Home remedies to boost the odds of becoming pregnant include thinking positive thoughts and placing a pink or blue ribbon under a bed pillow, depending on whether a mother-to-be is hoping for a girl or boy.
But women who want to try something with a bit more science behind it can start by changing their eating habits. So say Harvard doctors who recently completed a study on women's diets and fertility.
Their findings suggest that certain foods and lifestyle factors can significantly affect hormone levels and improve fertility in women with ovulation problems -- a common cause of infertility, says Dr. Jorge Chavarro, lead author of the study, which was published last month in the journal Obstetrics & Gynecology.
What he and his colleagues found supports a growing body of evidence that diet can greatly affect hormone levels, particularly insulin, which then affects fertility. Although the research does not prove that certain foods have a direct effect, it does suggest that a woman can increase the odds of becoming pregnant without risky, costly or invasive treatments -- something many women, and their doctors, may overlook.
"Making changes to your lifestyle should be a first step when people are facing problems with fertility," says Chavarro, a research fellow at the Harvard School of Public Health's department of nutrition.
In the study, women who followed five or more lifestyle or dietary recommendations reduced their risk of ovulatory infertility by as much as 80%, compared with women who engaged in none of the recommendations.
Ovulation problems -- in which women ovulate irregularly or not at all -- account for 18% to 30% of all infertility cases, Chavarro says. Doctors often prescribe fertility drugs as treatment, but the medication can raise the risk of conceiving twins or higher-order multiples.
The study should open some eyes in the field of reproductive medicine, says Dr. Fady Sharara, a Virginia fertility doctor who has studied fertility and body mass index and has long supported the value of a healthful diet for fertility.
"I'm so happy that this paper came out," says Sharara, medical director of the Virginia Center for Reproductive Medicine. "I've been telling my patients for years that you have to change your diet. I personally believe that this is very important for many women, not just those who are overweight."
Few studies have specifically examined diet and infertility. The recent findings were culled from the long-running Nurses' Health Study II, an epidemiology study of registered nurses launched at Brigham and Women's Hospital in 1989. For the fertility analysis, the researchers analyzed data collected from 17,544 women who had no history of infertility over eight years as they tried to become pregnant or became pregnant. They surveyed the women on their diets, exercise habits, weight and many other health factors.
In general, the study's findings point to factors that can disrupt the delicate balance of hormones needed for reproduction. Though the researchers aren't sure why certain foods seem to influence fertility, they have some strong hunches based on other scientific studies, says Chavarro, who has written a book based on the recent findings, "The fertility Diet," with Dr. Walter Willett of Harvard. Willett is a widely published researcher and one of the nation's leading nutrition epidemiologists.
Research has shown, for example, that women with a disorder called polycystic ovary syndrome frequently experience ovulatory infertility due to insulin sensitivity and high testosterone levels. They are more likely to get pregnant after they lose weight or are treated with medications to improve insulin sensitivity.
Thus, one recommendation in "The Fertility Diet," is for women to avoid refined carbohydrates such as white bread, potatoes and sugared sodas, which quickly raise blood sugar and insulin, disrupting the balance of hormones. In the Nurses' Health Study II, women who had the highest glycemic load -- a measure of the amount of carbohydrates in the diet and how quickly carbohydrates are turned into blood sugar -- were 92% more likely to have had ovulatory infertility than women in the lowest glycemic load category.
"There are a lot of papers in the literature on body mass index and its effects on fertility," says Dr. G. David Adamson, president of the American Society for Reproductive Medicine who was not involved in the study. "This study certainly adds some very interesting data. There is no question that weight and diet are very important in ovulatory disorders." He cautioned that the study only finds a link between certain foods and infertility and that the theory should be tested in a more rigorously scientific manner, such as through a randomized, controlled trial.