Researchers in Germany have found that a daily cup of black tea can help stop excess iron damaging the bodies of people who suffer from haemochromatosis.

It is estimated that around 1.5m Americans suffer from the disease, which is thought to be passed on through the genes.

The US Centers for Disease Control calls it by far the most common genetic disease in the USA.

One in nine people is a carrier while one in 300 is affected.

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

It is also linked to impotence and arthritis.

The disorder is also thought to be common in Britain.

Regular operations

The researchers tested 18 haemochromatosis patients over a year.

The patients were divided into two groups. One was given black tea to drink with their meals and the other was given other drinks.

An overload of iron in the blood can be fatal

Tannin, the drug contained in tea, is known to stop iron being absorbed into the body.

People with haemochromatosis or other iron overload syndromes such as refractory anaemia currently have to undergo regular operations to bleed off excess iron.

But the researchers say these are "rather cumbersome and invasive".

A short-term solution is to reduce iron intake, but it is not possible to live without iron for a long period.

Writing in Gut magazine, published by the British Medical Journal, the researchers said they found that drinking black tea reduced excess iron by a third.

Joint pain

They say the reduction was much smaller over time than had been expected from experiments on single doses of tea.

They believe that drinking black tea daily alone will not solve the problem of iron build-up.

But they say it could be used as "an additional therapeutic tool" for the maintenance of normal iron levels.

And it should mean that fewer bleeding operations will be required by patients.

The average age at which patients show signs of haemochromatosis is between 40 and 60.

Early symptoms include joint pain, impotence and abnormal or no periods.