Trans-fatty acids implicated in diabetes

BOSTON, MASSACHUSETTS. Researchers at the Harvard School of Public Health have just released a major study aimed at determining the relationship between dietary fat intake and the risk of developing type 2 diabetes. Their study involved 84,204 female nurses who were between the ages of 34 and 59 years at their enrollment in 1980. The nurses completed extensive food frequency questionnaires in 1980, 1984, 1986, and 1990. By 1994 a total of 2507 of the participants had developed type 2 diabetes.

After adjusting for other known risk factors the researchers concluded that total fat intake is not associated with diabetes risk. However, they did find that a high intake of polyunsaturated fats markedly reduced the risk while a high intake of trans-fatty acids and cholesterol substantially increased it. The increase was particularly significant in obese and physically inactive women. A high intake of marine fish oils (eicosapentaenoic acid and docosahexaenoic acid) was found to decrease diabetes risk by about 20 per cent. The researchers also provide some very interesting estimates of the effect of various dietary modifications on the risk of diabetes:

Replacing 5 per cent of energy from polyunsaturated fats with the same amount of energy from carbohydrates is associated with a 58 per cent greater risk of diabetes.
Replacing 5 per cent of energy from saturated fatty acids with energy from polyunsaturated fatty acids is associated with a 35 per cent lower risk.
Replacing 2 per cent of energy from trans-fatty acids with polyunsaturated fatty acids is associated with a 40 per cent lower risk.

The researchers conclude that replacing trans-fatty acids in the diet with non-hydrogenated polyunsaturated fatty acids would substantially reduce the incidence of type 2 diabetes – perhaps by as much as 40 per cent.
Salmeron, Jorge, et al. Dietary fat intake and risk of type 2 diabetes in women. American Journal of Clinical Nutrition, Vol. 73, June 2001, pp. 1019-26
Clandinin, M. Tom and Wilke, Michaelann S. Do trans fatty acids increase the incidence of type 2 diabetes? American Journal of Clinical Nutrition, Vol. 73, June 2001, pp. 1001-02 (editorial)