Absorption of Iodine from Ingested Watercress

Abstract

WATERCRESS (Nasturtium officinale, R.Br.) is a rich source of iodine, the amount it contains probably depending on the amount of iodine available to it during growth¹. The availability of the iodine in cress to man was studied by von Fellenberg², who concluded from balance studies on himself that only about 65 per cent of the iodine ingested was absorbed. We have examined this problem further by using watercress grown in water containing iodine-131. The plant was grown in a greenhouse in water culture, starting from shoots of commercial origin. After 4 weeks' growth, carrier-free iodine-131 was added to the nutrient solution. The watercress was harvested one week later, and amounts containing 25 µc. were fed to two hospital patients who were recovering from myocardial infarction. These patients also received carbim-azole in a dose of 15 mg four times daily in order to prevent the uptake of iodine-131 by the thyroid gland. Urine and fæces were collected for the next three days and their content of iodine-131 was measured. In both patients there was complete recovery of the ingested iodine-131 in the urine, and negligible amounts were detected in the fæces. This indicated complete absorption of the iodine from the gastro-intestinal tract.