High levels of omega-3, omega-6 could decrease cancer risk

Cancer remains a major health issue worldwide, responsible for an estimated 18.1 million new cases in 2020 alone. Among these cases, breast, lung, and colorectal cancers make up more than 30% of diagnoses.

Scientists continue to study various factors that could influence cancer development, including the potential role of polyunsaturated fatty acids (PUFAs). Known as essential "healthy fats," PUFAs are found in fatty fish, nuts, and certain plant oils and include omega-3 and omega-6 fatty acids.

Although PUFAs are widely known to benefit heart health and mental wellness, research suggests they may also reduce cancer risk. However, existing studies offer mixed results, and the relationship between PUFAs and cancer remains complex.

According to recent research from the University of Georgia (UGA), increasing omega-3 and omega-6 intake could help protect against a range of cancers. This study builds on previous findings and brings more insight into how these fatty acids might impact cancer prevention and survival.

The UGA study, which involved data from over 250,000 participants, found that higher levels of omega-3 and omega-6 fatty acids were associated with a decreased risk of developing cancer. Yuchen Zhang, the study’s lead author and a doctoral student at UGA’s College of Public Health, highlighted the findings: “Higher omega-3 and omega-6 levels were associated with lower rates of cancer. These findings suggest that the average person should focus on getting more of these fatty acids in their diets.”

Participants with high omega-3 levels showed lower rates of several cancers, including colon, stomach, and lung cancers. Omega-6 levels were associated with decreased rates of 14 different types of cancer, such as brain cancer, malignant melanoma, and bladder cancer. These findings support the potential protective effect of PUFAs and suggest they may lower the risk of developing at least 19 types of cancer.

Despite these findings, the broader scientific community remains cautious about declaring PUFAs as cancer preventatives. A comprehensive umbrella review of meta-analyses on omega-3 intake and cancer risk revealed no convincing evidence that omega-3 consumption significantly impacts the risk of most cancers. The review did find weak associations between omega-3 intake and reduced risks for liver, breast, and brain cancers, yet overall results were inconclusive.

Some meta-analyses focused on cancer survival rather than prevention, examining whether PUFA intake could affect mortality rates in cancer patients. These studies indicated that fish or marine omega-3s were linked to lower mortality among cancer patients, although total omega-3 intake did not show the same benefit.

Omega-6 effects remained unclear due to low-quality evidence and high variability across studies. Researchers noted significant limitations, including short follow-up times, small sample sizes, and reliance on self-reported dietary information.

Addressing these limitations, the UK Biobank study stands out as a landmark in PUFA research. This large-scale prospective study has followed over 500,000 participants since 2006, providing valuable data with a long follow-up period. Recent metabolomic analyses from the Biobank's baseline plasma samples allowed researchers to evaluate circulating PUFA levels, offering more objective data than dietary self-reports.

Preliminary studies using UK Biobank data found that both omega-3 and omega-6 levels were associated with lower cancer mortality. This association appeared independent of common risk factors like body mass index (BMI), alcohol consumption, or physical activity. The UK Biobank data supports the idea that circulating PUFA levels may better predict cancer outcomes than self-reported PUFA intake.

Given the limited dietary intake of omega-3 and omega-6 sources, many Americans turn to fish oil supplements to meet their nutritional needs. Fish oil supplements, one of the most popular dietary pills on the market, are praised for their potential to reduce cholesterol and improve heart health. However, the UGA study suggests that taking fish oil is not necessarily beneficial for everyone.

Kaixiong Ye, the study's corresponding author and an associate professor at UGA’s Franklin College of Arts and Sciences, noted that high omega-3 levels could slightly increase the risk of prostate cancer. Ye stated, “For women, it’s an easy decision: Eat more omega-3.”

Younger participants, particularly women, experienced stronger protective effects from omega-6 fatty acids. This finding points to potential age and gender differences in PUFA benefits, suggesting that health recommendations should be tailored based on individual risk factors.

Most previous studies on PUFAs and cancer risk relied on self-reported dietary data, which can be inaccurate due to recall errors and measurement challenges. For a more precise measure, researchers turned to circulating biomarkers—blood levels of omega-3 and omega-6.

A meta-analysis of prospective studies showed that blood omega-6 levels, but not intake, correlated with a lower overall cancer risk. Similarly, higher blood omega-3 levels were linked to a reduced risk of colorectal cancer.

These biomarkers offer a more reliable method to assess PUFA status and reveal insights into their potential roles in cancer risk. Monitoring blood levels rather than relying solely on dietary intake could refine future studies and help clarify the PUFA-cancer link.

PUFA research has come a long way, yet the field still faces challenges in establishing definitive conclusions. The UGA study adds to a growing body of research suggesting omega-3 and omega-6 fatty acids might help reduce cancer rates. However, conclusive evidence remains elusive due to study limitations and the need for more comprehensive data.

The UK's extensive Biobank study and recent advances in metabolomics hold promise for understanding PUFAs’ impact on cancer risk. But, as the current evidence shows, the benefits of these fatty acids are not one-size-fits-all. Individual factors, including age, gender, and specific cancer types, play a role in how omega-3 and omega-6 fatty acids affect cancer outcomes.

With additional research, scientists hope to pinpoint more precise recommendations on PUFA intake. Until then, a balanced diet rich in essential fatty acids appears to offer general health benefits, potentially extending to cancer prevention.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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