Studies paint mixed health picture of caffeine

LONDON (Reuters) - Two new studies paint a conflicting health picture for women coffee drinkers, with one suggesting caffeine may lower the risk of ovarian cancer and the other showing it doubles the chances of miscarriage.

A waiter prepares cappuccino in a file photo. Caffeine appears to lower a woman's chances of developing ovarian cancer, U.S. researchers said on Tuesday, while smoking cigarettes and drinking alcohol do not. REUTERS/Osman Orsal

The research published this week in separate medical journals adds to mounting evidence indicating the amount of caffeine a person consumes may directly impact one’s health.

“With regard to caffeine and caffeine-containing beverages, we generally observed a lower risk of ovarian cancer with increasing intake,” Shelley Tworoger of Harvard Medical School and colleagues wrote in the journal Cancer on Tuesday.

The researchers, who examined data taken from health questionnaires of more than 121,000 women aged 30-35 as part of a Utah study, said further work was needed to pinpoint the biological reasons behind the protective benefits.

Current or past smoking or drinking alcohol did not seem to effect overall ovarian cancer risk, though cigarettes seemed to raise the likelihood of one rare form of the disease, they said.

Risk also appeared to decline the more total caffeine and coffee a woman consumed, the study found. Decaffeinated coffee had no apparent benefit.

But for pregnant women caffeine may prove harmful, another team of U.S. researchers reported on Monday. They said pregnant women who drink two or more cups of coffee a day have twice the risk of having a miscarriage as those who avoid caffeine.

The research may finally put to rest conflicting reports about the link between caffeine consumption and miscarriage, they added.

“Women who are pregnant or are actively seeking to become pregnant should stop drinking coffee for three months or hopefully throughout pregnancy,” said Dr. De-Kun Li of Kaiser Permanente Division of Research, whose study appears in the American Journal of Obstetrics and Gynecology.

This risk appeared to be related to the caffeine, rather than other chemicals in coffee, because they also saw an increased risk when the caffeine was consumed in soda, tea, and hot chocolate.

Li said many researchers think caffeine is harmful because it stresses the fetus’ immature metabolism. It may also decrease blood flow in the placenta, which could harm the fetus.

“To me, the safe dose is zero,” Li said. “If you really have to drink coffee, try to limit it to one cup or at the most two cups.” Or better yet, switch to decaffeinated beverages, he added.

Reporting by Michael Kahn and Julie Steenhuysen in Chicago; Editing by Jon Boyle