Iron 'rusts' up blood vessels

Kidney dialysis patients might at risk

Scientists believe they have worked out why high iron levels are linked to heart disease - the answer is rust.

A team from Kurume Medical School in Japan has found evidence that iron can increase so-called oxidative stress on the lining of the blood vessels.

Oxidation is the same process seen in iron outside the body when it rusts.

The finding could mean that patients who are given intravenous supplies of iron might be put at risk of heart disease.

Lead researcher Dr Hidehiro Matsuoka said 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.

Our study shows that we should recognise iron as a risk factor for atherosclerosis and understand the need to control our body iron levels to prevent cardiovascular disease

Dr Hidehiro Matsuoka, Kurume Medical School

There have been a number of studies that suggest iron stores are closely linked to the incidence of heart attack and coronary artery disease.

For instance, men who regularly donate blood and pre-menopausal women, who regularly lose blood, and thus iron, through menstruation, have a lower risk of heart disease.

Dr Matsuoka's team studied 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 one study of 10 healthy men, they overloaded them with iron intravenously and then looked at their blood vessels using ultrasound.

Chemical marker

The iron overload raised levels of the chemical malondialdehyde.

This is a tell-tale sign of oxidation and of impaired endothelial function.

The researchers then 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.

Dr Matsuoka said: "Our study shows that we should recognise iron as a risk factor for atherosclerosis and understand the need to control our body iron levels to prevent cardiovascular disease."

His theory is that iron somehow interferes with nitric oxide, a chemical that relaxes blood vessel walls, allowing the blood to flow more freely.

He believes that doctors should measure endothelial function as part of a standard physical exam, just as blood pressure is now measured.

Dr Matsuoka also noted that kidney dialysis patients, because they are anaemic, 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.

A spokeswoman for the British Heart Foundation said: "The idea of a link between iron levels and heart disease has been touted for over a decade.

"However, most studies have failed to prove that excess iron in the blood can lead to a greater risk of coronary heart disease.

"This Japanese study proposes some interesting ideas.

"However, further research is clearly important to discover the role iron plays."

Dr Matsuoka was speaking at a conference of the American Heart Association's Council for High Blood Pressure Research.