Fish Oil Side Effects

Omega-3 and Omega-6 fish oils have been promoted not only for dyslexia and ADHD but also heart disease,high blood pressure, rheumatoid arthritis, asthma, bipolar disorder and cancer. In some cases there is good evidence to support fish oils as a treatment and in others the evidence is unclear. But what are the health risks of taking fish oils? Lots of producers of fish-oil capsules promote large dosages of supplements so are there any side effects from fish oils?

The US National Institute of Health classifies low intake of omega-3 fatty acids from fish as “Generally Regarded as Safe”. However they do highlight certain fish oil side effects that may trouble some people. The omega-3 in the fish oil may increase the risk of bleeding when taken in large doses. The bleeding can take the form of strokes, nosebleeds and blood in the urine. As the fish oils seem to decrease platelet aggregation, bleeding times may be longer.

A major worry with fish oils and the fish they are created from is poisoning from heavy metal and other pollutants. Mercury, dioxins and polychlorinated biphenyls (PCBs) are found in some species of fish. However, mostly this fish oil side effect is associated with eating fish directly as the oil, even in contaminated fish, carries little of the pollutants.
Stomach upset are a common side effect of fish oil supplements. Diarrhea may also occur, with potentially severe diarrhea at very high doses. There are also reports of increased burping, acid reflux/heartburn/indigestion, abdominal bloating, and abdominal pain. Fishy aftertaste is a common effect. Gastrointestinal side effects can be minimized if fish oils are taken with meals and if doses are started low and gradually increased.

People with low blood pressure or those taking blood-pressure reducing medicines should take care. One of the reported side effects of fish oil is a reduction of blood pressure. The impact on blood pressure appears to be dose dependent.

Vitamin E plays a part in metabolizing omega acids so large doses of fish oil place high demands on the body’s vitamin E supply. To avoid this fish oil side effect, vitamin E is added to many commercial fish oil products. As a result, regular use of vitamin E-enriched products may lead to elevated levels of this fat-soluble vitamin. Fish liver oil contains the fat-soluble vitamins A and D, and therefore fish liver oil products (such as cod liver oil) may increase the risk of vitamin A or D toxicity.

One side effect of fish oils and their fatty acids is an increase low-density lipoprotein levels (“bad cholesterol”) by 5-10%. This is dependent on the dose used. The oils have also been noted to have an effect on blood glucose levels in people with Type 2 / Adult Onset Diabetes but this is short-term and no long-term effects have been reported.

Overall omega-3 and 6 rich fish oils have few side effects and can be considered safe the vast majority of the population.

Source: Omega-3 fatty acids, fish oil, alpha-linolenic acid from the NIH.
See also: The Omega-3 Diet, ALA to DHA: The Fish Oil Alphabet and The Incredible Brain: A Miner Recovered.

253 Comments

  • Dane from Milwaukee says:

    I started taking Omega 3 fish oil recently and the side effect that I noticed, is that I’m extremely flatulant of late. The pills make me very “gaseous!!!” I’ve also experienced mood differences. I’m still investigating and will probably stop taking the pills. It has gotten so bad that the people at work call me “Ode (as in odor) of environment!”

  • Karen from Michigan says:

    We started taking Omega 3 hoping it would help with ADD tendencies. Both of my kids experienced side effects…depression and irritability. I experienced joint pain.

  • KANIKA says:

    I JUST DONT UNDERSTAND WHY WOULD YOU ALL MEANING, THE PEOPLE AT SPRING VALLEY PUT PROPYLENE GLYCOL-AN INGREDIENT THATS FOUND IN AUTOMATIC BRAKE FLUID AND PAINT THINNER,INSIDE OF YALL VITAMINS.DO YOU ALL KNOW PROPYLENE GLYCOL CAN CAUSE LIVER AND KIDNEY ABNORMALTIES,AS WELL AS CANCER.THATS A SHAME BECAUSE ABVIOUSLY IF THE PERSON IS TAKING THE VITAMINS SUCH AS OMEGA 3 FISH OIL,THEY ACUALLY WANT TO GET HEALTHYER NOT DEVELOPE A MORE SEREOUS HEALTH PROBLEM TO BEGANE WITH.I WILL BE ALSO GIVING YOU ALL A CALL AND CHECKING WITH SOME HELTH OFFICIALS TO SEE IF THEY CAN MAKE YALL TAKE THAT CRAP OUT OF THERE.IM WILL NO LONGER BUY YOU ALL PRODUCTS. I HAVE BEEN TAKING YOU ALLS VITAMINS FOR YEARS AND IM VERY UPSET.I JUST READ THE LABLE THIS MORNING AND FOUND OUT.

What are your personal experiences with ADD / ADHD, autism or dyslexia?