Published May 11, 2012
People who eat plenty of fish may have a lower risk of colon cancer and, even more, rectal cancer, according to an analysis of 41 studies from around the world.
The analysis, which appeared in the American Journal of Medicine, is the latest report that ties fish consumption to a number of possible health benefits.
Jie Liang of Xijing Hospital of Digestive Diseases in Xi'an, China, and colleagues combined the results from 41 studies published between 1990 and 2011 that measured fish consumption and tracked cancer diagnoses. This included research from the United States, Norway, Japan, Finland and elsewhere.
"Our findings from this meta-analysis suggest that fish consumption is inversely associated with colorectal cancer," Liang and his colleagues wrote.
Overall, regularly eating fish was tied to a 12 percent lower risk of developing or dying of colon or rectal cancer, the researchers found.
That was after taking into account study participants' age, alcohol and red meat intake, family history of cancer and other risk factors.
"People who rarely eat fish may experience health benefits in a variety of areas - heart disease, reproductive and now colon cancer - by increasing their fish consumption somewhat," said Michael Gochfeld, a professor of environmental and occupational medicine at University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School.
The protective effect tied to fish consumption was stronger for rectal cancer than colon cancer.
People who ate the highest amounts of fish had a 21 percent lower risk of getting rectal cancer than those who ate the least. That compared to just a four percent lower risk of colon cancer - so small that it could have been due to chance.
The new study focused specifically on fresh fish, and the authors noted that they were unable to pinpoint what types of fish people ate or the manner in which fish was prepared in the prior studies.
"Cooking temperatures might affect the risk of colorectal cancer," Liang said in an email to Reuters Health, citing recent evidence that suggests eating lots of meat and fish barbecued or grilled over high heat may actually be tied to an increased cancer risk.
His team also did not investigate why eating fish may have a positive effect on colorectal cancer risk. The study also can't prove that it's the fish, itself, that was responsible for a lower cancer risk in some participants.
"It doesn't tell us whether the benefit you get from fish has to do with specific nutrients in the fish, or with the fact that people who tend to eat fish often adopt other healthful lifestyles, such as avoiding red meat or processed meats," said Gochfeld, who was not involved in the study.
If fish indeed is behind the lower colorectal cancer risk, the added benefit could be coming from the omega-3 essential fatty acids found in certain fish such as salmon and sardines, he added. But it remains unclear if fish-oil capsules and other supplements would have the same benefit.
A study that appeared in February showed that women who eat about three servings of fish per week have a somewhat lower chance of having colon polyps, which can develop into cancer, than women who eat less than a serving a week.