Does giving blood reduce your chances of getting heart disease?
Our building is having a blood drive, and I noticed the following on the promotional materials left in our office: "Donating blood is a health benefit for all men, and women over 50, by removing excess iron from the blood. Studies show that excess iron can damage cells in the arteries which can cause the growth of plaque and cause harm to the heart." I know women under 50 are premenopausal and lose some blood naturally. Am I to believe that a regular schedule of bleeding is good for what ails you? This smacks of the days when leeches were used to cure illness. Please set the record straight!
I agree, the bloodletting angle is pretty medieval. Next thing you know they'll be handing oujt homeopathic pills. Besides, the "iron hypothesis" is far from proven. Right now the only sure benefits for blood donors are the cursory physical exam, free doughnuts, and the warm glow of having done a good deed.
The iron hypothesis arose from the observation that premenopausal women have a much lower incidence of heart disease than men but that after menopause the difference narrows dramatically. Originally it was thought this had something to do with sex hormones. However, men given estrogen suffer more heart disease than normal, and women who stop menstruating due to surgery but still have estrogen-producing ovaries suffer increased heart problems nonetheless.
In 1981, trying to make sense out of this, pathologist Jerome Sullivan proposed an alternative explanation: "The greater incidence of heart diseases in men and postmenopausal women is due to higher levels of stored iron in these two groups." Evidence: (1) diseases that cause iron buildup often result in heart failure; (2) the older a man gets, the more iron he accumulates; (3) after menopause, stored iron in women rises to the level found in men; and (4) the types of heart disease found in affluent countries are rare among impoverished peoples with iron-deficient diets. Sullivan's recommended treatment: "regular phlebotomy," medicalese for having someone extract your blood.
Some later research supported Sullivan's theory. The most recent study I've seen, published in Heart by David G. Meyers et al, examined 3,900 male participants in the Nebraska Diet Heart Study and found that nonsmokers who had donated blood in the past three years had a 30 percent lower risk of major heart problems. (Curiously, donating multiple times during the three years, as opposed to once or twice, brought no additional benefit.) Other researchers conjectured that iron interacts with LDL (bad) cholesterol to promote atherosclerosis, and there's a lot of stuff about free radicals and so on that I don't have the heart to explain.
Obviously all of this was good news for blood banks. When a story about Sullivan and his hypothesis appeared in a newspaper in Melbourne, Australia, local blood donations reportedly doubled the following week.
To their credit, few blood centers, with the evident exception of the place you dealt with, have made a big deal out of the possible health benefits of blood donation — mostly because those benefits may prove to be illusory. Critics of the Meyers study point out that the donors and nondonors weren't evenly matched in terms of their health-risk characteristics — the donors, you won't be surprised to learn, tended to lead healthier lives. Once risk-factor differences were corrected for, the apparent benefit of blood donation largely disappeared. The iron hypothesis isn't completely out the window, but the evidence that donating blood will protect you from heart disease seems pretty scant right now.
But let's not give up on bloodletting too quickly. For a few conditions it remains the treatment of choice. For example, in congenital hemochromatosis, an ailment that usually doesn't surface until you're in your 30s, toxic levels of iron build up in your tissue, eventually leading to heart failure. The treatment is to have blood drawn periodically to keep iron levels under control. An equally serious disease is polycythemia vera, in which your red-blood-cell count is too high and your blood gets "sludgy," as one of my informants puts it, possibly leading to leukemia or other bone marrow diseases. Bloodletting helps keep the cell count down, so the practice isn't always as barbaric as it seems. But unless you suffer from an exotic disease, chances are it won't help you to be a quart low.