Fruits and Vegetables Reduce Colorectal Cancer Risk for Men, Not Women

In a recent study, eating more fruits and vegetables protected men to some extent from colorectal cancer, but there wasn’t a similar benefit for women. After adjusting for calories and other known colorectal cancer risks, men in the study who ate the most fruits and vegetables had about a 25 percent reduced risk of getting cancer compared to those who ate the least.

86,000 men and 105,000 women filled out food frequency questionnaires at the beginning of the study. Over an average follow-up period of seven years, 1,100 men and 1,000 women were diagnosed with colon or rectal cancer. Using the questionnaires, a research team divided people into five groups (quintiles) ranging from those who ate the most fruits and vegetables to those who ate the least.

Men in the highest quintile had a 26 percent decreased in colorectal cancers over those in the lowest.  Fruit alone boosted chances that men wouldn’t get colorectal cancer 15 percent, while vegetables decreased risk 20 percent.  Risks were reduced more for colon than rectal cancer.

However, women showed no benefit from higher intake.

The amount of grains eaten made no difference for either men or women.

Abraham Nomura and his team concluded,

The intake of vegetables and fruit was inversely related to colorectal cancer risk among men but not among women. The association appears stronger for colon than for rectal cancer.

The NIH-AARP Diet and Health study found similar results.  In that study, nearly half a million men and women were followed for five years after filling out a food frequency questionnaire.

The amount of fruit reported eaten showed no difference in the development of colorectal cancer for either men or women.  The men who ate the smallest total of both fruits and vegetables had a 26 percent decrease in colorectal cancer, and leafy green vegetables seemed to give the most benefit.  There was no similar benefit for women.

Yikung Park and the team at the National Cancer Institute concluded,

In this large, prospective cohort study with 2,972 incident colorectal cancer cases and extensive information on diet and other colorectal cancer risk factors, we observed that vegetable intake was associated with a lower risk of colorectal cancer for men but not for women. The association was stronger among individuals with very low intakes of fruits and vegetables, suggesting a certain minimum amount of daily fruit and vegetable consumption to avoid increased risk of colorectal cancer. Among subgroups of vegetables, green leafy vegetable intake was inversely associated with risk of colorectal cancer for men.

It’s important to note that studies that try to relate diet to cancer are difficult to conduct and often have conflicting results.  Participants may have difficulty recalling what they ate or may overstate their intake of what they perceive to be healthy foods.

Last year a pooled analysis of 14 diet studies that included over 756,000 men and women found no association between reported consumption of fruits and vegetables and colorectal cancer.  Reported in the Journal of the National Cancer Institute in September 2007, the study found a weak link between how many fruit and vegetables were eaten and cancer in the lower part of the colon but no association overall for either men or women.

SOURCES

Nomura et al., American Journal of Clinical Nutrition, Volume 88, Number 3, September, 2008.

Park et. al., American Journal of Epidemiology, Volume 166, Number 2, July 15, 2007.

Koushik et al., Journal of the National Cancer Institute, advance access published online September 25, 2007.