The report, published online in the International Journal of Cancer, found that people who drink 15 grams of alcohol a day – equivalent to about two units – have about a 10 per cent increased risk of bowel cancer.
Those who drank more than 30 grams of alcohol – equivalent to three to four units which is less than a couple of pints of strong lager – increased their bowel cancer risk by around 25 per cent.

Source: Internatinal Journal of Cancer July 2007