【Nutritionist Column】What is Fish Oil? A Comprehensive Guide to Omega-3, EPA, DHA, Recommended Intake, and Safety Precautions

Annabelle is a Registered Dietitian Nutritionist (RDN) and a member of the Hong Kong Dietitians Association. She graduated from New York University with both a Bachelor’s and a Master’s degree, both earned with honors. With three years of clinical experience, she has worked at two top-tier private academic medical centers in New York, accumulating solid clinical nutrition care experience. She specializes in evidence-based medicine to design dietary treatment plans for patients that are truly sustainable in the long term.

Fish oil is often touted as a "panacea" for heart, brain, and anti-inflammatory health, but what exactly is it? How much should you take? How should different groups choose the right fish oil? These questions often leave consumers feeling hesitant. This article will provide an in-depth look at fish oil and guide you through answering these common questions.

**This article is based on information from the Centre for Food Safety in Hong Kong, the Hong Kong Consumer Council, and international organizations to clarify the role, target audience, and safety limits of fish oil. This is a health education article and does not replace personalized advice from doctors, pharmacists, or registered dietitians.

Omega-3 What exactly is it?

Omega-3 is a group of polyunsaturated fatty acids. These fatty acids are essential components of human cell membranes, used to maintain cell membrane health, enhance immunity, and provide raw materials for the body to synthesize important substances. They are especially vital for eye and brain health. Since the human body cannot produce sufficient amounts of Omega-3 on its own, they are considered essential fatty acids.

l ALA (Alpha-linolenic acid): Primarily found in plants such as flaxseeds and chia seeds. It can be converted into EPA and DHA in the body, but the conversion rate is very low and insufficient to support daily human requirements.

l EPA (Eicosapentaenoic acid): Primarily found in deep-sea fish, it helps promote cardiovascular health, regulate blood lipids, and reduce inflammatory responses.

l DHA (Docosahexaenoic acid): Primarily found in deep-sea fish, it is the "building block" for the brain and retina.

Common Misconception: Fish Oil ≠ Cod Liver Oil; don't get them confused!

When buying supplements, many people often confuse "fish oil" with "cod liver oil," sometimes even assuming they are the same thing. Beware! The sources, ingredients, and effects of these two products are completely different. If you take large daily doses of cod liver oil as if it were fish oil, it could potentially lead to fat-soluble vitamin poisoning!

Comparison Item	Fish Oil	Cod Liver Oil
Extraction Source	Muscle and fat of deep-sea fish	Liver of fish
Core Ingredients	Omega-3 (mainly EPA and DHA)	Vitamin A, Vitamin D
Main Benefits	Regulate internal inflammation, cardiovascular health, maintain brain agility, and vision	Eye protection (preventing night blindness), bone development, general immunity boost
Overdose Risk	High safety	High risk! Vitamins A and D accumulate in the body; excess may cause liver strain or poisoning

What are the actual benefits of fish oil? Dosages and scientific evidence for pregnant women, those with high triglycerides, and daily heart health explained.

Pregnant women: Because the fetus receives DHA from the mother through the placenta for brain and retinal development; DHA accumulation is particularly active during the later stages of pregnancy. The European Food Safety Authority (EFSA) suggests: general adults should intake 250 mg of EPA+DHA daily; pregnant and lactating women should increase this by an additional 100–200 mg of DHA. Some studies show that pregnant women who rarely eat fish may help reduce the risk of preterm birth by increasing Omega-3 intake during pregnancy. 9 16 17

People with high triglycerides: Some studies indicate that a daily dose of 4g of prescription-grade Omega-3 (including EPA+DHA formulas or pure EPA formulations) can be used to treat specific high triglyceride conditions, but this must be assessed and monitored by a doctor.7

Daily cardiovascular health: Currently, consistent research supports incorporating fish into an overall healthy dietary pattern. Generally, healthy adults are advised to eat fish at least twice a week (about 85–150g per serving). If fish intake is usually insufficient, consider taking 250–500 mg of EPA+DHA in fish oil capsules as a dietary supplement.

What is the recommended daily intake of Omega-3?

The Hong Kong Centre for Food Safety recommends that the public maintain a balanced and varied diet, including moderate amounts of a variety of fish as part of a healthy diet.

Healthy adults do not need to obsess over calculating the exact milligrams of EPA+DHA in every meal. A more practical approach is:Eat fish at least twice a week, rotating different types, and including one or two servings of fatty fish. The European Food Safety Authority (EFSA) uses 250 mg of EPA+DHA per day as an appropriate intake for healthy adults and children to maintain general cardiovascular health.6

Many fish oil products on the market provide 500–1,000 mg or more of EPA+DHA per serving. This is primarily designed based on different target audience requirements and convenience. It does not mean that exceeding the standard recommended intake is "too much." Consumers are advised to choose whether to supplement with fish oil based on their own physical condition and dietary habits.

How much is "too much"?

EFSA states that there are no safety concerns for healthy adults consuming up to 5 grams of EPA+DHA daily from supplements; the US FDA also notes that dietary supplements with no more than 5 grams of EPA+DHA per day, when used as recommended, are generally considered safe.1 6

At a Glance: How to choose fish oil for different groups?

For modern people, eating enough fish in their daily diet is harder than one might think. With hundreds of fish oil products on the market, all listing various ratios of EPA and DHA on their packaging, how should you choose? In fact, different lifestyles and age groups require completely different fish oil formulas. Below is a fish oil selection guide to help you understand in one minute which one is best for you or your family:

Group / Situation	Core Need	Recommended EPA:DHA Ratio	WHC Product Recommendation
Healthy Adults	Combat chronic inflammation, basic cardiovascular care, retinal and brain health maintenance	3:2 (The most common golden ratio)	Little Thousand Gold Little Golden Egg
Pregnant, Pre-conception, or Lactating individuals	Baby’s brain and retinal development, mommy’s postpartum mood support	DHA-rich (e.g., 1:2 or 1:3)	Little Red Riding Hood
School-age children and teenagers	Brain development, focus, vision health	DHA-rich (e.g., 1:2 or 1:3)	Little Superman Little Elf
High risk of "Three Highs"	Cardiovascular health, lower blood lipids	High EPA or pure EPA	Little Angel

Who needs to consult a doctor first? Contraindications and precautions for fish oil.

In addition to the common groups mentioned above, if you or your family members have the following conditions, you must consult a professional physician:

- Fish or seafood allergies

- Currently taking anticoagulants, antiplatelets, or blood pressure medication

- Bleeding tendencies, blood clotting disorders, or recent unexplained bleeding

- Upcoming surgery, tooth extraction, or invasive examinations

- History of atrial fibrillation or other heart rhythm issues

- Late-stage pregnancy

- Recipients of organ transplants, those taking immunosuppressants, or those with complex chronic diseases

References

1. National Institutes of Health, Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals.whc_fish_oil_education_blog_zh-hk.docx
https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/

2. Consumer Council of Hong Kong. “Fish oil supplements: Absorbing good fats and harmful pollutants?” Choice Magazine, Issue 553, 2022.consumer.org
https://www.consumer.org.hk/tc/article/553-fish-oil-products/553-fish-oil-products-dha-epa-knowledge

3. Centre for Food Safety, Hong Kong. “Benefits of Eating Fish,” 2018.consumer.org
https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsf_108_01.html

4. Centre for Food Safety, Hong Kong. “Balancing the Risks of Methylmercury and the Benefits of DHA and EPA,” 2019.cfs.gov
https://www.cfs.gov.hk/english/multimedia/multimedia_pub/multimedia_pub_fsf_154_01.html

5. U.S. Food and Drug Administration. Advice About Eating Fish: For Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1–11 Years.consumer.org
https://www.fda.gov/food/consumers/advice-about-eating-fish

6. European Food Safety Authority. Scientific Opinion on Dietary Reference Values for Fats, Including Saturated Fatty Acids, Polyunsaturated Fatty Acids, Monounsaturated Fatty Acids, Trans Fatty Acids, and Cholesterol. EFSA Journal. 2010;8(3):1461.consumer.org
https://doi.org/10.2903/j.efsa.2010.1461

7. Skulas-Ray AC, Wilson PWF, Harris WS, et al. Omega-3 Fatty Acids for the Management of Hypertriglyceridemia: A Science Advisory From the American Heart Association. Circulation. 2019;140(12):e673–e691.cfs.gov
https://doi.org/10.1161/CIR.0000000000000709

8. National Health Service. Pregnancy Vitamins and Supplements.consumer.org
https://www.nhs.uk/pregnancy/keeping-well/pregnancy-vitamins-and-supplements/

9. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the Tolerable Upper Intake Level of Eicosapentaenoic Acid, Docosahexaenoic Acid and Docosapentaenoic Acid. EFSA Journal. 2012;10(7):2815.cfs.gov
https://doi.org/10.2903/j.efsa.2012.2815

10. Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 Fatty Acids for the Primary and Secondary Prevention of Cardiovascular Disease. Cochrane Database of Systematic Reviews. 2020;3:CD003177.consumer.org
https://doi.org/10.1002/14651858.CD003177.pub5

11. National Center for Complementary and Integrative Health. Omega-3 Supplements: What You Need To Know.cfs.gov
https://www.nccih.nih.gov/health/omega3-supplements-what-you-need-to-know

12. National Institutes of Health, Office of Dietary Supplements. Dietary Supplements and Life Stages: Pregnancy—Health Professional Fact Sheet.consumer.org
https://ods.od.nih.gov/factsheets/Pregnancy-HealthProfessional/

13. Centre for Food Safety, Hong Kong. Advice for Pregnant Women, Women Planning Pregnancy and Young Children on Fish Consumption.cfs.gov
https://www.cfs.gov.hk/english/programme/programme_firm/files/Fish_advice_for_Pregnant_women.pdf

14. U.S. Food and Drug Administration. Dietary Supplements: What You Need to Know.cfs.gov
https://www.fda.gov/food/buy-store-serve-safe-food/dietary-supplements

15. Hong Kong Department of Health, Centre for Health Protection. Healthy Eating for a Healthy Pregnancy.cfs.gov
https://www.chp.gov.hk/en/healthtopics/content/466/46698.html

16. Middleton P, Gomersall JC, Gould JF, Shepherd E, Olsen SF, Makrides M. Omega-3 fatty acid addition during pregnancy. Cochrane Database of Systematic Reviews. 2018;11:CD003402.cfs.gov
https://doi.org/10.1002/14651858.CD003402.pub3

17. Makrides M, et al. (2019). A Randomized Trial of Prenatal n-3 Fatty Acid Supplementation and Preterm Delivery (ORIP). NEJM. https://pubmed.ncbi.nlm.nih.gov/31509674/