Women who want to get pregnant are often among the healthiest eaters. They stock up on high-fiber foods such fruits, vegetables and whole grains so they'll be at their best for pregnancy. A new study however, suggests that a fiber-filled diet may actually cause some women to ovulate less; and this could be a factor in infertility.
Research published in the American Journal of Clinical Nutrition says that women who get the recommended amount of fiber in their diets may have lower estrogen levels and ovulate less often than women who eat less fiber. In the study, 250 women between ages 18 and 44, all healthy and having regular menstrual periods, had their reproductive-hormone levels measured over two menstrual periods. Those women that reported the highest fiber intake (22 grams per day or more) were more likely to have at least one period without ovulation (anovulation) over two months. When the researchers accounted for other factors that could affect ovulation-including body weight, race, exercise levels and calorie intake-high fiber intake itself was linked to a roughly 10-times higher risk of anovulation. Women who reported getting most of their fiber from fruit consumption had the lowest reproductive-hormone levels.
Why does high fiber reduce ovulation? The study isn't certain about the link, but researchers suspect it may be because high-fiber diets decrease activity in certain intestinal enzymes, leading to less estrogen reabsorption in the colon. Fiber can also cause more estrogen to be excreted from the body through bowel movements. They also found lower levels of other reproductive hormones.
This research contradicts information published in an article in Newsweek, citing studies that show high-fiber diets with complex carbohydrates (the kind found in fruits, vegetables and whole grains) are linked to improved fertility. This article says, "Choosing slowly digested carbohydrates that are rich in fiber can improve fertility... More than any other nutrient, carbohydrates determine your blood-sugar and insulin levels. When these rise too high, as they do in millions of individuals with insulin resistance, they disrupt the finely tuned balance of hormones needed for reproduction. The ensuing hormonal changes throw ovulation off-kilter."
So should women eat or avoid high-fiber diets? The answer isn't definitive. But women and their health care providers should consider the issue of fiber when dealing with infertility. Other causes of anovulation or irregular menstrual cycles include thyroid disorders, polycystic ovarian syndrome, obesity, too little body fat, anorexia, excess exercise, diabetes and other health issues. Some women particularly benefit from high-fiber diets include those with irritable bowel syndrome, Chrone's Disease, diabetes, and those trying to lose weight.
High-fiber diets that include fruits and vegetables, whole grains, beans, nuts and legumes are important and healthy for overall nutrition. The American Congress of Obstetricians and Gynecologists, The American Heart Association, American Cancer Society and American Diabetes Association all recommend generous amounts of high-fiber foods as part of a healthy diet.
