There are two primary sources of trans fats in the human diet: natural and artificial. Natural trans fats are present in small amounts in dairy products and the meat of some animals.Artificial trans fats, or trans fatty acids, are the primary source of trans fats in the diet and are the product of an industrial process that adds hydrogen to vegetable oil to make it solid.According to the American Heart Association, consumption of trans fats can raise the risk of heart disease, stroke, and has links to a higher risk of type 2 diabetes.In a recent Neurology paper, the new study authors describe how they linked trans fats to a higher risk of dementia using data from an ongoing health study of people living in the town of Hisayama in Japan.“These results,” says senior study author Toshiharu Ninomiya, “give us even more reason to avoid trans fats.” He adds that “In the United States, the small amounts still allowed in foods can really add up if people eat multiple servings of these foods, and trans fats are still allowed in many other countries.”Ninomiya is a professor in the department of epidemiology and public health at Kyushu University in Japan.