.97; 2.92), Cu (1.89; 1.80) (Mattila et al. 2018).

Dietary fiber

Fibrous hemp nuts contain 20 to 30% carbohydrates, a significant portion of which is fiber, mostly insoluble (Rupasinghe et al. 2020; Teleszko, Zając, and Rusak 2022). Dietary fiber can be divided into two fractions: soluble and insoluble. It represents the part of plant material that is resistant to digestive enzymes and includes cellulose, non-cellulosic polysaccharides such as hemicellulose, pectin, gums, mucilage, and lignin (a non-carbohydrate component). Callaway et al. (1996) showed that the total carbohydrate content of whole hemp seeds for the Finnish variety Finola was 27.6 g/100 g (Mattila et al. 2018). On the other hand, authors Teleszko, Zając, and Rusak (2022) compared Polish varieties Białobrzeskie and Henola. In their study, they showed that the post-food fiber content of these two varieties was 28.88% − 27.42%, respectively. The digestible carbohydrate content of Henola variety was higher than that of “Białobrzeskie” variety (4.48%). However, the seeds of “Białobrzeskie” cultivar had higher content of dietary fiber (28.88%). Seed husks contained more carbohydrates (69.7 g/100 g); but less protein (14.2 g/100 g), fat (12.5 g/100 g) and ash (3.5 g/100 g); than whole seeds: 34.4 g/100 g carbohydrate; 25.6 g/100 g protein; 34.6 g/100 g fat and 5.4 g/100 g ash (Mattila et al. 2018).

Australians during the famine of the 19^th century used hemp seeds as a source of protein and fiber (Chauhan 2021), which increases the volume of food content, which was common in the diets of less affluent communities (Ivan and Hrušková 2015). Total Dietary Fiber (TDF) content is 27.6 and up to 33.5 g in 100 g of seeds, which accounted for 98% of total carbohydrates (Andre, Hausman, and Guerriero 2016; Farinon et al. 2020). The high dietary fiber content of whole hemp seeds may negatively impact protein digestion, but at the same time provides a number of health benefits in the human body by acting as a prebiotic. It has been shown that fiber can improve insulin sensitivity; reduce appetite and post-food intake, thereby reducing the risk of obesity and diabetes (Mattila et al. 2018).

Given the health benefits of dietary fiber, whole, unhulled seeds should be consumed because almost all of the fiber is in the hull of the hemp fruit (Farinon et al. 2020; Mattila et al. 2018).

Whole fibrous hemp seeds (nuts) were characterized by a higher content of total sugars compared to seed husks (on a dry weight basis). In whole seeds, 2.09 g/100 g of sugars were found, including monosaccharides: fructose (0.46 g/100 g), glucose (0.40 g/100 g) and disaccharide-sucrose (1.11 g/100 g). In the seed husk, total sugars of 1.03 g/100 g were determined, including monosaccharides: fructose (0.50 g/100 g), glucose (0.41 g/100 g), and disaccharide-sucrose (0.37 g/100 g) (Mattila et al. 2018).

Cannabinoid content of fibrous hemp nuts

Disparate information is available in the publicly available literature regarding the content of cannabinoids including the psychoactive Δ9-THC and CBD in the seeds. Oil pressed from hemp seeds is known for its nutraceutical and pharmaceutical properties, among others. However, it is significant that its health-promoting qualities are closely related to its variable chemical composition including, for example, the presence of cannabinoids, which is influenced, for example, by the method of production, genotype – hemp variety, and seed purification.

According to some authors, hemp seeds, as the only organs of the plant, are devoid of these active substances, primarily the psychoactive compound tetrahydrocannabinol and its antagonist cannabidiol (Lachenmeier and Walch 2005; Ross et al. 2000). This is not supported by the results of laboratory analyses by other authors (Citti et al. 2019). The authors showed that in addition to tetrahydrocannabinol and cannabidiol, an additional 30 cannabinoids were identified for the first time in hemp seed oil generally available on the market. The results obtained confirmed multivariate statistical analyses, showing highly significant differences in chemical composition, (cannabinoid content) in the ten hemp oil samples analyzed. Cannabinoids are produced in glandular trichomes, which contain a resinous oil composed mainly of phytocannabinoids and terpenes. Such glandular cells are produced on the female flowers and therefore in the pericarp (highest concentration in the bracts, the two small leaves surrounding the seeds) (Small 2015). Seeds, although internally devoid of cannabinoids, can be contaminated on the outer surface with a sticky resinous oil secreted by the numerous glandular trichomes present on these bracts (Ross et al. 2000). As a result, the surface of the seed will be covered with a sticky resin with all the cannabinoids present in it. Since the seeds are mainly used for oil production, if they are properly purified before extracting the oil from the cannabis seeds, the latter will contain only trace amounts of cannabinoids, or will be completely devoid of them. The reason for the finding of low cannabinoid content in hemp nuts may be due not only to their poor cleaning from the husk, but also to the remains of glandular hairs (trichomes) stuck to the nut shells. Thus, it is reasonable to hypothesize that cannabinoids may be labeled in hemp seed oil. Numerous literature reports support the above thesis of determining THC and CBD concentrations in hemp seed oil (Bosy and Cole 2000; Lachenmeier et al. 2004; Leizer et al. 2000).

Divergent information regarding the psychoactive Δ⁹-THC content in seeds is available in the public literature. According to some authors, hemp seeds, as the only organs of the plant, are devoid of the psychoactive compound tetrahydrocannabinol (Lachenmeier and Walch 2005). This is not confirmed by the results of laboratory analyses by other authors. A study of the Δ⁹-THC content in seeds of narcotic and fibrous varieties showed that this compound could be detected as a result of inaccurate cleaning of fibrous hemp seeds from the seed shells (Ross et al. 2000; Yang et al. 2017). Although after successive chloroform rinses of the seeds, the Δ⁹-THC content decreased significantly, traces of Δ⁹-THC were determined by gas chromatography, higher in typically narcotic varieties (<2 µg/g), lower in fibrous varieties (<0.5 µg/g). Despite the thorough cleaning of the seeds from the seed husk, the results clearly indicated the trace presence of cannabinoids in the hemp seeds of the tested cultivars (Crescente et al. 2018; Fetterman et al. 1971; Jang et al. 2020; Leizer et al. 2000). Significant amounts of cannabinoids, especially THC, were detected in 5 of the 11 hemp oil samples tested on the Croatian market, suggesting that their presence is due to the use of improper processing procedures and the illegal source and use of narcotic hemp varieties (THC+CBN/CBD ratio >1) for food purposes. Pure hemp oil is devoid of the psychoactive cannabinoid Δ⁹-THC (Dąbrowski and Skrajda-Brdak 2016).

Uses of fibrous hemp nuts

For thousands of years, hemp nuts have served as food for many animal species such as birds, including poultry (methionine beneficial to birds), fish and young mammals (Deferne and David 1996; Rodriguez-Leyva and Pierce 2010). By using hemp nuts-based feeds, poultry farmers can achieve maximum weight gain naturally, without chemical growth promoters. Feeding hemp cakes to laying hens did not significantly affect the number of eggs laid, but significantly improved egg quality (Silversides and Lefrançois 2005). As the proportion of this feed increased, the content of linoleic acid and α-linolenic acid in egg yolks increased, while the content of palmitic acid, responsible for increased levels of total cholesterol in blood, decreased. Other authors have shown that a 20% addition of hemp seeds to feed did not significantly affect egg production, but had a significant effect on egg weight, and enrichment of the diet with an additional 4% of hemp oil improved yolk quality, with an increase in the content of omega 3 and omega 6 acids (Gakhar et al. 2012). Hemp seed husks are a valuable plant fertilizer, and 10 t of seed husks have the same value as 40 t of natural organic fertilizer produced from various plant and animal wastes resulting from partial aerobic decomposition by microorganisms (Elena, Stefania Surdu, and Asaftei 2009).

Hemp is a high-protein crop that is becoming increasingly popular in a healthy and balanced diet. Through the high protein content of the nuts, the plant is increasingly used in vegan and vegetarian cuisine. Hemp protein is highly digestible, 84–86% for the seed in its pure form and 83–92% for the meal made from the seed. Based on studies, hemp protein digestion has been shown to produce peptides that have antibacterial, cytomodulatory, antioxidant and blood pressure-lowering effects. The production of hemp oil results in a by-product such as hemp oil cake, and due to its high protein content, i.e. 33.5%, among other things, it can be added to food to improve its nutritional value, finding its application in the cereal industry, among others. Compared to hemp cake, hemp flour is a better raw material for protein supplementation, as it was observed to have higher nutritional values (lower fat content and higher protein content) based on analysis. A study was conducted on pasta with the addition of 30% hemp flour. It was observed that this product with very good organoleptic properties, and it is also a high-protein and high-fiber product (Teterycz et al. 2021). In addition to hemp flour and hemp cake, hemp protein concentrate has also been produced, made from dehulled and defatted seeds or by dissolving the non-protein components of the seeds in water. Hemp protein isolate is also available. This is an enriched form of a commercial protein product, the most purified (>90% protein). This product was developed to meet food processing needs. Hemp protein is a widely used ingredient that is becoming an important alternative source of protein in food products. We can see hemp protein in baked goods, beverages, dairy mixes, infant formulas (hemp milk, nutritional powder) and processed meat products, among others (Qingling and Xiong 2019).

Rusu et al. (2021) undertook the characterization of hemp (Cannabis sativa L.) flour (Dacia Secuieni and Zenit varieties), comparing its properties with wheat flour, type 550, which is generally available on the market. In the study, they showed that in hemp flour, total protein was present in higher amounts by more than 35% compared to wheat flour, and lipids reached a threshold of 28%. In addition, the amount of minerals exceeded 3% in hemp flour, and fiber was 26%, compared to 0.61% for wheat flour. In the conducted study, 12 mineral elements were determined in hemp cake samples: copper(Cu), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), iron (Fe), manganese(Mn), calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (p). The dominant minerals were K, Ca, Mg, p, Fe and Mn. The laboratory results confirm that the highest amounts of minerals were recorded for hemp flour (in this experiment for the Zenith variety). In contrast, the lowest amounts of minerals were recorded in the wheat flour sample, some of which were even absent. It was further shown that unsaturated fatty acids dominated over saturated ones. Linoleic acid was found to be dominant, followed by oleic and gamma-linoleic acids. As for amino acids, the highest amount was found in glutamic acid for hemp flours. As carbohydrates, sucrose is found in the highest amount, followed by glucose and fructose. The authors showed that hemp flours have better properties compared to wheat flour, enriching food with essential components for the proper functioning of the body.

The authors of Rusu et al. (2021a) obtained similar, very good results. In their experiment, they showed that bread with the addition of hemp flour has significantly better nutritional properties compared to wheat bread. In the study, hemp flour (in various proportions of 5%, 10%, 15% and 20%) from Dacia Secuieni and Zenit varieties was added to bread. The goal of this experiment was to improve the nutritional properties of the resulting product. The protein content of the new products increased from 8.76 to 11.48%, lipid content increased from 0.59 to 5.41%, mineral content from 1.33 to 1.62%, and fiber content from 1.17 to 5.84%. Elasticity and porosity decreased from 95.51 to 80% and 78.65 to 72.24%, respectively. K, Mg, Ca, P, Mn and Fe were the main minerals in bread with hemp flour regardless of the variety tested. The total amount of unsaturated fatty acids in bread samples with hemp flour ranged from 67.93 g/100 g to 69.82 g/100 g. The tests revealed the presence of eight amino acids, three of which were in the highest amounts (lysine, phenylalanine, histidine). Lysine, which is found in small amounts in wheat bread, increased from 0.003 to 0.101 g/100 g. There was a decrease in sucrose and fructose, while glucose was not shown after the addition of hemp flour. The addition of hemp flour also had a positive effect on the inhibition of yeast and mold growth, which significantly decreased during the first three days of storage.

Hemp seeds can be consumed whole as a bread additive (5–10%); ground, used as flour (Ivan and Hrušková 2015) and to prepare gruel when mixed with milk; germinated seeds, as a salad dressing; pressed oil from them for cold use; and pomace (cake) as a high-protein food and animal feed. The most popular vegetable oil until World War II was actually oil pressed from fibrous hemp seeds (Rodriguez-Leyva and Pierce 2010). Hemp oil has also found use in the rapidly growing cosmetics industry as an additive to creams and lotions due to its anti-inflammatory and antibacterial properties. Cosmetics to which hemp oil is added have a slightly nutty smell (Kaniewski et al. 2017). Currently, hemp seed oil is also used in pharmaceutical industry (the so-called CBD hemp extract, i.e. CBD cannabinoid extracted from hemp combined. It is available in liquid, paste or capsule form. It is usually sold under the misleading name CBD hemp oil/oil). The oil is also used as an additive in animal foods (Andre, Hausman, and Guerriero 2016; Elena, Stefania Surdu, and Asaftei 2009).

Legislative changes regarding the cultivation of hemp in Poland

In November 2021, the European Parliament adopted a final Common Agricultural Policy (CAP) proposal for member states in favor of restoring the allowable level of THC in cannabis seeds from 0.2% to 0.3% (EIHA 2022).

The Common Agricultural Policy (CAP), is a partnership between EU member states, involving cooperation between the public and a country’s agricultural sector. Under this program, beginning January 1, 2023, agricultural producers will be able to apply for direct payments for hemp crops, for all registered varieties whose THC cannabinoid content does not exceed the 0.3% limit. The amendment creates a potential increase in the area under hemp cultivation and the number of cultivated varieties admitted and listed in the Community CCA Catalog and the National Register of Agricultural Plant Varieties (KR). The catalogs are official lists of, among others, agricultural plant varieties whose certified seed material may be produced and traded in Poland and the European Union (EIHA 2022).

In Poland, all fibrous hemp varieties permitted for cultivation must be registered in the Community Catalog of Varieties of Agricultural Plant Species (CCA) and in the National Register of COBORU – the Central Center for Research on Varieties of Cultivated Plants in Słupia Wielka (COBORU 2022).The increased content level from 0.2% to 0.3% applies under the condition that agricultural producers wish to apply for direct payments for hemp cultivation in a country where national legislation allows it. For example – in Italy the limit is 0.6% THC, while in the Czech Republic the limit cannot exceed 1% (EIHA 2022).

On of May 7, 2022, the Act on Counteracting Drug Addiction was amended in Poland. The current legal act in Poland is the Act of March 24, 2022, item 764 (Dz. U. z dn. 6.04.2022. Poz. 764) on amending the Act on Counteracting Drug Addiction and certain other acts, among others, introduces the following changes in the Act of July 29, 2005 on Counteracting Drug Addiction: Journal of Laws of 2020, item 2050 and of 2021, item 2469 and of 2022, item 763 (Dz. U. z 2020 r. poz. 2050 oraz z 2021 r. poz. 2469). In Article 45, paragraph 3 shall be replaced by the following:,,The cultivation of fibrous hemp may be carried out: 1) for textile, chemical, pulp and paper, cosmetic, pharmaceutical and energy purposes; 2) for seed and scientific research purposes; 3) for breeding varieties of fibrous hemp, land reclamation and remediation; 4) for food, veterinary, fodder, beekeeping, fertilizer and insulation purposes; 5) for the production of composite materials, building materials and natural plant protection products.”

The second, parallel to the above, Act of March 24, 2022 amending the Act on Counteracting Drug Addiction, Item 763 introduces the following changes in the Act of 29 July 2005 on Counteracting Drug Addiction (Journal of Laws of 2020, item 2050 and of 2021, item 2469), among others changing the definition of fibrous hemp:,, Fibrous hemp – plants of the species hemp (Cannabis sativa L.) in which the sum of the content of delta-9-tetrahydrocannabinol (Δ⁹-THC) and tetrahydrocannabinolic acid (delta-9-THC-2-carboxylic acid) in the flowering or fruiting tops of plants from which the resin has not been removed does not exceed 0.3% on a dry weight basis; this sum shall be rounded to one decimal place” (EIHA 2022).

Conclusions

Hemp seeds (Cannabis sativa L.) are counted among the so-called superfoods due to their richness in nutrients. Cannabis sativa L. seeds are rich in essential polyunsaturated fatty acids and highly digestible proteins, with excellent nutritional value. Indeed, their distinctive feature, which distinguishes them from other foods, is their ideal ratio of omega-3 and omega-6 fatty acids. They provide more unsaturated omega-3, omega-6 and omega-9 fatty acids than nuts and flax. These fatty acids stimulate the human body’s immune system and have a beneficial effect on the biochemical processes of cells In fact, in no other food product is the content of these acids so perfectly balanced as precisely in hemp seeds. The ratio in which omega acids are present is important because omega-6 acids have a pro-inflammatory effect, and omega-3 acids have an anti-inflammatory effect. They contain the most complete, perfectly digestible and hypoallergenic protein of all plants in the world. They are a source of vitamin E, which protects against free radicals. They are characterized by a high content of vitamins B1, B2, E, macro- and microelements. They add variety to the taste and increase the nutritional value of home baked goods: cakes, cookies and bread. Depending on our preferences, we can choose a different form of hemp seeds for consumption. The seeds come in different forms – shelled, unshelled, ground. If we want to provide our body with a high content of protein and fats, it is definitely worth choosing the shelled form. If we are looking for dietary fiber, it is worth choosing unshelled seeds, which are characterized by their high content. Ground hemp seeds will work great as an addition to smoothies or liquid drinks. However, regardless of the form, it is safe to say that hemp seeds are an ideal addition to many types of dishes. Hemp seeds are categorized as superfoods mainly by their rich source of vitamins and active ingredients that have a positive effect on our health, a tasty and wholesome component of a proper and perfectly balanced diet.

Ethical approval

We confirm that all the research meets ethical guidelines and adheres to the legal requirements of the study country. The research does not involve any human or animal welfare related issues.

Acknowledgments

Words of gratitude to Prof. Dr. hab. Małgorzata Łochyńska for provided substantive support, Mr. Grzegorz Oleszak for provided technical and substantive inputs, and MSc. Eng. (Agr.) Maria Mackiewicz-Talarczyk for the advisory inputs.

Disclosure statement

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

Additional information

Funding

This work was supported by the Institute of Natural Fibres and Medicinal Plants – National Research Institute (IWNiRZ-PIB). Grant number I/5/2020.