Fruits and veggies may prevent bowel cancer but not fruit juices: Study

By Dr. Ananya Mandal, MDSep 26 2011

Scientists claim that a glass of juice contains so much sugar it actually increases the risk of certain cancers, rather than preventing them. In fact, by the time the drink has been processed and packaged, many of the ingredients in fruit that protect against tumors have been lost, they say. 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.

Australian researchers had sought to establish how effective different fruits, vegetables and juices were at preventing the development of bowel cancer. They examined the diets of 2,200 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.

Unsurprisingly they 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.

The research, published in the Journal of the American Dietetic Association, found that those drinking more than three glasses a day were more likely to develop rectal cancer, a form of bowel cancer. Scientists believe the high sugar content in juice may trigger certain tumors.  For years, Department of Health guidelines have advised the public to eat five portions of fruit and vegetables a day, which can include a glass of juice.

WA Institute of Medical Research Epidemiology Group head and lead investigator Professor Lin Fritschi said previous studies had been inconsistent, so the institute had taken a new approach by examining three different sections of the bowel - proximal colon, distal colon and rectal - separately. “Fruit and vegetables have been examined extensively in nutritional research in relation to colorectal cancers…However, their protective effect has been subject to debate, possibly because of different effects on different sub-sites of the large bowel,” she said. The findings were based on research carried out on 918 people with colorectal cancers and 1021 control patients. According to the study, recommending which foods to eat as opposed to which nutrients were beneficial worked better from a public health perspective.

But 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 suggest that people shouldn’t 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-fiber foods can reduce the risk. Many fruits and vegetables are a good source of fiber, 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.”

Cancer Council spokesman Terry Slevin said it only reinforced the theory that eating lots of fruit and vegetables was good for health. “The bottom line is basically eating lots of fruit and vegetables is good for you, which won't be news to anyone…This study looks at the same disease in a different way to back up the idea that eating lots of fruit and veg and maintaining a healthy body weight causes a decrease in the risk of all types of cancer, diabetes and heart disease, once again reinforcing our message to Go for 2&5.”