After doing further research on this claim, I do find it to be misleading. While it is true that bananas do contain magnesium, a substance known to regulate diverse biochemical reactions in the body, I found a lack of evidence supporting that they reduce the reaction of period cramps.
The link in the original claim was written on the Flo app, an app many women use to track their hormonal cycle. While the article does do a great job on informing women what foods to assist their period cramps, it lacks mentioning the sources of food with the highest content of magnesium. The National Institutes of Health mention that the average banana contains 32 grams of magnesium. It also states that roasted pumpkin seeds are the richest in magnesium, containing 156 grams per one ounce. Following that is chia seeds, with 111 grams of magnesium per one ounce. To me, this just makes the Flo article not seem as credible because if they're trying to advertise foods with high magnesium, and not mention the richest magnesium foods, then what else are they not mentioning?
Probably how period cramps are even created. Period cramps are caused when mass amounts of prostaglandins, an inflammatory chemical, are released into the uterus. The uterus muscles then contract, resulting in a painful sensation for the host. Magnesium comes into play here as it helps relax the muscles of your body. Yet, there is no studies or arcuate evidence that states that bananas reduce the reaction of period cramps all together. In fact, OBGYN Dr. Salena Zanotti states that some claim it does very little, but most say it does nothing at all (Cleveland Clinic).
I was a little disappointed to hear that bananas don't really do much for period cramps, as I know a lot of women who experience mounds of pain due to their period. However, I find this claim to be an exaggeration, and only true to a very little extent.