Things may get more blurry if you have too many, but scientists say one drink of beer a day will help people's sight by preventing cataracts.

Beer, particularly ales and stouts, contain high levels of antioxidant chemicals, believed to cut the risk of heart disease.

Scientists in Canada carried out tests on rat lenses and found antioxidants, like those in beers, protected cells in the eye which, if damaged, lead to an increase in cataracts.

They recommend that one drink of beer a day is enough to offer protection.

Diabetics in particular could be helped by the finding.

Cataract causes

Scientists have identified that high glucose levels damage key elements of cells called the mitochondria.

These are mini-organs which are responsible for converting glucose into the energy needed by cells to function properly.

When the mitochondria found in the cells of the outer lens of eye are damaged in this way it can lead to the development of cataracts.

Dr John Trevithick, who presented the research to the International Chemical Conference of Pacific Basin Societies in Honolulu on Sunday, said the ingredients in the beer could help.

"Antioxidants protect the mitochondria against this damage. We think that may be one of the factors that's contributing to the lower risk of cataracts in people who have one drink a day."

In America, reducing by 50% the number of cataract operations could save $2bn a year.

Heart benefits

In a separate study, Pennsylvanian researchers are looking at how beer can halve the rates of arteriosclerosis - thickening of the arteries.

Professor Joe Vinson carried out the tests by giving hamsters the human equivalent of two beers a day.

He said other research had shown health benefits from antioxidants in wine and that the alcohol in beer and wine helped protect against heart disease.

But he said he believed his study was the first to show the antioxidants in beer also helped to protect against heart disease.

Antioxidants in tea and grape juice could also help reduce arteriosclerosis, he added.