A TWIN STUDY OF GENETIC AND ENVIRONMENTAL-INFLUENCES ON THE INTAKE OFFLUIDS AND BEVERAGES

The heritability of fluid and beverage intake was investigated with 10 9 identical and 86 fraternal adult twin pairs who were paid to maintai n 7-day diaries of everything they either ate or drank. Both classical analysis of heritability and linear structural modeling revealed that the amount of fluids ingested daily or in bouts is strongly influence d by heredity in males and by familial environment in females. This wa s true for the total amount of water ingested, regardless of source, t he amount of fluid ingested in excess of digestive requirements, and t he amount ingested in the form of drinks. Linear structural modeling r evealed that these influences act primarily on the overall total intak e of fluids and affect drink fluid intake only indirectly. Significant influences of the genes and the environment were also found on the in gestion of particular beverages, independent of the effects of age and the total intake of fluids. In particular, significant genetic influe nces were identified on the intake of alcohol, sugared soda, coffee, a nd milk, and significant familial environmental influences on the inta ke of diet soda and fruit juice. These results suggest that both the a mounts and the types of fluids ingested are complexly influenced by he redity and the environment, depending upon the gender of the individua l and the type of beverage investigated.