Does drinking alcohol increase the risk of colorectal cancer? Here's what you can do →

Compiled by: Gong Zixin

Colorectal cancer is the third most common cancer worldwide, with an estimated 2 million new cases in 2022. Incidence varies widely, with higher rates in high-income countries and lower but increasing rates in low-income regions. Studies targeting dietary and lifestyle modifications have suggested that modifiable factors play a role in the etiology of colorectal cancer. Despite this, data on how specific dietary components influence colorectal cancer risk are insufficient.

Recently, researchers from the Cancer Epidemiology Unit at the University of Oxford and collaborators from international institutions found that there is a positive correlation between alcohol consumption and colorectal cancer, while calcium and dairy-related foods have a protective effect.

In this study, published in Nature Communications, the researchers aimed to resolve the uncertainty surrounding the relationship between diet and colorectal cancer using a large-scale dietary analysis.

The study involved 1 million female participants in the UK Study who completed a dietary questionnaire detailing their intake of 97 dietary factors. The study recorded data on 542,778 women for an average of 16.6 years, during which time 12,251 women were diagnosed with incident colorectal cancer.

This figure shows the results of the Dietary Range Study approach to assess the association between 97 dietary risk factors and colorectal cancer risk

A targeted genetic analysis involved data from the Interdisciplinary Study of Colorectal Cancer, the Colon Cancer Family Registry, and the Colorectal Cancer Genetics and Epidemiology Consortium, based on multivariable models adjusted for demographic, lifestyle, and clinical factors. The study adjusted for confounding factors such as body mass index, smoking status, and family history of colorectal cancer.

Alcohol and red/processed meat were again listed as carcinogens. Drinking alcohol was associated with an increased risk of colorectal cancer, with each 20 grams of alcohol consumed per day increasing the risk by 15%. Eating red and processed meat was associated with an increased risk, with each additional 30 grams (a slice of bacon) per day increasing the risk by 8%.

Why is calcium considered a protective factor against colorectal cancer? This may be due to its role in binding intestinal bile acids and reducing exposure to carcinogens in the colon. An additional 300 mg of calcium intake per day (a glass of milk) is associated with a 17% lower risk of the disease.

Milk, yogurt and other foods rich in calcium, magnesium, riboflavin and potassium were also associated with a reduced risk of colorectal cancer. Further analysis showed that calcium was the main factor in these associations. Genetic analysis showed that for every 200 grams of milk consumed per day, the risk of colorectal cancer decreased by 40%.

Some grains, fruits, and nutrients have also been linked to a reduced risk of colorectal cancer:

Eating 20 grams of whole grains per day (half a slice of whole-wheat bread) was associated with a 10% lower risk

Eating 40 grams of breakfast cereal per day (about one serving) was associated with a 7% lower risk

An apple a day (containing 5 grams of fiber) can reduce the risk by 8%

Adding 200 grams of fruit (about one cup) was associated with a 10% lower risk

Eating green leafy vegetables (100 micrograms of folic acid) daily was associated with a 12% lower risk

Higher vitamin C intake (100 mg, or the amount in one orange) is associated with a 10% lower risk of colorectal cancer

These potentially protective effects were attenuated when other lifestyle and dietary factors were taken into account, as high intakes often overlap with other healthy choices.

Sensitivity analyses ruled out reverse causality and revealed consistent results across colorectal cancer subsites (proximal colon, distal colon, rectum). This study suggests that further research is needed to explore the protective mechanisms of calcium and evaluate the health effects of high calcium intake. By adjusting our dietary habits, we may be able to better protect ourselves from the threat of this common cancer.