Fact Buster

Q: Can raspberry cordial kill stomach bugs in contaminated water?

A: Yes. Raspberry and blackcurrant cordials can kill bacteria that cause some stomach bugs.

Our expert: Dr Heather Cavanagh



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Conditions of Use

For most of us, cordial is off the shopping list; we avoid it because it's full of sugar, bad for our teeth and some of its artificial colourings can make some kids hyperactive.

But raspberry cordial has some very loyal fans, who don't necessarily enjoy its sweet taste.

These people keep it in the pantry because they swear it can prevent  and possibly treat  stomach bugs. And they may be right, says microbiologist Dr Heather Cavanagh, whose research found some raspberry juice and blackcurrant juice cordials can kill at least 12 different types of nasty bacteria responsible for stomach bugs, including E. Coli and several strains of salmonella.

Cavanagh first became interested in the use of raspberry cordial as a preventative and treatment of stomach bugs when she heard that some farmers in parts of New South Wales and Victoria were adding raspberry cordial to their livestock's drinking water to treat diarrhoea.

She also began to hear stories of other people using raspberry cordial to treat stomach bugs: "I heard anecdotal reports from as far away as Queensland and Western Australia, I heard of how people used it to treat themselves and their family. Not just their animals".

So she decided to see if there was any science to support these anecdotal reports.

Antibacterial properties

In the lab, Cavanagh tested juice made from a number of fresh berries  including raspberries, blackberries, blackcurrants, cranberries, mulberries, loganberries and boysenberries  as well as commercially available cordials made from these berries (these cordials were made with real berry juice, not apple juice and artificial colours as is sometimes the case).

These juices and cordials were then diluted down with water to different strengths, the strongest was one part water to five parts cordial and the weakest was 1:100. Then each type of bacteria was mixed with each of the berry drinks. The researchers found a number of the raspberry and blackcurrant juice cordials killed most of the bacteria.

And while there has been some speculation that it's the sugar content of cordials that kills bacteria, Cavanagh says there is something unique to raspberry and blackcurrant juices, which seems to be responsible.

Those cordials that had the best antibacterial properties contained at least 35 per cent raspberry or blackcurrant juice, and worked when diluted down to one part cordial in 10 parts water. Undiluted raspberry juice and blackcurrant juice worked just as well as the cordials.

No human tests

But, Cavanagh says, there's a hitch. While her research suggests there's some truth to the red cordial story, there haven't been any clinical trials testing whether raspberry cordial can prevent or treat stomach bugs in humans or animals.

"We know for certain that adding the right amount of these cordials to water will reduce the number of bacteria in the water," she says.

"[But] we cannot say for certain that the cordial will definitely prevent stomach bugs in people, and we don't know yet if it will help as a treatment if you are already feeling sick. Although again there is some anecdotal evidence to suggest that it might."

And even if red cordial does work, stomach bugs (gastroenteritis) are caused by a range of things other than bacteria  such as viruses, parasites, and certain medications  and raspberry cordial won't help in these cases.

Also be careful about drinking too much cordial (even diluted at a 1:10 ratio) if you have vomiting or diarrhoea. Drinks with a high sugar content  such as undiluted soft drinks, sports drinks, juices or strong cordials  can promote fluid loss into the bowel and worsen dehydration, which is a risk for anyone with vomiting and diarrhoea.

Dr Heather Cavanagh is a senior lecturer in microbiology at the School of Biomedical Sciences at Charles Sturt University. She spoke to Claudine Ryan.