In what they've confirmed as the largest study looking at the effects of diet on rates of colon cancer, researchers in the UK say that calcium-rich foods offer significant protections against the disease. Alcohol and red meat? Not so much.
In the study, the researchers looked at data from over 542,000 women who had participated in the Million Woman Study, a collection of dietary and health information captured from following the habits and health of over 1.3 million women in the UK. The study team looked at data for an average of a 16-year period, during which 12,251 of the women were diagnosed with colorectal cancer. The researchers then tracked the effects that 97 different foods had on bowel cancer risk.
After adjusting for factors including demographics, lifestyle, body mass index, smoking habits, and family history of bowel cancer, they concluded that getting 300 mg of calcium every day resulted in an average of a 17% decreased risk of getting colon cancer. That's about the amount found in an eight-ounce glass of milk, although the study also revealed that the effects of the mineral on lowering cancer risk existed whether the calcium came from dairy sources or non-dairy sources such as leafy green vegetables or tofu.
Sadly, calcium from ice cream and cheese did not offer the same benefits, nor were the researchers able to investigate the effects of calcium supplements on the disease.
‘This is the most comprehensive single study ever conducted into the relationship between diet and bowel cancer, and it highlights the potential role of calcium in the development of this disease," said study lead author Keren Papier, from Oxford University. "Further research is needed to understand the potential health impacts of increasing calcium in different populations."
Skip the cheeseburger
In the bad-news column, the study also upheld the well-established data that alcohol and red meat increase colon-cancer risk. The researchers say that colon cancer risk increased by 29% per 100 grams (3.5 oz) of daily red meat consumption and 15% per every 20 grams of alcohol drank each day, which is about the amount in a six-ounce glass of wine.
While the study didn't look at why calcium seems to ameliorate bowel cancer risk, the researchers do have some theories which they included in the study published in the journal Nature Communications. One is that calcium can bind to bile acids in the colon and lower their potentially carcinogenic effects. It can also protect the lining of the colon from these acids and other potentially harmful substances. Another thought was that calcium may help support the process in which unspecified cells become epithelial cells and enhance apoptosis, the process by which old cells are removed from the colonic lining.
“Every twelve minutes, someone in the UK is diagnosed with bowel cancer, making it the fourth most common cancer in the country," said Dr. Lisa Wilde from Bowel Cancer UK, who was not involved in the study. "We already know that around half of all bowel cancers could be prevented by having a healthier lifestyle and this new research supports this, with a particular focus on dairy. 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."
Source: Oxford Population Health