Omega-3 Side Effects

Omega-3 Safety Risks & Dangers

Generally, omega-3 is safe to take. The FDA state that up to 3 grams a day of omega 3 is safe [8] (see also omega 3 dosage).

There have been no reported deaths from omega-3 consumption and no reported serious illnesses from omega-3 consumption.

Side Effects Of Omega-3 Fatty Acids

Any omega-3 side effects are normally mild and often take the form of gastrointestinal disturbance (stomach upset).

Following a review of omega-3 studies, the United States Agency for Healthcare Research and Quality (AHRQ), found that in 6.6% of those taking omega-3 supplements had gastrointestinal disturbance compared to 4.4% who had a placebo.

Therefore, only a small percentage experienced gastrointestinal disturbance as a side effect of taking omega-3 rich fish oil.

A fishy after taste may be another possible side effect from taking fish oil based omega-3 supplements. Taking fish oil with food may help prevent this.

Risk Of Omega-3 Fatty Acids Side Effects

The American Heart Association (AHA) has produced a table of the risk of omega-3 side effects. An adapted table is shown below.

Omega-3 Dosage & Risk Of Side Effects
Daily Dosage Gastrointestinal Disturbance Fishy Aftertaste
Less Than 1 Gram Per Day Very Low Low
1 -3 Grams Per Day Moderate Moderate
More Than 3 grams Per Day Moderate Likely

Risks Of Fish & Fish Oil Based Omega-3

Fish and fish oils are a popular source of omega-3. However these sources of omega-3 can bring their own risks.

The benefits of fish and fish oils usually far outweigh any risks.

Depending on the species and the environment from where they are caught or farmed, there may be a slight risk of carcinogenic dioxins or heavy metals in fish. These contaminants may have accumulated in the fish over time sourced from the food chain.

The gradual accumulation of dioxins over a lifetime may lead to a greater risk of cancer.

Due to the slight risk of dioxins present in fish and fish oils, people considering taking fish oil supplements should ensure they buy high quality fish oils which don't contain high levels of dioxins. For example, a 2003 study of mercury levels in branded fish oil supplements [10] found a range of mercury levels between them.

The study showed that CVS fish oil had mercury levels of 10ag/l compared to Nordic Ultimate fish oil which had less than 6 ag/l.

There have been no reported cases of mercury poisoning following fish consumption in the US in over 35 years [11].

However it would be prudent to avoid regular consumption of fish listed by the FDA as having potential high levels of mercury [9].

Fish with potentially high levels of mercury include:

  • king mackerel
  • shark
  • swordfish
  • tilefish

It should be reiterated that the benefits of fish in the diet usually outweigh the concerns or risks just mentioned.

This statement is reflected by the American Heart Association (AHA) recommendation that 2 portions of fish (preferably fatty fish rich in omega-3) should be consumed each week.

One serving or portion of fish being 100gram (3.5 ounce) cooked weight, or approximately 3/4 cup of flaked fish.