Here's what I think / know about the subject.
The first fish oil softgels that were commercially available, other than Cod Liver oil, were EPA/DHA 18%/12% in the triglyceride form. The fish oil came with about 2 IU per gram of D-Alpha Tocopherol added to it to prevent rancidity. The capsules were encapsulated with the oil being blanketed with nitrogen to keep the oil from accidently getting exposed to oxygen during encapsulation. There are a lot of old small clinical studies supporting this type of capsule. They were usually done with MaxEPA brand fish oil and the fish oil raw material came from Arista. Just do a search for MaxEPA in Google Scholar if you want to see all of the old original studies on this type of fish oil capsule and their effects on the body.
Then a Canadian company came up with a very successful marketing campaign where they promoted ethyl ester fish oil at the 18%/12% as being "Moleculary distilled" to purify the oil. It was basically slick marketing making people suspicious of impurities for any fish oil that wasn't molecularly distilled. Soon afterwards the ethyl ester fish oils took over the market. The previous leader in the market tried to fight back by showing that the old 18/12 triglyceride fish oil had better bioavailability in the body but they weren't successful in stopping the rise in popularity of the Molecilarly distilled ethyl ester type. After that came the higher potency ethyl esters with the EPA and DHA amounts specified and then the low cost 30% Omega 3 ethyl esters (with variable amounts of the different Omega 3's that totaled 30% but could be in a different ratio each time).
That's pretty much where it is still at today. But recently some companies that are still using fish oil either in the natural triglyceride form and/or reesterified triglyceride forms are starting to redo the bioavailability studies showing that the triglycerides are absorbed better. However, most companies are still just focusing on higher potency ethyl esters touting more EPA/DHA per capsule or are using the low cost 30% Omega 3 ones (which are sometimes ethyl ester and sometimes reesterified triglycerides). I guess the bioavailability isn't as marketable.
There ares also difference in the ways people come up with the amounts of Omega 3's in the products that confuses the issues more. Area percent assays versus assays with standards is one example. Another is adding just the EPA and DHA versus adding in a bunch of other lesser known Omega 3-s. Another little known thing is that if a manufacturer use triglycerides (either natural or reesterified to be condisered roughly the same as natural) then they are technically allowed a looser specification than with the synthetic ethyl esters. If it is considered natural the specification for the raw material and capsules can be as low as 80% of label claim but the synthetic has a spec of not less than 100%. If you look at the results from a recent fish oil study at Consumer Labs you will find that they failed a bunch of them for being less than 100% of their label claim, but if you look at the results you will see that the ones they failed are typically in that 80% range. Noone bothered to tell Consumer Labs, but if you dig enough you will find that many of these are the triglyceride ones and the manufacturers are using the 80% spec. The 80% rule is to allow for natural ingredients to have their natural variation but synthetic stuff is supposed to be 100% because there isn't "natural" variability. All of these differences in the ways the numbers or specifications can be done will throw off any comparison studies for bioavailability if you try to compare different products. You would have to do a controlled study with all of these variables being controlled for if you really wanted to know for sure what is going on.
Then there are the Krill type products where the Omega 3's are in a phospholipid form and/or the ones where they are chemically combining fish oil with phospholipids to duplicate the natural phospholipid Omega 3's. Those ones might end up being shown to be better than the triglycerides. It is early days for those ones though. The theories make sense though.
Just about all of the various fish oils use either D-Alpha Tocopherol or Mixed Tocopherols at 1 or 2 IU per gram to prevent oxidation of the fish oil raw material. The algal DHA typically uses ascorbyl palmitate and mixed tocopherols to keep the raw material from oxidizing. The encapsulators typically use some type of nitrogen blanketing of the oil during encapsulation to prevent oxidation. As long as they don't make leakers this is typically acceptable. If you take fish oil in high amounts you should take additional oil soluble antioxidants of different types to lessen the chance of oxidation in your body. At least take some form of Vitamin E. You don't have to take them at the same time though. This is for the long term. I don't think it would hurt anyone to take fish oil without antioxidants for short periods of time.
The only fish oil capsule I am aware of that doesn't have any antioxidants in the raw material to protect it when it is a raw material and during encapsulation is the prescription stuff. The original clinical trials for the prescription fish oil used purified ethyl ester fish oil with no antioxidants so they aren't allowed to change it without having to redo the drug applications and the clinicals. The material is so prone to oxidation that it's containers can't be opened before encapsulation and a much more elaborate nitrogen purging and blanketing system had to be devised to encapsulate it without ruining it. I'd definitely take extra oil soluble antioxidants with that one.
Then you have the enteric fish oils. In the beginning, they were said to be more bioavailable with less stomach acid degredation of the Omega 3's. But nowadays you just hear about the enteric coating just for stopping burping and indgestion. I think Fisol is still touting that the enteric coating protects the oil and results in about 3 times the bioavailability as non-enteric. They have a smaller capsule and claim it is as good as taking the bigger capsules of the non enteric (the product is in a 10 minim oval capsule rather than the typical 20 or 24 minim oblong). Most of the other enterics aren't touting this though and are big 20 or 24 oblongs or are very high potency ethyl esters in a 12 oval size and just claim to be equal to the regular potency larger fish oil capsules only in a smaller easier to swallow size with no mention of being more bioavailable. I'm not sure why. It might be TG versus EE or it might be true enteric coating (methacrylates or phthalates) versus semi enteric food grade enteric coating (ethylcellulose, alginates, shellac) or it might be that noone gets good sales touting bioavailability since the focus shifted to more Omega 3's per capsule instead.
Sorry if this post is confusing / rambling. Just trying to say a lot of different things at the same time.
Edited by MrSpud, 31 March 2011 - 04:54 AM.
