In one study, researchers studied the diet of more than 3,000 women over 10 years and found that those who consumed 1,200 milligrams of calcium and 400 IU of vitamin D a day through food had up to a 40 percent less chance of experiencing PMS. And it appears that choosing the low-fat versions of high-calcium foods made a difference. Women who drank 2 per­cent milk or lower had fewer symptoms than women who drank whole milk.

This study didn’t find a benefit from calcium supplements, but another study by researchers at Columbia University in New York City did. They found that women who supplemented 1,200 milligrams of calcium a day reported a 48 percent decline in PMS symptoms.

It isn’t clear exactly why calcium relieves PMS, but researchers suspect that it eases the muscular contractions that lead to cramping.

And those aren’t the only studies to find a connection between cal­cium and PMS. A small study at the USDA Grand Forks Human Nutri­tion Research Center in North Dakota found an intriguing connection between a diet low in both calcium and the trace mineral manganese and PMS. Women who experienced PMS on a low-calcium, low-manganese diet had fewer symptoms when their diet was supplemented with the two minerals.

What’s interesting is that the diet that produced the worst premenstrual symptoms is actually closest to the way most American women eat. Studies show that most women get about 587 milligrams of calcium a day, nowhere near the 1,000 milligrams they’re supposed to get to build healthy bones and prevent osteoporosis.