The Data

Participants completed detailed questionnaires on their lifestyles and medical histories at enrollment and at 2-year intervals thereafter. Information included smoking habits, regular use of aspirin or nonsteroidal inflammatory drugs, and type and frequency of exercise. Participants also provided food histories at 4-year intervals. The Food Frequency Questionnaires categorized consumption from never or less than once a month to 6 or more times a day. Data on consumption of marine omega-3 PUFAs (EPA, DHA, and DPA) from foods and fish oil supplements were also collected.


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Every time participants completed the biannual questionnaire, they were asked if they had received a diagnosis of colorectal cancer in the prior 2 years. If the response was “yes,” the researchers asked for permission to obtain the patients’ medical records and pathology reports. If a participant had died from colorectal cancer, the research team asked the next-of-kin for permission to review the patient’s medical records and pathology reports. There were 561 deaths due to colorectal cancer, 153 due to cardiovascular disease, and 113 due to other cancers.1

Higher Intake, Lower Risk

An association was seen between higher intake of marine omega-3 PUFAs after colorectal cancer diagnosis and a lower risk of cancer-specific death. The investigators found that participants who increased their consumption of marine PUFAs after diagnosis had the lowest risk of dying from colorectal cancer. A moderate reduction in all-cause mortality was also seen in this group regardless of whether their marine omega-3 intake was in the form of oily fish or fish oil supplements.1

In addition, participants who increased their marine PUFA consumption tended to exercise more but drank alcohol more; however, they were less likely to smoke. These participants also took vitamin D, multivitamins, and enriched their diets with fiber. Other noteworthy factors in participants in whom the association between increased marine omega-3 intake and reduced risk of death was the clearest included these patients were not on aspirin therapy, they had a body mass index (BMI) of less than 25 kg/m2, and they were taller.

An increase in marine omega-3 intake of at least 0.15 g daily after colorectal cancer diagnosis produced a 70% reduction in risk of dying from colorectal cancer. Conversely, reducing daily marine omega-3 intake was associated with a 10% increase in risk of dying from colorectal cancer.

These results prompted the research team to recommend patients with colorectal cancer increase their intake of marine omega-3 PUFAs. The researchers also call for additional studies to validate their findings.1

Reference

1. Song M, Zhang X, Meyerhardt JA, et al. Marine ω-3 polyunsaturated fatty acid intake and survival after colorectal cancer diagnosis. Gut. 2016 Jul 19. doi: 10.1136/gutjnl-2016-311990. [Epub ahead of print]