A common preservative found in soft drinks has the ability to switch off vital parts of DNA, a new study has said.

The problem -- more usually associated with ageing and alcohol abuse -- can eventually lead to cirrhosis of the liver and degenerative diseases such as Parkinson's, Peter Piper, a professor of molecular biology and biotechnology at the University of Sheffield, has found.

The findings could have serious consequences for the hundreds of millions of people worldwide who consume fizzy drinks. They will also intensify the controversy about food additives, which have been linked to hyperactivity in children, The Independent newspaper has reported.

Sodium benzoate has been used in large quantities to prevent mould in soft drinks. It is also added to pickles and sauces.

Sodium benzoate has already been the subject of concern about cancer because when mixed with the additive vitamin C in soft drinks, it causes benzene, a carcinogenic substance.

A Food Standards Agency survey of benzene in drinks last year found high levels in four brands which were removed from sale.

Piper found that benzoate was damaging an important area of DNA in the "power station" of cells known as the mitochondria.

"These chemicals have the ability to cause severe damage to DNA in the mitochondria to the point that they totally inactivate it: they knock it out altogether," he said.

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