Diet is second only to tobacco as a leading cause of cancer and, along with alcohol, is responsible for nearly a third of cases of the disease in developed countries, a leading researcher said on Tuesday.
Dr. Tim Key, of the University of Oxford, told a cancer conference that scientists are still discovering how certain foods contribute to cancer but they know that diet, alcohol and obesity play a major role.
“Five percent of cancers could be avoided if nobody was obese,” he said.
While tobacco is linked to about 30 percent of cancer cases, diet is involved in an estimated 25 percent and alcohol in about six percent.
“We know that obesity and alcohol are important,” said Key.
Obesity raises the risk of breast, womb, bowel and kidney cancer while alcohol is known to cause cancers of the mouth, throat and liver. Its dangerous impact is increased when combined with smoking.
Both alcohol consumption and obesity rates are rising in many countries.
Obesity linked to cancers
Key told the meeting of the charity Cancer Research UK that other elements of diet linked to cancer are still unknown but scientists are hoping that the EPIC study, which is comparing the diets of 500,000 people in 10 countries and their risk of cancer, will provide some answers.
Early results of the study have revealed that Norway, Sweden and Denmark have the lowest consumption of fruit and vegetables among European countries while Italy and Spain have the highest. Eating at least five portions of fruit and vegetables a day is recommended to reduce the risk of cancer.
Key, principal scientist on the EPIC study, said it is looking at dietary links to some of the most common cancers including colorectal, breast and prostate.
So far it has shown that obesity is linked to an increased risk of colorectal cancer, while processed and red meat also probably raise the chances of developing the disease and eating lots of fruit and vegetables decrease the odds.
“Hormones are the key factor in breast cancer. There is currently about a five-fold variation in breast cancer rates around the world. Much of that variation is due to parity, the number of children (a woman has) and breast feeding,” Key said.
But he added that obesity and alcohol can also raise the risk of the disease. Scientists working on the study have not positively identified any dietary factors associated with prostate cancer.