A healthy plant-based diet may reduce the risk of colon cancer in men

A diet rich in whole grains, vegetables and legumes and low in refined grains, fruit juices and added sugars may reduce the risk of colorectal cancer in men, according to a study recently published in the journal. BMC Medicine. A study found that eating a plant-based diet is associated with a reduced risk of disease.

Jihye Kim, corresponding author, said: “Colorectal cancer is the third most common cancer in the world, and the lifetime risk of developing colorectal cancer is one in 23 for men and one in 25 for women1. Although previous studies have shown that a plant-based diet may play a role in the prevention of colorectal cancer, the effect of the nutritional quality of plant-based foods on this association has been unclear. Our results suggest that eating a healthy plant-based diet is associated with a reduced risk of colorectal cancer.”

Researchers from Kyung Hee University (South Korea) found that among 79,952 American men, those who ate the highest average daily amount of healthy plant foods had a 22% lower risk of rectal cancer compared to those who ate the least amount of healthy plant foods. However, the authors found no significant associations between the nutritional quality of plant-based diets and colorectal cancer risk among 93,475 American women.

Jihye Kim said, “We hypothesize that antioxidants found in foods such as fruits, vegetables, and whole grains may help reduce the risk of colorectal cancer by suppressing chronic inflammation that can lead to cancer. Because men tend to have a higher risk of rectal cancer than women, we hypothesize that this may help explain why eating more healthy plant-based foods was associated with a lower risk of rectal cancer in men but not in women.”

The authors found that the association between the nutritional quality of plant-based diets and colorectal cancer risk among men varied by race and ethnicity. Among Japanese American men, the risk of rectal cancer was 20% lower for those who ate the most healthy plant-based foods per day than for those who ate the least. Among white men, those who ate the most healthy plant-based foods had a 24% lower risk of rectal cancer than those who ate the least. The authors found no significant associations between plant-based diets and colorectal cancer risk among African Americans, Hispanics, or Native Hawaiians.

Jihye Kim said, “We hypothesize that the association between plant-based diets and colorectal cancer risk may have been strongest in Japanese Americans and white men because of differences in other risk factors for colorectal cancer between racial and ethnic groups. However, more research is needed to confirm this.”

To examine the relationship between plant-based diets and risk of colorectal cancer, the authors analyzed data collected from adults who were recruited from Hawaii and Los Angeles (USA) for a multiethnic cohort study between 1993 and 1996. On average, male participants were in their 60s. and participants were aged 59 at the start of the study period. 24,138 (30.2%) male participants were Japanese, 20,663 (25.8%) were, 19,198 (24.0%) were Hispanic, 10,381 (13.0%) were African American, and 5,572 (7 .0%) were Native Hawaiian.

Participants reported their usual food and drink intake over the previous year, and the authors assessed whether their diet was high in plant-based foods that they classified as healthy – such as whole grains, fruit, vegetables and legumes – or unhealthy – such as refined grains, fruit juices and added sugars – relative to other participants.

They then calculated the incidence of new cases of rectal cancer through 2017 using data obtained from cancer registries. The authors took into account participants’ age, family history of colorectal cancer, BMI, smoking history, physical activity level, alcohol consumption, multivitamin use and treatment, and daily energy intake. They also took into account the female participants’ use of hormone replacement therapy. 4,976 participants (2.9%) developed colorectal cancer during the study period.

The researchers caution that the observational nature of their study does not allow for conclusions about a causal relationship between plant-based food consumption and colorectal cancer risk. In their analyses, they also did not take into account the beneficial effects of foods such as fish and dairy products on reducing the risk of rectal cancer. Also, because the participants’ diets were recorded at the start of the study, they may not be consistent with their lifetime diets.

The authors suggest that future research is needed to examine genetic and environmental factors that may influence the association between plant-based food intake and colorectal cancer risk across racial and ethnic groups.

Reference: “Plant-Based Diets as Predictors and Colorectal Cancer Risk by Gender and Race/Ethnicity: A Multi-Ethnic Cohort Study” Jihye Kim, Carol J. Bouchy, Lynn R. Wilkens, Christopher A. Hayman, Loic Le Marchant, and Song-Yi Park, November 29, 2022. BMC Medicine.
DOI: 10.1186/s12916-022-02623-7

The study was funded by the National Research Foundation of Korea and the US National Cancer Institute.