Common preservative sodium benzoate, widely used in soft drinks and other foods, is again at the centre of health concerns after research emerged linking it to cell damage.
News of the research, conducted by professor Peter Piper at the University of Sheffield, prompted prominent UK politician Norman Baker to call for an immediate inquiry into the safety of sodium benzoate in foods.
Professor Piper's research, which suggests that benzoate contributes to faster ageing and degenerative diseases such as Parkinson's, increases the pressure on soft drinks makers to find alternative ways to preserve their products.
But Richard Laming, of the British Soft Drinks Association, defended the industry's continued use of sodium benzoate. "It is approved for use by the Food Standards Agency and we follow the guidance of the regulatory authorities."
He said sodium benzoate was the "most effective preservative currently authorised". It is used widely in soft drinks and was included in 44 new food and drink products across the UK over the last year, according to data from Mintel's Global New Product Database.
Yet it is the third time in around 12 months that sodium benzoate, also known as E211 in the EU, has been publicly linked with health concerns.
Last year, an investigation by BeverageDaily.com revealed soft drinks industry leaders had known the preservative may break down to form benzene, a potentially cancerous chemical, in drinks also containing ascorbic acid (vitamin C) or citric acid.
And more recently, sodium benzoate was one of seven 'E-numbers' again linked to behavioural problems in children.
"We are feeding very large amounts of preservatives like this to children. Is this a completely safe practice? I think the question has to be put there," said Professor Piper, in an interview with BeverageDaily.
He said some children's livers were "working overtime" to process the amount of sodium benzoate entering their bodies.
Piper, an expert in molecular biology and biotechnology, tested benzoate on yeast cells in his lab. He found the preservative spurred an increase in production of oxygen radicals, or free radicals, which several studies have linked to serious illnesses and ageing in general.
In his study, first completed in 1999, benzoate appeared to attack the 'power station' of the cells, known as the mitochondria. It damaged the cells' ability to prevent the oxygen leaks that create free radicals. Too much alcohol is thought to inflict similar damage.
Yeast cells were used because of their similarity to human ones, but no research on humans has been done.
"I suspect that it does not increase production of free radicals so that levels are going up dramatically. And the body has very successful systems for mopping up 99 per cent free radicals."
"But it is that one per cent that could be the problem. Over the longer term, this is a major component of why we age and why we progressively lose function."
Professor Piper called for new safety tests on sodium benzoate taking into account a growing body of science on free radicals.
And he advised soft drinks firms to put more resources into alternative preservation methods. "I understand industry concerns about shelf life, but they have to ask - is this [sodium benzoate] completely necessary?"
The UK Food Standards Agency (FSA) reviewed professor Piper's original 1999 study but found its relevance to humans was "unclear".
Richard Laming, of the British Soft Drinks Association, said: "The FSA has assured us that the apparent concerns regarding sodium benzoate have already been investigated and it sees no reason to change its view that sodium benzoate is safe."
Most major supermarkets, including Asda, Sainsbury's and Tesco, will remove artificial additives from their private label soft drinks by this summer. Their actions reflect a general drift towards natural ingredients in the soft drinks industry.
New industry guidance on benzene in drinks, published last summer, asks firms to consider removing sodium benzoate from products where possible.
Laming said decisions to remove sodium benzoate stemmed from consumer demand for products without the preservative, as well as other artificial additives, and not from any safety concerns.