IODINE NUTRITION IN THE UNITED-STATES - TRENDS AND PUBLIC-HEALTH IMPLICATIONS - IODINE EXCRETION DATA FROM NATIONAL-HEALTH AND NUTRITION EXAMINATION SURVEYS I AND III (1971-1974 AND 1988-1994)

Iodine deficiency in a population causes increased prevalence of goite r and, more importantly, may increase the risk for intellectual defici ency in that population. The National Health and Nutrition Examination Surveys [NHANES I (1971-1974) and (NHANES III (1988-1994)] measured u rinary iodine (UI) concentrations. UI concentrations are an indicator of the adequacy of iodine intake for a population. The median UI conce ntrations in iodine-sufficient populations should be greater than 10 m u g/dL, and no more than 20% of the population should have UI concentr ations less than 5 mu g/dL. Median UI concentrations from both NHANES I and NHANES III indicate adequate iodine intake for the overall U.S, population, but the median concentration decreased more than 50% betwe en 1971-1974 (32.0 +/- 0.6 mu g/dL) and 1988-1994 (14.5 +/- 0.3 mu g/d L). Low UI concentrations (<5 mu g/dL) were found in 11.7% of the 1988 -1994 population, a 4.5-fold increase over the proportion in the 1971- 1974 population. The percentage! of people excreting low concentration s of iodine (UI, <5 mu g/dL) increased in all age groups. In pregnant women, 6.7%, and in women of child-bearing age, 14.9% had UI concentra tions below 5 mu g/dL. The findings in 1988-1994, although not indicat ive of iodine deficiency in the overall U.S. population, define a tren d that must be monitored.