Plant-based diets can lower risk of colorectal cancer — but only in men

SEOUL, South Korea — Plant-based diets can lower the risk of colorectal cancer by nearly a quarter, but only for men, a new study reveals.

Even amongst men, researchers in South Korea say the effect of the diet depends on your ethnicity, with white men benefiting more than some other races. Out of almost 80,000 men in their study, those who ate high amounts of healthy plant-based foods had a 22-percent lower risk of colorectal cancer.

However, researchers did not identify any significant links between the nutritional quality of plant-based diets and colorectal cancer risk among almost 94,000 women in the study.

“Colorectal cancer is the third most common cancer worldwide and the risk of developing colorectal cancer over a lifetime is one in 23 for men and one in 25 for women,” says corresponding author Dr. Jihye Kim, a professor in the department of medical nutrition at Kyung Hee University, in a media release.

“Although previous research has suggested that plant-based diets may play a role in preventing colorectal cancer, the impact of plant foods’ nutritional quality on this association has been unclear. Our findings suggest that eating a healthy plant-based diet is associated with a reduced risk of colorectal cancer.”

“We speculate that the antioxidants found in foods such as fruits, vegetables, and whole grains could contribute to lowering colorectal cancer risk by suppressing chronic inflammation, which can lead to cancer. As men tend to have a higher risk of colorectal cancer than women, we propose that this could help explain why eating greater amounts of healthy plant-based foods was associated with reduced colorectal cancer risk in men but not women,” Dr. Kim adds.

Race also appears to play a role in cancer risk

The team also found that this link varied depending on race and ethnicity. Among Japanese American men, colorectal cancer risk was 20 percent lower for those who ate the highest amount of healthy plant-based foods.

This type of food also had a positive impact on white men. Those who ate high amounts of healthy plant-based foods were 24 percent less likely to suffer from colorectal cancer. However, there was no significant difference between men who did and did not eat a healthy plant-based diet among African Americans, Latinos, or Native Hawaiian men.

“We suggest that the association between plant-based diets and colorectal cancer risk may have been strongest in Japanese American and white men due to differences in other colorectal cancer risk factors between racial and ethnic groups. However, further research is needed to confirm this,” the professor continues.

A healthy plant-based diet includes eating whole grains, vegetables, and legumes. Conversely, unhealthy plant-based foods include refined grains, fruit juices, and products with added sugar.

Study methodology

The team analyzed the data from 79,952 men and 93,475 women from Hawaii and Los Angeles, California. On average, male participants were 60 years-old and female participants were 59 at the beginning of the study. Of all the people involved, 30.2 percent of men were Japanese American, 25.8 percent were white, 24 percent were Latino, 13 percent were African American, and seven percent were Native Hawaiian.

Each participant reported their usual food and drink intake during the previous year. The researchers then assessed whether their diets were high in plant-based foods. Finally, they calculated the incidence of new colorectal cancer cases until 2017 using data from cancer registries.

The team accounted for each participant’s age, family history of colorectal cancer, BMI, smoking history, physical activity levels, alcohol consumption, multivitamin use and treatment, and daily energy intake. They also considered the use of hormone replacement therapy among women.

Of all the participants, 2.9 percent developed colorectal cancer during the study period. Due to the observational nature of their study, however, the researchers urge caution as their results cannot be fully conclusive. This could be because they didn’t take into account the positive effects of other foods such as fish and dairy products.

Similarly, since respondents recorded their diets at the beginning of the study, they may not be representative of their diet throughout their lifetime.

The findings appear in the journal BMC Medicine.

South West News Service writer Alice Clifford contributed to this report.

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