What is personalised nutrition?

Improving diet and physical activity (PA) behaviours has the potential to reduce the global burden of non-communicable diseases, but a more personalised approach may be necessary for a more effective physiological and behavioural change.

Personalised nutrition requires greater knowledge of the characteristics of the person receiving the dietary intervention (1). It considers the interactions between nutrients and biological processes, including internal interactions with genetics, gut microbiota and metabolome and external interactions: diet, PA and other environmental factors (2).

There are preventative and predictive reasons for using personalised nutrition. However, there are challenges related to the technological infrastructure and new biomarkers that are required (2).

The science surrounding personalised nutrition is still emerging, but it has demonstrated significant benefits. It can motivate people to make more healthy choices than a one-size-fits-all approach and is more likely to facilitate a meaningful and beneficial change in behaviour.

Beginning with nutrigenomics and looking at the whole genome interaction with dietary patterns, personalised nutrition now encompasses other internal factors, such as the gut microbiota. The assumption is that the more metrics that can be measured, the more effective the personalisation can be (3).

Gut microbiome in personalised nutrition

The gut microbiome, the ecosystem of microorganisms in the gastrointestinal tract, is mechanistically involved in the health of a number of organ systems in the body. Alterations to the gut microbiome’s composition can lead to its dysfunction, and since diet is a major contributor to gut microbiome composition, a dietary intervention could be utilised for the maintenance of health (4).

The gut microbiome is essential to the fermentation of non-digestible substrates of the diet such as, dietary fibre. The fermentation leads to specialist bacteria producing short-chain fatty acids (SCFAs), and the production of SCFAs is associated with positive health outcomes. Lower bacterial diversity is associated with negative health outcomes (5).

Fibre is a key aspect of the diet for a beneficial composition of the gut microbiota, whereas some medications (antibiotics) and some ultra-processed foods can lead to alterations in the balance of the gut microbiome. This change can encourage the growth of potentially pathogenic bacteria (5).

Diet appears to be dominant in the inter-individual differences of the gut microbiome. Comparatively, there appears to be a personal response to dietary factors that could be due to the microbiome composition. An example of this is that in a population of healthy individuals, an improved glucose metabolism due to consumption of barley-kernel bread was found in those with a higher abundance of Prevotella species of bacteria (6).

Similarly, higher baseline levels of Akkermansia muciniphila led to a greater improvement in insulin sensitivity in obese people in response to a calorie restricted diet (6). Some individuals respond to a dietary or exercise intervention and others do not. They are described as responders and non-responders, which is thought to be influenced by the presence of certain species of bacteria in the gut microbiome (6).

Determining the personal gut microbiome composition could give an insight into which foods the individual can positively respond to in terms of health.

In response to dietary intakes, inter-individual differences in the gut microbiota are apparent. For example, non-caloric artificial sweeteners can cause glucose intolerance in some individuals and the glucose response after a meal is modulated by the gut microbiome (7).

A personalised dietary approach could be utilised to account for individual dietary responses to nutrient and non-nutritive food components. However, there are questions about health inequality with personalised nutrition, due to the technological and testing requirements for genetics and the gut microbiome. The costs mean that currently, personalised nutrition is not accessible or affordable to the majority of people (1).

A simplified approach to personalised nutrition can be looking at microbial enterotypes. The enterotype is a gut microbiome classification using compositional patterns of bacteria species.

In western countries, Prevotella and Bacteroides abundance can explain individual differences. Enterotypes respond differently to diets and can lead to different health outcomes. People with a Prevotella enterotype tend to lose more weight than other enterotypes on a high-fibre diet (8).

Enterotypes could provide a similar approach to personalised nutrition to tailor the diet more specifically than a one-size-fits-all approach, but with less prohibitive costs than extensive personalised nutrition.

Relying completely on enterotypes can be detrimental to classification of a more varied microbial community. Although using enterotypes can give direction to personalising the diet according to the gut microbiome, it is not as individually tailored as the personalised nutrition approach, and puts people into microbial ‘boxes’, rather than considering how unique the gut microbiome is for each individual (9).

Applications of personalised nutrition

The Food4Me study demonstrated that personalised nutrition can be more effective in certain groups of subjects and the approach needs to be improved for others (10). Older adults, women and those with less healthy diets benefitted from a 6-month personalised nutrition online intervention. The groups who benefitted improved their dietary intake - and lost weight - where appropriate.

In the future, a tailored personalised nutrition approach for other population groups should be investigated (10). This suggests that where personalised nutrition stands currently, it could be harnessed for beneficial effects in specific population groups, while personalised nutrition continues to be developed.  

There is rationale in adopting a personalised approach in sports nutrition due to the high inter-individual variability in training response in athletes and it is suggested that the gut microbiome can affect the individual metabolism of foods. Personalisation in sports nutrition could be utilised by determining specific bacterial taxa that improve athletic performance in response to the diet (11).

Individual recommendations are becoming more common for those with food allergies, as technology in diagnostics and knowledge of allergic phenotypes develops. Since food allergies result from disruptions to immunological tolerance due to an aberrant gut microbiome and interactions with dietary factors, personalised advice is now being utilised to improve the nutritional intake in children with food allergies.

Children with food allergies can lack dietary diversity and have insufficient nutrient intakes, therefore personalised nutrition could be beneficial to their overall health as it becomes more feasible for people with food allergies (12).

Personalised dietary advice can be delivered by apps, both the public and nutrition professionals have shown interest in this method. Research demonstrates that apps can be a practical method to give nutrition advice through clear food choices that enables dietary change, rather than being focused on nutrients (13).

Nutrigenomics is used to give food recommendations, but it is still an emerging science and would require nutrition professionals to have knowledge on genetics. Since there are other factors that contribute to health outcomes as well as genetics, such as the gut microbiome, multidisciplinary studies are needed to give dietary recommendations appropriate to individuals (14).

Although personalised nutrition is a promising approach for public health in the future, there are research considerations to be made, such as large cohort randomised controlled trials and longitudinal research (3). The growing evidence base in gut microbiome science could be useful in the development of personalised nutrition and the application to individuals.

A challenge could be the greater health inequality associated with personalised nutrition testing and monitoring. This suggests that utilising enterotypes, or a more generalised approach, could be the steppingstone needed to utilise personalised nutrition in public health.

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