Abstract
Tests with rats showed that the feeding of heated soybean, Natto (a fermented soybean without sodium chloride), Miso (ditto with sodium chloride) or Tofu (congealed soybean curd) produced a high incidence of thyroid enlargement in rats, but the enlargement was prevented by increasing of small amount of iodine in the diets.
The inclusion of sodium chloride in iodine-deficient diets at levels of 3 per cent caused a pronounced hypertrophy of the thyroid and weight loss in rats. In this case the supplementation of iodine alone could not prevent the weight loss, but only the dosing of methionine together with iodine could. It was reported by Axcelrod et al. that thyroxine production was increased with increasing sodium chloride intake in rats. Thus the effects of a large intake of sodium chloride resembles in some respects those of administration of thyroxine.
It is well established that thyroxine increases the metabolic rate and oxygen consumption of animals and beyond small and very critical levels the thyroid hormone decreases growth and feed efficiency.
Charkey found that all of these effects of thyroxine can be reversed by methionine. The present findings that methionine prevented the weight decrease of rats fed a diet of high sodium chloride content may be explained by the antithyrotoxic effect of methionine.
