Last Updated on December 5, 2025

WHAT IS FISH OIL?

Fish oil is a supplement made from the fats and/or livers of fish such as cod, salmon, mackerel, herring and sardines.

Fish oil provides a variety of benefits when supplemented. It can reduce the risk of heart attacks and strokes, to treat high triglycerides and high blood pressure, and to improve symptoms of rheumatoid arthritis. It can also decrease the risk of diabetes and several forms of cancer, including breast cancer.

Fish oil extracted from cod liver oil is also rich in vitamins A and D. For example, 1 tablespoon of cod liver oil contains about 13,000 international units (IU) of vitamin A and 1,300 international units (IU) of vitamin D.

Omega-3 Fatty Acids

Many people focus on the dosage of fish oil to take, like 1000 mg or 2400 mg, but it is the types of omega-3 fatty acids to focus on.

In a standard 1000 mg capsule of natural, unaltered fish oil, you usually get about 300 mg total omega-3s, of which ~180 mg is EPA, ~120 mg is DHA, and only a few milligrams (often <10 mg) of DPA. The remaining ~700 mg is other fats (mono- and polyunsaturated fatty acids, triglycerides, etc.). Concentrated or “laboratory altered” fish oils can raise omega-3 content to more.

1. Types of Omega-3 Fatty Acids

1. EPA (Eicosapentaenoic acid): To promote a healthy inflammatory response and support healthy blood vessels, and joints.
2. DHA (Docosahexaenoic acid): To support brain health, eye health, and nervous system health.
3. DPA (Docosapentaenoic acid) : To support clean arteries and power your body’s natural artery-cleaning system.

DPA is a lesser-known long-chain omega-3 fatty acid that acts as a metabolic bridge between EPA and DHA. It’s sometimes called the “missing omega” because it’s not often listed on supplement labels, yet it plays unique roles in cardiovascular and inflammatory health. DPA converts into EPA or DHA depending on body needs.

2. Species Variability of Omega-3s

• Anchovy/Sardine oil: EPA ~18%, DHA ~12%, DPA ~<1%.
• Cod liver oil: DHA-rich (~25%), EPA lower (~15%), DPA trace.
• Menhaden oil: Balanced EPA:DHA with slightly more DPA than other variables (~5–10 mg per gram).

How Much EPA and DHA Do I Need?

Health care organizations propose intake of two servings of oily fish per week for healthy adults, which equates to approximately a daily total of 500 mg EPA+DHA.
A standard unaltered 1000 mg fish oil softgel usually provides around 300 mg of omega-3s (180 mg EPA & 120 mg DHA), and to meet the 500 mg EPA and DHA recommendation, a minimum of two softgels would be necessary.

Note: Make sure to read the “Supplement Facts” label to determine the amount of EPA and DHA in a fish oil/omega-3 supplement. 1,000 mg of Omega-3 and 1,000 mg of Fish Oil are not the same! It’s important to consider how much EPA and DHA is in a supplement, not just how much fish oil it contains.

1. Omega-3s Daily Recommendations From Supplements

• Recommended dose: 250-500 mg of Omega-3 per day.
• For Optimum Health: 1,000 mg Omega-3 per day.
• Omega-3 deficiency-related conditions: 2,000 mg or more Omega-3 per day. You shouldn’t take more than 3,000 mg of omega-3 fatty acids per day without your doctor’s supervision.

Omega-3 Fish Oil and Safety

Too much fish oil could thin your blood, creating problems with clotting and bruising. People who are planning surgery are advised to stop taking omega-3 supplements a week or two before the procedure.

1. The ratio of EPA to DHA

The ratio of EPA to DHA in supplements is also important. A recent study found that patients with higher levels of DHA than EPA, were more at risk for heart problems. Thus, for cardiovascular health, EPA-dominant formulations are preferred. Cod liver oil or DHA-rich blends might be prioritized for neurocognitive and eye support.

2. Vitamin A Toxicity

Fish oil from cod liver oil can increase the risk for vitamin A toxicity. For example, 1 tablespoon of cod liver oil contains about 13,000 international units (IU) of vitamin A. The tolerable upper limit for adults is 10,000 IU of vitamin A daily.

3. Vitamin E Depletion

The only vitamin that fish oil may interfere with is vitamin E. Some clinical studies have noted that vitamin E levels gradually drop in people who consume fish oil supplements long-term, according to the “Natural Standard Herb & Supplement Reference: Evidence-Based Clinical Reviews.” The theory is that absorbing fish oil uses vitamin E, so your body’s requirement for the vitamin is greater when taking fish oil supplements.

What Should I Look For In An Omega-3 Fish Oil Supplement?

Given the increasing environmental pollution of our oceans, it is important to purchase fish oil from a reputable manufacturer that follows Good Manufacturing Practices (GMPs) and takes the necessary steps to purify the oil. Molecularly distilled or re-esterified triglyceride forms are cleaner and better absorbed.

Recommended Fish Oil Supplements

Reference:
https://nccih.nih.gov/health/omega3/introduction.htm
https://examine.com/supplements/fish-oil/
https://omegavia.com/fish-oil-dosage-how-much-is-too-much-fish-oil/
https://www.medicalnewstoday.com/articles/heart-health-not-all-omega-3s-are-equal
https://vitalibrary.com/dpa-omega-3-heart-brain/