High fibre intake may affect ovulation

Women who get the recommended amount of fibre in their diets may have lower oestrogens levels and ovulate less often than women who eat less fibre.

High-fibre diets are associated with many health benefits, including lower risks of heart disease, diabetes, colon cancer and breast cancer. Experts generally recommend that adults get 20 to 35 grams of fibre each day, depending on their calorie intake.

Higher fibre intake, particularly from fruit, was also linked to a higher risk of having anovulatory menstrual cycles – where the ovaries fail to release an egg.

Anovulation can have various causes, including excessive exercise, having either too little or too much body fat, thyroid gland dysfunction and polycystic ovarian syndrome (a hormone disorder that is a common cause of infertility). Women who are not ovulating regularly often have irregular menstrual periods or none at all. However, some women do continue to have periods.

Researchers studied 250 women in America ages 18 to 44 years for 2 cycles to determine if fibre consumption is associated with hormone concentrations and incident anovulation in healthy, regularly menstruating women. All the participants were healthy and having regular menstrual periods. The researchers gauged anovulation by measuring the women’s reproductive-hormone levels over two menstrual periods and they also assessed the dietary fibre intake of all the participants.

It was found that those women who reported eating the recommended amounts of fibre had the lowest blood levels of oestrogen and other reproductive hormones. Those women who reported the highest fibre intake – 22 grams per day or more (in line with general recommendations) – were more likely to have at least one anovulatory cycle over two months. Of the total menstrual cycles in this group, 22 percent were anovulatory, compared with 7 percent among women with lower fibre intakes.

When the researchers accounted for other factors that could affect ovulation – including body weight, race, exercise levels and calorie intake – high fibre intake itself was linked to a roughly 10-times higher risk of anovulation.

Looking at specific sources of fibre, the researchers also found that fibre from fruit, specifically, was most clearly associated with anovulation. The researchers explain that high-fibre diets decrease activity in certain intestinal enzymes, leading to less oestrogen reabsorption in the colon. Fibre can also cause more oestrogen to be excreted from the body in faeces.

In line with that, the researchers found that women with the highest fibre intakes generally had the lowest oestrogen levels over the course of their menstrual periods. They also had lower levels of other reproductive hormones, including progoesterone, luteinising hormone and follicle-stimulating hormone.

The findings raise the possibility that women who are trying to conceive should lower their fibre intake.

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