Six cups of coffee every day reduces the risk of bowel cancer, say researchers.
Those study participants who drank four cups a day saw their risk of a tumour drop by about 15 per cent.
But volunteers who downed six or more cups were up to 40 per cent less likely to fall victim to the disease, the Daily Mail reported.
Bowel cancer is responsible for high mortality rate - around 16,000 a year - because many victims ignore early warning signs and only seek medical help once the cancer has advanced.
Diets high in fat and red meat, as well as lack of exercise, are thought to be among the main risk factors.
Some previous studies have hinted coffee could have a protective effect, although the findings have been inconclusive.
In the latest investigation, researchers at the US National Cancer Institute in Rockville, Maryland, looked at nearly 490,000 men and women who took part in a diet and health study from the mid-nineties onwards.
They analysed their eating and drinking habits and compared bowel cancer rates among coffee drinkers and non-drinkers.
They found a small but significant fall in tumour risk among those on four to five cups a day. But the greatest benefits were seen when consumption topped half-a-dozen cups a day, with the risk plummeting by almost 40 per cent for certain types of tumour.
"It is particularly encouraging to see that coffee consumption may lower the risk of bowel cancer given that over 40,000 men and women are diagnosed with it in the UK every year, making it the third most common cancer," said Dr Euan Paul, Executive Director of the British Coffee Association.
But he stressed that pregnant women should follow NHS advice to moderate their intake of caffeine to 200mg per day from all sources, as it can increase the risk of miscarriage in high doses.
The results were published in the latest American Journal of Clinical Nutrition.