Saturated fatty acids and type 2 diabetes: more evidence to re-invent dietary guidelines.

Although saturated fatty acids (SFAs) are undoubtedly biologically active, several complexities preclude oversimplified predictions of their health effects. First, although attention has historically focused on blood LDL cholesterol, SFAs affect many other physiological pathways, including other blood lipids and lipoproteins1 and glucose— insulin responses.2 Second, different SFAs exist, with chain lengths ranging from 6 to 22 or more carbon atoms, and they have varying biological effects. Third, the relative effects of these SFAs also depend on the comparison nutrient, for example, other specific fatty acids, types of carbohydrate, or proteins.1, 3 Fourth, dietary SFAs are obtained from remarkably diverse foods—red meat, poultry, processed meats, yoghurt, milk, cheese, butter, vegetable oils, and nuts, among others—that contain many other components that could modify their overall health effects. Finally, SFAs are derived not only from diet but also from endogenous synthesis (hepatic de-novo lipogenesis) in response to large, rapidly delivered doses of carbohydrate or total calories, which is especially important for even-chain SFAs (eg, 14:0 and 16:0).