Is Your Fish Oil Rancid?

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For many people fish oil supplementation has been a way of getting the right amount of omega-3 in order to decrease inflammation or help with brain/vision function. But what happens when the fish oil you take is rancid? Here is all you need to know about your fish oil pills going bad.

Are Your Fish Oil Pills Rancid?

Have you ever had a fish oil pill and swore them off completely because of the disgusting after-taste? Well, you’re not alone – and the problem isn’t because that’s the way fish oil supplements are supposed to be, it’s because your pills have gone rancid. Norway has been amongst the leaders in developing fish oil supplements. In fact, they make up to around 40% of the world’s fish oil market. A recent major study from Norway looked at 113 different over-the-counter fish oil capsules and found that 95% of them were rancid (4). Good, right? Not at all actually.

Unsaturated Oil And Rancidity
Omega-3 oil is a poly-unsaturated fatty acid. This is a little Chemistry 101 here but stick with me – it basically means that it is a long fatty acid and it is rather unstable. At a few points in it’s acid chain it’s very easily able to become oxidized and break down. The exact point of this in it’s molecular make up is at its double bonds. The double bond point makes it easier to become oxidized. Because of this, the oil can rapidly “fall apart” so to say as it’s being stored (1).

Are Fish Oil Pills Bad For You?
Not at all – as long as it’s not rancid. However, as the omega-3 becomes oxidized free radicals become a by product. Your body doesn’t like free radicals. Free radicals encourage inflammation and cancer. A study different than the Norwegian one found between 11%-62% of over-the-counter fish oil pills showed oxidation. Obviously, consuming pills that have become oxidized increases free radical exposure. With that said, there’s not that much data on human studies that look at negative effects of oxidized omega-3 from fish oil. However, animal studies show that oxidized fats may cause organ damage, inflammation, carcinogenesis, and atherosclerosis (1). The potential for these damaging effects can’t be over-looked especially when one is taking fish oil supplements for decades at a time. In fact, when looked at in rats, the long term feeding of fatty poly-unsaturated fatty acids caused growth retardation, intestinal irritation, liver and kidney enlargement, hemolytic anemia (when your blood cells burst), decreased vitamin E (an anti-oxidant great at trying to combat free radicals), and inflammatory changes (2).

How Do I Tell If Fish Oil Pills Are Rancid?
Have you ever gotten a whiff of a rotting fish? No? Well, then you’re missing out. If your fish oil smells fishy and foul – then it’s bad. Isn’t fish oil supposed to be fishy? Yes, but not overly. If you’re burping it up, that’s not a good sign. Also, some companies try to eliminate fishy odors by a practice that involves high temperatures. This can make the fatty acids even more unstable and breakdown even quicker (1). The breakdown of fatty acids not only produces rancid odors and flavors, but it can also decrease the nutritional quality because the chemical makeup is actively being changed (3).

How Long Are Fish Oil Pills Good For?
What’s the expiration date on the bottle say? Is it expired? Then throw them it out. There’s a whole discrepancy of information out there on the internet in forums saying that it’s okay to keep pills past the expiration date. Well, it’s not. Especially in the case of fish oil. As the storage time progresses so does the oxidation and breakdown of the oil. At some point that supplement which is supposed to be good for you is no longer going to be beneficial (1).

How To Store Fish Oil Pills
Well, you definitely should not be storing them at room temperature – and you should definitely never buy fish oil pills that have been sitting on a shelf at room temperature from the store. Fish oil breakdown is influenced by light, heat, and oxygen concentration (1). What this means is that if the bottle doesn’t keep light out, then don’t buy it. Next up, once you take the bottle home and break the seal when you open it, oxygen gets in. Oxygen helps to break down the beneficial oil even more. Fish oil supplements stored in the dark at 4° Celcius (39° Farenheit – just above freezing) can rapidly become rancid within just a month of storage (1). Based off of that data, I would suggest freezing them. But even prolonged freezing can still lead to oxidation so if they start to taste funky, toss them.

Is Fish Oil With Added Anti-Oxidants Safer?
Probably not. To date there is not any valid research out there that I’m aware of that shows fish oil with added anti-oxidants to improve shelf life of omega-3. Some supplements might contain synthetic antioxidants, such as butylated hydroyanisole (BHA), butylated hydroxytoluene (BHT), and ter-butyl hydroquinone (TBHQ). They have been used as additives in order to slow the oxidation process down. These fake anti-oxidants are cheaper than adding real ones such as Vitamin E. But the problem is that recent studies are suggesting that they pose health risks such as cancer and carcinogenesis. The above additives are actually banned in some countries (2). Because of that scientists are looking at ways to add natural anti-oxidants to increase shelf-life but as of now, any anti-oxidant with claims of that are likely advertising hog-wash (2). One fish oil marketing myth is that tocopherols (a natural anti-oxidant and a form of Vitamin-E) increases shelf-life. Research indicates that while it may slow oxidation, it virtually has no effect on the rancidity of the oil (2).

The Bottom Line:
1. Fish oils pills are highly susceptible to becoming rancid.
2. Do not buy your omega-3 capsules over the counter if they have been sitting out in light or at room temperature.
3. To ensure that you’re getting the best benefit that omega-3 has to offer – get your omega-3 from REAL FOOD, not supplements. If you must though, be smart about your purchases.
4. If your pills taste weird and leave a fishy after-taste, throw them out.
5. Be aware of any marketing out there about anti-oxidants increasing shelf life. If you want, just take a Vitamin E capsule along with your omega-3 supplement.

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1. Albert, B. Cameron-Smith, D. Hofman, PL. Cutfield, W. “Oxidation of Marine Omega-3 Supplements and Human Health.” Journal of Biomed Research International. Published online 2013 April 30.
3. Frankel E. N. 1996. Antioxidants in lipid food and their impact on food quality. Food Chemistry, 57, 51-55.

  • Klosh

    Isn’t burping normal with uncoated caps?

  • Your Living Body

    Klosh, thanks for checking us out – what do you mean by uncoated caps? I’m assuming you mean non-enteric coated?

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    Omega 3 Capsule helps to reduces symptoms like inflammation, stiff and Joint Inflammation in rheumatoid arthritis patients.

  • Your Living Body

    Inflammation is huge for Omega-3. See our Omega 3 vs. Omega 6 post here. Thanks for checking us out.


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