The suggestion came after scientists established that one person in 10 has double the risk of such conditions thanks to a faulty gene that interferes with the body's ability to regulate iron levels.

Meat is a prime source of iron

They had previously thought the risk factor - caused by a mutated gene - only applied to one person in every 250.

Pairs of the mutated gene can prevent the body processing iron correctly in a condition known as haemochromatosis.

But now doctors have found that even with only one copy of the gene - which a tenth of the population has - the risk of the condition is doubled.

Donating blood could reduce iron levels and so reduce the risk of disease, they said.

Double investigation

Two teams of scientists have been studying the condition, and they published their findings in the medical journal Circulation.

Both discovered that a much greater proportion of the population was at risk from the haemochromatosis gene than had previously been thought.

The condition can lead to people having far too much iron in their blood's haemoglobin - most people have two to four grams of but those with haemochromatosis may accumulate 20 grams or more.

It is not easy to spot the condition because it has no real symptoms, although in some cases the patient's skin will turn rusty orange.

It can prove fatal in itself since severe iron overload can lead to cirrhosis of the liver, liver cancer, heart failure and diabetes.

Risk levels shoot up

Dr Mark Roest and colleagues at Utrecht University Medical School in the Netherlands studied 12,239 middle-aged women and found that carriers of one copy of the gene had double the risk of dying from a heart attack or stroke.

Those who had the gene and two other risk factors - smoking and high blood pressure - were 19 times more likely to die from these causes.

"This is the first large study to find a significant association between women who are carriers of the gene and cardiovascular disease," Dr Roest said.

The study also supported the theory that women before their menopause are protected from heart disease because they lose iron during menstruation.

The effect on men

The other team, from the University of Kuopio in Finland, had earlier discovered that people who donated blood were less likely to suffer a heart attack.

They checked for the haemochromatosis gene in 1,150 men.

"Carriers of the gene have more than twice the risk for a heart attack compared to non-carriers," Dr Jukka Salonen and colleagues said.