It’s no secret that coffee has an effect on our bodies, as evidenced by our bleary-eyed zombie crawl to the Keurig machine every morning. But what is it doing to our menstrual cycles?

Well, for one, it’s shortening them. A study of over 400 healthy, premenopausal women found that women who consumed a lot of caffeine (over 300 mg daily) were twice as likely to have a short menstrual cycle (less than 25 days) compared to women who didn’t drink coffee. “The mechanism by which caffeine may alter the duration of the menstrual cycle is not clear, but such an effect could occur via the effect of caffeine on sex hormones or the hormone receptors,” the researchers write.

Caffeine drinkers were also less likely to have long periods, likely because of the constriction of uterine blood vessels. Shorter periods sound nice, but the implications for women’s long-term health aren’t necessarily positive (other research has linked caffeine consumption to delayed conception).

It’s actually that constriction of vessels, combined with the diuretic effect of caffeine, that could have other less than welcome side effects, like more painful cramps. And that’s just the beginning.

“Caffeine is a stimulant,” explains Dr. Angela Jones. “What goes up must come down… eventually the ‘high’ achieved from caffeine wears off.” That means an exacerbation of menstrual symptoms like cramping, but also bloating, fatigue, mood changes, anxiety, and headaches.

Your stress hormones are a key player in this, too. “[Caffeine] gets our bodies all amped up by its direct effect on hormones, such as norepinephrine, epinephrine, and cortisol.” It’s those hormones that are responsible for giving your heart rate and blood pressure a boost in stressful situations, making you more tense and anxious. Perhaps a well-needed boost when you’re racing to finish a work project by deadline and throwing back a latte with an extra espresso. Not so great when you’re already feeling the mood-altering and physical effects of PMS.

Your stress hormones are a key player in this, too.

Chest feeling in need of an ice pack? If you’re prone to breast tenderness or have fibrocystic breast disease, you might want to consider switching to decaf — both have long been associated with caffeine consumption, says Dr. Jones. “In patients that complain of breast tenderness, I oft times suggest cutting their caffeine intake by half,” she says. “They are amazed at the improvement in symptoms.”

Not giving up your coffee even if your uterus writes you a handwritten letter asking you to? We get it. Just be mindful of how your body is reacting and stay open to cutting back temporarily, even if just during the beginning of your period or when you’re most susceptible to PMS symptoms. Since caffeine clears the body in a matter of hours, you can still decrease symptoms by just cutting back for part of the month. And don’t forget that you may be ingesting hidden sources of caffeine you’re not totally aware of — aka that super-size bar of chocolate the night before your period starts.

Plus, if you’re taking any medication to address symptoms before or during your period, check the ingredients list. “You should be sure that you are monitoring your caffeine intake when taking medications, such as Midol, with caffeine in them,” says Dr. Jones. “[It’s] intended to decrease fatigue and bloating, [but] once it wears off, we are right back where we started with other common PMS symptoms of fatigue and crampiness as a result of dehydration.” Drink responsibly.

Diana Vilibert is a freelance writer and copywriter living in Brooklyn, NY. She loves flea markets, martinis, to-do lists, traveling, and wearing leggings as pants. You can see more of her writing at www.dianavilibert.com and follow her on Twitter at @dianavilibert.