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Ask the Doctors: Certain foods may affect fertility but not that cut and dry

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Dear Doctor: I recently read that fast food interferes with a woman’s chances of conceiving. What’s the connection?

Dear Reader: Fast food would seem to be an easy fall guy for our current health status: The United States ranks first in the amount of money we spend on healthcare, but 31st in overall longevity. But as much as we’d like to blame a specific industry for our unhealthy habits, the situation is much more complex than that. Further, we as individuals are the ones who, of our own free will, order the burgers, french fries, onion rings, sodas and milkshakes.

The study you mentioned looks at different foods and the role they play in pregnancy and fertility. In it, 5,628 pregnant women from New Zealand, Australia, Ireland and the United Kingdom were given dietary questionnaires 15 weeks into their pregnancy. The questions had to do with the consumption of fruits, green leafy vegetables, fish and fast food in the month preceding conception. A midwife researcher also asked questions about the time it took for the women to become pregnant. A timespan greater than 12 months was defined as infertility.

The study did not find an association between green leafy vegetables or fish and time to pregnancy (TTP). But it did find an association between fruit intake and TTP. Compared to women who ate fruit three times per day, those who ate fruit only one to three times per month had a 19 percent longer TTP and a 29 percent increased rate of infertility.

Fast food, which included burgers, french fries, pizza and fried chicken, had an even greater association with TTP delay and infertility. Compared to women who ate fast food four times or more per week, those who ate fast food two to four times per week had an 11 percent shorter TTP and an 18 percent lower infertility rate; and those who ate it less than twice a week had a 21 percent quicker TTP and a 34 percent lower infertility rate. Women who reported no fast food intake had a 24 percent quicker TTP and a 41 percent lower infertility rate, compared to the women who ate it four times or more per week.

Among the study’s problems: It was based on dietary recall and thus subject to recall bias. For example, a woman who had difficulty conceiving may have overestimated a factor she believed could have caused a delay in her conception. Further, 90 percent of study participants identified themselves as Caucasian, so the results may not be applicable in a multi-racial society. And lastly, fast food and lack of fruit in the diet may simply be markers of an unhealthy lifestyle. The authors did appear to adjust for this in their study, however.

That said, the results are concerning and point to the importance of diet in fertility. Many fast food restaurants have healthier options, and while these are intermixed with unhealthy food, they at least give women a choice. Of course, a better option is going to the market, selecting healthy food and taking the time to prepare it well. Even if there’s no time for the latter steps, major markets now have readymade food that is both healthy and fast.

Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.