Eating trans fats may increase infertility risk

NEW YORK Thu Jan 18, 2007 11:47pm GMT

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NEW YORK (Reuters Health) - Women who want to get pregnant may want to stay away from fast food French fries not just to avoid putting on some extra pounds, a new study shows.

The more trans fats a woman eats, the more likely she is to be infertile, Dr. Jorge E. Chavarro of the Harvard School of Public Health in Boston and colleagues found.

Trans fats are found in fried foods, packaged snacks, commercial baked goods and other sources, and are known to increase the risk of heart disease and diabetes. "Even for somebody who's not trying to get pregnant, it is a very good idea to stay away from them," Chavarro told Reuters Health.

Trans fats can interfere with the activity of a cell receptor involved in inflammation, glucose metabolism and insulin sensitivity, Chavarro and his team note in the American Journal of Clinical Nutrition. Drugs that activate the receptor have been shown to improve fertility in women with a condition known as polycystic ovary syndrome.

To investigate how trans fat consumption might affect fertility, the researchers analyzed data from 18,555 healthy women participating in the Nurses' Health Study. All were married and trying to get pregnant between 1991 and 1999.

For every 2 percent increase in the amount of calories a woman got from trans fats instead of carbohydrates, the researchers found, her risk of infertility increased by 73 percent. The risk rose by 79 percent for every 2 percent of energy in trans fats if they replaced omega-6 polyunsaturated fats. And for every 2 percent of calories derived from trans fats instead of monounsaturated fats, the risk of infertility more than doubled.

For a woman eating 1,800 calories a day, 2 percent of energy intake in trans fats equals 4 grams, Chavarro noted. "It's not very hard to get 4 grams of trans fatty acids every day," he said. "It's really a small amount of trans fatty acids that we observe having a significant effect on infertility."

The Food and Drug Administration now requires manufacturers to state on their label if a food contains a half gram of trans fat per serving or more, Chavarro noted, but foods with less than a half gram are allowed to claim that they have zero grams of trans fat. To cut trans fats out of the diet completely, he added, people should avoid all foods that list hydrogenated or partially hydrogenated oils in their ingredients.

SOURCE: American Journal of Clinical Nutrition, January 2006.

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