Nature versus Nurture. Are we determined by our genes or our environment?
Of course the answer is both: it is nature and nurture, not nature versus nurture. Take sporting capability. You can be born with the potential to be an explosive strong powerlifter, but unless you train and fuel your body with the nutrients to develop that neural and muscular potential, you aren’t going to be winning Olympic medals any time soon.
And it typically isn’t a single gene that defines your potential. Which makes sense. To lift a heavy weight you need nervous signals from your brain to your muscles, you need your muscles to respond to that signal, you need energy to be produced, and you need your muscle to contract fast enough. That’s a hell of a lot of things, and a hell of a lot of genes involved.
The same can be said of metabolism. It is complex! There are disorders that arise from mutations in a single gene that can impact what we can and can’t eat, or how well we metabolise a certain food item. Coeliac disease, lactose intolerance and caffeine sensitivity, for example. However for the most part the metabolism of our food is impacted by the complex interplay of multiple genes expressed in certain forms, in certain tissues, at certain times. And the expression and function of these genes is impacted not just by the gene itself (nature), but also by the environment and the very food we eat (nurture). In fact, even in the case of caffeine sensitivity we it can typically be trained, and is also dependent on our physiological state!
In short: our genetics impacts our optimal diet, but our optimal diet is not determined by our genetics. Our environment (training, lifestyle, body composition) is also important. And what is more, our environment and the food we eat alters the expression of the genes themselves!
At this point I should flag that our bodies are also damn clever. They have many ways to get to the same endpoint. Maybe you don’t express a certain gene that we would usually use to metabolise a food – say, a chocolate brownie! The body will usually have another route to metabolise that brownie. Instead of going from A to B, it might have to go from A to D to C to B … but it gets to B.
Why do I raise all of this? Because it is very important in this emerging era of genetic testing. There are so many companies out there offering to do a DNA test to advise on your optimal diet. The truth is we don’t yet know enough about the gene variants involved in metabolism, or the interplay between environment and genetics, to make these bold claims. If you don’t believe me, send your DNA to multiple companies. I would be willing to bet that the results you get back from each don’t exactly match. Because each of those tests is looking at just a small and incomplete sample of ‘you’, without any regard for your environment and how that impacts what you need, and the very expression of those genes.
Whilst it won’t pinpoint the genes involved, you can typically learn more about the impact of your genetics on your optimal diet by simple trial and error of dietary tweaks followed by assessment of the impact on your health and sporting performance. And by doing this you are also implicitly considering the impact of your environment. Double win!
So we know that our genetics impacts dietary requirements, but we don’t know how and so can’t use it? Is it all doom and gloom for genetics and nutrition?! Not at all. It is a very promising area of research and may greatly inform personalised nutrition in the future. But for now, for the most part, personalised nutrition remains dependent on combining research findings with trial and error of your performance in training and competition to develop your optimal diet.