Understanding the role of diet for human health: a call for omic-based approaches in nutritional epidemiology

In the field of nutritional science, the importance of embracing plant-based dietary patterns has gathered significant attention over the last decades (Willett et al. 2019). Supported by a robust body of scientific evidence showing their impact on human health and environmental preservation and corroborated by endorsements of international organisations, the integration of diverse plant-based foods and beverages into daily diets stands as a cornerstone of preventive medicine and sustainable food systems (Grosso et al. 2020). Central to the health-promoting properties of plant-based foods lies their richness in vitamins, antioxidants and fibre, all nutritional elements indispensable for optimal health and well-being (Satija and Hu 2018). While the precise mechanisms through which these bioactive compounds exert their effects remain only partially elucidated, emerging research emphasises the pivotal role of the gut microbiota and the immune system in mediating the health benefits conferred by plant-based diets (Gentile and Weir 2018; Grosso et al. 2022). As technological advancements propel the frontier of nutritional epidemiology forward, traditional methodologies are gradually giving way to more sophisticated approaches, facilitating a deeper understanding of the intricate interplay between diet, health outcomes and the underlying molecular mechanisms (Brennan and Hu 2019). At the vanguard of this paradigm shift lie omic-based methodologies, encompassing genomics, metabolomics and other “omic” sciences, which hold the promise of unravelling the multifaceted tapestry of associations between dietary exposures and health outcomes with unprecedented precision (Ramos-Lopez et al. 2022). Emerging research highlights the potential of metabolomic analyses in elucidating the intricate nexus between dietary patterns and metabolic pathways, offering invaluable insights into the biochemical underpinnings of health and disease (Karczewski and Snyder 2018). By interrogating the “omic” signatures of individuals following plant-based dietary regimens, researchers can glean profound insights into the physiological responses elicited by these dietary factors, paving the way for personalised nutritional strategies tailored to individual needs (Laddu and Hauser 2019). Through the integration of multi-omic data sets, researchers can construct intricate networks delineating the molecular pathways underpinning the health-promoting effects of plant-based diets, offering a holistic perspective on the complex interplay between diet and health (Phillips et al. 2019). Within the pages of this issue of the International Journal of Food Sciences and Nutrition, a series of studies have further delved into these pivotal subjects, shedding light on various facets of the relationship between plant-based diets and health outcomes.

A comprehensive review by Antonogeorgos et al. has synthesised existing literature, revealing an inverse association between adherence to the Mediterranean diet or a healthy diet rich in fruits and vegetables and the occurrence of childhood asthma (Antonogeorgos et al. 2023). In another observational study conducted in the context of the China Health and Nutrition Survey, Wu et al. reported that consumption of fruit and vegetables was associated with lower risk of type-2 diabetes in more than 13,000 adults followed-up for a median of 4 years (Wu et al. 2023). However, amidst the interesting findings, the certainty of these associations remains relatively low, underscored by the observational nature of the studies and the lack of mechanistic insights connecting the exposures with the outcomes investigated. This calls for a nuanced understanding of the complex interplay between dietary patterns and health outcomes, urging researchers to delve deeper into the underlying mechanisms at play. On this matter, the work of Salvesi et al. showed that extra virgin olive oil selectively stimulated Lactobacillus spp. in human volunteers and increased the bifidobacteria population in general; moreover, short-chain fatty acid production was slightly increased (Salvesi et al. 2023). Moreover, a mechanistic study from Abot et al. in which they administered Limosilactobacillus reuteri (known as Lactobacillus reuteri) BiO7251 (L. reuteri BiO7251) derived by a clementine orange from Corsica showed its effect on decreasing the subcutaneous adipose tissue mass and decreases glucose absorption and food intake in obese/diabetic mice (Abot et al. 2023). Concerning metabolomic analyses, a large case-control study from Cheng et al. conducted on about 500 patients with gastric precancerous lesions and an equal number of controls showed that a healthy plant-based dietary pattern was inversely associated with such a condition (Cheng et al. 2023). Interestingly, the authors also performed an untargeted metabolic analysis finding various metabolites (and metabolic pathways) correlated with gastric precancerous lesions, out of which, luteolin 7-sulphate and N-acetyl-dl-tryptophan were also correlated with adherence to a plant-based dietary pattern. Finally, a study from Zhou et al. applied a Mendelian randomisation approach to explore the causal relationship between dietary vitamin intake and lymphoma risk, showing that vitamin B₁₂ intake may reduce the risk of Hodgkin’s lymphoma and play a protective role (Zhou et al. 2023).

While the benefits of plant-based diets on human health are well-established, the need for deeper insights into their mechanisms of action and individualised responses remains urgent. By including omic-based methodologies in nutritional epidemiological studies and adopting interdisciplinary approaches, researchers can significantly improve the validity of their results and provide a better understanding of the importance of diet on well-being across the lifespan. In the pursuit of precision nutrition, the convergence of omic-based methodologies with traditional epidemiological approaches heralds a new era of scientific inquiry, empowering researchers to unravel the enigmatic complexities of dietary patterns and their impact on human health. Let us answer the call to go farther, challenge presumptions and clear the path for a time when everyone has access to individualised nutrition as a reality rather than simply a potential as custodians of scientific knowledge.

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