Sorry guys, if you're trying to have a baby, you may want to skip that grilled cheese sandwich at lunch today. According to a new study from the Harvard School of Public Health, men who eat more than three slices of cheese per day may be putting their fertility at risk.
Why cheese? The hidden culprit here seems to be fat content—and hormones. In the study, researchers compared the diets of 189 men aged 19 to 25. As the UK's Daily Mail reports, none of the men were overweight—they were all very fit and regularly exercised.
Researchers asked guys to fill out questionnaires indicating how often they ate dairy products, fruit, meat and other types of food during a typical week; they also obtained sperm samples. Results showed that men who ate more than three portions of full-fat dairy food a day, including full-fat cheese, whole milk, and full-fat ice cream, had sperm—on average—25 percent poorer in quality than those who ate less full-fat dairy.
"Full-fat dairy food intake was associated with lower semen quality among young active men," says Myriam Afeiche, PhD, a postdoctoral Research Fellow at Harvard School of Public Health, in the study summary. The connection? Afeiche explains that milk fat tends to contain higher amounts estrogen hormones compared to milk liquid—and it's the estrogen content in cheese, whole milk, and ice cream that seems to affect men's fertility. Additionally, pesticides, which can also impair healthy sperm production, tend to be found in dairy fats, too, and may also play a role.
So does this mean no more cheese and crackers? No milk and cookies? No... Ben & Jerry's?
Probably not, say fertility experts, who point out that while eating full-fat dairy can lower sperm quality, it still doesn't put it in the "red zone" of male infertility.
"For a man in a fertility clinic, we wouldn't worry about that," Dr. Allan Pacey, Chairman of the British Fertility Society, tells the Daily Mail. Pacey thinks not enough is known about diet's impact on male fertility to make recommendations like avoiding dairy. "I wouldn't want to scare men out of drinking milk. In a separate study, the same researchers found that young men who ate lots of carbs had a lower sperm count," he adds.
The takeaway here? It may be the time-tested truth of "all things in moderation." Eating one or two portions a day of full-fat dairy seems to be fine, by this study's standards. What can two portions get you? A lot! Two portions of full-fat dairy equals two scoops of ice cream, two ounces (about two slices) of cheese, or two glasses milk.
OK, so make that triple-cheese sandwich a double, and it seems like you're good to go!