2 Very Important Tips to Prevent Fish oil Side Effects From Supplements

Image headline for fish oil side effects postAs anyone who is reading this page probably knows by now, fish oil supplements are all the rage nowadays as the benefits of omega 3 have become more and more evident in a lot of research. 10,000 years ago most human beings probably had a 1:2 or 1:3 ratio of omega 3 to omega 6 and currently this ratio has been heavily pushed towards omega 6. In a typical North American diet on average is now 1:15 to 1:17. The reason? Omega 3 consumption has gone done and omega 6 consumption has gone up thanks to the overuse of vegetable oils. The easy way (but not necessarily the best long term solution) is to take fish oil supplements, but are there side effects to these? Here are a few things to consider in terms of fish oil side effects. None of these are deadly BUT you can easily avoid some of these if you take the necessary precautions, you don’t want to cancel out the health benefits of adding extra omega 3 to your diet right?

1) The most important side effect of fish oil supplementation that could happen is consumption of heavy metals that the fish initially absorbed.

The most common and well known of these poisonous metals is mercury. Good quality brands will be pharmaceutical grade fish oil which means they went through a refinement process that removed these. Ideally, the brand you choose should be certified by the USDA to have been tested and came out clean (or in reality, with very very low levels of heavy metals to the point it’s not longer a health threat). As a side note, Mercury is a problem if you also eat fish but… eating “real” fish meat means your body absorbs an important nutrients as well, a key one being selenium which helps prevent mercury toxicity. As Chris Kesser explains in this excellent blog post on why eating fish might be better than supplementation,

eating fish is still ideal to supplementation to avoid side effects“Selenium is plentiful in many ocean fish species, but the public is unaware of its protective role against mercury. Selenium has high binding affinity for mercury. This means that when the two elements are found together, they connect, forming a new substance.

This new substance makes it hard for the body to absorb the mercury separately. Simply put, when selenium binds to mercury, mercury is not longer free to bind to anything else – like brain tissue.”

Once again though, pharmaceutical grade fish oil will have the mercury removed or brought to such a low level that it should not affect your health. It’s important to see that “real fish” is not necessarily a nono because of the heavy metals it contains!

2) Make sure the fish oil is not rancid/oxidizing/expiring.

Omega 3 fats are highly susceptible to oxidize damage. Basically, if you let your fish oil gel caps on the counter too long (a few weeks/months) the fats inside will start to oxidize and this will cause a lot of inflammation to your body (exactly what you are trying to prevent by taking fish oil supplements!). To prevent this, first off do not buy too much fish oil, 2-3 months supply at most is probably best. Also, store it in an area that will not be reached by sunlight, preferably in a fridge. Also limit the exposure to air! Obviously when you open the bottle you can’t prevent air exposure but make sure to close it after! Freshness is definitely important to prevent any fish oil supplementation side effects!

A rancid fish smell can lead to side effects due to OxidationIt’s hard to determine if your current fish oil supplements are expired… The best way is to try noticing a rotten fish smell, this is much easier if you take oil instead of gel caps. The gel caps prevent the odor from leaving the supplement… you could try opening a few (cut the gel cap, smell the “fat” in the middle of it) and smelling the content to assess if the remaining supplements in your order are still alright. I personally go for supplements in an “oil format” when I’m at home and I only use gel caps when I am traveling (since oil in a glass container could break).

Also, “fish burps” are a commonly noted fish oil side effect from supplementation… This is very often due to the brand you choose and is very often a symptom of a midly rancid fish oil supplement. So if you get them… Beware! Try another brand, don’t consider it “normal” like some manufacturers want you to believe.

carlson cod liver oil 250ml bottleYou most likely should try a higher quality brand. I personally use Carlson Labs, Norwegian Cod Liver Oil, Lemon Flavor, 8.4 fl oz (250 ml) which you can find on amazon.com if you are inside the USA or iherb.com (use IFI934 for $5 off your first order) if you are from outside of the US.. They also have a 500ml version but I always get the 250ml one because it lasts around a month and a half. The 500ml is probably a good alternative that ends up saving you money if you share it with a spouse. I live alone so it would last too long and go rancid :(. Also make sure that the sun does not come into contact with the bottle and limit it’s exposure to air!

Carlon labs also sells gel caps, and another well known brand I use is Nordic Naturals for my gel caps which I use for traveling (and I store them in the fridge when at home). I prefer the cod liver oil when at home because it also contains some vitamin A and vitamin D and the lemon flavor actually gives it a pleasant taste :).


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  1. I’ve been a huge fan of Omega 3 supplement. Been using it as an alternative for muscle and joint pains.

    Great point of not leaving the container open after use and the proper storage to make sure that the supplement stays fresh and working as intended. I’ll start reminding myself that every time I take a cap out to return the container in and not on top the fridge….

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