Eating a plant-based diet, rich in healthy plant foods, such as whole grains, vegetables, and legumes, and low in unhealthy plant foods, including refined grains, fruit juices, and added sugars, is associated with a lower risk of colorectal cancer in men, according to a new study published in the open access journal BMC Medicine.
Jihye Kim, the corresponding author of the research, recalls that “colorectal cancer is the third most common cancer worldwide and the risk of developing it throughout life is one in every 23 men and one in 25 women”.
“Although previous research has suggested that plant-based diets may play a role in the prevention of colorectal cancer, the impact of the nutritional quality of plant foods on this association has not been clear,” he acknowledges. Our results suggest that consumption of a healthy plant-based diet is associated with a lower risk of colorectal cancer.”
Researchers from the University of Kyung Hee (South Korea) found that among a population of 79,952 American menthose who ate the highest mean daily amounts of healthy plant-based foods had a 22% lower risk of colorectal cancer, compared with those who ate the lowest amounts of healthy plant-based foods.
However, the authors did not identify any significant association between the nutritional quality of plant-based diets and the risk of colorectal cancer among a population of 93,475 US women.
“We speculate that antioxidants found in foods such as fruits, vegetables, and whole grains might help reduce the risk of colorectal cancer by suppressing chronic inflammation, which can lead to cancer,” he says. As men tend to have a higher risk of colorectal cancer than women, we propose that this could help explain why consumption of greater amounts of healthy plant-based foods was associated with reduced risk of colorectal cancer in men, but not in women.
The authors found that the association between the nutritional quality of plant-based diets and the risk of colorectal cancer among men varied according to race and ethnicity. Among Japanese American men, the risk of colorectal cancer was 20% lower for those who ate the most healthy plant foods per day than for those who ate the least.
Among white men, those who ate the most healthy plant foods had a 24% lower risk of colorectal cancer than those who ate the least. The authors did not identify any significant association between plant-based diets and colorectal cancer risk among men. African American, Latino, or Native Hawaiian.
“We suggest that the association between plant-based diets and colorectal cancer risk may have been stronger in Japanese American and white men due to differences in other colorectal cancer risk factors between racial and ethnic groups. However, more research is needed to confirm it.” Jihye Kim.
To examine the relationship between plant-based diets and colorectal cancer risk, the authors analyzed data collected from adults who were recruited in Hawaii and Los Angeles for the Multi-Ethnic Cohort Study between 1993 and 1996.
On average, the male participants were 60 years old and the female participants 59 at the start of the study period. 24,138 (30.2%) male participants were Japanese American, 20,663 (25.8%), 19,198 (24.0%) were Latino, 10,381 (13.0%) were African American, and 5,572 (7.0%) were Native American from Hawaii.
Participants reported their usual intake of food and drink over the past year and the authors assessed whether their diets were high in plant-based foods that they classified as healthy – such as whole grains, fruits, vegetables and legumes – or unhealthy – for example, refined cereals, fruit juices and added sugars – relative to other participants.
They then calculated the incidence of new cases of colorectal 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 levels, alcohol consumption, multivitamin use and treatment, and daily energy intake. They also took into account the use of hormone replacement therapy by the women. 4,976 participants (2.9%) developed colorectal cancer during the study period.