Just two drinks a night sends bowel cancer risk soaring, major new study finds - as experts pinpoint the amount you CAN drink without increasing danger
Just a couple of alcoholic drinks a night could almost double the risk of certain types of bowel cancer, troubling research suggests.
The US study drew on a long-running trial tracking tens of thousands of adults aged 18 and over for two decades.
Researchers compared people's drinking habits across adulthood with who later developed bowel cancer – and found the biggest risks were seen in the heaviest regular drinkers, particularly for cancers in the rectum.
They classed drinking as light, moderate or heavy using US guidelines – up to seven drinks a week for women, and up to 14 for men, with anything above that tipping into heavier drinking.
In the UK, adults are advised to drink no more than 14 units a week on a regular basis – roughly six pints of beer or six medium glasses of wine.
The study found that those having 14 or more drinks a week – just two a night – had a 25 per cent higher risk of colorectal cancer overall, and a 95 per cent higher risk of rectal cancer, compared with light drinkers.
Those who drank no more than one drink a week had no increased risk of colorectal cancer, the research revealed.
Researchers also split people into never drinkers, current drinkers and former drinkers – and found no sign of higher risk among those who had quit, suggesting cutting back, or stopping altogether, may help protect against bowel cancer.
New research now reveals that higher lifetime alcohol consumption is also associated with a higher risk, especially for rectal cancer, and that quitting drinking can lower a person's risk
Dr Erikka Loftfield, an epidemiologist at the National Cancer Institute and study co-author, said: 'Our study is one of the first to explore how drinking alcohol over the life course relates to... colorectal cancer risk.
'Cumulative exposure over the life course – and not only drinking status in older age – may be an important risk factor for cancer.'
The research, published in Cancer, analysed health data from 88,092 US adults enrolled in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial who were cancer-free at the outset.
Over a follow-up of around 20 years, 1,679 cases of colorectal cancer were identified.
Also known as bowel cancer, colorectal cancer refers to cancer found anywhere in the large bowel, which includes the colon and the rectum. It's one of the most common cancers in the UK.
Last week, colon – also known as rectal – cancer was identified as the leading type of cancer diagnosed in Americans aged 50 and under.
Rectal cancer forms in the tissues of the rectum with tell-tale signs including blood in the stool or a change in bowel habits.
Whilst there are many risk factors for bowel cancer – including heavy drinking, smoking and poor diet – many of these do not directly cause cancer.
Dame Deborah James, nicknamed the 'bowel babe', raised more than £11.3m for Cancer Research and is credited for increasing awareness of the disease, which killed her in 2022 aged 40
Rather, they increase the chance of DNA damage in the cells that lead to cancer.
The researchers put forward a number of potential mechanisms that could explain the link between alcohol and the abnormal growth of cells in the body that can result in cancer.
Firstly, they explained: 'Alcohol produces acetaldehyde, an established carcinogen, which causes DNA mutation and oxidative stress in the colon and rectum.'
This toxin also inhibits the absorption of folate which has been linked with an increased risk of some cancers, such as colon cancer.
Drinking alcohol is also known to damage the gut microbiome, resulting in cell death.
Conversely, the authors noted: 'There is also some evidence that moderate alcohol intake may reduce inflammation and lower DNA damage', explaining why 'those who kept within the guidelines experienced a lower risk'.
But they concluded: 'Future research, including consortium efforts and new cohort studies with data on lifetime alcohol intake, is needed to strengthen evidence on the role of alcohol drinking reduction and cessation in the development of colorectal cancer.'
It comes as the NHS is set to increase the accuracy of bowel cancer tests in England, in a move NHS bosses believe will save hundreds of lives.
Bowel cancer is the second most common cancer in the UK, with around 44,100 new cases and 17,400 deaths each year.
Risk factors include eating processed meat, being overweight and drinking alcohol, leading Cancer Research UK to conclude that more than half of cases – 54 per cent – are preventable.
Now, the health service is lowering the amount of blood detected in a stool test needed to trigger the patient being sent for further investigation.
'Testing at a lower level threshold will now provide a better early warning system for bowel cancer, helping us to spot and treat cancers earlier, often picking up problems before symptoms occur,' said Prof Peter Johnson, NHS England's national clinical director for cancer.
