Women are somewhat protected from developing heart disease – until we hit menopause, that is.
Many cardiologists believe that the hormone estrogen is women’s secret cardioprotective weapon, until our production of estrogen tapers off and our heart attack rates rise dramatically at menopause to surpass men’s rates. That’s an increasingly controversial theory, however.
Researchers from Finland, for example, now question this estrogen theory in light of a remarkable study that appears to link iron depletion with protection of heart health. This hypothesis has actually been kicked around by scientists since 1981, when they first observed that the lower rate of heart attacks in menstruating women was associated with relatively low levels of stored iron.
Study participants in Finland who typically ate iron-rich foods face a higher likelihood of heart attack than did those who had an iron-poor diet, Finland’s Dr. Jukka T. Salonen of the University of Kuopio says. Red meats are rich in both iron and saturated fats.
Participants with high concentrations of ferritin in their blood (more than 200 micrograms per litre) were twice as likely to suffer a heart attack as those with lower ferritin values.
Ferritin is a molecule that stores iron in the blood and other parts of the body. The researchers found that every 1% increase in blood ferritin was associated with >4% rise in the risk of heart attack. American researchers at the University of Minnesota found similar results when high levels of ferritin were detected in all severely diseased heart muscle cells they studied.
Dr. Salonen proposed that, although people do need a trace amount of iron in their diets to remain healthy, too much iron can promote the formation of free radicals. Free radicals can injure the cells lining our artery walls, damage heart muscle, and may also lead to the formation of oxidized LDL (bad) cholesterol in the blood. Scientists believe that oxidized LDL cholesterol is more likely than non-oxidized LDL to stick to artery walls and thus trigger the buildup of the fatty plaque. This can lead to heart attack, and is considered a more significant risk factor for coronary disease than total blood cholesterol levels.
Results from this Finnish study also made sense to Dr. Jerome Sullivan of the University of South Carolina. He claims:
“When I saw those results for iron acquisition in men and women, I really had a ‘eureka’ moment. Men build up their iron stores steadily, while women don’t start accumulating iron until menopause.”
Sullivan joins others in the medical community who now believe that younger women may be relatively shielded from heart disease not from estrogen, but because we lose iron every month during menstruation. Typical menstrual blood loss amounts to 30-60 ml per month, a loss of about 360 mg of iron per year.
When menstrual iron loss stops for any reason (such as menopause), there seems to be a resulting increase in our heart disease rate. Men, of course, lack this menstrual iron leak. By age 45, men have roughly four times more iron stores than women. But after menopause, the stored iron in a woman’s body builds up rapidly – and women’s heart health advantage disappears as our iron depletion goes away.
In Canada, approximately 20% of women, 50% of pregnant women, but only 3% of men are iron deficient.
This iron theory helps to explain why aspirin and fish oil might also protect people from heart attacks, Dr. Sullivan adds. Both substances may increase chronic blood loss through minor bleeding and subsequent loss of iron. Protective effects of iron depletion, in fact, is also thought to be involved in the low heart disease rates among populations in many poorer countries.
“In these populations, the rise in stored iron is blunted by high-fibre diets that retard absorption of iron, and by common parasites that cause chronic minor blood loss”.
Dr. Sullivan now believes that our present epidemic of heart attack in developed countries like the U.S. and Canada may be due to our improved iron stores, caused by advances in modern public sanitation that protects us from those iron-wasting gastrointestinal parasites, and of course our high consumption of red meat.
The Finland study findings, if confirmed, could force public health experts to rethink our dietary recommendations for iron. Even normal levels of stored iron may prove damaging, Dr. Sullivan says.
“Over-the-counter vitamin supplements often contain iron, as do some enriched foods such as cereals.”
Not everybody agrees with the Finns, however. Other studies have not confirmed the association between total iron intake (from diet alone or diet plus supplements) and coronary risk. In only three of 22 subsequent studies was a statistically significant association found in the sample overall. Two of those studies reported a significant association in smokers only, and another in women but not in men.
And physician Dr. W. Gifford Jones of Toronto (coincidentally, a controversial voice I’ve written about here) claims that the ferritin levels of people living in East Finland happen to be much higher than those of North Americans. He says:
“Our levels of serum ferritin are in all probability not high enough here to trigger heart problems.”
Are there any recommendations for those of us who are worried about the possible iron-heart disease connection? According to Dr. Sullivan:
“Adults should avoid iron supplements unless they have iron-deficiency anemia, a very serious condition which can actually damage the heart. And I think people should also consider blood donation!”
© Carolyn Thomas www.myheartsisters.org
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