These days, fish oil is all the rage. Everyone has a reason to take some. Depressed? Moody? Anxious? Take some fish oil! At risk for a heart attack? Take some fish oil! Eat too many Omega-6 fats? Take some fish oil! Perfectly healthy? Take some fish oil!
Is fish oil really all that good for you? The answer is complicated. Yes, fish oil can be a helpful supplement. But it should be taken with caution. In this case, there really is such a thing as too much of a good thing.
The Standard American Diet (SAD) has many things wrong with it. Yet in regards to the essential fatty acids, the two biggest dietary sins are:
1) eating far, far too many of them (more than 4% of total calories), and
2) eating the Omega-6 and Omega-3 fatty acids in the wrong ratios (an n6:n3 of more than 4:1) (source).
In light of the second point, many doctors recommend supplementing with extra Omega-3 fatty acids from fish oil. The idea is that by increasing the intake of Omega-3 fats, you’ll get the ratio of Omega-6 to Omega-3 fats in balance. Pretend, for example that in your diet, you consume about 30g of Omega-6 fats and only 2g of Omega-3 fats. That’s an n6:n3 of 15:1. You want to get it down to 4:1 or less, so you supplement with 6g of Omega-3s. Now you’re consuming 30g of Omega-6 fats and 8g of Omega-3 fats, for an n6:n3 of 3.75:1.
The problem with this, of course, is that by “correcting” #2 this way, you run afoul of #1.
Furthermore, regularly supplementing with high doses of fish oil long-term may be dangerous:
Researchers in the 1970s suggested that the high content of omega-3 fatty acids in the diet of the Greenland Inuit may have protected them from heart disease by lowering their cholesterol and triglyceride levels.75 Since then, dozens of randomized, controlled trials have tested the effect of fish oil supplementation on total and cardiovascular mortality…. These studies suggested that about one gram of long-chain omega-3 fatty acids per day may prevent arrhythmia in patients prone to chronic heart failure or in patients recovering from a recent heart attack. They also suggested that long-term use of fish oils for more than four years may actually increase mortality from heart disease and all causes. (source)
Why is that? How can something that’s good for you in the short term be bad for you in the long term? My theory is that in the short term, the better balance of Omega-6 to Omega-3 fats reduces the symptoms of Omega-3 deficiency since the Omega-6 fatty acids are no longer out-competing the Omega-3 fatty acids in the body. Yet in the long term, the excess polyunsaturated fat content of the diet is causing a rise in systemic inflammation. Over time, the excess inflammation leads to the development of heart disease, diabetes, and even cancer. (source)
Furthermore, the low incidence of heart disease among the Greenland Inuit probably has very little to do with the Omega-3s in their diet:
Many other groups eating traditional diets appear to be free or nearly free of heart disease, and a high intake of marine oils is not a universal trait of these diets. The main source of fat for the Masai, for example, is highly saturated butterfat. The inhabitants of Tokelau consume a diet based mostly on coconut and to a lesser extent on seafood, and even the seafood they prepare contains only two percent of its calories as long-chain omega-3 fatty acids.76 The inhabitants of Kitava consume about two percent of their total calories as omega-3 fatty acids,77 which is greater than the amount that Tokelauans consume but much lower than the amount that the Inuit consume. The traditional diet of Crete provides most of its fat as saturated butterfat from cheese and as monounsaturated olive oil, and contains very little fish.78 If we are to offer a hypothesis about what protects all these groups from heart disease, we must first identify what their traditional diets share in common. The most obvious place to start is the complete absence of refined foods. A very high intake of marine oils, by contrast, is a specific peculiarity of the Inuit diet. (source)
So what’s the solution?
In his own summary of this topic, Chris Kresser concluded:
That is why the best approach is to dramatically reduce intake of omega-6 fat, found in industrial seed oils and processed and refined foods, and then eat a nutrient-dense, whole-foods based diet that includes fatty fish, shellfish and organ meats. This mimics our ancestral diet and is the safest and most sane approach to meeting our omega-3 needs – which as Chris Masterjohn points out, are much lower than commonly assumed.
Some may ask why I continue to recommend fermented cod liver oil (FCLO), in light of everything I’ve shared in this article. There are a few reasons. First, I view FCLO as primarily a source of fat-soluble vitamins (A, D, K2 and E) – not EPA and DHA. Second, in the context of a nutrient-dense diet that excludes industrial seed oils and refined sugar, and is adequate in vitamin B6, biotin, calcium, magnesium and arachidonic acid, the risk of oxidative damage that may occur with 1g/d of cod liver oils is outweighed by the benefits of the fat-soluble vitamins.
So I still recommend eating fatty fish a couple times per week, and taking cod liver oil daily, presuming your diet is as I described above. What I don’t endorse is taking several grams per day of fish oil, especially for an extended period of time. Unfortunately this advice is becoming more and more common in the nutrition world.
More is not always better, despite our tendency to believe it is.
What if you can’t take Fermented Cod Liver Oil?
Many people have bad reactions to FCLO. It makes them nauseous, causes rashes, etc. While there’s been a ton of debate about the whether or not FCLO is as good as it claims to be, I’ve mostly kept myself from dipping my toe into the online discourse.
I personally can’t stomach the stuff.
I take a different regimen instead. See: What to Take Instead of Cod Liver Oil.