Mercury content in 70% DHA Fish Oil?

That's a totally ridiculous claim. Frankly, that dude seems to be on a crusade against anything that even uses ethanol in the production process. He seems to be Saudi Arabian, and has a religious issue with alcohol in general. There is absolutely no scientific basis for his claim at all.

To start, almost all fish oils are in ethyl ester form. This is because that is the process that allows for ultra-high purification of the fish oil. That's how we can get zero detectable mercury in them. They are esterified and then molecularly distilled under a vacuum, which allows you to concentrate the omega-3s to levels you would not be able to get otherwise, and to remove any of the unwanted compounds naturally found in fish. Any fish oil with high levels of DHA/EPA have gone through an esterification process, followed by a distillation process. Your body converts the ethyl esters to triglyceride forms after you absorb them. That's how almost all the fish oil sold today works. Then some companies decided to try an set themselves apart, and to do another step afterwards to convert the ethyl esters back into triglyceride form. They then started using faulty science and hyperbole to make it seem like triglyceride forms were much better, but the science does not match their claims.

Ethyl esters and triglycerides are both technically classified as esters. Triglycerides are bound to a glycerol backbone. Ethyl esters are esterified to an ethanol backbone. Most of what is naturally found in fish oil is the triglyceride form. There are some free fatty acids, but most of it is in triglyceride form. The issue with triglyceride forms is that you don't get very high EPA/DHA. This is where converting to ethyl esters and concentrating using distillation comes into play. You replace the glycerol on the backbone with ethanol, which allows you to ability to distill it and concentrate the omega-3s. That is how you can get the high levels of EPA and DHA like we have in our fish oils. This also affects how it can work in the body, as the process of hydrolyzing ethyl esters is slower than that for triglycerides. So you get a slower and more sustained release. Triglycerides are hydrolized quicker, so you get a larger peak in plasma levels, but they are not as sustained. Triglyceride forms of fish oil are slightly more bioavailable (~20-30%). However, their AUC is shortened. So you get a quick peak and then a quick drop off. Ethyl ester forms absorb slower, but are more controlled in release. So while you will get higher peak plasma levels with the same dose of a triglyceride form compared to an ethyl ester, the effects don't last as long. Pair that with how much more expensive triglyceride forms are, and it just makes more sense to have a higher dose of an ethyl ester form. The people out there promoting triglyceride fish oil, and trying to make people fear ethyl esters, are not doing it in good faith. They are trying to get people to fear ethyl esters so they go and buy their much more expensive fish oils. We could offer triglyceride options for people, but I honestly do not feel they are worth the cost. Moreover, the VAST majority of clinical studies on fish oil are using the ethyl ester form. That's what we have the most data on. To make the claim that ethyl ester fish oil causes birth defects is so asinine. It's much safer for a pregnant woman to take a purified fish oil softgel in ethyl ester form than to eat wild fish every day, due to the naturally high levels of things like mercury and other compounds found in fish. When you molecularly distill the oil to remove all those contaminants, it is much safer and more controlled for a pregnant mother. To claim anything else is not a good faith argument. Also, let's look at the ethanol claim itself.

So our 70% DHA product has a dose of 1 gram. The gross weight is about 1,330mg and the total omega-3 content is 822.9mg EE/g. The average molecular weight of the omega-3's (ALA, SDA, ETA, EPA, DPA, DHA, Nisinic) readily available on Wikipedia is 310g/mol, and ethanol has a MW of 46g/mol. This means that 822.9mg EE/g at one softgel a day is 1.094457g EE omega-3 per day. The mass fraction of ethanol to the average omega-3 mass is 46/310 = 0.14838. 0.14838*1.094457g EE omega-3/day = 0.1624g ethanol created, or 162.4mg. Ethanol has a density of 0.789g/mL, so that is 0.205mL of ethanol, or 205uL. That's nothing. Let's compare that to the natural ethanol content of every day foods. Burger rolls contain as much as 1.28 grams per 100g. That's 1.28% ABV. Bananas contain 0.4g per 100g (0.4% ABV). The more ripe the are, the more ethanol they contain. Rye bread contains up to 0.18g per 100g (0.18% ABV). White vinegar contains up to 2.64g per liter. Grape juice contains up to 0.86g per liter. Orange juice contains up to 0.73g per liter. Apple juice contains up to 0.66g per liter. Soy sauce comes in about 2% ABV.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5421578/

How much you want to bet the guy above is eating and drinking some or all of those things on occasion? A large banana is roughly 130g. You would be getting roughly 520mg of ethanol per banana. That's 3.2 times a 70% DHA fish oil softgel. Has your doctor advised you to stay away from bananas? What about burgers because of the ethanol content in the burger rolls? An average burger roll/bun weighs 60 grams. That's 768mg of ethanol per bun, or 4.7 times as much as a 70% DHA softgel. Do we have children having birth defects from mothers in the Midwest having too many burger cookouts or eating too many ripe bananas? The claim that ethyl ester fish oil is causing birth defects, without any scientific data even hinting in that direction, frankly pisses me off! Anybody can go online these days and make unscientific and false claims, then stir people up and cause fear over nothing. The internet has become a den of lies and deceit trying to get people emotionally charged about topic after topic. It feels like a nonstop effort to try and counteract those claims every day.