These were the key findings of a meta-analysis, which assessed the relationship between colorectal cancer and 12 major food groups — whole grains, refined grains, vegetables, fruit, nuts, legumes, eggs, dairy, fish, red meat, processed meat and sugar-sweetened beverages (SSBs).
“Worldwide, colorectal cancer is the second most common cancer in women and the third most common cancer in men. In 2012, around 694, 000 men and women died because of colorectal cancer,” said the researchers.
Cancer risk reduction
The team of European researchers reported that a healthy diet characterised by high intake of fruit, vegetables, whole grains, olive oil, fish, soy, poultry, and low-fat dairy was associated with a 20-25% decreased risk of colorectal cancer, while a high intake of red and processed meat was associated with a 20-40% increased risk of colorectal cancer, with stronger associations for colon cancer compared to rectal cancer.
They also said that whole grains, fruit and vegetables are sources of minerals, and fruit contains a wide range of antioxidant vitamins, flavonoids and carotenoids, and that studies suggested a potential protective role these types of food have against colorectal cancer.
In relation to dairy, they found that both dietary and supplementary calcium intake were related to a decreased risk of colorectal cancer. Dairy products also contain other beneficial components that have been suggested to inhibit colon carcinogenesis.
Moreover, in colon cancer cell lines, an anti-proliferative effect was recently also observed for Lactobacillus bacteria isolated from dairy products.
On the other hand, red and processed meat contain heme iron and multiple carcinogenic chemicals. The amount of these chemicals in meat products depends on processing and preparation.
Optimal consumption & results
According to the researchers, optimal amounts of consumption of the ideal food types are: six servings per day for whole grains, six servings per day for vegetables, three servings per day for fruit, and six servings per day for dairy.
Consumption of this amount together results in a 56% reduction of risk of colorectal cancer, compared to non-consumption of these foods.
The highest reduction in risk of colorectal cancer in terms of servings is for dairy: Six servings per day was associated with a 30% risk reduction, compared to non-consumption of dairy.
In comparison, the researchers added: “We could further calculate that a consumption of risk-increasing foods of two servings per day of red meat and four servings per day of processed meat is associated with a 1.8-fold increased risk, compared to non-consumption.”
They also said that not consuming these foods at all would reduce the risk of colorectal cancer by about 44%.
“Thus, a plant-based diet as a modifiable lifestyle factor should be promoted regarding colorectal prevention,” concluded the researchers.
Source: International Journal of Cancer
“Food groups and risk of colorectal cancer”
Authors: Lukas Schwingshackl, et al.