Researchers found that men who ate the largest amounts of healthy plant-based foods had a 22 per cent lower risk of bowel cancer compared to those who ate the least.
However, there was no link between a similar diet and the risk of bowel cancer for women, the study said.
It involved 79,952 men in the US as well as 93,475 women.
Published in BMC Medicine, participants were asked how often they consumed certain foods and drink from a list of more than 180 items. They were also asked about portion sizes.
Those involved in the study could tick that they consumed each food or drink item “never or hardly ever” to “four or more times a day”.
Food groups were classed into “healthy plant foods”, which included whole grains, fruits, vegetables, vegetable oils, legumes like lentils and chickpeas, tea, and coffee; “less healthy plant foods” such as refined grains, fruit juices, potatoes, added sugars; and “animal foods” including animal fat, dairy, eggs, fish or seafood, and meat.
The researchers, from Kyung Hee University in South Korea, then divided the daily consumption per 1,000 kilocalories into quintiles, from the biggest consumption to the least.
On average, the study involved men aged 60 while women were aged 59.
Researcher Jihye Kim said: “Colorectal (bowel) 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.
“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 the reduced risk of colorectal cancer.”
The study’s authors posited that antioxidants found in such foods, including fruits, vegetables, and whole grains, could “contribute to lowering colorectal cancer risk by suppressing chronic inflammation”.
Explaining why there was no link between diet and cancer risk for women, Kim said: “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.”
The authors also found that the link among men varied by race and ethnicity, with the risk reducing further among white men (24 per cent) compared to Japanese American men (20 per cent).
They called for more research on the differences between ethnicities. The study also took into account factors likely to influence the results, such as weight. During the course of the study, 4,976 (2.9 per cent) developed bowel cancer.