What Causes Period Cramps—The Science, Explained

Posted by Courtney Mayszak, RDN, LDN

Dec 03, 2021

Understanding what causes period cramps may actually help you manage them better.

Scientists know a lot about what causes cramping when you’re on your period. Research also reveals that certain lifestyle factors may make cramps worse, but knowing your triggers—and that you have options for relief—can be game changers for your cycle.

This article breaks down the science behind what causes period cramps, what can worsen them, and what’s been shown to help naturally.

Key takeaways:
  • Period cramps are caused by an overproduction of inflammatory compounds in the uterus. They can make uterine muscles contract so tightly, they pinch off blood vessels that supply the uterus with oxygen, leading to painful cramps.
  • Things that promote inflammation or constrict blood vessels can cause period cramps to become more intense, more frequent, or last longer. We list some top offenders.
  • You can help relieve period cramps naturally with foods, supplements, and habits that reduce inflammation, relax uterine muscles, or promote healthy blood flow to the uterus.

What causes period cramps

In a nutshell, inflammation is what causes period cramps. Specifically, menstrual cramps are triggered by pro-inflammatory compounds called prostaglandins [1].

Your body is home to many different types of prostaglandins, some that cause inflammation, and others that reduce it. The prostaglandins that accumulate in your uterus right before your period are the type that cause inflammation—but for good reason.

Not all inflammation is “bad”. Sometimes it’s part of your body’s master plan, as is the case with your menstrual cycle. Uterine prostaglandins’ job is to tell the uterine muscles to contract, or tighten up. While sometimes uncomfortable, this process is critical for regulating your flow [2].

At the beginning of your period, those rhythmic muscle contractions help detach the uterine lining from the wall so bleeding can start. Afterward, they help clot the uterine wall before too much blood is lost [3].


But if some muscle contraction is necessary, why do period cramps have to be so painful?

They don’t. Muscle contraction itself isn’t painful. When you flex your bicep, for example, it shouldn’t hurt.

Menstrual cramps shouldn’t hurt either, but they often do because, as modern humans, we tend to overproduce prostaglandins. When we make more prostaglandins than we need at the beginning of our period, uterine muscles contract too tightly [4, 5].

The muscles that make up the uterus are particularly strong—among the strongest in the body, in fact [6]. When triggered by prostaglandin overload, they can contract so powerfully, they pinch off the blood vessels that supply the uterus with blood, oxygen, and nutrients.

And while muscle contraction itself isn’t painful, not having oxygen around definitely is. The medical term for body parts that don’t have enough blood flow and oxygen is ischemia.

When ischemia happens elsewhere in the body (e.g. the heart) it’s usually related to a serious medical condition (e.g. a heart attack), and it’s usually painful. While most cases of period cramps aren’t related to an underlying issue (however there are exceptions), they’re no less painful.

Some experts have compared period pain to that of a heart attack [7]. Others say this comparison doesn’t go far enough, and period cramps can be even worse [8].


Period cramps are caused by pro-inflammatory prostaglandins that, when overproduced, make uterine muscles contract too tightly, cutting off the flow of oxygen to the uterus in the process. Period cramps hurt because it’s painful for muscles to not have enough oxygen.


What causes period cramps to get worse

Now that scientists know what causes period cramps (inflammation > muscles contraction > ischemia), researchers are starting to understand more about lifestyle factors that exacerbate this process. The science is still emerging, but here’s what we’ve learned so far about what makes period cramp worse:


Stress is a major contributor to hormonal imbalances and inflammation [9]. Stress and period problems are so closely linked [10, 11], it’s rare that stress doesn’t result in some menstrual issue, be it more intense cramps, new or worsened PMS symptoms, irregular periods, or heavy flows.

Inflammatory foods

Conveniently, the same types of foods with obvious links to chronic disease are also the best-known period cramp offenders. Regularly drinking soda [12], binging on sweets [13], and eating lots of highly-processed, salty snacks [14] have all been associated with worse period cramps. However there’s no need to deprive yourself completely if you love these foods. Our health is a product of the things we eat often, not every once in a while.

Smoking cigarettes

This inflammation-promoting habit can have a big impact on your cycle. One study showed women who smoked 10-30 cigarettes a day were nearly twice as likely to have painful periods compared to women who never smoked [15]. Another found women who smoked 10 or more cigarettes a day were also significantly more likely to have irregular periods [16].


Caffeine is considered a vasoconstrictor, which means it narrows blood vessels so less blood and oxygen can flow through—precisely what happens in the uterus to cause period cramps [17]. Studies show the higher one’s caffeine’s intake (especially from coffee), the more intense or frequent their cramps [18, 19], and the higher their risk of irregular cycles and PMS [20].

Some medication

While there hasn’t been much research on the relationship between specific medications and period pain, many medications are well-documented vasoconstrictors that may put users at risk of worsened cramps [21]. Common ones include adderall, Sudafed, asthma inhalers, and migraine or headache medications, but there are hundreds of vasoconstricting drugs. Always ask your doctor or pharmacist about all the side effects of any new medication.

Not enough sleep

The sleep cycle regulates the secretion of various hormones, including ones that influence your menstrual cycle. Mounting evidence shows too little sleep can have major implications for your period [22]. One large study found girls were significantly more likely to have severe period cramps if they slept less than 6 hours a day [23]. Another found that women working the nightshift had more irregular periods—that stayed irregular for years [24].

What can help with period cramps

Our top recommendation for how to help with period cramps is Cramp Aid—our fast-acting, use-as-needed supplement for period pain. We formulated it by obsessing over all the best studies of nutrients and herbs for period cramp relief, meticulously choosing the safest, most effective ingredients, and putting them (in amounts that matter!) into rapid-release liquid capsules.

In our survey of 140+ random Cramp Aid users, 92% reported finding relief—83% within one hour of taking one dose! That’s about as effective as a typical over-the-counter painkiller [25], minus any scary safety warnings from the FDA.


Other natural, evidence-based ways to help with period cramps include:


One team of researchers reviewed 5 studies involving a total of over 500 women, and found light exercises like stretching and yoga were associated with a large reduction in period pain—even better than that of painkiller drugs [26]. But not all studies show a strong connection between period cramps and exercise [27].


Heat helps with period cramps because it soothes uterine muscles, preventing them from contracting too tightly. But research shows period pain reduction from heat pads or wraps is moderate at best, and less powerful than painkillers or exercise [26]. While consistently good at dulling cramps, heat can’t prevent prostaglandins from forming in the first place, like ginger or zinc, for example, have been shown to do [28].

Healthy foods

Check out our definitive guide to foods that balance hormones. The foods on this list help reduce inflammation and improve overall menstrual health.

Additionally, one study found that women who ate fish, eggs, and fruit often were less likely to get period cramps [29]. Another study found that high-fiber foods like whole grains, beans, and legumes have also been associated with less period pain [30]. And while dairy gets a bad rap, research shows women who eat 3-4 servings of dairy each day are significantly less likely to have painful periods compared to women who didn’t eat dairy [31]—potentially because dairy foods are rich sources of calcium, a key menstrual health nutrient found in our Steady Mood formula.


This information is for educational purposes only. It is not a substitute for professional medical advice, and is not intended to diagnose, treat, cure, or prevent any condition.


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