Drilling into the statistics revealed that elevated levels omega-6 and omega-3 were associated with significant reductions in 14 and five site-specific cancers, respectively, according to data published in the International Journal of Cancer.
The analysis was performed by scientists at the University of Georgia, Vanderbilt University and Cornell University in the United States using data from over 250,000 participants in the UK Biobank over a period of about 13 years. During that time, almost 30,000 people were diagnosed with cancer.
“Our study laid a solid foundation for future mechanistic studies into the roles of PUFAs [polyunsaturated fatty acids] in the etiology of various cancers,” wrote the authors, led by Yuchen Zhang, a doctoral student in the University of Georgia’s College of Public Health.
“It also provided insights into the development of cancer prevention strategies by managing circulating PUFAs.”
Omega-3 and omega-6
The study adds to the overall body of science supporting the myriad health benefits of omega-3 fatty acids, such as the marine-derived eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3) and alpha-linolenic acid (ALA, C18:3 n-3) from plants like flax.
Omega-6 fatty acids are found in vegetable oils, nuts and seeds, and include linoleic acid (18:2 n-6), arachidonic acid (20:4 n-6) and gamma-linolenic acid (18:3 n-6).
Study details
The new study analyzed data from 253,138 people, with 29,838 people being diagnosed with cancer during the average follow up of 12.9 years.
Crunching the numbers revealed that overall omega-3 and omega-6 intakes were linked to a 1% and 2% reduction in the risk of overall cancer, respectively.
Analysis of 19 site-specific cancers showed that elevated levels of omega-6 were linked to reductions in the risk of 14 of these, while higher omega-3 levels were linked with a reduction in five site-specific cancers, including colon, stomach and lung cancer.
“The associations of omega-6 PUFAs were stronger in the younger age group and in women, whereas the associations of omega-3 PUFAs were more prominent in the older group, in men, and in current smokers,” wrote Zhang and her co-workers.
However, a positive association was reported for higher omega-3 levels (and DHA specifically) and a slight increase in the risk of prostate cancer, which the researchers noted is at odds with “most studies [which] did not find significant associations with dietary intake or blood level of omega-3 PUFAs.
“Further studies are warranted to explore the roles of individual omega-3 PUFAs in the etiology of prostate cancer,” they added.
Commenting independently on the study's findings, Harry Rice, PhD, VP of regulatory and scientific affairs at the Global Organization for EPA and DHA Omega-3s (GOED), told NutraIngredients: "I would call the finding of a positive association between plasma long-chain omega-3s and prostate cancer to be spurious at best. Honestly, I thought we put this issue to bed a decade ago.
"In 2013, following the media frenzy around the publication of research reporting a potential link between long-chain omega-3s and the risk of prostate cancer, GOED commissioned a comprehensive systematic review and meta-analysis to estimate the potential association between long-chain omega-3s and prostate cancer. The review included separate analyses of dietary intakes and blood biomarkers. In 2014, the results were published and without getting into the weeds, the results did not support an association between long-chain omega-3s and prostate cancer. To this day, there is no plausible biological mechanism for long-chain omega-3 cancer tumorigenesis."
Source: International Journal of Cancer
Published online ahead of print, doi: 10.1002/ijc.35226
“Associations of plasma omega-6 and omega-3 fatty acids with overall and 19 site-specific cancers: A population-based cohort study in UK Biobank”
Authors: Y. Zhang, et al.