B. Johnson Posted over 2 years ago What is the most controversial issue in nutrition The ability to digest milk (or lactose) throughout the life span, not just as an infant, was a mutation which arose and probably proved to be of survival value for some groups. The ability is called lactase persistence (for the enzyme which persists in some, but becomes inoperative in other folks after about the time of weaning.) I think nutritional controversies are rampant, and the other posters have hit on some of the major ones. My list includes these (some already mentioned): paleo or some variant of low carb vs. broader ingestion of things we call foods; whether sugar or fat is the primary culprit in all sorts of ailments from diabetes to heart disease; whether gluten sensitivity is a spectrum disorder that may be afflicting more people than we imagine; how our bodies might react to GMO foods; the whole arena of nutroceuticals (foods as medicines), and then, possibly of interest to those involved in social policies, especially "food stamps," just what is a FOOD, and what should EBT be allowed to buy as a "food." to promote nutrition.