Effects of Omega-3 Fatty Acids on Cancer Risk

Southern California Evidence-Based Practice Center, RAND Health, Santa Monica 90407-2138, USA.
JAMA The Journal of the American Medical Association (Impact Factor: 35.29). 02/2006; 295(4):403-15. DOI: 10.1001/jama.295.4.403
Source: PubMed


Omega-3 fatty acids are purported to reduce the risk of cancer. Studies have reported mixed results.
To synthesize published and unpublished evidence to determine estimates of the effect of omega-3 fatty acids on cancer risk in prospective cohort studies.
Articles published from 1966 to October 2005 identified through MEDLINE, PREMEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and CAB Health; unpublished literature sought through letters to experts in the neutraceutical industry.
A total of 38 articles with a description of effects of consumption of omega-3 fatty acids on tumor incidence, prospective cohort study design, human study population; and description of effect of omega-3 among groups with different levels of exposure in the cohort were included. Two reviewers independently reviewed articles using structured abstraction forms; disagreements were resolved by consensus.
Two reviewers independently abstracted detailed data about the incidence of cancer, the type of cancer, the number and characteristics of the patients, details on the exposure to omega-3 fatty acids, and the elapsed time between the intervention and outcome measurements. Data about the methodological quality of the study were also abstracted.
Across 20 cohorts from 7 countries for 11 different types of cancer and using up to 6 different ways to categorize omega-3 fatty acid consumption, 65 estimates of the association between omega-3 fatty acid consumption were reported. Among these, only 8 were statistically significant. The high degree of heterogeneity across these studies precluded pooling of data. For breast cancer 1 significant estimate was for increased risk (incidence risk ratio [IRR], 1.47; 95% confidence interval [CI], 1.10-1.98) and 3 were for decreased risk (RR, 0.68-0.72); 7 other estimates did not show a significant association. For colorectal cancer, there was 1 estimate of decreased risk (RR, 0.49; 95% CI, 0.27-0.89) and 17 estimates without association. For lung cancer one of the significant associations was for increased cancer risk (IRR, 3.0; 95% CI, 1.2-7.3), the other was for decreased risk (RR, 0.32; 95% CI, 0.13-0.76), and 4 other estimates were not significant. For prostate cancer, there was 1 estimate of decreased risk (RR, 0.43; 95% CI, 0.22-0.83) and 1 of increased risk (RR, 1.98; 95% CI, 1.34-2.93) for advanced prostate cancer; 15 other estimates did not show a significant association. The study that assessed skin cancer found an increased risk (RR, 1.13; 95% CI, 1.01-1.27). No significant associations between omega-3 fatty acid consumption and cancer incidence were found for aerodigestive cancer, bladder cancer, lymphoma, ovarian cancer, pancreatic cancer, or stomach cancer.
A large body of literature spanning numerous cohorts from many countries and with different demographic characteristics does not provide evidence to suggest a significant association between omega-3 fatty acids and cancer incidence. Dietary supplementation with omega-3 fatty acids is unlikely to prevent cancer.

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Available from: Marika Suttorp Booth, Oct 01, 2015
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    • "Previous systematic review [36] have evaluated the impact of omega-3 fatty acid supplementation on cancer incidence on the basis of observational studies. These studies encompass a large body of literature spanning numerous cohorts, from many countries, with different demographic characteristics and do not provide any evidence to support a significant association between omega-3 fatty acid and cancer incidence. "
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    ABSTRACT: Omega-3 fatty acids are known to prevent cardiac death. However, previous observational studies have suggested that omega-3 fatty acids are associated with cancer risk in adults. We conducted a meta-analysis based on randomized controlled trials to evaluate the effect of omega-3 fatty acids on the risk of cancer incidence, nonvascular death, and total mortality. In February 2013, we performed electronic searches in PubMed, EmBase, and the Cochrane Library to identify randomized controlled trials on cancer incidence, nonvascular death, and total mortality. Relative risk (RR) was used to measure the effect of omega-3 fatty acid supplementation on the risk of cancer incidence, nonvascular death, and total mortality using a random-effect model. The analysis was further stratified by factors that could affect the treatment effects. Of the 8,746 identified articles, we included 19 trials reporting data on 68,954 individuals. These studies reported 1,039 events of cancer, 2,439 events of nonvascular death, and 7,025 events of total mortality. Omega-3 fatty acid supplementation had no effect on cancer incidence (RR, 1.10; 95%CI: 0.97-1.24; P = 0.12), nonvascular death (RR, 1.00; 95%CI: 0.93-1.08; P = 1.00), or total mortality (RR, 0.95; 95%CI: 0.88-1.03; P = 0.24) when compared to a placebo. Subgroup analysis indicated that omega-3 fatty acid supplementation was associated with a reduction in total mortality risk if the proportion of men in the study population was more than 80%, or participants received alpha-linolenic acid. Omega-3 fatty acid supplementation does not have an effect on cancer incidence, nonvascular death, or total mortality.
    BMC Public Health 02/2014; 14(1):204. DOI:10.1186/1471-2458-14-204 · 2.26 Impact Factor
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    • "Long-chain n-3 PUFA have a wide range of well attested health benefits, primarily in brain development in young children and as an important modulator of immune system function, especially the inflammatory response (Simopoulos 1991). As inflammation is central to many chronic disorders of aging and obesity, this subject is important and is regularly reviewed (MacLean et al. 2006; Schmitz and Ecker 2008; Simopoulos 2008; Nicholson et al. 2013). Although a-linolenic acid (C18:3 n-3) is found in leafy green vegetables, some nuts and some oil seed, it appears that only animals or algae can synthesise the long-chain n-3 PUFA docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (Sprecher 2002). "
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    Animal Production Science 01/2014; 54(7):831-855. DOI:10.1071/AN13536 · 1.29 Impact Factor
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    • "Globally , fish provides about three thousand million people with almost 20 % of their daily intake of animal protein (FAO 2012a). Some of the benefits attributed to the incorporation of fish (fish oils) in diets are mental health (Lin and Su 2007), dementia (Lim et al. 2006), cancer (MacLean et al. 2006), asthma (Woods et al. 2002), multiple sclerosis (Farinotti et al. 2012), diabetes (Hartweg et al. 2008), and early neurologic development (Simmer et al. 2008). In this setting, the growth of aquaculture has been considered as the production sector that could compensate for the declining wild-fish stocks and continue to supply the fish markets (FAO 2012a). "
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    ABSTRACT: Through a comparative analysis of prices in capture fisheries and aquaculture sectors, the objectives of this paper are a) to investigate three the trends in prices of forage catches to feed the aquaculture species, b) to analyze the amount of fish species need to feed aquaculture species in order to assess the level of efficiency in resource use, and c) to examine the degree of economic concentration either in wild-catch industry and aquaculture sectors. The results show that prices of cultivated species are higher than prices of the same species when harvested from the sea. We explain this fact by the interplay of three forces. First, the amount of wild fish to feed aquaculture species continues to improve over time. Second, the pressure of fishing activities has not been reduced since catches of most forage fishes are declining, which induce higher prices of capture species that feed aquaculture production. Third, the level of seafood market concentration is significantly higher in aquaculture than in wild catches, which generates higher prices in aquaculture.
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