Contribution of water and diet supplements to nutrient intake

Information about food consumption, water consumption, and diet supplement use was collected in a survey of 410 women in the age groups 20 to 35 and 55 to 80 years in two rural communities. The investigators found that one-third of the women supplemented their diets with commercial nutritional preparations, a level that is half the amount reported in some other studies. However, even at that lower supplementation level, failure to include the contribution of supplements and water intake as a source of some nutrients leads to significant underestimation of the group's mean intake of particular nutrients. Underestimation of mean population intake could range from a 20% underestimation for calcium to more than a 65% underestimation for vitamin D. The contribution of diet supplements and water as a source of some nutrients is sufficiently great and the practice of supplement use sufficiently extensive that investigators may want to characterize separately the mean nutrient intakes of subpopulations such as supplement users and nonusers. Failure to address issues related to those multiple nutrient sources may potentially obscure relationships, either positive or negative, between diet and health status.