The effect of diet on the spontaneous insulin dependent diabetic syndrome in the rat.

We have fed rats prone to developing spontaneous insulin dependent diabetes mellitus (IDDM) defined diets in which casein was the sole source of protein and the fat content was either menhaden oil, safflower oil, or corn oil. The incidence of IDDM was compared to that in litter mates fed rat chow. Animals receiving the defined diets had a lower frequency of overt IDDM than did animals receiving rat chow. The effect was seen only when the diet was introduced before the animals had reached the age of 30 days. The defined diets did not affect the distribution of peripheral blood T lymphocytes. Rats fed defined diets had decreased intensity of expression of Class I major histocompatibility complex (MHC) products on the endocrine cells of the pancreas compared to animals receiving rat chow.