Do vegetarian and vegan diets affect menstrual cycles?

Cristen Conger

Does vegetarianism cause irregular periods? Dwight Eschliman/Getty Images

A Stuff Mom Never Told You listener wrote in a couple weeks ago inquiring whether vegetarian and/or vegan diets can affect a woman's periods. After doing some digging for studies and expert opinions, the simple answer is that there is no simple answer. A host of things can throw a menstrual cycle off-kilter, including "stress, travel, weight changes, exercise, thyroid problems, ovarian cysts and pregnancy" (via Ask Pat).

Studies on vegetarian versus nonvegetarian diets and menstruation are also muddied due to methodological hiccups. Exhibit A: 1991 study "Menstrual differences due to vegetarian and nonvegetarian diets," which concluded: "The incidence of menstrual irregularity was 4.9% among nonvegetarians and 26.5% among vegetarians." But closer examination from the University of British Columbia countered that the study potentially suffered from recruitment bias, self-reporting and didn't account for oral contraceptive use among participants, which could certainly affect menstruation.

The U. of British Columbia study also pointed out how study results of a vegetarian diet's influence on menstrual may be different in real world than they are in the lab. Even in menstrual research that has isolated, say, soybean isoflavones (hello, tofu), the results can't be extrapolated to the general population because they don't take into account variations in daily eating habits and how those soybean isoflavones might interact with other nutrients that may having counterbalancing effects on hormones.

From what I found of diet-period studies, vegetarianism itself wasn't a culprit in altered menstrual cycles. While some studies found correlations between low-fat vegetarian/vegan diets and altered menstrual cycles, it was unclear whether the lack of animal products was responsible. Rather than not eating meat, attendant lifestyle factors, such as stress and eating and exercising for weight loss were associated with irregular periods. A 2003 study supports the need for more conclusive research to determine how nutrition interacts with menstruation: "...despite the existence of some evidence to the possible association between vegetarian diet and menstrual disorders, it is still not clear if this association is due solely to the vegetarian diet or due to the overall inadequate nutrition with decreased proportions of fat and protein in the diet."

Whether you're carnivorous or not, the Mayo Clinic recommends women see their doctor if they experience any of these menstrual changes:

  • Your periods suddenly stop for more than 90 days
  • Your periods become erratic after having been regular
  • You bleed for more than seven days
  • You bleed more heavily than usual - soaking through more than one pad or tampon every hour or two
  • Your periods are less than 21 days or more than 35 days apart
  • You bleed between periods
  • You develop severe pain during your period
  • You suddenly get a fever and feel sick after using tampons

Follow-up podcast listening: "Do gal pals sync up periods?"