A daily pint of beer or large glass of wine increases the risk of bowel cancer by 10%, reported the Daily Mail . “And the more you drink, the greater the threat” it said. People who drank two pints or two glasses of wine increased their risk by up to 25%, it said.
The Mail reported that men have a “one in 20 chance of developing [bowel cancer]… while for women the risk is slightly higher at one in 18”. The researchers acknowledge, however, that “the increase in risk is not large”, and suggest that cutting alcohol consumption can reduce the risk of developing many types of cancer, not just bowel cancer.
These reports are based on a large study, which looked at the link between alcohol consumption and the risk of bowel cancer in almost half a million people. The results of this study do demonstrate a link between alcohol and bowel cancer but do not suggest that alcohol on its own is a cause..
Where did the story come from?
The study was conducted by Pietro Ferrari and a large group of European researchers and was funded by a number of European charities and governmental organisations, including the European Commission. It was published in the International Journal of Cancer .
What kind of scientific study was this?
Researchers recruited 478,732 adult volunteers from 10 western European countries, including the UK, who did not have cancer, and asked them detailed questions about how much alcohol they currently consumed (baseline consumption) and how much they had consumed over their lifetime.
These people were then followed up for about six years, and it was recorded whether they developed bowel cancer.
The researchers then used statistical methods to look at whether people who drank more were more likely to develop bowel cancer. They adjusted these analyses for other factors that might potentially affect risk of bowel cancer, including age, gender, weight, smoking, physical activity, and education level.
What were the results of the study?
About four people in every thousand volunteers developed bowel cancer during the study. The researchers found that a higher lifetime alcohol intake increased the risk of developing bowel cancer.
Bowel cancer risk over the six-year period increased by about 8% on average for every 15 grams extra of alcohol consumed per day. Alcohol consumption higher than 30 grams a day was associated with higher levels of bowel cancer risk than consumption of up to 4.9 grams a day. Similar results were found for alcohol consumption at baseline.
What interpretations did the researchers draw from these results?
Researchers concluded that higher baseline or lifetime alcohol consumption increases the risk of developing bowel cancer.
What does the NHS Knowledge Service make of this study?
This was a very large, good quality study, and its results are reliable. Studies of this type do have some limitations, which include:
- Other unknown factors may also influence the risk of developing bowel cancer, other than the factor assessed, for example, dietary fibre intake. In this study, researchers tried to control for these other factors, which increases the reliability of their results.
- People may not accurately remember how much alcohol they drank in the past, or may underestimate their consumption because of the stigma associated with excessive drinking. However, results of this study were very similar for participant-reported lifetime drinking (which requires better recall), and for participant-reported baseline drinking (which has been shown to be a relatively accurate), which suggests that findings are valid. Also, any under-reporting of alcohol consumption might be expected to decrease any association with cancer outcomes, so the fact that an association between alcohol consumption and bowel cancer was found does suggest that such a link does exist.
- People who got cancer were mainly identified by looking at national cancer registry databases and health insurance records. This may mean that not all cases might have been identified. However, researchers also made contact with volunteers and their next of kin, so this should have reduced the possibility for error.
- These results were obtained in the European population; it is possible that the effects of alcohol consumption on bowel cancer might differ in other populations with different ethnic backgrounds.