The findings come from an eight-year study of 18,555 married female nurses by Harvard researcher Jorge E. Chavarro, MD, ScD, and colleagues.
Chavarro tells WebMD he was surprised to find that:
- Women who ate two or more weekly servings of low-fat dairy foods had an 85% higher risk of ovulation problems than women who ate one or fewer servings each week.
- Women who ate one or more daily servings of high-fat dairy foods were 27% less likely to suffer ovulation problems than women who ate one or fewer servings each day.
"These findings were unexpected. We certainly were not expecting low-fat dairy to have an effect on ovulation," Chavarro says. "Clearly more research needs to be done before recommendations can be made for women."
He notes that while high-fat dairy foods seem to increase fertility, even modest servings have this effect.
"This should not signal women to get buckets and buckets of ice cream. That would be bad for fertility and bad for their overall health," Chavarro says.
Although the findings require confirmation, Chavarro is resigned to the fact that some women who want to get pregnant will switch from low-fat to high-fat dairy foods.
"If you want to try something like this, make it a temporary measure while trying to get pregnant, not a permanent lifestyle change," he warns. "And a woman should eat high-fat dairy foods only when she maintains a stable caloric intake. So if you're going to do this, try to eliminate other high-saturated-fat foods from your diet."
Fertility expert Celia Dominguez, MD, assistant professor of gynecology and obstetrics at Emory University in Atlanta, notes that most of the women in the Harvard study were at near-normal weight. Since obesity is a major factor for women with ovulation, she warns overweight women against gorging on ice cream.
"Nobody needs to run off to eat Haagen-Dazs to get pregnant," Dominguez tells WebMD. "But things like fat may not be as bad in a diet as perceived. We tell people balance is really important. I tell people to have some fat -- no fat is no good -- but balance is the key."
Gregory D. Miller, PhD, executive vice president for science and innovation at the National Dairy Council, notes that the Chavarro study linked low-fat dairy foods not to infertility in general, but only to a specific type of infertility.
"The government's dietary guidelines recommend three servings of low-fat milk and milk products a day for women as part of a healthy diet, but the guidelines also allow for so-called discretionary calories in whatever part of the diet a person chooses -- and that includes higher-fat dairy products," Miller tells WebMD. "So bon appetit, ladies."
The study by Chavarro and colleagues appears in the Feb. 28 online issue of Human Reproduction.