Excessive iodine intake may have adverse effects on thyroid function, including permanent hypothyroidism. Large regional variations in iodine intake have been reported in Eastern Africa, from deficient to excessive intakes.We evaluate the determinants of excess iodine intake and its effects on thyroid function, and identify current barriers to achieving optimal iodine nutrition.
At purposefully chosen sites in Tanzania and Kenya with previously documented excessive iodine intakes, we measure iodine status and thyroid function of: infants 0-6 mo, infants 6-18 mo, school-age-children, women of reproductive age, lactating and pregnant women (n = 300 for each group).We combine these results with a review of existing data from Somalia to provide programmatic guidance and develop advocacy tools during a regional workshop.
Preliminary results (Tanzania) suggest iodine excess: median urinary iodine concentration (UIC) in school-age-children was 520 µg/L (IQR 329-758 µg/L) and in women of reproductive age 474 µg/L (IQR 322-689 µg/L).We hypothesise that salt iodised above the national standard is accountable for excessive intakes in Tanzania and Kenya, but high water iodine levels are responsible in Somalia.
We provide countries in the region with guidance on the effects of long-term exposure to excess iodine, and inform program guidelines for optimum iodine nutrition through the continued success of universal salt iodization. We elaborate on the optimal UIC thresholds to define excess iodine intakes in populations, and provide recommendations on measures required to reduce any excessive iodine intakes observed.