What's the catch with Omega 3's?

Category: Heart Health
Heart Health

 Omega 3 fatty acids are considered essential fatty acids. This means they are necessary for human health but the body can’t make them - you have to get them through food. Omega 3s come from a family of fats called PUFAs (polyunsaturated fatty acids). Omega 3 fats are also known as EPA (Eicosapentanoic acid) and DHA (Docosahexanoic acid)

Evidence suggests that omega 3s may be helpful in protecting your heart from heart disease. They do this by:

  • Helping the heart to beat more regularly;
  • Reducing the 'stickiness' of the blood, making it less likely to clot;
  • Protecting arteries, which carry blood to the heart, from damage;
  • Reducing levels of triglycerides in the blood (a fat that can increase risk of heart disease);

As well as benefits for your heart, omega 3s are:

  • Thought to help with bone/joint health;
  • Important in healthy brain development during pregnancy;
  • Sometimes used in the management of certain cancers, Alzheimer’s disease and inflammatory bowel disease.

Where can omega 3s be found?

  • Salmon
  • Shark and Marlin
  • Sardines
  • Swordfish
  • Mackerel
  • Kippers
  • Trout (Rainbow)
  • Fresh tuna
  • Herring
  • Pilchards

Choose fish that is fresh or tinned in brine, water or tomato sauce such as sardines, mackerel, salmon and herring. These fish are good sources of omega 3. Tinned tuna is the only exception to this rule as it loses its omega 3 during the manufacturing process. Choose varieties tinned in fresh water, brine or tomato sauce. For even  more health benefits, avoid those tinned in oil and avoid crumbed/battered/deep fried fish as a source of omega 3.They are high in calories and when drained from the tin, can also be lower in omega 3.

How much do I need?

For the general population (adults and children older than 5 years of age) guidelines recommend to consume 2 portions of fish per week, oily fish is best. A portion for adults equals the thickness and size of the palm of the hand or 140g in weight of fresh fish or 1 small can of tinned fish.

Women past childbearing age or intending to have children, men and boys can eat up to four portions of oily fish a week. Women who are pregnant or breastfeeding, or likely to become pregnant, and girls should have up to two portions a week. Shark, swordfish and marlin contain concentrated sources of mercury that may be harmful to the developing baby’s nervous system and so should be avoided by women who are pregnant or planning a baby and all children under 16 years. All other adults, including breastfeeding women, should eat no more than one portion a week.

Current research recommends that for people who have had a recent heart attack, they too should include oily fish as part of a healthy or Mediterranean style diet.

What if I don’t like fish?

Ideally omega 3 from fish is the best way to get omega 3, as supplements are not routinely recommended for healthy adults and children, however some people may have an allergy to fish or cannot manage to eat their recommended amount on a weekly basis.

If you wish to use omega 3 supplements in this case the recommendation for adults equals 250-500mg per day of pure omega 3. This is a personal choice unless recommended by a GP, consultant, cardiac rehab/practice nurse or dietitian. An algae based supplement may be more suitable for those with a fish allergy or those who are vegan, however if you have a life threatening allergy please consult your GP before taking a supplement.

What about plant-based sources or products marketed as containing omega 3?

The best way of ensuring we are taking enough EPA and DHA is to eat foods rich in these fats. Fish, and especially oily fish, are best sources while plant based foods are less reliable sources of EPA and DHA. People who do not eat fish can get some omega-3 from the following foods:

Plant sources of omega 3 are suitable as part of a balanced healthy diet;

Oils - Rapeseed or canola oil, Walnut or Soya oil

Dark green leafy vegetables – spinach and kale

Nuts – almonds, walnuts, peanuts

Flaxseeds or linseeds oil

Soya and soya products

omega 3 enriched foods e.g. yoghurts/spreads/milk/orange juice/eggs

Some foods may claim to be a rich source of omega 3 e.g. enriched eggs/spreads/milk may be from plant or fish origin, have a look before investing in a more expensive version of the product, if the omega 3 is from a plant source e.g. flaxseed oil it may not be worth the extra cost.

What about over the counter fish oil/fish oil capsules?

Availability of omega 3 containing supplements over the counter is vast.  Unfortunately the strength of these supplements varies from 100-1000mg/d in the recommended doses. However it is not as simple as increasing the doses to meet your needs as some of these supplements also contain potent vitamins e.g. Vitamin A which can be dangerous to the body in large amounts. 

Do not take supplements containing vitamin A if you are pregnant or planning a baby. Choose an age-appropriate supplement – children will need less than adults.

Many contain other supplementary products e.g. Coenzyme Q10, glucosamine, omega 6, Chondroitin, and ginseng which cannot be recommended as part of a healthy diet as they may not be suitable with other medication and have as yet no strong evidenced based benefits.

A combination of an over the counter supplement could be used with a smaller quantity of oily fish if you are not able to consume the recommended amount per week.

Below is an example of a label on an omega 3 supplement

Nutritional Information
Each capsule contains: %EC RDA*
Fish Oil 1,360mg **
typically providing:  
EPA (Eicosapentaenoic Acid) ** 400mg
DHA (Docosahexaenoic Acid) ** 550mg
Total omega-3 Fatty Acids 950mg **
Vitamin E 1.85mg a-TE (2.75 I.U.) 20%

*RDA=Recommended Daily Allowance

**No RDA established

To check the amount of omega 3 in a fish oil capsule:

  • Look at the nutritional information panel as pictured above
  • EPA and DHA are both words used to describe omega 3
  • Add the two figures beside these words /letters together to find the total amount of omega 3 in the recommended dose:

EPA (Eicosapentaenoic Acid) 400mg
DHA (Docosahexaenoic Acid) 550mg
Total omega-3 Fatty Acids 950mg

  • If the information is given per capsule i.e. “Each capsule contains…” and the recommended dose is 2 capsules per day; therefore multiply the total amount by 2 to see the amount of omega 3 per recommended dose.
  • If ALA or Flaxseed oil appears as a source of omega 3 this should be disregarded as a source of omega 3 as it is not as reliable as EPA or DHA in the body. ALA has to be converted to EPA/DHA by the body and the amount needed has not been accurately determined.
  • Look for other ingredients e.g. vitamins, minerals and other supplements and check the dose.

Recommended amounts of Vitamin E per day are:

Men= 8mg Women=6mg

Recommended amounts of Vitamin A per day are:

Men = 700 μg Women = 600μg

Recommended amounts of Vitamin D per day are:

  • 5-10 μg people aged between 5-50 years
  • 10 μg people 51yrs or more

  • If the recommended amount is lower than what is recommended for you and this is the only source of omega 3 in your diet than consult with your doctor on other options.

These values are for a healthy population, do not use if you have other medical conditions where these levels are unsuitable.  Seek advice from a registered dietitian if in any doubt, email the INDI for help.

The Food and Drugs Administration recommends that consumers not exceed more than a total of 3 g per day of EPA and DHA omega 3 fatty acids, with no more than 2 g per day from a dietary supplement. Some people may need larger amounts under supervision of a medical professional.

What about Cod Liver Oil?

Cod liver oil is not recommended as a supplement as it is concentrated from the liver of white fish. This also means that large volumes of vitamins e.g. Vitamin A which can be dangerous to the human liver may also be present in large amounts. Also fish filter toxins from sea water in their liver i.e. dioxins and PCB’s and there may be a risk that these are also present in cod liver oil.

What about Supplements providing omega 3, 6 and 9?

If you want to buy an omega 3 supplement it should contain only omega 3. There is no benefit of supplementing omega 6 or 9 as we have more than enough sources of these in our diet. They are also considered to be unhelpful as they compete with omega 3 to be used in our body therefore can actually lower the amount of omega 3 our body will absorb from the supplement.

What about Krill Oil?

Krill Oil is a new addition to the omega 3 oil family. There is relatively little research or advice from official organisations e.g. Food Standards Agency of Ireland, European Society of Cardiology with regards to usage of this type of oil and it’s safety long term.

What if I am taking Warfarin?

Fish oil capsules may not be recommended with certain medication e.g. warfarin as they can affect INR readings and may contain other substance that may interfere with warfarin.  Please check with your doctor or warfarin nurse before taking any supplements contain omega 3.

Are large amounts of fish safe?

Safety concerns surrounding fish is largely due to there content of chemicals e.g. mercury, dioxins and PCB’s. For most of us i.e. men and non childbearing women there are no concerns from eating up to 4 portions weekly. Maximum amounts have been set for women of childbearing age and pregnant or breastfeeding women at 2 portions per week. This group and children under 16 years of age should also avoid shark, marlin and swordfish as these fish may contain concentrated sources of mercury.


Created by members of the Cardiac Interest Group, July 2016.

© 2014 Irish Nutrition and Dietetics Institute, INDI. Review date July 2019. All rights reserved. May be reproduced in its entirety provided source is acknowledged. This information is not meant to replace advice from your medical doctor or individual counselling with a dietitian/clinical nutritionist. It is intended for educational and informational purposes only.

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