The influence of dietary levels of vitamin a and fat on colon cancer

Rats fed diets high (24%) or low (5%) in fat were given dietary levels of vitamin A (retinyl acetate) ranging from 0.3 to 30 μg/food. The lowest tumor incidence was in the group fed diets high in vitamin A and low in fat. When the diet was high in fat and low in vitamin A, tumor incidence and frequency were significantly increased over that in rats fed the high‐fat diet with normal levels of vitamin A (10 μg/g feed). However, even with a high level of fat in the diet, raising the level of vitamin A above 10 μg/g feed had no further beneficial effect. Thus, although there was a significant interaction between vitamin A and fat, it is the latter that appears to require the most attention, once the vitamin A intake is adequate. These data support the view that we should set as a goal an adequate, diversified diet that is low in fat but that an excessive intake of vitamins such as vitamin A that are toxic should be avoided.