Omega-3 and fish oil supplements

Omega-3 fats are found in many cells in your body, especially in cells in your brain and eyes. They play an important role in helping your blood vessels, heart, immune system and lungs work properly.

On this page, you can find the following information:

What are omega-3 fatty acids?

Omega-3 fatty acids are a type of polyunsaturated fats. Polyunsaturated fats are often referred to as ‘good fats' as they are important in your diet. The main omega-3 fatty acids are:

  • docosahexaenoic acid (DHA)
  • eicosapentaenoic acid (EPA)
  • alpha-linolenic acid (ALA).

These are found naturally in some foods.

Diagram of different types of omega-3 fatty acids

ALA is an essential fatty acid, meaning that your body can’t make it. Your body can convert some ALA into EPA and then to DHA, but only in very small amounts. Therefore, you need to get most of your EPA and DHA from food.

Omega-3s can reduce your triglyceride levels, a type of fat found in your blood. DHA and EPA/DHA combination products can increase LDL cholesterol levels, while pure EPA products do not. Read more about cholesterol and fats and oils

Why are omega-3 fatty acids important?

Omega-3 fats are found in many cells in your body, especially in cells in your brain and eyes. They play an important role in helping your blood vessels, heart, immune system and lungs work properly. This is why including foods that are high in the omega-3 fats EPA and DHA, such as oily fish, is encouraged as part of a healthy balanced diet. 

How often should I eat oily fish?

In New Zealand it’s recommended that men have 610mg of long chain omega-3 daily and women have 430mg daily to reduce the risk of heart disease. This is 2 servings of oily fish a week.3 A serving of fish is:

  • 125–150g raw fish, which is about the size of your hand (palm and fingers)
  • a 95g tin of tuna, which has about 100mg of omega-3
  • a 105g tin of pink salmon, which has about 120mg of omega-3.

The amount of omega-3 in fish varies between species of fish and whether they are farmed or fresh fish. Oily fish like fresh tuna, fresh or tinned salmon, sardines, pilchards and mackerel are higher in omega-3. White fish and sea food (oysters, eel and prawns) have a lower omega-3 content.

  • Tinned salmon, mackerel, sardines and pilchards can be a great way to get more omega-3.
  • Fish tinned in brine is high in sodium which can increase blood pressure and increase your risk of heart disease.
  • Choose fish tinned in spring water, or rinse the fish thoroughly to remove the brine and sodium.
  • Remember that flavoured tinned fish may also contain added sugar and sodium.

Omega-3 and fish oil supplements 

There are a variety of omega-3 and fish oil supplements that can be bought from pharmacies, supermarkets, health shops and online. They are available as capsules, tablets and liquid. There are currently no New Zealand recommendations for taking omega-3 and fish oil supplements.

It is best to get omega-3 from food. A well-balanced diet that includes 2 serves of oily fish per week will provide an adequate amount of omega-3 that your body needs.

Not all fish oil supplements are created equally. Unlike medications, fish oil supplements do not need to be approved by the medicines regulatory organisation in New Zealand, Medsafe. This means that manufacturers can sell supplements simply with "claims" of safety and effectiveness.

A recent analysis of ten fish oil supplements available in New Zealand highlighted the ongoing challenges associated with the regulation of “health claims” associated with dietary supplements in New Zealand. The authors confirmed that the literature on health effects is contradictory and clearer definitions of the types of health statements that can be made and the research necessary to support them requires regulatory clarification.4

Fish oil supplements – what is the evidence?

Fish oil can slightly reduce blood pressure and heart rate.2 However, statin medications are much more effective in lowering cholesterol and the risk of heart problems in people with heart disease or those at high risk of developing heart disease. There is no benefit to taking a fish oil supplement if you are already on a statin. Read more about statins

Randomised trials have not shown a benefit for fish oil supplement reducing dementia risk, but high-dose DHA supplementation may be beneficial to those carrying the APOE4 gene.5 

Fish oil may slightly reduce inflammation, and very high dose fish oil (5.5 grams) can be helpful in rheumatoid arthritis in certain situations.6

Tips about using omega-3 and fish oil supplements

When choosing fish oil supplements
Look at the amount of EPA and DHA contained in the capsule, tablet or liquid, rather than the fish oil content. For example, the product label on a fish oil supplement may say the following: 

Each capsule contains: Fish oil – Natural 1.5g equiv. 
Eicosapentaenoic acid (EPA) 270mg, Docosahexaenoic acid (DHA) 180mg.

  • In this example, each capsule has EPA + DHA = 270mg + 180mg = 450mg of omega-3. 
  • If you are unsure about how to read the labels of fish oil supplements, ask your pharmacist for advice.
  • EPA content is the most important for heart health, but very high doses are required (above 1800mg daily) for any benefit.
  • Meanwhile the DHA in fish oil supplements can increase LDL cholesterol ('bad cholesterol'), and high doses can increase the risk of atrial fibrillation, bleeding, stomach upset, abnormal liver tests and rash. 

Not all fish oil supplements are created equally. It is possible that omega-3 fatty acids might be lower than those stipulated on the labels because unsaturated fatty acids are susceptible to oxidation and degradation. 

Interactions with medicines 
Omega-3 can have blood thinning effects when taken in high doses. Seek medical advice before taking doses of omega-3 supplements, especially if you are taking anticoagulant medication such as warfarin.

Seafood allergy
Although the risk of allergic reactions to fish oil supplements is considered to be low in people allergic to fish due to the method of purification, it is recommended that you seek medical advice before taking fish oil supplements. Read more

Learn more

The following links have more information about omega-3. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

Omega-3 fatty acids National Institutes of Health, US
Omega-3 The Association of UK Dietitians, UK 
Sources of  omega-3 Heart Foundation, Australia
Omega-3 and mood disorders Black Dog Institute, Australia
Allergic and toxic reactions to seafood Australasian Society of Clinical Immunology and Allergy

References

  1. Omega-3 fatty acids National Institutes of Health, US
  2. Omega‐3 fatty acids for the primary and secondary prevention of cardiovascular disease Cochrane Library, 2018
  3. Guide to eating for a healthy heart Heart Foundation, NZ
  4. Are over-the-counter fish oil supplements safe, effective and accurate with labelling? Analysis of 10 New Zealand fish oil supplements NZMJ September, 2020
  5. Association of docosahexaenoic acid supplementation with Alzheimer disease stage in apolipoprotein E ε4 carriers: a review. JAMA Neurol. 2017 Mar 1;74(3):339-347. 
  6. Fish oil in recent onset rheumatoid arthritis: a randomised, double-blind controlled trial within algorithm-based drug use. Ann Rheum Dis. 2015 Jan;74(1):89-95. 
  7. Kai moana – food from the sea Heart Foundation, NZ

Reviewed by

Katrina Pace is a New Zealand Registered Dietitian. As a freelance nutrition, health and wellness writer she specialises in making complex health concepts easy to understand.
Jeremy Steinberg is a GP with special interests in musculoskeletal medicine, evidence-based medicine and use of ultrasound. He's been reviewing topics for Health Navigator since 2017 and in his spare time loves programming. You can see some of the tools he's developed on his website.

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr Jeremy Steinberg, FRNZCGP; Katrina Pace, New Zealand Registered Dietitian Last reviewed: 19 Feb 2020