[Nutrition and gene expression]

The genetic information stored in the DNA is transmitted to an RNA molecule through transcription and protein molecules are obtained from the RNA using translation techniques. Each of the processes forming part of this chain is the object of complex regulation (gene expression regulation). Some nutrients may affect gene expression by taking part in these regulatory mechanisms, such as sterols, glucose, vitamins A, D and B12, various fatty acids or some components of dietary fibre. These phenomena may have come about through the adaptation of the primitive beings to the various changes in the nourishment available. The successive changes over centuries have led to the determination of individuals' phenotypes not only by their genotype but also by environmental factors such as diet. Our genes have adapted to the changing sources of nourishment surrounding our ancestors; modern diets are, however, very different from those of the past. The inability of our genetic store to adapt to modern diets may be the reason for the appearance of certain chronic diseases in developed countries. One well-analyzed case is that of the thrifty genotype which provided evolutionary advantages in the past, but may now be contributing to obesity and diabetes. Further examples of genotype interaction with various environmental factors to produce different phenotypes are provided by the apolipoproteins: some mutations in the genes of these proteins, in combination with different diet types, are associated with altered lipid levels and the risk of various cardiovascular diseases. These diet-genotype interactions mean that it is fundamentally important to take into account the genetic variability of individuals before recommending dietary measures to prevent the so-called "first-world" diseases.