Total Shape is a reader-supported site. Purchases made through links may earn a commission. Learn more.

How to Choose Fish Oil? (According to a Dietitian)

Isaac Robertson
Published by Isaac Robertson | Co-Founder & Chief Editor
Last updated: August 2, 2023
We personally test every product featured in our reviews and guides. By ordering products anonymously and getting a group of independent testers, we are able to get first-hand experience and provide data-driven recommendations. Learn more.

Science has found that 90% of Americans don’t get an optimum intake of the EPA and DHA omega-3s through their diet.

So instead of eating fatty fish like salmon and trout at least twice a week, most people use omega-3 supplements to increase their intake, boost nutrition, and improve well-being.

Seeking the best supplements can be frustrating in today’s oversaturated market.

So, we’ve decided to talk to our dietitian team, discuss how to choose a high-quality omega-3 fish oil supplement, and teach you how to read content on the labels.

Here’s their expert advice.

Quick Summary

  • When choosing a fish oil, check if it contains the perfect balance and amount of DHA, and EPA types of omega-3s.
  • Ensure that the freshnessand high quality standards have been maintained by the manufacturer for the selected fish oil brand.
  • Opt for fish oil with either TG or FFA molecular structure, rather than EE.

What Should I Look for When Buying Fish Oil?

A hand holding a plenty of fish oil supplement

Here’s what you should look for when buying fish oil:

Types of Omega-3 Fatty Acids It Contains

Many fish oils contain small amounts of the most important types of omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).

Make sure your omega-3 supplement includes both EPA and DHA because each can provide different health benefits.

Which Form the Fatty Acids Take

It’s crucial to be aware of the forms omega-3 fatty acids take in different fish oil products because they affect how omega-3s get incorporated into your tissue.

In whole foods like fatty fish, you’ll typically find omega-3s as free fatty acids (FFA), phospholipids (PLs - commonly found in krill oil), or triglycerides (TG).

In conventional supplemental fish oil, the triglyceride form of omega-3s is the most common.

In processed, refined fish oils, the triglycerides are often converted into ethyl esters (EE) to enable manufacturers to reduce the production costs and adjust the DHA and EPA concentration in the oil.

(Note: The ethyl ester form is more prone to rancidity and oxidation and gets less absorbed.)

Also, it’s possible to convert the ethyl esters from processed fish oils back into so-called reformed triglycerides (rTG).

The difference in the quality of these forms is comparable to the difference between natural orange juice from freshly squeezed fruit and its concentrate.

In summary, for enhanced absorption, tend to pick free fatty acids, triglyceride, or phospholipid form, rather than ethyl esters from more processed fish oils.

What’s the Concentration of EPA and DHA

Fish oil supplements on a bottle and on a spoon

When you take a closer look at the list of ingredients, you’ll probably notice that supplement companies often show how much fish oil or all omega-3s their product contains in total.

For example, a supplement label may show that it contains 1,000 mg of fish oil per capsule, but that only 320 mg of that content is EPA and DHA.

That’s why another important point to keep in mind when choosing the right supplement for yourself is the exact concentration of EPA and DHA it contains per capsule (or serving size if you’re taking the supplement in a liquid form instead of soft gels).

Why does it matter?

It helps your doctor provide medical advice and determine the appropriate and safe dosage based on your age, sex, health condition, and needs. Taking higher doses may cause an increased risk of bleeding, abnormal heart rhythm, etc., and interact with your prescription medications.

So, ensure you check the product label for the exact amount of each omega-3 fatty acid type included in a single serving.

Remember that natural fish oil typically includes up to 30% of EPA and DHA, and the rest belongs to other fats. Some products might contain even up to 90% of EPA and DHA.

The Fish Oil Supplement Purity

A hand pouring supplements on table

Besides highly valuable omega-3s, fish fatty tissues also usually contain environmental contaminants, especially longer-lived species higher in the food chain and fish caught in contaminated oceans and sea zones.

The fish oil derived and extracted from the fish that eat other fish often contains heavy metals such as mercury, lead, cadmium, and arsenic, plus hundreds of other toxic compounds bio-accumulated in the fish, including PBBs (polybrominated biphenyls), PCBs (polychlorinated biphenyls), dioxins, and furans.

Many studies have shown that these pollutants can cause a range of adverse effects in humans, even at low levels.

For example, they’ve been linked to causing: 

  • Irreversible liver, kidney, and other organ damage,
  • Memory loss and a variety of brain and nervous system disorders,
  • Problems with endocrine, immune, and reproductive system functioning,
  • Muscle spasms,
  • Loss of coordination
  • Skin problems,
  • Chronic bronchitis
  • Blindness,
  • Deafness, and even
  • Death.

Not every oil supplement undergoes an advanced purification process to eliminate heavy metals and other contaminants.

So, it’s important to find a highly purified omega-3 supplement, possibly sourced from short-lived smaller fish species like sardines, herring, anchovies, or mackerel, that contain fewer pollutants.

Also, pay attention to the other compounds added to boost omega-3 health effects (often complementary fat-soluble nutrients - vitamins D and A), and stay away from artificial components, fillers, preservatives, etc.

The Product Freshness

Getting a piece of capsule on a plate

Since omega-3s are prone to oxidation and can go rancid fast, the next critical step for consumers is to ensure fish oil products are fresh, effective, and haven’t lost their potency.

Like with seafood or krill oil, a fishy or rancid smell is an indicator that your fish oil isn’t fresh.

So, always check the expiration date, the product smell (even taste), and whether it contains vitamin E or another natural antioxidant like astaxanthin to prevent oxidation that’s potentially detrimental to our cells.

The Supplement Quality, Authenticity, and Sustainability

To ensure you get a high-quality product (fish or krill oil supplements or other omega-3 supplements), you need to dive deeper for more information.

“When taking a supplement, be sure it comes from a reputable brand with transparent labeling and ingredients.”

- Tracy Lockwood Beckerman, RD

Taking a closer look at the label details is an easy way to find evidence of whether particular fish oil supplements meet all the required quality and sustainability standards.

Top-quality products from reputable brands recognized by the FDA and certified for their cGMP (current Good Manufacturing Practice) typically display the third-party seals, proving they’ve been tested and certified by independent bodies as safe and containing what they claim.

For example, a company that only uses sustainably caught wild water fish, eco-friendly equipment, and procedures when producing their dietary supplements can earn a traceability certificate by the Marine Stewardship Council (MSC), the Environmental Defense Fund, or a similar organization.

In addition, seals from the United States Pharmacopeia (USP), NSF International, IFOS, GOED, TGA, or other similar authorities provide authenticity and quality assurance.


How Much Fish Oil Should I Take Daily?

How much fish oil you should take daily depends on your age, sex, health condition, and needs. So it’s best to consult your doctor and read the instructions on the product label to find out how much EPA and DHA a particular product contains.

The recommended daily intake of combined EPA and DHA omega-3 fatty acids is 250–500 mg for the optimum overall health of most healthy adults in the US countries. [1] [2]

A higher dose may be beneficial for pregnancy or particular health conditions but may also be harmful.

What Does Fish Oil Do to Your Body?

Fish oil is an excellent source of both docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) polyunsaturated omega-3 fatty acids our body can’t produce.

These are biologically active forms of essential fatty acids that get faster and more easily absorbed than the alpha-linolenic acid (ALA) from plant-based sources like vegetarian algae oils, walnuts, flaxseeds, chia seeds, etc.

According to research, these nutrients are essential for: 

  • Brain health and development,
  • Preventing heart disease,
  • Lowering blood pressure,
  • Managing triglyceride and cholesterol levels,
  • Reducing anxiety,
  • Fighting inflammation,
  • Making your immune system stronger,
  • Aiding weight loss, among many other health benefits. [3]

No wonder fish oil is among the most popular complementary health supplements US adults use, according to the data from the National Center for Complementary and Integrative Health (NCCIH) within the National Institutes of Health.

So, How Do You Choose The Best Fish Oil Supplement?

Follow these easy steps on how to choose the best fish oil omega-3 supplement:

  • See whether your fish oil capsules contain a sufficient amount and perfect balance of both EPA and DHA types of omega-3s (and preferably an antioxidant to fight rancidity).
  • Learn which type of molecular structure the omega-3s have (opt for FFA or TG rather than EE).
  • Ensure purity, freshness, high quality, and sustainable fishing practices.

Do you agree that you could rely on these tips to help you wisely choose and buy a supplement you’ll benefit from?

Feel free to share your feedback and concerns with us.


Was this article helpful?

About The Author

You May Also Like

Write a Reply or Comment

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




Learn More