Australian researchers, who examined daily diets of more than 2,000 people, found that the fruit juice people drink daily contains so much sugar that it actually increases the risk of certain cancers, rather than preventing them.
In fact, they claimed, by the time the drink has been processed and packaged, many of the ingredients in fruit that protect against tumours have been lost, Daily Mail reported.
The researchers from the Western Australian Institute for Medical Research in Perth sought to establish how effective different fruits, vegetables and juices were at preventing the development of bowel cancer.
They examined the diets of over 2,000 adults, who filled in a questionnaire detailing their daily eating habits. The team then tracked the participants for two years to see how many of them developed the disease.
It was found that eating apples, sprouts, cauliflower or broccoli on a daily basis all reduced the likelihood. However, those who consumed lots of fruit juice had a higher risk.
They also found that those who drank over three glasses a day were more likely to develop rectal cancer -- a form of bowel cancer.
Detailing their study in the Journal of the American Dietetic Association, the researchers said: "Our findings indicate that the association between intake of fruit and veg and colorectal cancer may be different according to the location of the cancer."
The Perth team also said that many things found in fruit which help protect against bowel cancer -- including fibre, vitamin C and chemicals known as antioxidants -- are lost during the juice's processing.
Earlier this year, British researchers had claimed that fruit juice contains too much sugar to be counted as one of the five.
The scientists, of Bangor University, Wales, said people would be better off eating prunes or other dried fruit, as even freshly-squeezed juice contains as much as five teaspoons of sugar per glass.
However, other experts suggested that people should not shun fruit juice completely, as it is still healthier than other drinks.
Nell Barrie, of Cancer Research UK, said of the latest research: "This isn't a large study, and it doesn't give us clear answers about whether different fruits and vegetables affect the risk of cancer in parts of the bowel.
"It's very tricky to tease apart the effects of a person’s diet on their risk of bowel cancer, but reliable evidence shows that eating lots of red and processed meats increases the risk, while eating plenty of high-fibre foods can reduce the risk.
"Many fruits and vegetables are a good source of fibre, and eating a diet that’s high in fruits and vegetables could reduce the risk of other types of cancer as well -- so it's a good idea to get plenty of them in your diet."
