Donate Blood, Be Healthier? : Studies suggest phlebotomy cuts the risk of heart disease. But some experts say it isn’t so.
Dr. David Meyers is not being entirely altruistic when he donates blood a couple times a year. He hopes that he is also helping himself.
An internal medicine specialist at the University of Kansas Medical Center, he is among a small and possibly growing number of researchers and others who believe that giving blood may prevent or delay heart disease in men and perhaps post-menopausal women.
That rather bizarre idea has sparked controversy ever since a Florida physician-researcher proposed it 16 years ago. What makes the idea seem even more unlikely is the reasoning behind it, which holds that the goal of unloading blood is to rid the body of excess iron, an essential nutrient that few people think of as potentially harmful, never mind over-abundant.
Within the medical community, reaction to the “iron hypothesis,” as researchers call it, has tended to be sharply negative from the beginning. But two new studies, by Meyers’ team and by researchers at the University of Kuopio in Finland, suggest that the ancient practice of phlebotomy may help some people lower the risk of contracting the leading cause of death.
The studies, which involved more than 6,500 people and were published in reputable journals, found that heart attacks and other cardiac problems were less common among men who had donated blood compared to men who did not.
While scientists debate the evidence and await definitive evidence, health-conscious people cannot be blamed for wondering: Should they donate blood in an attempt to lower their heart disease risk?
Some researchers say no, arguing that it would engender false hope, distract from established preventive measures, and perhaps threaten the safety of the blood supply
by encouraging people who are not supposed to donate blood, such as those with infectious diseases, to do so anyway.
“There is nothing to this iron thing except some fairly extreme conjectures,” said Dr. William Weintraub, a cardiologist and researcher at Emory University in Atlanta, who evaluated the evidence last year in the Journal of Clinical Epidemiology. “I would hate to think that anybody would go out and get themselves bled in order to prevent heart disease.”
Proponents counter with a point that seems unique in the long and checkered history of unproven self-help techniques. Granted, they say, it is not known if occasionally yielding a pint to a blood bank staves off heart disease, but it does no harm to a healthy donor--and surely helps society at large by making more blood available to patients who desperately need it.
“Even if we are not correct” about blood donation protecting the heart, Meyers said, “it still has been the right thing to do. That very much influences the argument.”
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The impetus for this now-notorious idea was that men and women differ significantly both in their heart attack risks and body iron levels. A man typically builds up iron from food beginning in his teens--and his heart attack risk goes up steadily at the same time. In contrast, a woman loses enough iron through menstruation to keep her overall iron level low until menopause, which is precisely when her heart attack risk starts rising dramatically. An adult male has about 4 grams of iron in his body; an adult female, about 2.5.
Generally, for Americans 29 to 44, heart attacks are roughly 40 times more common among men than women, according to the American Heart Assn. But by their 70s men and women have roughly the same risk.
Seizing on such observations, Dr. Jerome Sullivan suggested in the medical journal the Lancet in 1981 that iron may play a key role in heart disease and, if so, that donating blood could be a “preventive therapy” for “men and post-menopausal women.”
Since then, he has been dismissed as a member of the wacko fringe, despite his PhD (Florida State) and M.D. (University of Florida).
Scientists have attacked the idea as absurd, saying that the supposed link between iron levels and heart disease risk is mere coincidence. Some studies have generated data that argue against such a link. And researchers have expressed horror that today’s high-tech medicine would hark back to the Dark Ages when bloodletting was a cure-all.
“It has been extremely frustrating,” said Sullivan, who is preparing to open a private medical practice in the Orlando area after 13 years running the clinical pathology laboratory at a Veterans Affairs hospital in Charleston, S.C. “Some prominent scientists appear to be in denial about the meaning of the evidence.”
To be sure, no one doubts that very large excesses of iron can be harmful to body tissues. People with hemochromatosis--a genetic condition that makes patients accumulate far more than the usual amount of iron--can develop diabetes, cancer, liver failure and, yes, heart disease as a result of iron-ravaged organs. Also, laboratory experiments on human tissues in test tubes and on rodents have found that large amounts of iron can acutely damage living cells.
The focus of the current debate is whether iron reserves that are typical of healthy men and post-menopausal women promote heart disease. Sullivan, Meyers and other advocates of the iron hypothesis speculate that the physiological ideal is to have no iron reserves but rather just enough of the nutrient to function--the iron “status,” as doctors put it, of healthy young women.
They base that speculation largely on an analogy: Even young women who have an inherited disorder that makes their blood cholesterol skyrocket do not have heart attacks, whereas young men with the same condition do. “The young women are protected from the development of heart disease as long as they continue to lose excess iron through regular menstrual blood loss,” Sullivan wrote last year in a defense of his theory in the Journal of Clinical Epidemiology.
As for the critics, they say that women have less heart disease than men generally because the female hormone estrogen somehow protects them from coronary artery disease and other problems. Clear evidence for that, they add, are clinical studies showing that post-menopausal women who undergo hormone-replacement therapy have less heart disease than similar women who do not receive such therapy.
Christopher Sempos, a nutritional epidemiologist at the National Heart, Lung and Blood Institute, has reviewed virtually all the published studies addressing the iron-heart question.
“I don’t think there is a lot of sound evidence to recommend that people start donating blood to reduce their iron stores and their risk of heart disease,” he said.
Writing in Nutrition Reviews last year, Sempos and co-authors said that only one out of 12 studies that analyzed heart problems and indirect measures of body iron stores (including serum iron and the transport compound transferrin) clearly showed a correlation. And only one out of the six published studies that used the more direct measure of iron reserves known as ferritin correlated iron levels and heart disease. The “vast majority” of published results, the authors concluded, “have failed to support the original hypothesis.”
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Swimming against that tide are the two new blood donation studies. In the study of nearly 4,000 people by Meyers and his team, published in August in the journal Heart, found that heart attacks or other cardiac problems were roughly 30% less common among men who had donated blood at least once in the previous three years. Significantly, men who smoked did not appear to benefit from donating blood, and neither did the women subjects, presumably because their iron stores were lower to begin with.
In the Finland study, which involved 2,682 men and was published in March in the British Medical Journal, one of the 153 subjects who donated blood, or 0.7%, had a heart attack, compared to 226, or 9.8%, of those who did not donate blood. After adjusting for other factors like blood pressure and family history of heart disease, the researchers concluded that the “blood donors’ risk of myocardial infarction was 86% less than that of the nondonors.”
The study’s lead author, Dr. Jukka Salonen, said in an e-mail interview that he and his co-workers “have already repeated the finding based on three more follow-up years. . . . This is quite strong evidence in favor of a real association” between donating blood and having a lower heart-attack risk, he said.
Salonen presented an update of his study, which used a novel, presumably more accurate method for assessing body iron stores than used in previous studies, to an American Heart Assn. meeting in Orlando, Fla., last week. “We believe the current evidence . . . is strong enough to justify screening for high iron stores at least in high-risk persons,” he said in a statement.
For its part, the AHA says that “additional research is needed to prove iron’s role in heart disease before screening can be recommended.”
Medical researchers have criticized the Kansas and Finland studies as flawed and incomplete. For instance, said Dr. Ernest Beutler, a blood specialist and geneticist at the Scripps Research Institute in La Jolla, people who donate blood are generally healthier than people who do not, so it’s not surprising that donors tend to have fewer heart attacks. Similarly, people with preexisting heart disease are typically discouraged from giving blood for health reasons. “The data are not compelling,” he said of those studies.
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Both sides of the iron-heart debate say that the question will not be settled until researchers conduct a rigorous clinical trial in which they randomly divide a large number of otherwise healthy people into donors and nondonors; wait for years to go by and for substantial numbers to develop heart disease; and then analyze the data “blindly,” without knowing whether a person was a donor or nondonor.
Sullivan strongly cautions that anybody considering lowering body iron stores through blood donation should first consult a physician, to rule out medical conditions precluding donation such as heart arrhythmia and also to measure body iron stores.
Although the question of donating blood to avert heart disease remains unanswered and indeed highly controversial after all these years, it appears that mainstream medical authorities now view it as a question worth asking. Dr. Lawrence Friedman, director of epidemiology and clinical applications of the National Heart Lung and Blood Institute, said that the institute would consider sponsoring a controlled clinical study of blood donation and heart disease.
“We don’t know whether donating blood has health benefits,” he said. “We can’t imply that it does or doesn’t . . . until we have the results of a clinical trial.”
