Data from the 10-Country Prospective Study of Cancer and Nutrition (EPIC) in Europe attribute the anti-inflammatory properties of fish oil to its effect in reducing this risk.
“Our analysis makes a significant contribution to the growing body of evidence linking fish consumption to a potentially lower risk of CRC,” the study says. “Consumption should be encouraged as part of a healthy diet.”
The World Cancer Research Fund (WCRF) concludes that there is “limited but suggestive” evidence that fish lowers the risk of CRC.
Nevertheless, there is still uncertainty as to whether the consumption of fish is beneficial for CRC prevention and how the consumption of different types of fish (e.g. fatty / oily, white / lean) affects the CRC risk.
Human studies examining the association between dietary omega-3 LC PUFA and CRC risk generally show inverse relationships.
Additionally, balancing omega-6 and omega-3 PUFA intakes may be more relevant to health outcomes than absolute omega-3 LC PUFA intake due to their different metabolic effects on inflammation.
The inconclusive nature of previous studies has evolved into further prospective studies in different populations that clarify the relationships between omega-3 LC PUFAs, their relative balance with omega-6 LC PUFAs, their metabolism, and CRC risk.
Study details .
From 1992 to 2000, the cohort study involved 521,324 people living in Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden and the United Kingdom.
Among other things, the team collected data on height and weight as well as details on lifestyle and diet. The researchers also drew blood samples.
Results from 476,160 people (333,919 women) who did not have cancer at the start of the study were also included.
Another subgroup was also included in the study. This consisted of 461 people who developed cancer alongside 461 matching controls. A case-control study comparing their blood levels of fatty acids was also conducted.
After an average of 14.9 years, the team found 6,291 people diagnosed with CRC (1.3%).
Further analysis found that those who ate the most fish were diagnosed with 12% less colon cancer than those who ate less than one serving. The team found a similar link for “oily” oily fish.
The results for “lean” whitefish were comparable but were on the edge of statistical significance.
The team also assessed amounts of omega-3 fatty acids derived from fish oils in their diet, and found that those who consumed more omega-3 fatty acids had a comparatively reduced risk of colon cancer.
In contrast, a higher intake of omega-6 fatty acids compared to omega-3 was associated with a higher risk.
Additional findings revealed no association between the fatty acid levels in the blood of subjects with and without colon cancer.
“We found inverse associations between fatty and lean fish intake and CRC risk,” the International Agency for Research on Cancer (IARC) team said among a variety of other organizations.
“This suggests that fish consumption in general (regardless of type) may benefit the development of CRC.
The team commented on one possible mechanism of action as follows: “Omega-3 LC PUFAs can inhibit carcinogenesis by producing eicosanoids with anti-inflammatory properties.”
Very little risk reduction.
Great Britain NHS websiteAlso rated the study noting that it was important not to get carried away by its effects.
“The risk reductions were all very small. Although those for all types of fish and oily fish tended to scratch just as statistically significant while whitefish did not, they were all pretty close to the limit of significance. .
“It is possible that some of these results came about by chance. This makes it harder to conclude with certainty that each type of fish is better than another. “
The analysis also found that only 1.3% of all people in the study developed colon cancer in absolute terms.
“If this were taken as the baseline risk of colon cancer, a 7% risk reduction for eating fish once or twice a week would result in an absolute cancer risk of 1.2% instead of 1.3%. So these are pretty small absolute risk reductions. “
Source: Clinical Gastroenterology and Hepatology.
Published online: doi.org/10.1016/j.cgh.2019.06.031.
“Consumption of fish and long-chain n-3 polyunsaturated fatty acids is linked to a reduced risk of colon cancer in a large European cohort.”
Authors: Agalo EK, Huybrechts I., Murphy N. et al.