Low-fat dairy food renders women less fertile

Feb 28 2007

According to researchers in the U.S. eating low-fat dairy foods may render women less fertile.

The researchers from the Harvard School of Public Health in Boston, say they found that women who ate two or more servings of low-fat dairy foods a day had an 85 percent higher risk of a certain type of infertility than women who ate less than one serving of low-fat dairy food a week.

It appears that women who eat one serving of high-fat dairy food a day are 27 percent less likely to be infertile than women who avoid full-fat dairy foods.

Nutritionist Dr. Jorge Chavarro says the finding was unexpected.

Chavarro and his team were interested in whether dairy foods in general affected fertility as there was strong evidence from animal studies suggesting that a specific sugar in dairy, lactose, could be harmful.

As little work had been done in humans, Chavarro and colleagues examined data from the Nurses Health Study.

This is an ongoing longterm survey of tens of thousands of women who fill out regular questionnaires about their diet, activity and health.

Chavarro's team chose the records of 18,555 women aged 24 to 42 who had tried to become pregnant or had became pregnant between 1991 and 1999, most were of European origin, possibly an important factor because people of northern European descent are less likely to be lactose intolerant.

The researchers found that the women who ate the most low-fat dairy foods were the most likely to report they suffered from anovulatory infertility, when the body fails to produce enough egg cells.

Chavarro says no difference was found between women who ate the most dairy and those who ate little or none, the differences only appeared when he broke down the types of dairy products.

The team were surprised that high-fat dairy foods were positively related to fertility, and though it is unclear why they suspect dairy fat or the hormones in pregnant cows may be affecting ovulation in women.

Chavarro says more studies are needed before conclusions can be drawn.

In earlier studies Chavarro's team found that women who ate more iron from supplements and from plant foods were less likely to be infertile, and found no link between fertility and various types of fats.

However the researchers do not recommend that women try to conceive by consuming excess amounts of ice cream; they say one serving a day will confer the benefit.

Doctors say if women eat more high-fat dairy foods to try to boost their odds of conceiving, it is important they cut down on calories elsewhere to avoid gaining weight.

They say being too thin or too fat, both raise the risk of any sort of infertility.

The study is published in the journal Human Reproduction.