NUTRITION AND GOITER

Abstract

In this review the only dietary factors considered are plant and animal products (not iodine or any other minerals). "It is possible that under certain circumstances high protein diets are associated with the development of enlarged thyroid glands. Whether such glands are under or overfunctional, and whether the diets contain a positive goitrogen or are merely more nutritious, has not been determined." The cases in which diets high in fat have seemed to lead to an enlarged thyroid gland can probably all be explained by concomitant iodine deficiency. No recent work has tested the goitrogenic effect of a high carbohydrate diet; the early expts. were few and their results equivocal. Deficiency of vitamins has been held responsible for enlargement of the thyroid in man, birds, rats, and guinea pigs, but the rather crude technics used "and the inability of subsequent investigators to reproduce many of the conflicting results reported make it difficult to place much credence in the claims for the goitrogenicity of this or that type of diet." Goitrogenic properties for rabbits and other animals have been reported in cabbage, kale, kohlrabi, brussels sprouts, cauliflower, turnips, rape, soybeans, peanuts, peas, lentils, and the seeds of many of these. The factor is lacking in the cabbage of some regions, and the amt. varies seasonally and from year to year. It is affected by drying and cooking. There is marked variation in the response to a given goitrogen in different species. In man, rutabaga had the highest degree of activity. Some antithyroid action was also found in spinach, white turnip, peaches, pears, strawberries, and carrots. The active principle in rutabaga and turnip was isolated and identified as L-5-vinyl-2-thiooxazolidone. In rats and rabbits, the admn. of I along with a goitrogenic diet partially inhibited the effect; I administered to rabbits with goiter already developed is reported to have produced a picture similar to thyrotoxicosis. The mechanism of both effects remains to be explained. Certain food stuffs have been reported to prevent thyroid hyperplasia, but the author feels that the "antigoitro-genicity" of any substance has yet to be proven. Expts. on rats have settled the mechanism of action of at least one goitrogen thus: "a rape seed diet produced thyroid enlargement by interfering with the production of thyroxin. This, in turn, stimulated the pituitary to increased thyrotropin secretion. The thyrotropin acted upon the thyroid cells, causing hypertrophy and hyperplasia. Since the thyroid was unable to respond by increased hormone production, the high level of thyrotrophin and resultant goitrogenesis continued until the diet was changed or hypophysectomy was performed." In the overwhelming majority of patients with simple goiter it is impossible to connect their affliction with any definite dietary peculiarity. The increased incidence of simple goiter in Belgium, Holland, Denmark, and Norway during the years 1941-45 suggests a relationship to increased consumption of cabbage, turnip, and other foods. It is unlikely that goiter will result if these foods are eaten in normal quantity. Cooking the vegetables before eating will probably prevent any goitrogenesis.