WASHINGTON – Japanese researchers said Wednesday they may have figured out why high iron levels in the blood are linked with heart disease, and it may all boil down to rust.
They found evidence that iron can increase so-called oxidative stress on the lining of blood vessels.
Oxidation is the same process that causes standard iron to rust.
This could mean that the Western diet, rich in red meat, causes heart disease not only because it has so much fat but because it is too rich in iron, said Hidehiro Matsuoka, chief of the hypertension division at Kurume Medical School in Kurume, Fukuoka Prefecture.
“There have been a number of studies that suggest iron stores are closely linked to the incidence of (heart attacks) and coronary artery disease,” Matsuoka, who led the research, said in an interview.
For instance, men who regularly donate blood have a lower risk of heart disease, and premenopausal women, who regularly lose blood, and thus iron, through menstruation, also have a lower risk of heart disease.
“Many scientists attribute the significantly low risk of cardiovascular disease among premenopausal women to the protective effects of estrogen,” Matsuoka said.
“But the hypothesis has been raised that the iron depletion associated with menstruation also protects against heart disease,” he added.
And biochemical studies have shown that iron helps generate free radicals — the little charged particles that can cause damage to cells in the body.
Reporting to a conference of the American Heart Association’s Council for High Blood Pressure Research, Matsuoka said his team decided to see if they could link these two sets of findings.
They looked at iron’s effects on the endothelium — the layer of cells that lines blood vessels and which is intimately linked with heart and artery disease.
In the first study of 10 healthy men, they overloaded them with iron intravenously and then looked at their blood vessels using ultrasound.
The iron overload raised levels of the chemical malondialdehyde, a marker of oxidation and of impaired endothelial function.
Then they used a drug to lower iron levels in 10 healthy male smokers, and found iron removal lowered levels of the chemical and made the endothelium work better.
According to the American Heart Association, the Japanese study is the first to show that iron loading hurts the lining of the blood vessels.
“Our study shows that we should recognize iron as a risk factor for atherosclerosis and understand the need to control our body iron levels to prevent cardiovascular disease,” Matsuoka said in a statement.
He said he believes that iron somehow interferes with nitric oxide, a chemical that relaxes blood vessel walls, allowing the blood to flow more freely.
He believes doctors should measure endothelial function as part of a standard physical exam, just as blood pressure is now measured.
The test is simple and uses harmless ultrasound, Matsuoka said.
“It only takes 30 minutes,” he said.
He also noted that kidney dialysis patients, because they are anemic, often get intravenous iron, and that they also have very high rates of heart disease.
It could be that giving iron intravenously stresses the arteries.
Taking iron orally is safer, Matsuoka said, and kidney dialysis patients should be aware of the danger.
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