The Dietary Science Foundation
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About 5-10 percent of all women of reproductive age have polycystic ovary syndrome, PCOS, where periods are irregular and ovulation may not occur. One important cause is elevated levels of insulin in the blood. A few small studies have suggested that a diet that lowers insulin levels can restart ovulation, but larger studies are needed to establish a treatment.
In women suffering from PCOS, eggs sometimes are not released from the ovaries so they can move through the fallopian tubes and be fertilized. Instead, a string of egg follicles forms in the ovaries and menstruation becomes irregular. About 70 percent of all women with PCOS have what is known as insulin resistance; their bodies respond poorly to insulin, with the result that blood insulin levels rise. Insulin is best known as the hormone that lowers blood sugar, but it has many more functions; it also activates the body’s growth system and raises the level of free androgens (including testosterone) in the female body which in turn inhibits ovulation.
Women with PCOS often need hormone therapy to become pregnant, but it doesn’t always work. Another way to break the vicious circle is to reduce insulin production in some way. Overweight women are often advised to lose weight, because weight loss leads the body to become more sensitive to insulin. One alternative is to eat a diet that lowers insulin levels. In an Australian study, researchers looked at the effects of a low-GI diet (which includes only slow carbohydrates) compared to a conventional low-fat diet. 95 percent of the women on the low-GI diet had more regular periods. In the control group, who ate a conventional low-fat diet, the figure was 63 percent.
In a small American study, participants ate a strict low-carbohydrate diet. Eleven women were included in the study, out of which only five completed the dietary treatment. All five women lost weight and lowered their insulin and testosterone levels. Two of them became pregnant during the 24 weeks of the trial.
These small studies show that insulin-lowering diets can help with PCOS, but no large studies have yet been done. The Dietary Science Foundation wants to initiate high-quality studies investigating the effects of different insulin-lowering strategies, such as a low-GI diet, a strict low-carbohydrate diet and intermittent fasting.