Drinking one large glass of milk — including varieties fortified with calcium — or eating foods like yogurt that have the mineral each day may cut the risk of developing colorectal cancer by nearly one-fifth, according to a large study out of the United Kingdom.
The study, published Wednesday in Nature Communications, found that consuming an additional 300 mg of calcium daily (equivalent to a large glass of dairy milk or a yogurt cup) is linked to decreasing the risk of colorectal cancer by 17 per cent.
“This is the most comprehensive single study ever conducted into the relationship between diet and colorectal cancer, and it highlights the potential protective role of calcium in the development of this disease,” said Keren Papier, a nutritional epidemiologist at the University of Oxford and lead researcher of the study, said in a media release.
Colorectal cancer is the third most common type of cancer in the world. In Canada, it is projected to be the fourth most commonly diagnosed cancer in 2024 (excluding non-melanoma skin cancers), according to the Canadian Cancer Society. It ranks as the second leading cause of cancer-related death among men and the third among women.
The cancer is also increasing among young people, though the reasons for this trend remain unclear.
“Early age onset of colorectal cancer is the fastest-growing subgroup of patients in Canada and in the U.S., not necessarily the most amount of people. It’s just the fastest-growing segment,” explained Barry Stein, president and CEO of Colorectal Cancer Canada.
He said that while the finding that calcium may help reduce the risk of colorectal cancer is not new, the study out of the U.K. adds further confirmation to existing research on the topic.
“We have known this for a number of years, that there was a link between calcium and colorectal cancer, but this study makes it much more confirmatory,” he told Global News. “We have more evidence to say that it’s ‘more conclusive’ as opposed to ‘we think.’”
The World Cancer Research Fund and the American Institute for Cancer Research have previously said that there is convincing evidence that calcium may decrease the risk of colorectal cancer. It also argued that higher intakes of alcohol and processed meat increase the risk of this type of cancer.
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However, the U.K. researchers argue that there has been a “lack of consensus” regarding the relationship between dietary factors — other than alcohol and processed meat — and colorectal cancer, but hope this study will help fill that gap and add more clarity.
To further examine the link between diet and colorectal cancer, the researchers analyzed data from more than 540,000 women to explore the relationship between 97 dietary products and nutrients and the risk of developing bowel cancer over an average period of 16 years.
The study found that, among 17 dietary factors, alcohol and calcium had the strongest links to colorectal cancer risk. Alcohol intake was associated with a higher risk, while calcium intake showed a protective effect against bowel cancer.
Other foods like breakfast cereals, fruit, whole grains and vitamin C, were also linked to a lower cancer risk, but only slightly. On the flip side, red and processed meat were associated with a higher risk.
Of all these factors, calcium stood out as the most significant way to help reduce bowel cancer. However, the authors noted that they did not look into the link between calcium supplements and bowel cancer.
Calcium is a mineral most often associated with healthy bones and teeth, although it also plays an important role in blood clotting, helping muscles to contract and regulating normal heart rhythms and nerve functions.
The mineral can be found in dairy products, dark green vegetables like bok choy and broccoli, leafy greens such as kale and arugula, as well as certain fish and shellfish like clams and sardines. It is also in unsweetened, fortified plant-based beverages, including oat, soy and almond milk.
The amount of calcium you need depends on your age. For example, according to HealthLinkBC, people aged 19 to 50 should aim for around 1,000 mg of calcium per day.
So, why might calcium be a great way to help protect against colorectal cancer?
“We have some idea on why calcium has this effect,” Papier said in the media release. “It’s suggested that calcium might protect against bowel cancer by binding to bile acids and free fatty acids to form a type of a harmless ‘soap’, which stops them from damaging the lining of our gut.”
The authors pointed out that while the women in the study represent middle-aged and older women in the U.K., they’re mostly of European descent. So, the results might not apply to other populations, especially those where many people can’t digest lactose, like in many Asian populations.
Despite the limitations, the study concludes that the “analysis provides robust evidence supporting the protective role of dietary calcium. Additional research is needed to investigate overall health benefits or risks associated with higher calcium intakes.”
A key takeaway from this study, Stein said, is that calcium may help reduce the risk of colorectal cancer, but no single factor alone can prevent it.
“You can’t look at it in just a sort of like by itself. You have to look at it as part of a whole risk reduction,” he said. “When we talk about calcium or any other sort of thing to reduce your risk of colorectal cancer, we should look at it as a whole lifestyle.”
The first step in reducing your risk is knowing who is most likely to develop it, particularly those aged 50 and over. That’s why screening is crucial once you turn 50, he said.
Lifestyle is also a key factor in reducing the likelihood of developing colorectal cancer.
“Reducing alcohol consumption, red meat, increasing fiber intake, and now we can add calcium to that list. Healthy lifestyles, diet and exercise are combined as sort of mechanisms to help reduce the risk,” Stein said.