Nutrigenomics is the study of how the food you eat talks to your genes. The same plate can be kind to one person and unkind to another, because bodies are not copies of each other. This field asks whether a kind of fat, or a vitamin, can switch a gene on or off in a way that makes heart disease — or another illness — more likely, or less. It is a young science. In a university it is careful work with genes and diets. In an advert it can run ahead of the facts: a test that “tells you what to eat for your DNA” may be a shop product, not a settled medical answer. You will meet the word in health news and in expensive diet plans more than in everyday talk. Though actually, genes matter, and food matters, but we do not yet have a simple menu that fits every person’s genome.