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by Dr. Daniel J. Heller
Nonheme iron is linked to reduced risk of PMS, says study.
Leafy green vegetables, fruits, beans, and nuts top many lists of the healthiest foods, and they’re all rich vegetarian sources of iron. But until recently, no one had ever proposed iron as a remedy, or important nutrient, for PMS or PMDD. So we were interested when a recent study published in the American Journal of Epidemiology concluded that women who consume 20 mg or more of iron per day are less likely to develop and suffer from premenstrual symptoms.
Study Details Three thousand nurses were followed in this study, over a decade-long period. At the beginning of the study, none of them had premenstrual symptoms. At the end of the 10-year study period, one-third of the women had been diagnosed with PMS.
The researchers, from Harvard and University of Massachusetts at Amherst, analyzed the women’s diets and found that that those who consumed higher amounts of vegetarian (non-heme) iron from their diet and supplements were up to 40% less likely to develop PMS. It's worth noting that the daily recommended amount of iron for women is 18 mg.
Analysis While you may be inclined—especially if you are concerned about PMS or PMDD symptoms—to rush out to the grocery store or the health food store to pick up ground beef, spinach, and an iron supplement, there are several factors to consider regarding this study. One is that the most common source of iron in most people’s diet—meat and animal foods—had no relationship to PMS symptoms. That is, it didn’t make PMS or PMDD more or less likely.
There is also the problem, which is nearly impossible to purge from dietary studies, that studies like this can prove only correlation, not causation. What this means is that there is some relationship between these factors, but this study doesn’t tell us if it is a cause and effect relationship. In other words, it might be a coincidence.
A famous example of a medical study that showed correlation was one that determined that the more TVs there were in a household, the less likely the inhabitants were to have heart disease. Of course, TV ownership and TV watching don’t decrease heart disease. But the more affluent a household is, the more TVs they will have. Such a study, conducted in the current era, might find that these households have more computers and tablets and smart phones. And the more affluent people are, the more likely they are to get regular medical care, to be able to afford medication, to have a gym membership and to buy healthy food, and so forth. So, correlation is not causation. We don’t know whether iron has anything to do with PMS or PMDD.
Then there is the fact that this study was the first of its kind: in other words, there is no other research and no convincing basic science evidence indicating a link between iron status and PMS symptoms. Yes, it’s possible that vegetarian iron-rich foods can help lower the risk of developing PMS. But without additional studies, it would be a mistake to conclude that there is any relationship between iron, iron supplements, iron-rich vegetarian foods, and PMS symptoms.
Unfortunately, the authors of the study didn’t attempt to discern whether the benefit they attributed to iron was in fact a benefit of eating more fruits and vegetables, which seems like a logical question to ask. Of course, it’s not uncommon for flawed or very partial studies to be trumpeted in media reports as evidence of scientific certainty (something which, you may have noticed, is quite rare). This is yet another example where it’s very hard for you, the average consumer of food, supplements, and health information in the media, to decide whether a study and a headline have any valuable information to offer.
The bottom line is that eating vegetables, nuts, and fruits makes common sense for your health, and it may well prevent or improve PMS and PMDD symptoms, especially compared to a junk food diet. But, it is unlikely to be a cure, and in the end, this study—despite media reports—proves nothing.
by PMS Comfort
by Dr. Daniel J. Heller