Bowel cancer is one of the most common cancers in the UK, but it’s also one of the most preventable. According to Cancer Research UK, approximately 54% of bowel cancer cases are preventable.

But as well as upping your fruit and veg intake and cutting out meats like bacon and sausages (a poor diet is thought to be among the leading risk factors for bowel cancer), a new study has found there’s another way to cut your bowel cancer risk: more calcium.

The study from Oxford University and Cancer Research UK found that adding an extra 300mg of calcium to your diet every day can lower your risk of bowel cancer by as much as 17%.  

Published in the journal Nature Communications, the research, which used data from more than 500,000 women, set out to investigate the link between diet and bowel cancer risk. The scientists investigated the link between 97 dietary products and nutrients and bowel cancer risk over an average time of 16 years, making this the most comprehensive study in this area so far.

And despite a recent review stating that dairy products “probably” decreased the risk of bowel cancer, this study found that this impact is largely due to the high calcium levels in dairy, as a reduced risk of cancer was observed both in those who consumed lots of milk and yoghurt as well as those who opted for dark, leafy vegetables (which are also rich in calcium). But why is this? 

While more studies need to be carried out to decipher exactly why calcium has such a protective effect when it comes to bowel cancer, the scientists involved in the study have a theory.

“We have some idea on why calcium has this effect,” said Dr Keren Papier, lead researcher of the study. “It’s suggested that calcium might protect against bowel cancer by binding to bile acids and free fatty acids to form a type of harmless ‘soap’ which stops them from damaging the lining of the gut.” 

These new findings don’t mean you need to go out and add a calcium supplement to your routine – although the study’s authors have suggested that the impact of supplementation should be investigated in future studies. However, there could be benefits in assessing your calcium intake.

The study suggests that consuming an extra 300mg of calcium a day (on top of the NHS recommended amount of 700mg) is the key to reaping its cancer-protective benefits, which is equivalent to approximately 200g of cooked kale or a 250ml glass of milk. If you eat cheese, yoghurt, fortified plant-based milks and fortified bread and cereals, it’s likely you’re already consuming plenty of calcium every day; most of the women in the study were found to be consuming above the recommended 700mg mark.

It’s worth noting that one of the study’s other major findings was that drinking an additional large glass of wine a day, or 20g of alcohol, increases your risk of bowel cancer by 15%. In this way, it’s not enough to simply consume more calcium – harmful lifestyle habits can cancel out the positive effect. 

Dr Lisa Wilde, director of research and external affairs at Bowel Cancer UK, said key lessons could be learned from this study. “This study shows that drinking dairy milk is associated with a reduced bowel cancer risk,” she said. “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.

She continued: “Other changes you can make to help reduce your risk of developing bowel cancer include eating plenty of fibre from whole grains, 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.” 

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