A potential health hazard?

Harvard scientists found people who ate bacon at least five times a week were 59% more likely to develop the disease than those who never did.

They also found people who frequently ate skinless chicken had a 52% greater risk. Chemicals called nitrosamines and heterocyclic amines may be to blame.

The study appears in the American Journal of Clinical Nutrition.

The link between diet and cancer is complex and difficult to unravel

Dr Emma Knight

The Harvard team studied data on nearly 136,000 people. The participants were followed for up to 22 years, during which time 808 developed bladder cancer.

Nitrosamines, chemicals which are often found in processed meats and in particularly high levels in bacon, are known to be carcinogenic in high quantities.

Heterocyclic amines, also known carcinogens, form when meat is cooked at high temperatures.

Compared with skinless chicken, cooked chicken with skin is known to contain a smaller amount of heterocyclic amines.

More work needed

However, the research is far from definitive.

The researchers also found people who ate bacon and other processed meats frequently were also more likely to smoke and to take in more fat and fewer vitamins. They were also less likely to exercise.

Dr Emma Knight, science information manager at Cancer Research UK, said: "The link between diet and cancer is complex and difficult to unravel but we know that eating lots of red and processed meat can increase our risk of some types of cancer.

"More research is needed before we can say for sure whether or not eating bacon in particular affects bladder cancer risk.

"For now, our advice remains to eat a balanced diet that is low in fat, processed and red meat, and rich in vegetables, fruit and fibre."

More than 10,000 people a year are diagnosed with bladder cancer in the UK.