Study Finds Differences in Effect of Soda, Caffeinated Drinks on Fertility.

Should women who are trying to become pregnant steer away from caffeine?

It may depend on the type of caffeinated beverage they choose, according to a new study led by BU School of Public Health researchers.

The study, published in the journal Epidemiology, found little evidence that total caffeine or coffee consumption was associated with fertility, in a large sample of Danish women (3,628) trying to get pregnant. However, results differed depending on the type of caffeinated drink they consumed, indicating that total caffeine consumption may not be the best indicator of time to pregnancy.

Photo by Flickr user wolfman-kWomen who reported drinking sodas regularly — especially sugar-sweetened sodas — had lower fecundability, while women who drank tea had increased fertility. One possible explanation offered by the authors is that chemical additives or contaminants in some soft drinks, such as bisphenol A, may have an adverse effect on fertility. The researchers cautioned, however, that their findings may have been skewed by “dietary factors or other lifestyle characteristics” not measured by the study.

“We collected data on numerous potential confounders. Nevertheless, our findings may be affected by other unmeasured confounding factors,” the authors wrote. “Tea drinkers may have healthier lifestyles that could affect fertility, whereas women who regularly consume sodas may have more unhealthy lifestyles, as exemplified by the strong relationship between BMI and soda consumption.”

The authors noted that past research on caffeine consumption and fertility has produced varying findings. Most prior studies have found that neither total caffeine nor coffee consumption is associated with fertility, but also that regular consumption of sodas may reduce fertility.

Caffeine has been associated with alterations in estradiol and other hormones, which in turn may affect ovulation or other characteristics of the menstrual cycle. Soda, with and without caffeine, has been associated with increased insulin resistance, metabolic syndrome and weight gain, which are related to polycystic ovary syndrome, a leading cause of ovulatory infertility.

Elizabeth Hatch, professor of epidemiology, was the lead author on the study, which was conducted by BUSPH researchers affiliated with BU’s Slone Epidemiology Center and researchers from Aarhus University Hospital in Denmark. Other BUSPH researchers include: Lauren Wise, associate professor of epidemiology; Kenneth Rothman, professor of epidemiology; and Henrik T. Sørensen, adjunct professor at BUSPH and a professor of clinical epidemiology at Aarhus.

The study was supported by grants from the National Institute for Child Health and Development and the Danish Medical Research Council.

Submitted by: Lisa Chedekel

chedekel@bu.edu