The omega 3 fatty acids found in fish oil and fish oil supplements have loudly been touted as a crucial factor for the normal, healthy functioning of our bodies, right down to the cellular level. Omega 3s are necessary for normal brain development and functioning and help keep at bay numerous diseases, such as heart disease, high blood pressure, cancer, depression, neurological issues, skin disorders, psychological disorders, diabetes, immune disorders and arthritis. The benefits of fish oil are obvious, but are there any downsides to using fish oil supplements?

What are the most common fish oil side effects?

Fish Oil Side Effects

There are very few downsides to using supplementing with fish oil, and fish oil is generally safe for average healthy people.

The limited number of fish oil side effects that do occur usually only occur over time and with large doses. According to the U.S. Food and Drug Administration, taking up to three grams of omega 3 fatty acids a day from fish is generally regarded as safe.

Diabetics, people at risk for bleeding, people with high levels of low-density lipoprotein (LDL), people with fish allergies, young children and women who are breast-feeding or pregnant, however, should be careful because they may be at a higher risk when supplementing with fish oil.

People with congestive heart failure (or any other condition where the heart is receiving insufficient blood flow), people taking insulin, people who bruise easily, people who have disorders involving bleeding and people who take blood thinners should get a doctor's approval before taking fish oil supplements or increasing their intake of omega 3s if it's already a part of their diets.

The most common side effects from overconsumption of fish oil include:

  • Increased risk of bleeding. There's little evidence of risk if you don't take much fish oil, but if you take extremely large amounts (like eskimos have been known to do), there is an increased chance of hemorrhagic stroke, blood in the urine and nosebleeds. Why? Because fish oil seems to increase the breaking down of blood clots and decrease blood platelets from clumping together.
  • High intake of toxins (from fish meat). Contaminants like methylmercury, PCBs and dioxin can be found in some types of fish. Fish oil supplements, however, are usually filtered and don't have these toxins. Babies are most susceptible to these toxins and that's why young children and women who are pregnant or nursing should avoid eating too much fish - though supplementing with molecularly distilled EPA/DHA supplements from fish oil is recommended.
  • Vitamin toxicity. Fish liver and fish liver oils (like cod liver oil) contain high amounts of vitamins D and A. Fish oil, however, does not contain too much vitamin A or D. Also, vitamin E is sometimes added to fish oil products to make up for the vitamin E deficiency caused by taking fish oil over long periods of time (vitamin E is used to metabolize omega 3s and vitamin E supplies can go down with high intake of omega 3s).
  • Small reduction in blood pressure. The more omega 3s you take, the greater the reduction in blood pressure, so people that take blood pressure lowering medications or those with low blood pressure should be careful.
  • Slight increases in fasting blood glucose for type-2 diabetics. It seems, however, that scientific evidence doesn't show any long-term side effects on diabetics from taking fish oil.
  • 5 - 10% increase in bad cholesterol levels. Studies show that LDL levels increase with the more fish oil you take. But the amount is very small and insignificant when compared with the benefits of fish oil.
  • Swelling of upper respiratory tract. This has only been found in some patients who consume fish oil.
  • Allergic reactions -- skin rashes, itching, hives, swelling, difficulty breathing, swelling of the throat. This will only happen with people who have allergies to fish.
  • Stomach and gastrointestinal upset. Some people get diarrhea from fish oil and it only gets worse for them with higher amounts. Some people also claim symptoms like heartburn, bad breath, fishy aftertaste, burping, stomach pain and bloating, acid reflux, indigestion. These are the most common side effects of fish oil. (To reduce or eliminate these issues, store your fish oil in the freezer, take fish oil with meals, start taking a small dosage and slowly increase the amount you take.)
  • Too much DHA in infants and small children. Fish oil supplements may not be suitable for infants and small children because the brain doesn't need EPA and in trying to get DHA gets too much EPA.

Rare fish oil side effects that have been claimed include mania in people with bipolar disorder or major depression, restlessness and the sensation of ants crawling on the skin.

Fish Oil Symptom Action Items

Get emergency medical help if you have signs of allergic reaction, including:

  • hives
  • difficulty breathing
  • swelling of your throat, tongue, lips or face

Call your doctor and stop taking fish oil if you have any of these side effects:

  • uneven heart beats
  • flu symptoms, like fever, body aches or chills
  • chest pain

Consult your doctor before taking fish oil supplements if you:

  • have congestive heart failure (or any other condition where the heart is receiving insufficient blood flow)
  • people taking insulin,
  • bruise easily,
  • have a disorder involving bleeding
  • take blood thinners

Be careful when starting fish oil supplements if you:

  • are diabetic
  • are at risk for bleeding
  • have high levels of low-density lipoprotein (LDL)
  • have fish allergies
  • are breast-feeding or pregnant
  • give fish oil to young children, especially those under the age of five

Avoid any side effects fish oil may have and reap the benefits of fish oil instead

Since fish oil has so many benefits -- promoting a healthy brain, immune system, vision, complexion, mental state and heart, to name a few, it's clear that getting a sufficient dose of fish oil is imperative if you want a healthy body and to live a healthy life. So how can you take advantage of these fish oil pros and stay clear of any potential fish oil side effects?

  • Don't overdo it. Simply take the recommended amount of fish oil instead.
  • Get your fish oil in with a meal to avoid any of the potential fishy stomach side effects.
  • Keep your fish oil in the freezer to help with any gastrointestinal issues, at least at first.
  • Take fish oil supplements instead of wild fish to avoid toxic levels of contaminants.
  • Take fish oil capsules to avoid unsafe levels of vitamins A and D. (Fish oils from the flesh of the fish do not typically contain vitamin A like oils taken from the liver.)
  • Take fish oil supplements in recommended amounts to avoid unsafe levels of vitamin E.
  • Choose high quality fish oil supplements. High quality fish oil removes the toxins and has higher concentrations of omega 3s per mg so you don't have to take as much. They also generally don't have any other unnecessary fillers or other harmful ingredients, like preservatives. (Go to our Best Fish Oil article for a checklist on how to pick the best fish oil for you.
  • Try unrefined flaxseed oil or raw flaxseeds if you're allergic to fish.

Focus on the "positive side effects" of fish oil omega 3s

By positive side effects of fish oil omega 3s, we really mean the benefits, with the main benefit being that omega 3s keep your cells functioning properly (instead of breaking down and putting your body at risk) and allow you to live a happy, healthy life.

We recommend starting sooner than later with omega 3s because your body really does need them. To make it easy on yourself, you can start with high quality fish oil capsules ( or liquids (or flax seeds if you're a vegetarian). Start taking them slowly and then you can build up the dosage once you're sure you have no issues (which you most likely won't). You can read our recommended fish oil dosage article to see how much you should be taking.

Once you're in a fish oil groove, sit back, relax and enjoy feeling great, just as if you'd gone fishing!

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Our Story

EnergyFirst, a leading company in the all-natural protein and supplement industry, was founded in 1997. We, at EnergyFirst, believe that everyone can benefit from drinking a protein shake whether the goal is optimal nutrition in a meal replacement, an easy and healthy breakfast alternative, a weight loss aid, or a protein supplement for athletes. We also believe that your protein shake should be 100% natural and delicious. Nutritionist, educator, athlete, and EnergyFirst's CEO, Gerry Morton is committed to providing customers with all natural, science-based, effective products for optimal nutrition, weight loss, and a healthy lifestyle.

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