Clarifying the Confusing World of Fish Oil

Healthy Aging

So, is fish oil good for me?

The countdown is on until Simon & Schuster’s March 25th release of The Longevity Nutrient. This book tracks our 20-year scientific journey – starting with an unexpected discovery of C15:0’s health benefits while helping dolphins – which has culminated in a movement to improve global health. And dare we say, humanity?

In this series of Science Says!, we provide a behind-the-scenes science peek relevant to each of the book’s chapters – from surprising dolphin discoveries to longevity molecule must-haves, from how essential fatty acids are discovered to the many ways C15:0 works, from how a newly found nutritional deficiency accelerates aging to how fixing and optimizing our C15:0 levels can slow aging to help us live healthier, longer.

This week, let’s talk about what dolphins, kids from London’s Industrial Revolution, and Inuits from Greenland have to teach us about fish oil and omega-3s.

So, how did fish oil become popular?

Fish, of course, have been part of a healthy human diet for a long, long time. The commercialization of fish oil, however, didn’t kick in until London’s industrial revolution during the early 1800s.

To be more specific, not just fish oil. Cod liver oil. This is because there was so much pollution in the air that the sun didn’t reach developing children. And without sun to activate vitamin D, they developed vitamin D deficiencies (aka, rickets). Which resulted in poor bone health and bowed legs.

Thankfully, it was discovered that oil from cod livers (which was stored and rotted in vats – blech) was chock full of vitamin D,  as well as other key vitamins. Which, albeit smelly and gross, cured vitamin D deficiencies and rickets in children.

Thus, up through the 1990s (and beyond), cod liver oil maintained its role as a valuable source for vitamins – even when the pollution went away and the sun returned.

Okay, when did regular fish oil and omega-3s come into the picture?

Last week, we talked about how alpha linolenic acid (ALA, an omega-3 and precursor to EPA and DHA) was discovered as an essential fatty acid in milkfat around 1930. Excitement around omega-3s and fish oil, however, really didn’t gain traction until the 1970s.

This is when two scientists from Denmark (Bang & Dyerberg) heard that Inuits from Greenland had exceptionally low risks of developing heart disease and type 2 diabetes. While Chapter 5 in The Longevity Nutrient shares the details of this super interesting story, the key points are as follows:

• The Inuit diet consisted primarily of marine animals, which were understood to have high levels of polyunsaturated fatty acids (PUFAs).
• Inuits had lower triglycerides than people in Denmark, which led Bang & Dyerberg to conclude that the “Eskimo Diet” of high PUFAs in fish oil (especially omega-3s) explained their lower risk of heart disease and type 2 diabetes.
• This discovery resulted in the explosive growth in the fish oil supplement industry as a means to provide omega-3s to protect our heart health.
• Follow-up studies by Bang & Dyerberg, however, showed that two assumptions were wrong. First, Inuits actually had lower PUFAs in their blood than people in Denmark. Second, Inuits didn’t have a lower risk of developing either heart disease or type 2 diabetes.

Despite this somewhat false start to the omega-3 fish oil supplement world, there have been numerous studies over the past 50 years demonstrating a number of health benefits of omega-3s. These studies, however, have had mixed results.

What does science today say about omega-3 fish oil supplements?

Based on numerous meta-analyses, large clinical trials, and extensive reviews by both the National Institutes of Health and the American Heart Association, here’s where the world is at with omega-3 fish oil supplements:

On the downside:

• Among healthy people, omega-3 fish oil supplements do not appear to prevent heart disease.
• It is unclear whether omega-3 fish oil supplements help with many other prior claims, including cognitive decline, autoimmune disease, dry eye disease, depression, and frailty.

On the upside:

• Among people with existing heart disease, omega-3 fish oil supplements can help prevent a major cardiovascular event.
• At higher doses (albeit beyond what is recommended by the FDA), omega-3 oil supplements can lower triglyceride levels.
• Omega-3 fish oil supplements can help reduce symptoms of rheumatoid arthritis.

Looking beyond omega-3 fish oil supplements, there is more good news:

• Purified EPA (without DHA) prescription drugs do appear to lower the risk of heart disease.
• Eating fish (vs. taking omega-3 fish oil supplements) provides much clearer health benefits consistently across studies, including a lower risk of heart disease.

A half-century of studies have helped to elucidate when omega-3s are best for whom, based on the omega-3 source (supplement, food, or drug), and the desired outcome (lower triglycerides, overall health, or specifically heart health, respectively).

Why are the studies on omega-3 fish oil supplements so variable?

It really comes down to quality. Including the following factors:

• The quality and species of the fish, as well as the time of year they were caught. Different fish species have different fatty acid profiles, and even the same species can differ based on warmer versus colder waters.
• The variation of fatty acids in different fish oils. There are often more than a dozen different fatty acids in fish oil, including proinflammatory even-chain saturated fatty acids and omega-6 fatty acids.
• The natural susceptibility of omega-3s to attack by oxygen, resulting in lipid peroxidation and rancidity. Numerous studies have repeatedly shown that about half of randomly tested omega-3 fish oil supplements have lipid peroxidation levels above international voluntary safety standard levels.
• The potential for less EPA or DHA levels than what is listed on the bottle. Lipid peroxidation can lower the effective amounts of omega-3s in the bottle, which explains why many supplements contain less-than-advertised omega-3 levels.

All of this variation in quality helps explain why study outcomes vary, too.

In summary, there are proven health benefits of omega-3s, especially: 1) for people with existing heart disease, 2) with pure, prescription EPA drugs, and 3) for almost all people who get their omega-3 from routinely eating fish.