A large-scale study led by researchers at the University of Oxford’s Cancer Epidemiology Unit has found strong links between dietary habits and colorectal cancer risk.
The study, published in Nature Communications, analyzed data from 542,778 women in the UK over an average period of 16.6 years and identified key dietary factors that increase or decrease the risk of colorectal cancer.
Colorectal cancer is the third most common cancer worldwide, with nearly 2 million new cases in 2022. While it is more common in high-income countries, incidence rates are also rising in lower-income regions due to dietary and lifestyle changes.
This suggests that modifiable factors, such as diet and alcohol consumption, play a major role in the disease.
The researchers used detailed dietary questionnaires from participants in the Million Women Study and tracked 97 dietary factors to determine how they affected colorectal cancer risk.
They also conducted genetic analyses to better understand the impact of specific foods on cancer development.
The study confirmed that alcohol and red or processed meats are carcinogens, increasing colorectal cancer risk:
- Alcohol: Every 20 grams of alcohol per day (about two drinks) raised the risk of colorectal cancer by 15%.
- Red and Processed Meat: Every 30 grams per day (about one slice of bacon) increased risk by 8%.
These findings reinforce previous research that suggests reducing alcohol and processed meat intake can help lower cancer risk.
Protective Foods: Calcium, Dairy, Whole Grains, and Fruits
On the other hand, several nutrients and whole foods were linked to a lower risk of colorectal cancer:
- Calcium: A daily 300-milligram increase (about one glass of milk) reduced the risk by 17%.
- Dairy Products: Milk and yogurt were associated with a lower cancer risk, likely due to their high calcium content.
- Whole Grains: Eating 20 grams of whole grains per day (about half a slice of whole wheat bread) lowered the risk by 10%.
- Breakfast Cereal: A daily serving (40 grams) reduced risk by 7%.
- Fruits and Vegetables:
- An apple a day (5 grams of fiber) reduced risk by 8%.
- A cup of fruit (200 grams) lowered risk by 10%.
- Leafy greens (100 micrograms of folate daily) were linked to a 12% lower risk.
- Vitamin C (100 milligrams, the amount in an orange) reduced risk by 10%.
The study also found that people with genetic variants linked to higher milk consumption had a 40% lower risk of colorectal cancer for every 200 grams of milk consumed daily. This suggests that calcium may play a crucial role in reducing cancer risk by binding carcinogenic bile acids in the gut.
Limitations and Next Steps
While the study provides strong evidence, researchers noted that protective effects from diet tend to overlap with other healthy lifestyle choices. This means that people who eat more whole grains and fruits may also have other lifestyle habits that contribute to lower cancer risk.
Additionally, while calcium appeared protective, the researchers emphasized the need for further studies to confirm its long-term effects and evaluate the safety of high calcium intake.
This study reinforces the idea that diet plays a crucial role in colorectal cancer risk. To reduce risk:
- Limit alcohol and processed meat consumption.
- Increase intake of calcium-rich foods like dairy.
- Eat more whole grains, fruits, and leafy greens.
- Ensure adequate vitamin C and folate intake.
While genetics and other factors also play a role, small dietary changes could have a big impact in preventing colorectal cancer.
The research findings can be found in Nature Communications.
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