Evidence for a physiological regulation of food selection and nutrient intake in twins.

Making use of the Holzinger Index of Heritability, the genetic effect on nutrient intake was assessed in 13 monozygotic and 10 dizygotic pairs of healthy female adult Caucasian twins. From 3-day food records, intakes of total energy, protein, fat, carbohydrate, and alcohol as well as the concentrations of the energy sources as percentage of calories, were calculated. The diets of monozygotic twins were significantly more similar than were those of dizygotic twins for the protein concentration, the carbohydrate concentration, and the absolute intake of carbohydrate per day. The present findings support the hypothesis that in the free-living human primitive physiological mechanisms influencing food selection independent of total food intake are operative and that these mechanisms are subject to genetic influence.