Supplement Detective

Summary: In general, fish oil side effects are mild.  If you have any bleeding disorders, take certain blood thinners or are undergoing surgery in the near future you’ll want to discuss your decision with your doctor/pharmacist.

Q: I’ve been considering taking a fish oil to help with my intake of omega 3 fatty acids.  My question is are there any side effects I should keep an eye out for?

A: As with any supplement or medication there are always possible side effects.  Keep in mind, when you say ‘fish oil’ I’m assuming you really mean regular fish oil and not cod liver oil – as there are differences in ingredients, actions and side effects with both.

Also, I don’t know anything else about your medical history or if you are taking any prescription drugs – so those are additional things you’ll want to keep in mind and discuss with your doctor/pharmacist.

Most Common Fish Oil Side Effects

Bleeding Risk

One of the biggest benefits of taking fish oil is to boost your intake of omega 3 fatty acids as most people who eat the typical American fare have a much higher concentration of omega 6 fatty acids.

But, omega 3 fatty acids have been linked to increased risk of bleeding.  So, if you have had a stroke you’d want to exercise caution.  Also, what about other medications like warfarin (Coumadin) or a regular aspirin.

Keep an eye on cuts and/or bruises, nosebleeds and in extremem cases – blood in the urine.

Heavy Metal Poisoning*

Actually, I put this one in the list because it is asked about so often and it really shouldn’t be much of a concern (and has proven not to be).

Of course, you are probably aware that fish nowadays – even in ‘pristine’ waters – can have higher than average levels of mercury, lead, dioxin and so forth.  So, because fish oil obviously comes from fish consumers are concerned about heavy metal contamination.

But, a little chemistry lesson is in order: these metal ions are not fat soluble.  Instead, metal ions bind to protein.  Of course, in fish the protein is the actual meat/flesh.  So, eating the fish itself can put you at risk for heavy metal poising – but not the fish oil itself.

However, if fish oil is to contain impurities it would likely be fat soluble organics like DDT (dichlorodiphenyltrichloroethane) and PCBs (Polychlorinated biphenyls).  But, I wouldn’t trouble your head about these too much either.

Fish Aftertaste/Burps

In my experience the most common side effect is more of a nuicansce.  That is a ‘fishy’ aftertaste or burping after consuming the fish oil.

While I haven’t every discovered a full-proof way to avoid this they may be some things you can do to limit the annoyance of these side effects.

First of all, try to take your fish oil with a meal and eat slowly.  The more air you swallow during a meal the more burping you’ll have.  Secondly, if you use a fish oil liquid you may want to try and switch to a fish oil capsule.  It’s  broken down and gets into your system slower and may limit the burping/aftertaste.

one method I DON’T recommend is freezing your fish oil capsules or liquid.  Freezing – for certain nutrients – can denature them.  Essentially making them worthless.  Fish oil – in my opinion – is too delicate to freeze and should be avoided.

Gastrointestinal Side Effects

The last side effect is gastrointestinal side effects like stomach aches and diarrhea.

Frankly, I don’t experience this but if there is this type of indigestion or heartburn it can generally be avoided by taking the fish oil with a meal.

Well Tolerated

In short, fish oil is generally well tolerated.  If you are going to get side effects they are generally mild and will be stomach related like nausea or burping.  You do want to be cautious if you have any bleeding disorders, take prescription medications for bleeding disorders (warfarin, aspirin, Plavix) or will be undergoing surgery soon.