Fish oil: Benefits and dosage

By Jennifer Scheinman MS RDN Jun 16, 2023 • 5 min

While eating fish is a great way to increase your omega-3 fatty acid intake, you may be wondering how much fish you should eat or if a dietary supplement would be helpful. Fish oil has become a popular supplement due to purported health claims and for people who don't regularly eat fish.

What is fish oil?

Fish oil contains two important types of omega-3 fats: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). You can get these omega-3 fats from certain foods you eat or from taking a fish oil supplement. Dietary sources of DHA and EPA come from fish and seafood, especially salmon, mackerel, anchovies, sardines and herring. Your body can make DHA and AHA from another omega-3 fat called alpha-linolenic acid (ALA), but only in small amounts. ALA is found in many plant-based foods, such as seeds, nuts and vegetable oils.

What are some of the potential health benefits of fish oil?

The potential health benefits of omega-3s in fish oil are a hot topic in scientific research. It's known that people who eat fish have a lower risk of many chronic diseases. However, it's tricky to tell if this effect is due to the omega-3s in fish or something else.

Still, there seems to be a link between omega-3s and better heart health. Many studies show that people who eat dietary sources of fish oil at least twice a week as part of a healthy diet have a lower risk of developing heart disease. They also tend to have healthier blood pressure and triglyceride levels (a type of fat in the blood). While eating fish may help keep your heart healthy, taking a fish oil supplement appears to offer little protective effect if you don't already have heart disease. For people with heart disease, the American Heart Association recommends consuming about 1g per day of EPA plus DHA, preferably from oily fish. Fish oil supplements may be an option under the guidance of a healthcare provider.

Additional benefits

The potential benefits of omega-3s in fish oil may go beyond heart health. While results haven't been conclusive, studies show that fish oil may:

  • Help offer some relief for the symptoms of rheumatoid arthritis
  • Lower the risk of problems with cognitive function, such as Alzheimer's disease and dementia
  • Lessen the symptoms of attention deficit hyperactivity disorder (ADHD)

How much fish oil do you need?

The Dietary Guidelines for Americans recommends that adults eat two 4-ounce servings of fish a week to get enough of the omega-3s found in fish oil. Pregnant or breastfeeding women should avoid fish that may contain high levels of mercury. King mackerel, swordfish and bigeye tuna can contain high levels of mercury.

People who don't eat fish may choose to take a fish oil supplement. Consult with your healthcare provider for specific dosing guidelines.

What are the risks associated with taking fish oil?

Consuming fish oil from food sources is generally considered safe and is the preferred way to get these nutrients. For people unable to consume fish regularly, taking supplements may be an option. Fish oil supplements are generally considered safe when taken as recommended. However, they may cause mild side effects. The most common side effects from fish oil supplementation are digestive symptoms, an unpleasant taste in your mouth and headaches. Taking high doses may increase the rare risk of bleeding and possibly stroke. High doses of fish oil supplements might also interfere with the immune system by altering the inflammatory response (how the body reacts to disease or injury).

Fish oil supplements may interact with certain medications, such as those that thin the blood. It is unclear if fish oil supplements are safe for people with fish allergies.

The omega-3s in fish oil may play an essential role in health. Consuming fish regularly, as part of a healthy diet, is the recommended way to get these omega-3 fats. If you're considering taking a fish oil supplement, remember to talk to your healthcare provider, who will be able to answer any questions and provide recommendations.

Clinically reviewed and updated June 2023.

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