Recent research has highlighted a concerning link between moderate alcohol consumption and an increased risk of certain bowel cancers. The study suggests that consuming just two alcoholic drinks each night could nearly double the chance of developing these cancers.

Conducted by the National Cancer Institute in the United States, this extensive 20-year study involved over 8,000 participants. Interestingly, it found that individuals who consumed between seven and 13 drinks weekly had a reduced risk of colorectal cancers.

However, the study revealed that those indulging in 14 or more alcoholic drinks per week—equivalent to two drinks per night—faced a 25% higher risk of colorectal cancer and an alarming 95% increased risk of rectal cancer, compared to lighter drinkers.

The researchers noted that a history of heavy drinking throughout adulthood could elevate cancer risk by more than 90%. Yet, they found no significant risk increase among individuals who had stopped drinking, suggesting that reducing or quitting alcohol can lower the likelihood of bowel cancer.

Dr. Erikka Loftfield, an epidemiologist at the National Cancer Institute and co-author of the study, remarked, “Our research is among the first to investigate the relationship between lifetime alcohol consumption and the risk of both colorectal adenomas [non-cancerous tumors] and colorectal cancer.”

While data on former drinkers were limited, Dr. Loftfield added, “We are encouraged to see that their risk may revert to that of light drinkers.”

‘Alcohol drinking can vary by age, and 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 the journal Cancer, assessed the health records of 88,092 US adults enrolled on the Prostate, Long, Colorectal, and Ovarian (PLCO) cancer screening trial who were cancer free at the beginning of the study. 

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.

Over a follow-up of around 20 years, 1,679 cases of colorectal cancer were identified. 

They found heavy drinkers with an average lifetime alcohol consumption of 14 or more drinks a week had a 25 per cent higher risk of developing colorectal cancer compared to light drinkers, people who are defined as having less than one drink a week. 

This rose to 95 per cent when looking at rectal cancer risk alone. 

But occasional moderate or heavy drinking – compared with consistent light drinking below recommendations – carried no such risk. 

Current drinkers who had a moderate average lifetime intake – drinking less than 14 drinks a week – compared with those who had the lowest alcohol intake, had a lower cancer risk – particularly for distal colon cancer.

Dr Loftfield explained: ‘The inverse association with colorectal cancer was strongest in the screening arm of the trial, suggesting that screening has the potential to modify the association between alcohol drinking and CRC risk.’ 

The NHS states there is no completely safe level of drinking but recommends people drink no more than 14 units of alcohol – around 6 glasses of wine – per week.

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. 

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.

Dame Deborah James, nicknamed the ‘bowel babe’ raised more than £11.3mn for Cancer Research and is credited for increasing awareness of the disease, which killed her in 2022 aged 40

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% – 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.