Higher levels of omega-3 and omega-6 fatty acids are associated with a lower risk of several types of cancer, including brain, colon, stomach, and lung cancer, according to a study of more than 250,000 participants. In addition, the benefits of omega-6 are particularly effective for younger adults, especially women. The findings highlight the potential of these “healthy fats” in preventing cancer, regardless of BMI or lifestyle.
Cancer is a leading cause of morbidity and mortality worldwide, with an estimated 18.1 million cancer cases globally in 2020. Breast, lung, and colorectal cancers account for more than 30% of the total annual incidence.
Scientific research has sought to understand how polyunsaturated fatty acids (PUFAs), such as omega-3 and omega-6, can influence both the development and survival of different types of cancer.
PUFAs are essential components of cell membranes and are involved in important processes in the body, including regulating inflammation and metabolic pathways.
In particular, omega-3 and omega-6 have distinct properties. Omega-3, found in fish and flaxseed oil, for example, has been associated with anti-inflammatory effects and support for heart health. Omega-6, abundant in vegetable oils but also essential, may be linked to inflammatory responses that, in excess, can aggravate certain conditions.
Since cancer is strongly influenced by inflammatory and metabolic processes, researchers are investigating whether the presence of PUFAs could help reduce the risk of developing the disease.
However, the link between PUFAs and cancer is complex and the results, so far, have been inconclusive.
Previous observational studies have examined the relationship between PUFA intake (mainly omega-3) and the incidence of cancers such as liver, breast, and brain. These studies have suggested a slight inverse association between omega-3 intake and the risk of these types of cancer.
However, because much of this data comes from questionnaires on diet and supplement intake, the results are limited by inaccuracies, such as participants’ recall errors or inaccuracies in the dietary databases used to calculate intake.
A more recent meta-analysis of randomized controlled trials, which are considered more reliable, showed that increased intake of marine omega-3, found in fish, had no significant impact on cancer prevention or on reducing deaths from the disease.
The relationship between omega-6 and cancer is also uncertain, with the evidence so far being of very low quality. Given the variability and limitations of dietary methods, many studies now use blood biomarkers to obtain more objective and accurate measurements.
For example, using blood samples allows direct measurement of omega-3 and omega-6 levels in the body, eliminating the errors associated with self-reported dietary intake.
Studies using biomarkers have shown that higher blood levels of omega-6 are associated with a lower risk of cancer overall, while higher levels of omega-3 are correlated with a lower chance of developing colorectal cancer.
The ongoing research at the UK Biobank, one of the largest cohorts in the world with over 500,000 participants monitored since 2006, allows scientists to closely monitor the relationship between blood PUFA levels and cancer risk.
The UK Biobank offers unique data in that it has detailed information about the health and lifestyle of its participants, as well as blood samples for metabolomics analysis from about 60% of those enrolled.
Over more than 12 years of follow-up, about 29,838 UK Biobank participants were diagnosed with cancer. Using this data, researchers examined the percentages of omega-3 and omega-6 in the blood concerning the risk of developing different types of cancer.
The study found that both omega-3 and omega-6 were associated with a small reduction in overall cancer risk. Overall, of the 19 specific cancer types studied, 14 were inversely associated with omega-6 levels, while five were inversely associated with omega-3, indicating a possible protective action of these fatty acids for several types of cancer.
An exception was observed in prostate cancer, which showed a positive correlation with high blood levels of omega-3, suggesting that there are still important nuances to be explored.
This UK Biobank study highlights the potential of PUFAs as influencers of cancer risk, although the associations are subtle. With further studies using blood biomarkers, it is possible to better clarify the role of omega-3 and omega-6 fatty acids in cancer prevention.
Future studies could focus on larger populations and longer follow-up periods, and investigate the specific impact of different types of PUFA on cellular health and cancer mechanisms.
These findings may, in the long term, contribute to new prevention strategies based on diet and nutrition, especially for at-risk populations, and even aid in the development of more personalized therapeutic approaches to combat cancer.
Risk estimates of overall cancer incidence and specific cancer sites for 1-SD increase in plasma omega-6% and omega-3%. For esophageal cancer, additionally adjusted for baseline gastroesophageal reflux disease and waist-to-hip ratio. For colon cancer and rectal cancer, additionally adjusted for baseline diabetes, aspirin use, processed meat intake, waist-to-hip ratio, and family history. For pancreatic cancer, additionally adjusted for baseline diabetes. For lung cancer, additionally adjusted for family history. For malignant melanoma, additionally adjusted for skin color, ease of skin tanning, use of sun/UV protection, childhood sunburn occasions, and frequency of tanning/sunlamp use. For breast cancer, restricted to women, and further adjusted for age at menarche, hormone replacement therapy use, oral contraceptive use, number of live births, menopausal status, hysterectomy status, and family history. For uterine and ovarian cancer, restricted to women, and further adjusted for age at menarche, hormone replacement therapy use, oral contraceptive use, number of live births, menopausal status, and hysterectomy status. For prostate cancer, restricted to men, and further adjusted for family history.
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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
Yuchen Zhang, Yitang Sun, Suhang Song, Nikhil K. Khankari, J. Thomas Brenna, Ye Shen, Kaixiong Ye
International journal of cancer. 17 October 2024
Abstract:
Previous epidemiological studies on the associations between polyunsaturated fatty acids (PUFAs) and cancer incidence have been inconsistent. We investigated the associations of plasma omega-3 and omega-6 PUFAs with the incidence of overall and 19 site-specific cancers in a large prospective cohort. 253,138 eligible UK Biobank participants were included in our study. With a mean follow-up of 12.9 years, 29,838 participants were diagnosed with cancer. The plasma levels of omega-3 and omega-6 PUFAs were expressed as percentages of total fatty acids (omega-3% and omega-6%). In our main models, both omega-6% and omega-3% were inversely associated with overall cancer incidence (HR per SD = 0.98, 95% CI = 0.96–0.99; HR per SD = 0.99, 95% CI = 0.97–1.00; respectively). Of the 19 site-specific cancers available, 14 were associated with omega-6% and five with omega-3%, all indicating inverse associations, with the exception that prostate cancer was positively associated with omega-3% (HR per SD = 1.03, 95% CI = 1.01–1.05). Our population-based cohort study in UK Biobank indicates small inverse associations of plasma omega-6 and omega-3 PUFAs with the incidence of overall and most site-specific cancers, although there are notable exceptions, such as prostate cancer.
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