Not all saturated fats are created equal, it appears. A pair of new studies suggests that certain sources of saturated fat may be worse than others—especially when it comes to raising risk for type 2 diabetes.
In one study, published in the American Journal of Clinical Nutrition, researchers from Harvard University and the Universitat Rovira i Virgili in Spain tracked 3,349 Spanish adults for about 4.5 years. Overall, they found that people who consumed higher amounts of saturated fats and animal fats were twice as likely to develop diabetes than those who consumed a lower amount.
When the researchers broke down the results by specific food type, the consumption of butter (at 12 grams a day) and cheese (at 30 grams a day) were both linked to an increased risk of diabetes. On the other hand, people who ate whole-fat yogurt actually had a lower risk than those who didn't.
The researchers have several explanations for these findings. Yogurt contains healthful ingredients, like probiotics and protein, that may have protective effects when it comes to diabetes risk, says lead author Marta Guasch-Ferre, a nutrition research fellow at the Harvard T.H. Chan School of Public Health. Even though the results were adjusted to account for other food intake, unhealthy eating patterns may have influenced them. “Butter and cheese often come with carbohydrates, like toast or crackers,” Guasch-Ferre says. Plus, people who eat more yogurt tend to have better diets than those who don’t, she adds.
The study did not find any significant links between diabetes risk and consumption of red meat, processed meat, eggs or whole-fat milk. That was a surprise to the researchers, who suspect that other factors may have diluted these results. They point out that dietary patterns in Spain are different than those in the United States, and that many of the study participants were following a Mediterranean diet, so these findings may not apply to someone following a typical American diet.
“It’s safe to say, based on the findings of other studies, that processed meat and red meat are associated with cardiovascular disease and other chronic disease risks,” says Guasch-Ferre. “We know it’s beneficial to reduce the intake of these meats and to replace them with healthy fats from plant sources like nuts and olive oil.”
However, just because a fat may come from a plant doesn't make it healthy. Palm oil, used in a lot of processed foods, is very high in saturated fat. In another recent study, scientists demonstrate how even one dose of palm oil can affect metabolism and reduce the body’s sensitivity to insulin.
For this research, published in the Journal of Clinical Investigation, German scientists asked 14 healthy men to drink either a glass of plain water or a drink made with palm oil that contained as much saturated fat as a cheeseburger and French fries. When the participants drank one of these beverages, they experienced a reduction in insulin sensitivity, an increase in fat deposits in the liver and changes in their metabolism similar to those experienced by people with diabetes.
For healthy people, the authors say, the occasional fatty meal likely won’t cause any permanent damage. But people who regularly eat foods high in palm oil or other saturated fats may face bigger long-term consequences, like chronic insulin resistance and fatty liver disease. Both are risk factors for diabetes.
The American Heart Association recommends that no more than 10% of total calories come from saturated fat and encourages consumption of unsaturated fats and carbohydrates from vegetables, fruits, whole grains, nuts and legumes. Based on recent research, says Guasch-Ferre, these recommendations seem to be just as important for diabetes risk as they are for heart health—and not just because fatty foods can cause weight gain.
“I think it’s probably more that saturated fats have harmful effects on insulin resistance and other markers of inflammation, more than weight gain,” she says. More research is needed, she adds, to fully understand the connection or to make clear recommendations about specific foods.