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Side Effects of Taking Fish Oil Every Day, According to Experts

From lowering inflammation to causing bad breath, experts share what you can expect when you take a fish oil supplement every day.

What happens when you're told to go fish, but you don't have access to a fresh piece of salmon? Or if you simply don't like fish? Or if you don't have it in your budget to dine on halibut a few times a week?

You're not alone. Despite Dietary Guidelines recommending seafood as part of a healthy diet, "[seafood is] under-consumed in a typical American diet or eliminated from certain diets such as vegetarian or vegan diets," says Mastaneh Sharafi, PhD, RD, Vice President of Scientific and Clinical Affairs at Ritual.

"Most people do not consume enough fish on a daily basis to meet their requirements for essential omega 3 fatty acids, and many would prefer to take a supplement than eat fish daily or 3-4 times a week," says Alicia Galvin, RD, a registered dietitian for Sovereign Laboratories.

So when you can't go fish, supplements are your next best option—and a popular one, at that.

Fish oil supplements are the most commonly taken nonvitamin/nonmineral supplement in America, according to a National Health Interview Survey.

"Fish oil is known for its high content of omega-3 fatty acids. The body can't make omega-3s, so we must get them through the food we eat. For those who do not get optimal amounts of omega-3s from their diet, supplements can be useful and effective," says Danielle Gaffen, MS, RDN, a registered dietitian who specializes in autoimmune diseases.

Gaffen tells us that fish oil supplements contain two types of omega-3 fatty acids that occur naturally in fish and seafood: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). "Both are types of essential omega-3s that make unique and irreplaceable contributions to our body's function, like overall brain and nervous system functioning as well as lower inflammation," explains Gaffen.

There are many benefits of taking a fish oil supplement every day, but there are also some lesser-known negative side effects you should be aware of. So we asked experts about the side effects you can expect to experience when taking a fish oil supplement. Read on, and for more on healthy eating, don't miss 7 Healthiest Foods to Eat Right Now.

You may protect your brain

woman in sportswear with eyes closed training in fitness studio, calm fit millennial female practice yoga

"When it comes to making a list of foods that boost brain power, omega-3 containing foods [like fish oil] are generally at the top. This is because roughly 60% of the brain is made of fat, and half that amount is omega-3 type fats," says Trista Best, MPH, RD, LD, a Registered Dietitian at Balance One Supplements. "It has been found that omega-3 rich foods can help prevent cognitive diseases like Alzheimer's and slow mental decline. The brain requires omega-3 fat to make nerve cells, which are vital to memory and one's ability to learn."

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You may notice lower levels of inflammation

senior woman holding wrist with joint pain poor bone health

"Fish oil also may help decrease inflammation. This is due to fish oils' anti-inflammatory properties. This results in reduced joint pain and stiffness," says Allison Gregg, RDN, LD/N, a registered dietitian and Nutritional Consultant at Mom Loves Best. The National Institutes of Health (NIH) notes that omega-3 fatty acids may help relieve symptoms of rheumatoid arthritis—an autoimmune disease characterized by chronic inflammation of the joints—but more research is still needed to confirm this.

Related: 14 Tips to Reduce Inflammation to Lose Weight Faster, According to RDs

You may start to see healthier hair and skin

woman with good skin

"Having enough omega 3s is also important for skin and hair health, which can suffer if one is deficient in omega 3s," says Galvin.

You may experience some bad breath

bad breath

"When you take fish oil every day, you may experience some fishy breath for a couple of hours after taking it. This is unpleasant for many people, but can be avoided if you switch to a flaxseed oil supplement," says Megan Byrd, RD, a registered dietitian with a food blog called The Oregon Dietitian.

Galvin explains that this aftertaste may be more prevalent if you have a poorly functioning gallbladder, as "having a 'fishy aftertaste can be a side effect due to a reduced ability to properly digest fats."

Men may experience improved fertility

Couple sitting together

"Men who take fish oil supplements every day may experience improved fertility. In a recent study published in JAMA Network Open, researchers found that fish oil supplements resulted in improved sperm count and fertility hormone levels," says Lauren Manaker MS, RDN, LD, registered dietitian and author of Fueling Male Fertility.

Pregnant women may support their developing child's brain development

Female doctor is checking pregnant woman with stethoscope

"Omega-3s are essential for pregnant women because they're so important for a growing fetus' cognitive development," says Byrd.

Overdoing it may have a negative effect on your blood health

Fish oil capsules

As is the case with any supplement you're taking every day, it is possible that you could be consuming too much fish oil. Experts say you should be wary of fish oil's blood-thinning effects:

"More than 3,000 milligrams per day of EPA/DHA may increase the risk for bleeding, bruising, and elevation in blood sugar. Also, much caution needs to be given to people on blood-thinning medications and those with diabetes," explains Gaffen.

If you are experiencing any similar side effects, consult with your physician or dietitian.

You may lower levels of triglycerides

Medical worker making blood test for detection of antibodies and infections

Triglycerides are a type of fat found in the blood. Excessive levels of triglycerides may raise the risk of heart disease, but fish oil omega-3 supplements may help.

"Fish oil may help reduce elevated blood pressure, reduce high blood triglyceride levels, and improve HDL, 'good' cholesterol," says Gregg.

The NIH reports that high doses of omega-3s have been shown to reduce levels of triglycerides. To manage high triglyceride levels, the American Heart Association (AHA) suggests that 4,000 milligrams of prescription omega-3s (containing EPA plus DHA or EPA only) per day can help lower triglyceride levels when used alone or as adjuncts to other lipid-lowering medications.

You may consume more vitamin A than you need

Woman's face

Omega-3s aren't the only thing you'll find in some fish oil pills. "Many omega-3 supplements contain vitamin A, which, if taken in high doses, can lead to vitamin A overdose and toxicity. Some symptoms include joint pain, nausea, and rash or skin irritation. It could even lead to liver damage over time. It's important to pay attention to how much vitamin A is in your omega-3 supplement, as well as any other supplements you're taking to make sure you're not overdoing it," says Byrd. For example, some cod liver oil supplements may contain as much as 90% DV vitamin A.

Speaking of overdoing it, why don't you take a look at these Ugly Side Effects of Drinking Too Much Coffee, According to Science.

Olivia Tarantino
Olivia Tarantino is the Managing Editor of Eat This, Not That!, specializing in nutrition, health, and food product coverage. Read more about Olivia