The ideas of gene-culture coevolution have percolated all the way to the foodie-sphere, over at Epi-Log at Epicurious, The Health Trend of the Future: The Ethnic-Group Diet?:
So, maybe at some point in the future, a visit to the doctor will involve a full genetic workup followed by a prescribed diet tailored to our individual makeup. I might be advised to eat lots of whole grains and dairy products, while someone else might do better on mostly meat and vegetables. This is probably a long way off though—there’s still a lot of science to be filled in.
The “low hanging fruit” like lactose tolerance has been around a long time. Gary Nabhan wrote Why Some Like It Hot: Food, Genes, and Cultural Diversity in 2004. In any case, family background is obviously going to be important, but information from your ethnic background is also probably useful, especially if you have a small family. Ultimately nutrigenomics might advance far enough that we can get personalized recommendations, but if much of the genetic variation is part of the missing heritability than population-level information might be critical for a long time to come. Additionally, population-level information might be relevant as genetic variations which we know about may expression differently conditional on genetic background.
But a consideration that’s not totally trivial is that diets can change very fast. The Columbian Exchange resulted in the introduction of chili peppers to much of Asia, to the point where the extent of their usage in the local cuisine can be diagnostic as to regional origin. And of course potatoes are a relatively new staple in much of Europe. Though in both of these cases the basic nutritional value or culinary role simply substitutes for what was already on hand, starch in the case of the potato and spice in the case of chili pepper.