What our genes can tell us

CHIARA MURGIA: Genetic tests are becoming increasingly available. There’s a new one every day. Some of them already impact in the practice of medicine. For example, we can test for genes that increase the risk of colon cancer. And if a carrier of one of these mutations asks for advice, it can be given out, personalized advice of increasing the frequency of colonoscopy screenings, and also to modify the diet accordingly. For example, decreasing the amount of meat consumed. Understanding the role of these variations that scientists call polymorphins held the promise to make us understand the individual requirements and individual predispositions to diseases, individual responses to drugs, and of course, individual nutritional requirements.

The availability of all this information has impacted deeply all the branches of biomedical research. And it’s really affecting the way medicine is practiced in several fields. Studying inheritable rare metabolic conditions, such as some rare form of obesity, led to understanding genes that are involved in energy regulation. For example, we know now that the leptin gene that have the information to assemble the hormone leptin, if it’s mutated, if there is an error in that gene, the individuals that carry that mutation become, very early in life, severely obese. This is a very rare event. The vast majority of obesity is the result of a large number of gene variations that are affected also by diet and lifestyle.

Despite the incredible amount of progress in the understanding of the human genetics, most complex conditions are still unclear. For example, it’s way too early for genome scans to provide a complete picture of individual risk to metabolic conditions, like such obesity, and also type 2 diabetes. We don’t know all the gene variations that contribute to the development of those pathologies. And most of the variations we know– we know quite a few now– increase the risk of the pathology of a very small amount. So this is leading us to understanding how different people can respond to different dietary advice. And so it could be the end of the one size fits all way to the recommendation.

And although we still have a long road to go to make this happen, this is a really exciting new field of nutrition science. We call this nutrigenetics, or nutrigenomics, or more generally, nutritional genomics.