It is known that trans-fats, the trans fatty acids found in animal products and processed vegetable oils, increase levels of “bad” cholesterol. Studies have shown a connection between eating a diet high in trans-fats and higher risk of heart disease. As a result, the U.S. Food and Drug Administration requires food makers to disclose if trans-fats are present in their products, and many restaurants and schools banned their use. However, while the link between cholesterol and trans-fats is well-known, their affect on insulin and blood sugar has not previously been adequately explored. To investigate this issue, Dr. Christos Mantzoros of Harvard Medical School in Boston combined the data across seven experiments with a 208-person subject group. They found that trans-fats do not appear to have long-term impact on insulin, the hormone that regulates blood sugar levels, or levels of blood sugar.
Five of the studies compared blood sugar, insulin, and cholesterol between subject groups that ate a diet high in trans-fats with levels when the same subjects ate a diet with trans-fats substituted for other fats including palm and soybean oils. The other two studies compared the levels of two groups of people, one that ate trans-fats, and one that ate a diet without them. All studies found that the diets high in trans-fats showed increased “bad” LDL cholesterol, and decreased “good” HDL cholesterol. This effect was expected, which demonstrates a good research design. The studies found no difference in blood sugar and insulin levels between the groups. Yet, the researchers acknowledge that further, longer-term studies are required to determine potential metabolic effects. Some researchers believe the effects are irrelevant since the amount of trans-fats consumed has dropped so drastically, by as much as 58% between 2000 and 2009.