What Actually Happens to the Body When You Start Taking Fish Oil

Fish oil is derived from the adipose tissue of fish such as salmon, sardines, mackerel, herring, and lake trout. Healthy fats are our friends. In fact, fat is an integral part of a nutrient-rich diet, but not all fats are the same.

For example, omega-3 fatty acids, which are naturally found in fish, are much better for us than the partially hydrogenated oils found in ultra-processed and packaged foods. But if omega-3s are so good, should everyone take fish oil supplements for optimal health?

Here’s what the research says about what fish oil does, who may benefit from fish oil supplements and more.

What is fish oil?

Fish oil is derived from the adipose tissue of fish such as salmon, sardines, mackerel, herring, and lake trout. The main fats found in fish are omega-3 fatty acids, a type of polyunsaturated fat. The two main types of omega-3s found in fish are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Most fish oil supplements consist of marine-derived EPA and DHA. “The difference between products is the ratio of EPA to DHA, which can range from 0.3 to 3,” explains Tyler Preston, RD, nutritionist, performance coach, and founder of Preston Performance.

“If you’re looking to simply address a deficiency, a more balanced 1:1 ratio of EPA to DHA is appropriate,” Preston says. There are different types of omega-3 supplements, including fish oil, cod liver oil, and krill oil. According to the National Institutes of Health (NIH), cod liver oil contains vitamins A and D in addition to EPA and DHA.

Both EPA and DHA are essential for our health. “While DHA may have a stronger anti-inflammatory effect, EPA targets the balance between pro-inflammatory and anti-inflammatory proteins, illustrating their symbiotic relationship,” says Preston.

Effects of fish oil

Your triglyceride levels may decrease

According to Michigan Medicine, omega-3 supplements reduce elevated blood triglyceride (TG) levels. This is very important because high triglyceride levels are associated with an increased risk of heart disease.

According to an August 2019 study in the journal Circulation, prescription medications that contain high doses of omega-3 fatty acids (about 4 grams per day) reduce triglyceride levels by about 30 percent in people with hypertriglyceridemia.

But for the average person with healthy lipid levels and no fatty acid deficiency, fish oil supplements are not necessary if they eat fish regularly. Try to eat at least two servings of 3.5 ounces of fatty fish per week, as recommended by the American Heart Association.

FYI, people who ate fish twice a week had significantly greater reductions in LDL cholesterol compared to those who took fish oil supplements, according to a December 2017 study in the journal Nutrition & Diabetes.

Your mood may improve

Fish is called “brain food” for a reason. The anti-inflammatory fats found in fish help maintain the structure and function of cell membranes throughout the body, including in the brain. This may be why some studies have shown that people who eat more seafood have a reduced risk of cognitive decline, according to the National Center for Complementary and Integrative Health.

At the moment, there is little evidence that we should take fish oil pills to prevent conditions such as dementia, but supplements may be beneficial for other neurological conditions. Take depression, for example, research, suggests that fish oil supplementation, especially EPA, is associated with reduced symptoms of depression, according to an August 2019 meta-analysis in Translational Psychiatry.

One theory of the pathophysiology of depression is related to an imbalance of neurotransmitters in the brain. “By altering the number and function of serotonin and dopamine receptors, omega-3s could theoretically help correct these dysfunctional pathways in people with depression, improving their depressive status,” Preston said.

Since the evidence on the effectiveness of omega-3s in depression is mixed, experts agree that more research is needed before the capsules become a mainstay of mental illness treatment. This means: If you’re taking antidepressants, don’t stop taking your medication just yet – and always talk to your doctor before starting a new supplement or if you plan to stop your prescribed medication.

If you’re ready to eat seafood, start with the real thing, not fish oil supplements. In the meantime, get your good-mood food by eating at least two servings of fish a week.

Your blood pressure may decrease

Omega-3 supplements can help lower blood pressure in people with hypertension. “According to an NIH study, omega-3 fatty acids work by directly activating calcium-dependent, high-conductance potassium channels in blood vessels, which lowers blood pressure,” says Angela Marshall, MD, internist and CEO of Comprehensive Women’s Health.

Fish oil supplements with moderate amounts of DHA and EPA (think: the same amount you would get from two to three servings of seafood a week) was found to lower blood pressure by 5 mm Hg, according to a study published in The Journal of Nutrition in March 2016. While this may not sound like much, this 5-point reduction could potentially lead to a 20 percent reduction in heart disease risk, according to the researchers.

At the moment, most research supports a well-balanced, low-sodium diet that includes fruits, vegetables, heart-healthy fats (like fish!), lean proteins, and whole grains, rather than fish oil supplements to lower blood pressure.

Your joints may hurt less

“Studies show that omega-3 fatty acids help reduce joint inflammation, which is beneficial for people with inflammatory diseases such as rheumatoid arthritis,” says Dr. Marshall.

These healthy fats have been shown to inhibit the production of inflammatory compounds such as cytokines and interleukins in the body. Therefore, it is not surprising that fish oil supplements have been linked to improved symptoms in people with inflammatory conditions such as rheumatoid arthritis (RA), according to the University of Oregon. According to the Mayo Clinic, although the pain relief is often moderate, it may be enough to reduce the need for painkillers such as NSAIDs.

You may experience fishy burps and nausea

If you’re just starting to add fish oil supplements to your regimen, beware of a fishy flavor and aftertaste, as well as some not-so-pleasant gastrointestinal symptoms.

“Common side effects, although usually mild, can include heartburn, nausea, and gastrointestinal discomfort, which are common problems when taking too much fat in one sitting,” says Preston. You can avoid the fishy aftertaste if you store the bottle in the freezer or take a tablet with a meal, according to the Arthritis Foundation.

And keep in mind that the higher the dose, the higher the risk of adverse reactions. The Food and Drug Administration (FDA) recommends no more than 5 grams of EPA and DHA per day, along with supplements, according to the NIH. But if your doctor has prescribed fish oil for heart disease, the dosage may be higher.

Timing is everything when it comes to taking omega-3 supplements. “Fish oil supplements can be taken at any time during the day, but they can sometimes cause nausea when taken on an empty stomach,” Preston notes. “Since fish oil is a fat-soluble supplement, we can improve absorption by taking them with food.” If you eat seafood, choose oily fish more often before taking fish oil supplements.

“I always advise people to eat whole foods rather than supplements if they can,” says William W. Lee, M.D., physician and author of Eat to Beat Disease. “Regularly eating fatty fish such as salmon, sardines and anchovies is a great way to get omega-3s. Not only do you get healthy fats, but seafood is also a good source of protein.”

While fresh fish caught in the wild is the best option, instantly frozen seafood and even canned seafood can be just as nutritious and not to mention more economical. And if you don’t eat fish and are interested in taking supplements, remember: “it’s a good practice for anyone taking any supplements to talk to their doctor to discuss the possibility of medication-supplement interactions,” says Dr. Lee.

Avatar photo

Written by Emma Miller

I am a registered dietitian nutritionist and own a private nutrition practice, where I provide one-on-one nutritional counseling to patients. I specialize in chronic disease prevention/ management, vegan/ vegetarian nutrition, pre-natal/ postpartum nutrition, wellness coaching, medical nutrition therapy, and weight management.

Leave a Reply

Your email address will not be published. Required fields are marked *

Oysters: Why Eat Them and How to Cook Them

Nutritionist Explains Who Should Never Eat Onions