Seaweed and soya

Iodine is essential for good thyroid function, which in turn is necessary for good health. Seaweed and soya, both popular foods in Asia, have been reported to affect thyroid function in opposing ways. While seaweed contains iodine, soya has the potential to interfere with iodine uptake. In this study twenty-five healthy postmenopausal women were given five grams of seaweed (providing 475 micrograms of iodine) daily for seven weeks. A powdered soya protein isolate (providing 141.3 mg of isoflavones) was given daily during the last week. Blood and urine samples were collected before and after each treatment. Results showed that seaweed supplementation was associated with a small but statistically significant increase in thyroid hormones, whereas soya supplementation was not associated with changes in thyroid hormone concentrations. These results are consistent with previous work indicating that in healthy individuals, with an adequate iodine intake, soya does not adversely affect thyroid function.

Teas, J., Braverman, L.E., Kurzer, M.S., Pino, S., Hurley, T.G. and Hebert, J.R.  2007. Seaweed and soy: companion foods in Asian cuisine and their effects on thyroid function in American women. Journal of Medicinal Food. 10 (1) 90-100.