A major new study has found that what we eat may have a powerful effect on the risk of developing colorectal cancer, also known as bowel cancer.
Researchers from the University of Oxford’s Cancer Epidemiology Unit discovered that some everyday foods appear to increase the risk of this common cancer, while others may help protect against it. Their findings were published in the journal Nature Communications.
Colorectal cancer develops in the colon or rectum, which are parts of the large intestine. It is the third most common cancer in the world. Nearly 2 million people were diagnosed with the disease in 2022.
Although it has long been more common in wealthier countries, the number of cases is now increasing in many lower-income countries as diets and lifestyles become more similar to those in Western nations.
Scientists have known for many years that genes play a role in colorectal cancer. However, lifestyle choices, especially diet, are also important because they can often be changed. This means many cases may be preventable.
To better understand the connection between food and bowel cancer, researchers analyzed information from 542,778 women who took part in the Million Women Study in the United Kingdom.
The women were followed for an average of 16.6 years. During that time, the researchers examined 97 different dietary factors to see how they affected cancer risk. They also carried out genetic analyses to better understand how certain foods might influence the disease.
The study confirmed that alcohol and red or processed meat increase the risk of colorectal cancer. Every 20 grams of alcohol consumed each day, which is about two standard drinks, was linked to a 15% higher risk.
Every additional 30 grams of red or processed meat per day, roughly the amount in one slice of bacon, increased the risk by 8%. These results support earlier research showing that cutting back on alcohol and processed meats is an effective way to lower bowel cancer risk.
The researchers also found several foods and nutrients that were linked to a lower risk of colorectal cancer. Calcium showed one of the strongest protective effects.
An extra 300 milligrams of calcium each day, about the amount found in one glass of milk, was associated with a 17% lower risk of bowel cancer. Dairy foods such as milk and yogurt were also linked with lower risk, probably because they are rich in calcium.
Whole grains also appeared to be beneficial. Eating about 20 grams of whole grains each day, around half a slice of wholemeal bread, was linked to a 10% lower risk. A daily serving of breakfast cereal, about 40 grams, was associated with a 7% reduction in risk.
Fruit and vegetables also showed important benefits. Eating enough fruit to provide five grams of dietary fiber, roughly one apple, was linked to an 8% lower risk.
Eating around 200 grams of fruit each day, about one cup, lowered risk by 10%. Leafy green vegetables, which provide folate, were associated with a 12% lower risk, while consuming about 100 milligrams of vitamin C each day, similar to the amount in one orange, was linked to a 10% lower risk.
The genetic part of the study provided another interesting finding. People who carried genetic variants linked to drinking more milk had a 40% lower risk of colorectal cancer for every 200 grams of milk they consumed each day.
This supports the idea that calcium may help protect the bowel by binding harmful bile acids and other substances in the intestine before they can damage the cells lining the colon.
Even so, the researchers stressed that this does not mean one food alone prevents cancer. People who eat healthier diets often exercise more, smoke less, and maintain healthier body weights, all of which also reduce cancer risk. Because of this, it is difficult to separate the effects of individual foods from an overall healthy lifestyle.
The team also noted that more research is needed to determine the long-term benefits and safety of higher calcium intake. While calcium-rich foods appear to be beneficial, taking large amounts of calcium supplements without medical advice is not recommended.
Overall, this large study adds to growing evidence that everyday food choices can influence bowel cancer risk. Limiting alcohol and processed meat while eating more calcium-rich dairy foods, whole grains, fruits, and leafy green vegetables may help lower the chances of developing this common disease.
Small, healthy changes made over many years could make a meaningful difference to long-term health.
If you care about cancer, please read studies that artificial sweeteners are linked to higher cancer risk, and how drinking milk affects risks of heart disease and cancer.
For more health information, please see recent studies about the best time to take vitamins to prevent heart disease, and results showing vitamin D supplements strongly reduces cancer death.
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