A diet rich in vegetables, whole grains, beans and lentils can cut the risk of bowel cancer in men by more than a fifth, new research suggests.
The major study of 79,952 men in the US found those who regularly ate these foods had a significantly lower risk of bowel cancer than those who didn’t.
However, the researchers found no such link for women, who made up a further 93,475 of participants. The team suggested the link is clearer for men, who also have an overall higher risk of bowel cancer.
For the research, published in BMC Medicine, participants were asked how often they ate certain foods and drink from a list of more than 180 items. They were also asked about portion size.
The food groups were classed as healthy plant foods (whole grains, fruits, vegetables, vegetable oils, nuts, legumes such as lentils and chickpeas, tea and coffee); less healthy plant foods (refined grains, fruit juices, potatoes, added sugars); and animal foods (animal fat, dairy, eggs, fish or seafood, meat).
People could tick that they consumed each food item “never or hardly ever” right up to “two or more times a day”. For drinks, the responses ranged from “never or hardly ever” to “four or more times a day”.
Those men who ate largest amounts of healthy plant-based foods had a 22% lower risk of bowel cancer compared to those who ate the least.
Researcher Jihye Kim, from Kyung Hee University in South Korea, said: “We speculate that the antioxidants found in foods such as fruits, vegetables, and whole grains could contribute to lowering colorectal [bowel] cancer risk by suppressing chronic inflammation, which can lead to cancer.”
Bowel cancer is the third most common cancer worldwide and the risk of developing it over a lifetime is one in 23 for men and one in 25 for women.
“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,” Kim added.
The study authors also found the link among men also varied by race and ethnicity. Among Japanese American men, for example, the reduced cancer risk was 20%, while it was 24% for white men. The team said more research was needed on these differences.
Dr Helen Croker, head of research interpretation at World Cancer Research Fund, said: “We welcome this research which adds to our own evidence that eating vegetables, wholegrains and beans reduces the risk of developing bowel cancer. We also recommend that people limit the amount of red meat they eat and avoid processed meat altogether.”
She added that the difference in impact on men and women was interesting. “It’s speculated that one reason for this may be because men in general had a lower intake of plant foods and a higher intake of animal foods than women – so there was perhaps a ceiling effect to the benefits that women may experience.”
Beth Vincent, health information manager at Cancer Research UK, agreed that the study added to existing evidence on the benefits a balanced diet high in fruit, vegetables and fibre for both men and women. However, she said that because of the design of the study, and by the authors’ own acknowledgement, we can’t read too much into the results.
“The study relied on people remembering what they had eaten up to a year ago. It also made the assumptions that participants’ diets stayed the same over many years, and that all meat and animal products were unhealthy – which isn’t the case,” she said, adding, “Eating a well-balanced diet can help with maintaining a healthy weight, which reduces the risk of cancer.”