Similarly, eating dairy products appeared to lower risk by 13% to 19%, but the amount needed to protect against colon cancer was unclear.
Fiber intake was associated with a 22% to 43% lower risk, while fruit/vegetable consumption with as much as a 52% lower risk.
There was no evidence that vitamins E, C, multivitamins, beta carotene or selenium were protective against colon cancer, the review found.
Results on the impact of tea, garlic or onions, vitamin D either alone or combined with calcium, coffee and caffeine, fish and omega-3 were weak or uncertain, and there were inconsistent findings on whether vitamin A and the B vitamins offered any protection.
There was conflicting data on high calcium intake and cholesterol-lowering statin drugs.
Meat, particularly red and processed meat, was associated with a 12% to 21% increased risk of colon cancer.
Alcohol also was linked to significantly higher risk. Even one or two drinks a day increased colon cancer odds, and the more people drank, the higher their risk.
In a journal news release, the researchers noted that the level of evidence of nutrients, foods and medicines providing protection against colon cancer is low or very low in most cases.
Even so, they said their findings could help doctors advise patients on the best diet to reduce bowel cancer risk and also guide future research.
Worldwide, more than 2.2 million new cases of colon cancer and 1.1 million deaths are projected annually by 2030. In the United States, colon cancer strikes about 1 in 20 people.
The U.S. National Cancer Institute has more on colon cancer.
SOURCE: Gut, news release, Sept. 28, 2020