Nearly every woman dreads that time of the month, just before her period, when her insides cramp up, her head hurts, and the smallest misstep can incite anger or tears. Studies have shown that calcium supplements can sometimes make PMS symptoms go away quicker, but researchers from the University of Massachusetts, Harvard University, and the University of Iowa looked to see if calcium and vitamin D might stop PMS altogether.

What the researchers wanted to know: Do calcium and vitamin D prevent PMS?

What they did: Women who were enrolled in the Nurse's Health Study II, a large study of female registered nurses that has been going on since 1989, were eligible for this study. These women periodically completed food surveys that asked, in addition to other things, how often they ate calcium-rich foods like spinach and dairy, and how often they took calcium or vitamin D supplements. The researchers mailed some of the women a two-page questionnaire asking whether they had PMS symptoms. After they got the questionnaires back, they looked at the dietary habits of the 1,057 women who reported symptoms and the 1,068 who did not.

What they found: Women who had more vitamin D and calcium in their diets had less of a risk of PMS than other women. Women who got the vitamin D equivalent of at least seven cups of milk (nearly twice the recommended daily allowance) were 40 percent less likely to have symptoms of PMS than women who got the vitamin D equivalent of one cup of milk or less each day. Similarly, women who got the amount of calcium from food that was equal to at least 4 1/2 cups of milk (about 1 1/2 times the recommended daily allowance) were 30 percent less likely to suffer from PMS than women who took in less than half a cup of milk (or that equivalent in calcium) per day. Calcium intake from supplements was not associated with the risk of having PMS symptoms, though there may have been too few people in this group to adequately evaluate that risk.

What it means to you: When it's that time of the month, drink your milk, eat your spinach, and pack a yogurt in your lunch. Eating foods rich in calcium and vitamin D could help prevent PMS. Researchers say they're not sure exactly why, but it probably has something to do with how those nutrients fluctuate with changing levels of hormones. While there's no guarantee that you're not going to need a hot water bottle, some ibuprofen, or a bar of chocolate, drinking milk could help keep those monthly pains away.

Caveats: This study relied completely on women's self-reporting of their PMS symptoms and food intake habits. They asked the women to think back over several years; it's likely that some of the women did not remember accurately. But there's no reason to think that the women in either group would be less likely to remember than the other.

Find out more: The National Women's Health Information Center has a web page with frequently asked questions about PMS.

The American Academy of Family Physicians has a page with tips on how to control PMS.

Not everyone wants to reduce PMS episodes. This blogger celebrates that special time of the month: writingasjoe.blogspot.com

Read the article: Bertone-Johnson, E.R. et al. "Calcium and Vitamin D Intake and Risk of Incident Premenstrual Syndrome." Archives of Internal Medicine. June 12, 2005, Vol. 165, No. 11, pp. 1246-1252.

Abstract online: http://archinte.ama-assn.org