Reeling in the Lies: Fish Oil is Hurting, Not Helping You

By: DR DAVID FRIEDMAN

Fish oil supplements are heavily marketed as miracle capsules, promising to boost heart health, enhance brain function, and prevent chronic diseases. However, beneath these claims lies a troubling reality, a hidden world of toxic dangers backed by solid scientific evidence. There’s something fishy going on here! Below are the reel facts you need to  know:  

Hidden Toxins: What’s Lurking in Your Fish Oil?

As I share in my #1 bestselling book Food Sanity, many fish oil supplements contain alarming levels of PCBs (polychlorinated biphenyls)—industrial chemicals so toxic they were banned in the U.S. in 1979. These compounds are bioaccumulative, meaning they build up in fat tissue over time and do not leave the body easily, acting like molecular squatters in your brain, liver, and cells.

In a landmark California lawsuit, independent testing revealed that eight leading fish oil brands, CVS, GNC, Rite Aid, Nature Made, Solgar, and TwinLab, were contaminated with high levels of PCBs! 

But what’s more disturbing? No federal law requires fish oil manufacturers to test for PCBs or disclose their presence on the label. Consumers have no way of knowing what they’re swallowing or the damage to their bodies it can cause: 

• Carcinogenic: PCBs are linked to cancers of the liver, breast, skin, and prostate.
• Neurotoxic: These compounds disrupt normal brain development and function, particularly in children.
• Endocrine-disrupting: PCBs can mimic or block hormones, throwing your system into chaos and contributing to infertility, thyroid disorders, and early puberty.
• Immunosuppressive: Long-term PCB exposure has been associated with weakened immunity, increased infections, and autoimmune disease.

Even the World Health Organization (WHO) classifies PCBs as Group 1 carcinogens, on par with asbestos and tobacco. But here’s the kicker: PCBs are lipophilic, meaning they bond easily to oils and fats, which is exactly what fish oil is. Once they're in, they're nearly impossible to remove without destroying the oil’s structure.

The Rancid Truth

Fish oil is chemically fragile. From the moment it's extracted, it begins a race against time, and it usually loses. Exposure to heat, light, and oxygen sets off a chain reaction known as lipid peroxidation, turning healthy omega-3s into toxic aldehydes and free radicals that can wreak havoc inside the human body.

According to a Journal of Molecular Nutrition and Food Research report, even small amounts of oxidized oils promote DNA damage, cellular mutation, and inflammation, all hallmarks of chronic disease, aging, and cancer.

Here’s what you’re swallowing when fish oil goes rancid:

• Malondialdehyde (MDA): a known carcinogen and mutagen, found in oxidized oils and linked to liver damage and accelerated aging.
• 4-HNE (4-Hydroxynonenal): a byproduct of omega-6 and omega-3 fat oxidation that interferes with mitochondrial function and promotes neurodegenerative disease.
• Acrolein:  a pro-inflammatory compound also found in cigarette smoke, shown to harden arteries and damage the lining of the gut and lungs.

 What the Supplement Industry Doesn’t Want You to Know

And here's the jaw-dropper: Fish oil can go rancid before it even hits the bottle. Oxidation can occur at dozens of points during storage, transportation, and encapsulation. Yet manufacturers still stamp the bottle with 2- to 4-year shelf lives—a chemical impossibility.

Smelly fishy burps may turn away the person you are dating, but they're also a red flag for lipid peroxidation, meaning the oil has gone rancid, which can occur even in high-end brands. And if it smells like nothing, the manufacturer may have deodorized it, artificially removing the stench.

Scientific Studies Confirm Serious Health Risks

• Atrial Fibrillation & Stroke in Healthy Adults: A recently published extensive UK-BMJ Medicine observational study of over 400,000 healthy adults found that regular fish oil supplement users experienced a 13% higher risk of atrial fibrillation and a 5% increase in stroke risk compared to non-users
• Colon Cancer: Research published in Cancer Epidemiology, Biomarkers & Prevention found that fish oil supplementation was linked to increased colon cancer risk.
• Alzheimer’s Disease: A  study in the Journal of the American Medical Association (JAMA) found that fish oil potentially increases Alzheimer's risk rather than preventing it.
• Blood Sugar Problems: Diabetes Care, a peer-reviewed medical journal, revealed that fish oil supplements significantly raise blood sugar levels.
• Accelerated Aging: A  study from the American Journal of Clinical Nutrition associated fish oil consumption with faster cellular aging.
• Reduced Immunity: According to research published by The Journal of Immunology, fish oil supplements, particularly when consumed in high doses, have been shown to suppress immune function by reducing the activity of white blood cells and key inflammatory cytokines needed to fight infections.
• Cancer Mortality: Shockingly, a study published in the Journal of the National Cancer Institute found that women taking fish oil had up to a five-fold increase in cancer mortality risk!
• Increased Heart Attacks: NIH and Jefferson Health highlighted that high-dose fish oil supplementation did not protect and may even increase certain heart-related risks.
• Strokes: Harvard Health’s Report bluntly states: Despite the labels, there's no evidence that these amber capsules will improve your cardiovascular health or reduce your risk of strokes; they may contribute to these conditions! 
• Other Negative Side-Effects:   Recent health reviews (e.g., VerywellHealth, Healthline) have documented adverse effects including increased blood sugar, gastrointestinal issues, bleeding risk, LDL rise, and, notably, atrial fibrillation.

Still not convinced?...  

The Cochrane Collaboration, one of the most trusted sources in evidence-based medicine, published a major systematic review in 2018 examining the effects of omega-3 fatty acid supplements on heart health and all-cause mortality. This review pooled data from 79 randomized controlled trials involving over 112,000 participants.

Key Findings:

• No significant reduction in risk of death from any cause.
• No benefit for preventing heart attack, stroke, or other cardiovascular events.
• No meaningful reduction in triglyceride levels was noted.
• No beneficial effect on cardiovascular health, chronic disease prevention, or longevity.

Expert Insights: The “Sewage of the Sea”

As host of To Your Good Health Radio, I’ve interviewed some of the most respected voices in health, nutrition, and longevity. One memorable conversation I had was with Dr. Barry Sears, a world-renowned omega-3 expert and author of The Omega Rx Zone. Despite being one of the earliest champions of omega-3s, even he sounded the alarm on the current state of commercial fish oil supplements.

Dr. Sears didn’t mince words. He referred to many over-the-counter fish oil products as the “sewage of the sea.” Why? Because they’re often harvested from the scraps of industrial fishing operations—the eyes, guts, and leftover fish trimmings processed for animal feed and fertilizer. These parts are the most prone to contamination, absorbing heavy metals, PCBs, dioxins, and pesticides from polluted waters. Your Omega-3 “health” supplement is often made from the ocean's bottom refuse, and you're swallowing industrial waste, not a therapeutic nutrient.

To drive the point home, Dr. Sears recommended a simple at-home purity test:

Break open and freeze four or five fish oil gel caps in a shot glass. If the oil solidifies, it shows high levels of saturated fats, contaminants, and toxins. It’s likely a cleaner product with a better omega-3 concentration if it remains liquid.

The problem stems from poor sourcing, lack of regulation, and the chemical fragility of fish oil itself. Most fish oil supplements are deodorized, stripped of beneficial compounds, and cut with filler oils to improve texture or shelf stability, further degrading their quality.

Krill Oil: The Smarter, Safer Source of Omega-3s

If you want the benefits of omega-3s without the toxic baggage of fish oil, krill oil is the smarter choice. Instead of swallowing the “sewage of the sea,” you can go straight to the source—krill, the tiny crustaceans that whales, salmon, and other marine life rely on to build their omega-3 reserves.

Most people think salmon is the ultimate source of fish oil, but krill is what gives salmon their reddish-orange color. As I share in  Food Sanity, farm-raised salmon are actually gray because they’re deprived of krill, so producers dye them to fool consumers.

Krill live at the bottom of the food chain, feeding on plankton in some of Earth's cleanest, least-contaminated waters. That means they’re naturally low in mercury, PCBs, and other ocean toxins, giving krill oil a major edge in purity, safety, and sustainability.

But the benefits of krill go deeper:

• Built-in Protection Against Oxidation:
  Krill oil contains astaxanthin, a powerful natural antioxidant that prevents oxidation. This helps preserve the oil's quality without artificial preservatives and explains why krill oil doesn’t go rancid as easily as fish oil.

• Superior Absorption:
  The omega-3s in krill oil are bound to phospholipids—the same structure found in human cell membranes. This makes them far more bioavailable than most fish oils' triglyceride or ethyl ester forms. A study published in Lipids in Health and Disease found that krill oil led to significantly higher improvements in omega-3 blood levels and cholesterol reduction compared to fish oil at smaller doses.  

• Cardiovascular and Anti-Inflammatory Benefits:
  A randomized controlled trial in BMC Cardiovascular Disorders found that krill oil significantly reduced C-reactive protein (CRP), a key marker of inflammation, while also improving blood lipid profiles, without adverse side effects.

• No Fishy After taste: Krill oil doesn’t produce the dreaded fish burps or reflux for which fish oil is infamous. You can finally take an omega-3 supplement without tasting the ocean all day.

Plant-Based Sources of Omega-3s

There are several options if you're looking for plant-based alternatives to get omega-3s.

Algal oil is a standout plant-based source because it delivers the same long-chain omega-3s—EPA and DHA—found in fish, but without the contamination risks. Unlike seeds and nuts that provide ALA (which must be converted in the body), algal oil supplies ready-to-use omega-3s in their active form, making it especially beneficial for brain, eye, and heart health. Since fish get their omega-3s by eating algae, algal oil allows you to cut out the middle fish and go directly to the source. It’s also a sustainable and eco-friendly choice, produced in controlled environments free from ocean pollutants like mercury, microplastics, and PCBs.

Ground flaxseeds are another great option. They provide around 2,350 mg of ALA (alpha-linolenic acid) per tablespoon. They're also high in fiber and lignans, which support hormone balance and heart health. Chia seeds are another excellent choice, offering about 5,000 mg of ALA per ounce along with fiber and protein; they absorb liquid to form a gel, supporting digestion and hydration. Walnuts and hemp seeds are also notable sources of ALA.

The evidence is clear: fish oil supplements are not the health saviors they're marketed to be. Protect your body from harmful contaminants, oxidation damage, and hidden health risks by choosing safer, cleaner omega-3 alternatives like krill or Algal oil. Your body deserves real nourishment, not marketing myths.

If this information opened your eyes, there’s more where it came from. For insider health tips, uncovering food and supplement fraud, clean eating strategies, and the truth about what’s really on your plate, follow me:

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REFERENCES:

• Council for Responsible Nutrition. (2010). CRN Says There Are No Safety Issues with Fish Oil. http://www.crnusa.org/CRNPR10CRNNoSafetyIssueswFishOil030210.html
• Kanner, J. (2007). Dietary advanced lipid oxidation end products are risk factors to human health. Journal of Molecular Nutrition and Food Research, 51(9), 1094–1101.
• Cancer Epidemiology, Biomarkers & Prevention. (2010). Association between fish oil supplements and increased colon cancer risk.
• Quinn, J. F., et al. (2010). Docosahexaenoic acid supplementation and cognitive decline in Alzheimer's disease: a randomized trial. JAMA, 304(17), 1903-1911.
• Fish Oil & Blood Sugar Control. Fedor, D., & Kelley, D. S. (2009). Prevention of type 2 diabetes by n-3 polyunsaturated fatty acids. Current Diabetes Reports, 9(5), 360–366. https://doi.org/10.1007/s11892-009-0059-4
• Wakutsu, M., et al. (2011). Effects of fish oil supplementation on glucose and lipid metabolism in patients with type 2 diabetes mellitus. Diabetes Care, 34(2), 297–303. https://doi.org/10.2337/dc10-1283
• Fish Oil & Accelerated Aging. Farzaneh-Far, R., Lin, J., Epel, E. S., Harris, W. S., Blackburn, E. H., & Whooten, R. (2010). Association of marine omega-3 fatty acid levels with telomeric aging in patients with coronary heart disease. American Journal of Clinical Nutrition, 92(5), 1254–1260. https://doi.org/10.3945/ajcn.2010.29477
• Albert, B. B., Derraik, J. G. B., Cameron-Smith, D., Hofman, P. L., & Cutfield, W. S. (2015). Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA.
  Scientific Reports, 5, 7928. https://doi.org/10.1038/srep07928
• Brasky, T. M., et al. (2012). Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. Journal of the National Cancer Institute, 105(15), 1132-1141.
• Weil, A. (2007). Considering Krill Oil? Retrieved from http://www.drweil.com/drw/u/QAA400239/Consider-Krill-Oil.html

• Chen, G., et al. (2024). Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study. BMJ Medicine, 3(1), e000451. nih.gov+15bmjmedicine.bmj.com+15nutraingredients-usa.com+15
• Corliss, J. (2023, December 1). The false promise of fish oil supplements. Harvard Heart Letter, Harvard Health Publishing. harvard.edu
• com staff. (2024, July 10). Study: Fish Oil Supplements Tied to Increased Risk of Stroke, AFib in Some People. Health.com. medicalnewstoday.com+14health.com+14verywellhealth.com+14
• Verywell Health. (2023). If You're Healthy, Daily Fish Oil Supplements Might Come With a Risk. com
• (2024). Why Fish Oil Supplements Can Be Dangerous for the Heart. health.harvard.edu+15time.com+15pubmed.ncbi.nlm.nih.gov+15
• NutraIngredients-USA. (2024). Mixed results: Fish oil and cardiovascular events.
• Superior Absorption & Lipid Profile Comparison.
  Ulven, S. M., & Holven, K. B. (2011).
• Comparison of krill oil and fish oil on serum lipids and lipoproteins in healthy volunteers. Lipids in Health and Disease, 10, 108. https://doi.org/10.1186/1476-511X-10-108
• Anti-Inflammatory Effects and CRP Reduction. Maki, K. C., Reeves, M. S., Farmer, M., Griinari, M., Berge, K., Vik, H., & Hubacher, R. (2009).
• Krill oil supplementation reduces inflammation and improves lipid profiles in mildly overweight adults. BMC Cardiovascular Disorders, 9, 50. https://doi.org/10.1186/1471-2261-9-50
• Calder, P. C., et al., 2008. “Fatty acids and immune function: New insights into mechanisms.” The Journal of Immunology, 181(9), 5795–5800. https://doi.org/10.4049/jimmunol.181.9.5795)