Benzene: liquid supplements to be tested

By Jess Halliday

- Last updated on GMT

Related tags Dietary supplement Vitamin

Liquid dietary supplements that use the same preservative system as
some soft drinks could contain elevated levels of the carcinogen
benzene, according to Flora Research Laboratories, which has been
contracted to carry out tests.

Flora Research Laboratories (FRL) has been awarded a contract from the US National Institutes of Health's Office of Dietary Supplements to develop a new method of analysing benzene levels in consumer products. When the method is finalised, it will use it to evaluate benzene levels in liquid supplements.

In the last two months there has been much government concern and media coverage about benzene levels in soft drink products around the world, after it emerged that the FDA has re-opened a 15-year-old investigation into elevated benzene levels resulting from use of the preservative sodium benzoate.

The problem is caused when two common ingredients - sodium benzoate (a preservative) and ascorbic acid (vitamin C) - are used together. When placed in acidic conditions, sodium benzoate breaks down into benzoic acid.

This may result in benzene levels higher than the US and EU limits for drinking water.

Benzene is listed as a poisonous chemical shown to increase the risk of leukaemia and other cancers. But the soft drinks industry has said that it is a question of quality, not health, in drinks.

James Neal-Kababick, laboratory director at FRL and lead investigator in the project, told that several supplement products containing sodium benzoate and ascorbic acid have been found on shelves in the US, but that no analysis of these products is known to have taken place.

The combination is thought to be particularly common in liquid aloe vera and vitamin formulations, and FRL has been contacted by some companies that have expressed concern following the reports about the drinks sector.

Liquid supplements are often used by people such as children or the elderly, who may be unable to swallow tablets and capsules.

Joseph Betz, director of the ODS Dietary Supplement Methods and Reference Materials Program, told that: "There is no evidence whatsoever that benzene occurs in dietary supplements, but the method available for the detection of benzene in dietary supplements in liquid products is not well developed.

"It was worth spending money to to ensure the methods are in existence if anyone ever wanted to test dietary supplements for benzene."

He added that, in fact, devising a method for accurately detecting benzene in dietary supplements was first proposed before the publicity about benzene in soft drinks began.

Neal-Kababick also pointed out that the sodium benzoate-ascorbic acid reaction is accelerated in the presence of transitory metals such as copper and iron - a factor he said may lead to benzene formation in herbal products.

But Dr Steven Dentali, VP of scientific and technical affairs at the American Herbal Products Association told that the heavy metal connection is no more a problem with supplements than any other food.

"The perception of a heavy metal presence is not from supplements but with deliberately adulterated illegally imported patent medicines from countries with traditional systems of medicine that continue to employ heavy metals,"​ he said.

"I do not see that the ingredients going into the liquids that [FRL] intends to test should be at risk for higher than normal heavy metals than any other food."

Indeed it is possible that the same problem of benzene formation may also occur in other acidic liquid food products where sodium benzoate and ascorbic acid are present - such as lemon juice, conserves or sprays for meats.

Betz said: "We assume all liquid products will be put under scrutiny at some point. Hopefully the new method will be applicable for foods too."

Neal-Kababick said that the presence of benzene residue as a result of the chemical's use as a solvent for non water-soluble extracts is not an issue in the EU and US, where the chemical is banned for this use.

But he said: "We don't have control over this in other countries."

FDA has not yet released details of the tests it has conducted on soft drinks, and NIH's funding of a new analysis method was prompted by evidence that existing protocol actually raises the levels of benzene in the samples.

Chemical reactions are accelerated by heat, liquid and pressure - and the existing test protocol involves heating the sample to 80 to 90 degrees Celsius for 30 to 60 minutes in a sealed container.

"When you run the sample in a mass spectrometer, how do you tell what came from the product and what from the analysis?"​ said Neal-Kababick.

"It is not fair to take action based on scientific evidence that is not valid."

FRL's approach, meanwhile, removes these confounding factors and will be able to detect benzene at levels of 500 parts per trillion.

The method will be published in a scientific journal, and will be available for people to use in their own labs so that companies can monitor their own processes.

The agreement is for the method to be published within six months of completion of the study. FRL is currently ahead of schedule.

However it seems that the requirement for a new testing method may not be global. The FSA spokesperson told "The method we use would minimize any formation of benzene in the analytical phase."

He also said that there are no plans to survey dietary supplements sold in the UK at the moment - and no other countries are known to be testing supplements.

Neal-Kababick praised the US supplements industry for addressing the potential issue head-on. "The dietary supplements industry has been very proactive not reactive,"​ he said.

Dentali said: "Flora Research Laboratories is taking a common sense approach to see if certain liquid products that use preservative formulations similar to some soft drinks will, when properly tested, test positive for the presence of benzene.

"A proper safety evaluation begins with proper analysis and there appears to be questions about benzene analyzes done to date. Hopefully [FLA's] work will add to our understanding and provide industry with a useful tool to correct a problem if a genuine concern is found."

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