Oct. 25, 2000 (Washington) -- As the level of iron goes up in your bloodstream, so apparently does your risk for heart attack and stroke. A new study by Japanese researchers shows that high-level iron injections can cause almost immediate constriction of blood vessels. In fact, the scientists believe the iron damage could be the first step in a cascade of events leading to the thickening and hardening of the arteries known as atherosclerosis.
"Our study shows that we should recognize iron as a risk factor," says Hidehiro Matsuoka, MD, PhD, lead researcher and chief of the Kurume University School of Medicine's hypertension program. The cardiologist presented his findings Wednesday at the 54th Annual Fall Conference of the American Heart Association's Council for High Blood Pressure Research.
The debate over iron's effect on heart disease has preoccupied doctors for years. A number of studies have suggested a link. Those who suffer from abnormally high levels of iron in the blood are believed to have an elevated risk for heart problems. But people who donate blood, depleting their iron levels in the process, may be less prone to heart attack.
However, the Japanese study apparently is the first to show that deliberately increasing a person's iron interferes with the lining of the blood vessels, called the endothelium. After giving 10 healthy young men a megadose of iron, the researchers used high-resolution ultrasonography to measure any impact on blood flow.
According to Matsuoka, the normal blood vessel dilation was reduced by as much as one-third by the experiment. It's not clear what causes the change, but it could be that the iron generates oxygen free radicals, which have been linked to both cancer and heart disease.
"Iron loading impairs endothelial function, mostly due to oxidative stress," Matsuoka tells WebMD. He says the change in vessel dilation can be detected in as little as 30 minutes during a physical exam.
To test his claims further, Matsuoka studied the effects of reducing iron levels. He gave healthy smokers a chemical used to remove heavy metals from the blood. Smoking, as well as high blood pressure and age, can increase free-radical damage. The smokers experienced about a 30% drop in blood iron following the treatment, and their blood vessels began working normally.
It may be that premenopausal women are less likely to get heart disease because of the iron depleted during menstruation. This may be more important than estrogen's protective effect, especially since a major study showed no benefit from the hormone when given to postmenopausal women.
For Matsuoka, the main message is to control your consumption of iron, particularly from red meat, and that should have some protective effect. Taking iron in the short term is not the major issue, but over the long haul, the nutrient can chip away at the body's ability to circulate life-giving blood.