Women who eat a Mediterranean-style diet high in fruits, vegetables, fish and whole grains are less likely to have trouble getting pregnant, hints a new study from Spain.
The findings add to a growing body of evidence linking the Mediterranean diet to all kinds of health effects, including lower risks of obesity, diabetes and heart disease.
But Dr. Jorge Chavarro, who was not part of the study, cautioned that the new results are based on observations, not an experiment.
"There's always the possibility that this association is not causal," said Chavarro, who studies nutrition at the Harvard School of Public Health in Boston.
Researchers looked at nearly 500 women with fertility problems and more than 1,600 women of the same age who had at least one child. Based on questionnaires, they measured how closely women followed either a Western-style or a Mediterranean diet.
The Western diet consisted of red meat, fast food, whole-fat dairy products, potatoes, refined grains and sugar-sweetened soda, and was not linked to fertility.
In other words, there was no difference in fertility problems between women who followed this type of diet religiously and those who followed it less strictly.
But the picture changed for women with a Mediterranean diet. About 17 percent of those who stuck to it meticulously said they'd had trouble getting pregnant, while 26 percent of the women who followed that diet least closely had fertility problems.
"The Mediterranean type diet may have a protective effect on insulin resistance and type 2 diabetes," said study researcher Dr. Estefanía Toledo, who studies nutrition at the University of Navarra in Spain.
Insulin resistance means that the body's cells have a hard time absorbing sugar from the blood stream. But researchers have also found a link between insulin resistance and ovulation -- when the egg is released from the ovary and can be fertilized.
"Insulin has other functions in the body," Chavarro told Reuters Health. "It also regulates a number of hormones, in particular the amount of hormones needed for ovulation which is essential for reproduction."
Chavarro thinks the Mediterranean diet indirectly influences ovulation.
"The Mediterranean diet contains nutrients that help your body clear sugar from the bloodstream while using less insulin to do this job," he said. "This makes it easier for the body to keep the balance of reproductive hormones."
For women who are thinking about getting pregnant, Chavarro sees no harm in adopting the Mediterranean diet.
But for women who are having fertility problems, he said, "we don't have enough data to show that this diet pattern can help you get pregnant as a result of fertility treatment."
More than six million U.S. women of childbearing age have difficulty getting pregnant or staying pregnant, according to the Centers for Disease Control and Prevention.
But men might also want to watch their diet and lifestyle if they are interested in maximizing their chances of becoming fathers. A recent study by Chavarro and colleagues found that overweight men have lower sperm counts than their leaner peers.
"Other than that, there's very little we know about body composition and male fertility," he said. "That's an area that we're working on right now."