Drinking one glass of milk a day will 'cut risk of bowel cancer by almost a fifth'

According to the largest study of its kind, a daily glass of milk can reduce the risk of bowel cancer by nearly a fifth. Researchers from the University of Oxford have found the most compelling evidence yet that calcium provides protection against the deadly disease.

The team also discovered that consuming the equivalent of a daily glass of wine increases the risk of bowel cancer by 15%. Experts reacted to the study by advising people to maintain a balanced diet, keep a healthy weight, and quit smoking to lower their risk of bowel cancer, which affects over 44,000 individuals in the UK each year.

Statistics indicate that one in 20 women and one in 17 men in the UK will be diagnosed with bowel cancer during their lifetime. Over half of cases are preventable, with 13% caused by eating processed meat and 11% caused by overweight and obesity.

The latest research, published in Nature Communications, examined 97 dietary factors and their impact on bowel cancer risk among 542,778 women participating in the Million Women Study. During a follow-up period of almost 17 years, 12,251 women developed bowel cancer, with calcium and alcohol having the most significant effect on changing bowel cancer risk from all the dietary factors studied.

The researchers discovered that, on average, an additional 300mg of calcium per day – equivalent to a large 240ml glass of milk or a couple of pots of yoghurt – resulted in a 17% decrease in the risk of bowel cancer.

The study revealed that calcium intake, from both dairy and non-dairy sources, could reduce cancer risk, indicating that calcium itself is the key factor in lowering the risk. It did not assess the effects of calcium supplements.

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The researchers noted that calcium from various sources such as milk (including when added to tea and coffee), yoghurt, and vegetables contributed to the benefit, although the study did not clarify the impact of cheese and ice-cream. They speculated that there was no apparent reason why these would not be beneficial; it might simply be due to low consumption levels among study participants.

Additionally, the research found that consuming 20g of alcohol daily, about a medium glass of wine or a pint of beer, could increase bowel cancer risk by 15%. The findings also supported previous evidence that processed and red meat consumption heightens bowel cancer risk, with an additional 30g per day linked to an 8% increased risk.

Sophia Lowes, Cancer Research UK's senior health information manager, which funded the study, emphasised the importance of prevention, stating: "Bowel cancer is one of the most common cancers affecting people in the UK, which is why it’s so vital that we know how to prevent it.

"Maintaining a healthy, balanced diet, alongside keeping a healthy weight and stopping smoking, is one of the best ways to lower your risk of bowel cancer.

"This includes cutting down on alcohol and red and processed meat, and eating lots of fruit, vegetables and wholegrains. Dairy products like milk can also be part of a diet which reduces bowel cancer risk.

"We look forward to further research, including into the effects of specific ingredients like calcium, to ensure fewer people are impacted by this devastating disease."

The lead researcher of the study, Dr Keren Papier, noted that although more research is needed, they believe: "This is the most comprehensive single study ever conducted into the relationship between diet and bowel cancer, and it highlights the protective role of calcium in the development of this disease."

The researchers suggest calcium's ability to bind to bile acids and free fatty acids in the bowel may reduce their cancer-driving effects, suggesting dairy's potential protective properties could extend to both sexes. They additionally note experimental work in rats showing higher dietary calcium levels could help protect the structure of the bowel.

In reference to UK measures, one alcohol unit equates to 8g of alcohol.

Dr Lisa Wilde, director of research and external affairs at Bowel Cancer UK, highlighted the prevalence of the condition, stating: "Every 12 minutes someone in the UK is diagnosed with bowel cancer, making it the fourth most common cancer in the country. This study shows that drinking dairy milk can help reduce your bowel cancer risk.

"However, it is the calcium in milk that is important. If you don’t drink dairy milk there are other ways you can get calcium, for example from broccoli or tofu, and still reduce your bowel cancer risk.

"Other changes you can make to help reduce your risk of developing bowel cancer include eating plenty of fibre from wholegrains, pulses, fruits, and vegetables, avoiding processed meat and limiting red meat, being a healthy body weight, taking part in regular physical activity, stopping smoking, and cutting down on alcohol.

"Making lifestyle changes can be a challenge, but we believe it’s worth the effort."

Dr Helen Croker, assistant director of research and policy at the World Cancer Research Fund, said: "This new research reinforces how important diet is when considering cancer risk, especially given low public awareness surrounding factors such as alcohol consumption."

Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London (KCL), said: "The take home messages of this are that drinking above the safe limits of alcohol intake (more than 14 units/week) increases risk of colorectal cancer in women but that drinking about half a pint of cows’ milk a day (which would provide about 300mg calcium) is probably protective."