Fish oil is a concentrated source of DHA, a very special type of omega-3 fat that we use in our neurons, in our eye and heart tissue, and in sperm. In fact, some 30 million Americans take fish oil supplements daily simply to be sure they get enough of this very important fat. But, even though DHA is very important to health, I want to explain why it is a mistake to take fish oil supplements in any form.
DHA is one of several types of special fats known as omega-3 fats. Humans cannot make omega-3s from scratch, instead they must be part of our diet. Given that we cannot live without them, they are called essential fats. Plants make omega-3 fats but the types they make are shorter than DHA. When we eat plants rich in 3s, we elongate some of them into DHA but we do so very slowly. We can also get “pre-made” DHA if we eat wild fatty cold-water fish (such as salmon, mackerel, and sardines) because their diets are very rich in DHA. Given that DHA is needed in important parts of our bodies, such as our brain and heart, we have for many years been advised to eat significant amounts of DHA-rich seafood and/or take fish oil supplements to make sure we have enough DHA for our brain to function properly. Vegetarians, vegans, and those who do not eat seafood were (and frequently still are) told that they absolutely must take a DHA supplement to stay healthy.
But times have changed. Fish oil supplements are no longer deemed to be good for us. This complete turnabout is the result of two main realizations (although there are others). First, research failed to show any health benefits in those taking fish oil and instead began to show harm. Second, DHA proved to be very reactive and forms a variety of basically rancid fats as it reacts. It is well known that rancid fats are toxic.
Many, many studies show that eating fish has health benefits, including a lower risk of heart problems. It made sense to assume that the same health benefits would accrue in those who took DHA-rich fish oil supplements instead of eating fish. But, unfortunately, fish oil failed to provide the same benefits. Instead one study found an increased risk of atrial fibrillation (a type of heart arrhythmia) and prostate cancer in people taking fish oil supplements regularly. A different study confirmed that fish oil supplements increase the risk of atrial fibrillation. A very large study found that 2 servings of DHA-rich fish a week in two years decreased mortality by 29%. In a follow up study, where participants took fish oil instead, no health benefits were found; in fact, it revealed a trend for greater mortality. Other large studies also concluded that fish oil did not reduce the risk of heart attacks and other “cardiovascular events.” In angina patients, fish oil instead increased the death rate. Animals fed fish oil developed more malignant arrhythmias.
A very recent study found that mice fed fish oil were much more susceptible to infections such as tuberculosis, salmonella and listeria. When infected with a flu virus, mice taking fish oil ended up with viral load 7 times higher than mice not getting fish oil. And the mortality rate of the flu was much, much higher –a death rate of 47% compared to 10% in flu-infected mice taking fish oil. These are just a few of the studies that culminated in the current advice: People should NOT take fish oil supplements except in very special cases such as severe hypertriglyceridemia with danger of pancreatitis or in people whose diet is extremely poor (e.g. some types of tube feeding).
DHA is extremely beneficial but it is also very fragile and highly reactive. And when DHA reacts, it forms oxidized, troublesome fats. The speed of oxidation increases as the DHA is exposed to light, heat, and air. Even fish oil stored in the dark at near freezing (39F) can develop unacceptable amounts of “bad” fats within a month of storage. In studies, oxidized fats cause organ damage, inflammation, cancer, and atherosclerosis. Manufacturers use tests to measure the amount of oxidized fats in their fish oil but the standards used are based on palatability and taste, not on how they impact human health. Those tests do not measure all of the many types of oxidized fats and the limits set apply to the fish oil at time of bottling, not at time of consumption. As a result, fish oil supplements in reality are a mixture of beneficial fats, a variety of additives, and varying amounts of oxidized or toxic, rancid fats.
In a Canadian study, half of supplements on the store shelf exceeded these “palatability” limits. A US study found that 27% of fish oil tested had twice the recommended amount of oxidized fat. In South Africa and New Zealand, more than 80% exceeded these levels. And in another study about half of the fish oil supplements tested failed, with another 20% already very nearly rancid even though years remained on their shelf life.
The problem in large part is that fish oil is usually produced in a way that increases the likelihood of oxidation. Most are made from small fish caught off the coast of Peru or Chile. The fish are processed into oil once on land, after having been exposed to light, heat, and oxygen for unknown lengths of time. This oil is then stored in large tanks before eventually being shipped off for further refinement which usually takes place in China. Refinement includes heating the oil to high temperatures (deodorization) intended to remove compounds that add undesirable taste. This heat treatment greatly speeds up oxidation of DHA. Fish oil intended for human consumption then gets shipped to the supplement manufacturer for additional treatment such as microdistillation to remove persistent toxins. In some cases, camouflaging agents (such as lemon flavor) are added to make the end product taste better but which unfortunately appear to accelerate the formation of “bad” fats. In the end, consumers generally cannot tell exactly where their fish oil comes from or how far it has travelled on its way to the store shelf. But even were this known, there is no way of knowing how the oil was processed or how many oxidized fats it actually contains.
Conclusion: The studies do not tell us that taking fish oil is good for our health. Instead they strongly suggest that fish oil will increase our risk of heart problems, of cancer, or of catching a bad case of the flu. Most, if not all, of the fish oil contains rancid fats by the time we buy it and quickly develops more once we get it home. There is only one sensible response to these facts: Quit taking fish oil. Instead, eat a healthy diet with a good balance of essential fats from plant foods and to that, should you wish, add some wild, cold- water, fatty fish in moderate amounts.
P.S. Other types of DHA supplements have similar problems and in a subsequent blog, I’ll discuss why krill and algal supplements are not a better choice. And eventually a blog dealing with the mistaken notion that humans cannot make enough DHA and need to either eat fish or take DHA-rich supplements will also be forthcoming.
P.P.S. Interested in trying a science-based yet traditional approach to eating? We have TQIDiet classes starting soon, and our schedule, a syllabus, and testimonials are posted here
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