Many agree that the future of nutrition is personalized nutrition. However I also often hear that “we have been doing this for years”. Of course both claims are valid. Some form of personalisation has been the basis of the work of a sports dietitian or sports nutritionist. However, there are different levels of personalized nutrition.
Three tiers
Ronteltap and colleagues identified three different levels of personalized nutrition (1). At the basis we find the most traditional form of personalized sports nutrition: typical tailored advice of a dietitian that is based on an individual’s dietary intake. A dietary assessment is made and, based on the outcome, suggestions for improvement are communicated to the individual that are specific to that individual. The second tier of personalized nutrition is based on an individual’s diet as well as phenotypic markers such as anthropometric measurements or blood biochemical markers. Examples include the measurement of iron status or vitamin D levels. If iron or vitamin levels are low, the diet is modified or supplements are recommended. The third level, the top of the pyramid, builds on the previous two levels but includes genotypical information. A professional service including information about genotype is less readily available (2). Nevertheless, when personalized nutrition is discussed in the mainstream channels, the first two levels are often ignored and the focus is often on DTC (direct to consumer) test kits that provide genotypical information.
There are now several companies that specifically target consumers, suggesting they should test their genotype and adapt their diet accordingly. Although this is an attractive idea, the usefulness of such tests is subject to debate.
Is personalisation based on genotype better?
Although personalization could be achieved by taking into account dietary, phenotypic and genotypic characteristics, the big question is of course whether personalized nutrition will result in better, more sustainable, or more cost effective behaviour changes than conventional dietary advice. Will personalised nutrition result in better health or better performance for our athletes? One could argue that if personalized nutrition means that we can prevent iron deficiency, we can avoid gastro-intestinal problems and we can optimise glycogen resynthesis, this may in many cases result in improved exercise performance. But does personalisation based on genotype add any additional value? In order to answer this question we need to answer a few other questions first:
Is there sufficient evidence to base genotype-based dietary advice on?
If athletes receive genotype based advice are they more likely to change their behaviour?
If athletes receive genotype based advice will they see greater benefits than other forms of personalized nutrition.
At present we would have to conclude that there is limited evidence connecting genotypical information to nutrition and performance and there is no evidence that receiving genotypical information will induce behaviour changes or greater improvements in performance.
Reliability
The problems can also be illustrated by a simple example. A simple google search will reveal a number of examples of individuals who have sent off their saliva samples, with the same genetic information, to different DTC companies for genotyping. The companies then send a report back with recommendations. If this approach would work, we would expect some consistency in these reports. Unfortunately this is not the case. There is huge inconsistency in the analysis as well as in the reporting. Different companies will provide different advice, based on the same sample. Even when the outcome of the analysis is comparable, there is difference in the interpretation of the results and the recommendations that follow. We clearly need more research to connect certain genes to nutrition and health and a lot more research than we have to date connecting genes, nutrition and performance.
Conclusion
Personalized nutrition is important but at the moment, genotyping has no role to play in nutrition advice. Personalized nutrition based on genotype is not ready for prime time and it will be a long time before it will be ready…
In sport where performance is the main outcome of interest rather than health, we have far less research and therefore this timeline is even longer. For now, personalized sports nutrition is about clearly defining the goals of the athlete, and tailoring the advice to these goals, and the specific training needs of that individual.
References
1. Ronteltap, A., van Trijp, H., Berezowska, A., & Goossens, J. (2013). Nutrigenomics-based personalised nutritional advice: in search of a business model? Genes Nutr, 8(2), 153-163. doi:10.1007/s12263-012-0308-4
2. O'Donovan, C. B., Walsh, M. C., Gibney, M. J., Gibney, E. R., & Brennan, L. (2016). Can metabotyping help deliver the promise of personalised nutrition? Proc Nutr Soc, 75(1), 106-114. doi:10.1017/S0029665115002347