Goitrogenic Effect of Dietary Fat

Abstract

Marine 1 believes that thyroid activity may be more necessary for oxidation of fats than of carbohydrates. Harington 2 suggests that fats, especially unsaturated ones, may interfere with iodine absorption by the thyroid. Chidester 3-6 states that unsaturated fats absorb iodine from the body. Few positive experiments have been reported to support these beliefs. McCarrison 7 found that diets excessively rich in proteins and fats caused thyroid enlargement in pigeons. The Mellanbys 8 noticed that puppies receiving cod-liver oil as their only fat had small, normal thyroids, but with other fats there was always some hyperplasia, which was intensified when the amount of dietary fat was increased. Levine and Remington, 9 in a comprehensive review, do not refer to the goitrogenic action of fats.

White rats, weighing about 50 gm., were kept in cages which prohibited coprophagy. The diets are given in Table I. Olive and cocoanut oils were chosen so that the effects of relatively saturated and unsaturated fats might be compared, olive oil being a typical unsaturated fat, and cocoanut oil, saturated. The salt was the usual Osborne and Mendel 10 mixture, except that the potassium iodide was decreased. The salt mixture of diets A and B contained 13.5 mg. of potassium iodide per 500 gm., as compared with 4.6 mg. in diets C and D. The 2 diets containing olive oil differed only in the content of iodine. Levine, Remington, and von Kolnitz 11 have found that 1-2 gammas of iodine per day are sufficient to prevent goiter in the rat. The iodine in our salt mixtures supplied an excess well over the minimum requirement. (Table II.) The iodine content of the other dietary constituents was not determined. Vitamins were supplied by brewer's yeast, viosterol, and caritol.∗ At the end of 50-60 days, the rats were killed and the thyroids were removed, weighed immediately, and then preserved in formalin for histological study.