They claim that the omega-3 fatty acids in fish oil can oxidize and become rancid inside your body… unless they are protected by the red-orange antioxidant pigment (astaxanthin) natural to krill and salmon oils.
We recently received a letter from a reader who'd found a 1996 study that seemed to support that contention.
In fact, as we explain below, that study doesn't actually bolster fish-oil-oxidation fears, and virtually all of the available evidence instead refutes them.
There's no doubt that the long-chain omega-3s in fish oil (EPA and DHA) oxidize rapidly if they are exposed to air.
But fish oils are manufactured and preserved in ways that prevent that happening before you consume them… for more on that, see our sidebar below, "Omega-3s don't oxidize in your body... or in fish oil capsules”.
To be sure, if the omega-3s in fish oil were to become oxidized inside your body, they would generate free radicals that damage our cells and DNA.
But the available evidence indicates that supplemental (and food-borne) omega-3s do not oxidize inside human bodies, and actually reduce people's oxidation levels.

Omega-3s don't oxidize in your body… or in fish oil capsules
Fish oil and kill oil supplements contain one of two kinds of antioxidants, which serve to protect the omega-3s inside the capsule, before you consume them:
  • Wild salmon oil naturally contains astaxanthin (about 36mcg per 1000mg capsule of Vital Choice brand).
  • Krill oil naturally contains high levels of astaxanthin (100-200mcg per 1000mg capsule).
  • Standard (chemically refined) fish oil usually contains added tocopherol (usually synthetic), which is one of the molecules in the vitamin E family.
All reputable brandsincluding Vital Choicetest their oil for the presence of oxidation byproducts, to be sure that the antioxidants are doing their job.

And there is little doubt that almost all supplemental fish oil and krill oil capsules contain enough natural astaxanthin or synthetic vitamin E to prevent significant oxidation of the omega-3s in the oil.
In fact, tests by independent watchdog organizations confirm that it's rare to find significant oxidation of the omega-3s in supplemental fish oil.
Krill oil sellers who raise fears about fish oil make no mention of the human clinical trials and animal studies showing that dietary omega-3s do not present any oxidation risk (see the sources listed at the end of this article).
Our minds are open, so we invite those who claim that the omega-3s in fish oil raise oxidation levels in the body to support those assertions with published, peer-reviewed evidence.
Like krill oil, our Wild Alaskan Sockeye Salmon Oil is rich in astaxanthin, which wild salmon acquire by eating zooplankton… such as tiny, shrimp-like krill.
But because omega-3-oxidation fears concerning fish oil are baseless, we cannot in good conscience use false fears to promote our astaxanthin-rich oil.
Before we share our reader's letter about omega-3 oxidation inside the body, and our response, let's address the issue of oxidation of omega-3s inside fish oil capsules, before they are consumed.
One reader's question: Do fish oil omega-3s oxidize inside your body?
We recently received a reader's query concerning a 1996 clinical test, which, at a glance, seemed to raise some concern about oxidation of omega-3s in the body.
Fortunately, a close reading of the paper shows that it actually confirms the safety of moderate fish oil intake.
Here's the reader's question, and our (edited/expanded) answer.
Before your read them, it will help to know some terminology:
  • The scientific term in vivo means a study in animals or humans, while in vitro means a test tube study.
  • "Lipid peroxidation” means oxidation of body fats by the peroxide free radical, which is associated with rancid fats.
  • MDA stands for malondialdehyde, which is a byproduct of the peroxide free radical associated with oxidized omega-3s. Accordingly, MDA levels are commonly used as a marker for oxidation of omega-3 fats in the body.


Dear Vital Choice,

In your email newsletter from June 28, 2010, you had an article called "Omega-3s: Oxidation Victim or Vanquisher?”.
It mentions that the Australian team found antioxidant effects of fish oil.
You may be interested in a study in the September, 1996 edition of the American Journal of Clinical Nutrition. Pages 297 to 304 that mentions an antioxidant effect from fish oil after 30 days, but after 180 days, lipid peroxidation levels increased, and gamma tocopherol levels dropped to zero.
Randall F.

Dear Mr. F:
Thank you for bringing this to our attention.
We think that a close reading of the study dispels any fears, for three reasons.
First, as you may know, this clinical study employed an artificial oxidation-inducer called AAPH, to measure susceptibility of extracted red blood cells to oxidation, in vitro.
Past research on antioxidants and omega-3s alike indicates that studies performed in vitro, using synthetic pro-oxidants like AAPH do not necessarily match with what happens to dietary omega-3s in the body.
Second, Figure 2 on page 302 shows that the difference in MDA [oxidation] levels between people in the placebo group and the 2.5g per day fish oil group over 180 days are very small, versus the much larger rises in levels of MDA seen in blood taken from people in the higher-dose (5.1g/day and 7.7g/day) fish oil groups
These large, dose-related differences appear highly significant, because authorities such as the American Heart Association recommend daily doses of 500mg to 2g of omega-3s (EPA+DHA) per day.
And in this trial, significant rises in MDA [oxidation] levels only occurred at omega-3 doses five to 15 times higher than the ones experts recommend for most people.
Thus, it seems unlikely that taking fish oil supplements providing up to 2 grams of omega-3s per day would result in an increase in oxidation levels in the body.
For these reasons, we believe that the 1996 study's results do not overcome the opposing, positive results of the several recent trials we summarized.
Third, you noted that blood levels of gamma tocopherol (one of several vitamin E compounds) dropped to zero after 180 days in the highest-dose groups.
We should note that levels of alpha tocopherol did not drop.
Also, it is not clear what the drop in gamma-tocopherol means… it could be that once the omega-3 levels in blood cell membranes reach a certain high level, other parts of the body's antioxidant network take over, and the cells do not need this particular vitamin E component.
It comes as little surprise that if you ingest much larger amounts of omega-3 fish oil daily, you might burden the body's natural antioxidant defenses over time.

People taking five or more grams of omega-3s per day under medical guidance would
probably be wise to accompany the fish oil with a fat-soluble antioxidant like astaxanthin… which they could take separately, or choose a salmon or krill oil, which are naturally rich in astaxanthin.

Or, peoiple taking high doses of fish oil could accompany it with a vitamin E supplement that includes all of the major vitamin E tocopherols, including gamma, and the often-overlooked vitamin E tocotrienols.
Thanks again for taking the time to write.
Best regards,
Craig Weatherby
Editor, Vital Choices
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