The skeptical cardiologist recently gave a virtual presentation to the St. Louis University School of Medicine Grand Rounds on recent studies examining the therapeutic benefits of omega-3 fatty acids and fish oil supplements.
The conversation lasts about 45 minutes and is absolutely fascinating. Was just a joke. Actually, I am always amazed at how strangely and slowly I speak, even if I feel totally at ease and know the subject back and forth.
I started by pointing out that I was talking about a strangely interesting topic that encompassed nutrition, business, the nutraceutical-industrial complex, quackery and preventive cardiology, and fascinating insight into the obvious weaknesses of nutritional epidemiology, the hidden weaknesses of randomized clinical trials, supplies and the many sources of bias in scientific research.
Here is the video of my talk, which was followed by about 30 minutes of questions and comments, including a discussion on edible oils.
What I have mentioned can be reduced to a question that most of us have asked ourselves over 40 years: Should I take fish oil supplements to prevent cardiovascular disease?
Although almost all of my academic research and publications have been in the field of echocardiography, over the past twelve years I have developed into a clinical cardiologist with primary interests in preventive cardiology and an enlightened medical management of atrial fibrillation.
Over the years I have developed a healthy skepticism about medical and scientific information that has potential biases.
To educate my patients, myself, and the general public, I started writing a blog in 2013. First, I examined the scientific basis (or lack thereof) of current dietary guidelines regarding cardioprotection.
One of the first topics I looked at was fish oil supplements, which appeared to have solid scientific and policy support. Before delving into the subject, I recommended that patients with coronary artery disease or at high risk take fish oil supplements. But after looking at the evidence, I started taking patients from them.
The fish oil story began with observations that Eskimos in Greenland on an extremely high-fat diet rarely showed signs of coronary artery disease.
In the 1970s, two Danish doctors, Hans Olaf Bang and Jørn Dyerberg, went to Greenland because they had read that the Inuit had very little cardiovascular disease and that they ate seals, whales and fish.
When performing blood lipid analyzes on Inuit samples, they found very high levels of omega-3s and hypothesized that omega-3s may be responsible for lower levels of coronary artery disease in Greenlandic Inuit.
These observations have sparked tens of thousands of studies attempting to determine whether omega-3 fatty acids (OMFAs) are key to cardiovascular protection.
In the past 40 years there has been a marked movement to proclaim all saturated fats as bad and all polyunsaturated fatty acids (PUFAs) as good. Simplifying nutrition counseling in this way leads to simple public health messages, but it blurs the truth. For example, there is no solid evidence that milk fat, which is overwhelmingly saturated, has negative heart effects.
PUFAs have also found in PUFAs that people consume far too many omega-6 PUFAs, which are predominantly obtained from corn, thistle and soybean oil. Rapeseed oil, a product of the factory’s ultra-processing and genetic manipulation, is widely advertised as being very good for the heart.
The omega-3 family consists of long chain PUFAs (18 to 22 carbons) with a double bond on the third carbon from the omega end. The marine OMFAs of interest are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which mostly come from the consumption of seafood
The DPA levels are not associated with fish consumption and have minimal relevant physiological or clinical effects. DHA is a primary structural component of the human brain, cerebral cortex, skin, and retina. For organisms that don’t eat algae or animal products that contain DHA, DHA is made internally from alpha-linolenic acid instead. Alpha-linolenic acid is an essential n-3 PUFA with 18 carbon atoms that comes from vegetable sources.
In addition to long-chain 3-PUFA, fish provide specific proteins, vitamin D, selenium and other minerals and elements.
Observational studies have shown that higher dietary consumption of oily fish or omega-3s is associated with fewer cardiovascular events and that circulating levels of EPA or DHA are inversely correlated with cardiovascular risk.
Of course, all of these studies have not proven that consuming fish or taking OMFA supplements reduces the risk of CVD.
This does not prevent press releases and news related to these observational studies from promoting them as causality and implying an important role for supplementation in reducing heart disease. The 2005 American Heart Association Nutritional Guidelines, published by Dr. Co-authored by Bill Harris, arguably the world’s leading expert on OMFA, concluded that everyone in the population “should eat a variety of (preferably oily) fish” at least twice a week “their diet should” include oils and foods that are high in ALA (flaxseed, canola and soybean oils, flaxseed and walnuts). “
What Are the “Oily Fish” All Americans Should Consume Twice a Week? The amount of EPA + DHA in the recommended 3.5 ounce serving size of fish varies widely.
To make fish consumption more complicated, one needs to consider the mercury levels and the sustainability of the species that are consumed. The Environmental Defense Fund has a seafood selector that rates each fish species based on these three points. But even within a single type that you might think is incredibly healthy – the mackerel – the mercury levels vary widely between species.
As a result, most Americans threw up their arms in frustration and confusion and began buying millions of fish oil supplements in 1994, fueled by a burgeoning fish oil additives industry that was free of any legal restrictions.
This is how the era of fish oil began as snake oil, used by quacks like Dr. Oz, the “FISH OIL FOR ALL!” Recommended, was widely used.
At this point in the presentation, I recently detailed large randomized controlled trials of high dose omega-3 fish oil supplements. Spoiler alert, the STRENGTH study found no cardiovascular benefits.
Along the way, I addressed the weaknesses of observational epidemiology and the sneaky methods that the fish oil supplement industry uses to influence scientific publications.
My conclusion was that there is no compelling evidence of using over-the-counter fish oil supplements for primary or secondary prevention of cardiovascular disease.
I also discussed the reasons to question the benefits of Ikosapent-Ethyl (Vascepa) shown in the REDUCE-IT study and why there needs to be another study in which Ikosapent-Ethyl with a neutral one Oil is compared like corn oil instead of mineral oil.
Shortly before my presentation, I came across a study published in late 2020 that is the first prospective study in Inuit on the cardiovascular effects of long-chain n-3 polyunsaturated fatty acids. No effect was found that, in my opinion, closes the loop on our OMFA trip.
Anthony C. Pearson, MD, is a non-invasive cardiologist and professor of medicine at St. Louis University School of Medicine. He blogs about nutrition, heart tests, quacks, and other things that deserve skepticism at The Skeptical Cardiologist, which first appeared in a version of this post.
Last updated on January 17, 2021