Based on analysis of 234 core foods conducted by the Food and Drug Administration (1982–1991 (Pennington et al., 1995) and analysis of 60 additional core foods and intake data by the U.S. Department of Agriculture Continuing Survey of Food Intakes by Individuals (1994–1996), the median intake of iodine from food in the United States is approximately 240 to 300 μg/day for men and 190 to 210 μg/day for women (Appendix Table E-4). For all life stage and gender groups, less than 25 percent of individuals had intakes below the Estimated Average Requirement.

Information from the Third National Health and Nutrition Examination Survey (NHANES III) on the use of supplements containing iodine is given in Appendix Table C-17. The median intake of iodine from supplements was approximately 140 μg/day for adult men and women. In 1986, approximately 12 percent of men and 15 percent of nonpregnant women took a supplement that contained iodine (Moss et al., 1989; see Table 2-2).

The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects in almost all individuals. Although members of the general population should be advised not to routinely exceed the UL, intake above the UL may be appropriate for investigation within well-controlled clinical trials. Clinical trials of doses above the UL should not be discouraged, as long as subjects participating in these trials have signed informed consent documents regarding possible toxicity and as long as these trials employ appropriate safety monitoring of trial subjects. In addition, the UL is not meant to apply to individuals who are receiving iodine under medical supervision.

Most people are very tolerant of excess iodine intake from food (Pennington, 1990). Certain subpopulations, such as those with autoimmune thyroid disease and iodine deficiency, respond adversely to intakes considered safe for the general population. For the general population, high iodine intakes from food, water, and