Caffeine could impair fertility in women by reducing activity of the muscles in the fallopian tubes, which carry a woman's eggs from her ovaries to her womb, according to new research.
Researchers have shown that caffeine relaxes the cells that make up the smooth muscle of the fallopian tubes, said study researcher Sean Ward, of the University of Nevada School of Medicine.
"Caffeine inhibits the contractions of the muscles in the fallopian tube, so the egg stops getting transported," Ward told MyHealthNewsDaily.
If the eggs aren't transported to the womb, a woman will either have an unsuccessful pregnancy or she will be at risk for an ectopic pregnancy, which is when the embryo gets stuck and develops in the woman's fallopian tube, he said.
Ward and his colleagues studied the effect of caffeine on the fallopian tubes of mice, which he said are similar reproductively to humans. They found that when they applied caffeine to these tubes, the muscles relaxed.
Even though Ward's research was done on mice, he said the amount of caffeine that produced the infertility in mice was equivalent to that which is in about a couple cups of coffee for humans (though the study wasn't specifically on caffeine that is in coffee, but rather caffeine in general). But much more research is needed to determine how much caffeine is necessary to impair fertility in humans, he added.
Past research has also linked caffeine consumption with infertility. One study, published in 1993 in the American Journal of Epidemiology, showed that drinking at least three cups of coffee a day lowered the chance of conceiving a child by 27 percent.
However, caffeine affects everybody in different ways, and therefore may affect people's fertility differently, Ward said.
"It depends on the person — how long caffeine affects you, and then the downstream effects as well," which are the bodily processes that are then affected because of the caffeine in the body, Ward said.
Next, Ward said he hopes to study the effects of caffeine on human fallopian tubes.
The study was published today (May 26) in the British Journal of Pharmacology.
Pass it on: Caffeine may hamper fertility in women by relaxing the muscles of the fallopian tube, which brings the eggs from the ovaries to the womb.
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