Nutrigenomics explores both how dietary components affect gene expression and how genetic differences between individuals influence how they respond to these dietary components - and the science is developing rapidly, said Dr El-Sohemy, Canada Research Chair in Nutrigenomics at the University of Toronto and chief science officer at Nutrigenomix Inc.
There's also some encouraging evidence that when things get personal, we tend to sit up and take notice, he said, observing that generic admonitions to eat well and exercise more have proved frustrating ineffective, if the alarming rates of obesity, diabetes and heart disease are anything to go by.
While companies offering dietary advice to people on the basis of genetic data have attracted controversy, he said, responsible firms such as Nutrigenomix focus very specifically on known nutrient-genotype interactions, and don’t focus on the association between genes and diseases.
In other words, attempting to calculate someone’s risk of developing certain lifestyle-related diseases based on a handful of SNPs (single nucleotide polymorphisms) is irresponsible at this stage given that we’re still learning about the complex interplay between genes and environmental factors (of which diet is just one), and we don’t really know the extent to which we can modify this risk though specific dietary interventions, he said.
However, we do know that there is a genetic component to our ability to handle gluten and lactose, for example, he said. And we also know that about half of the population has a genotype that means they are fast metabolizers of caffeine, and seem to benefit from drinking lots of coffee (which has many beneficial components), while the other 50% are slow metabolizers, and struggle to get rid of caffeine.
And this goes a long way to explaining why the scientific data on coffee consumption is so contradictory (it appears to have a protective effect in some people; while apparently putting others at a higher risk of hypertension), he said.
As for sodium, give a group of people a high-sodium diet and some will be much more likely than others to develop hypertension, he said, while we also respond differently to vitamin C according to genotype (some people need more than others).
“We used to think that people who were showing the opposite results to everyone else in intervention trials were outliers, or they weren’t complying, when in fact there is usually a genetic explanation.”