Guide to Omega 3

Omega-3 fatty acids are so important for health that the shortest-chain omega-3, alpha-linolenic acid (ALA), is classed as essential and must come from the diet. Longer-chain omega-3s such as EPA and DHA can be made from alpha-linolenic acid in the body, but these conversions are inefficient so that EPA and DHA are often in short-supply.

Omega-3s have an anti-inflammatory action that is beneficial for joints and may help to protect against long-term inflammatory diseases such as asthma and psoriasis. Omega-3s may also reduce the low-grade inflammation of artery walls that is associated with heart attack and stroke.

Dr Sarah Brewer

What Do Omega-3s Do?

Omega-3 fatty acids act as building blocks for healthy cell walls, and are especially important within the brain. Omega-3s have a blood thinning action to reduce unwanted blood clots, and are converted into substances that reduce inflammation.

Within the EU there are authorised health claims that:

  • Essential fatty acids are needed for normal growth and development of children.
  • ALA contributes to the maintenance of normal blood cholesterol levels.
  • EPA and DHA contribute to the normal function of the heart.
  • DHA and EPA contribute to the maintenance of normal blood triglyceride levels at a daily intake of 2g of EPA and DHA.
  • DHA and EPA contribute to the maintenance of normal blood pressure a daily intake of 3g of EPA and DHA.
  • DHA contributes to maintenance of normal brain function and normal vision.
  • DHA contributes to the normal brain and eye development of the foetus and breastfed infants.


A good intake of omega-3 is important during pregnancy to ensure healthy development of the baby’s eyes and brain. Because of the risks of pollutants such as mercury, however, pregnancy women should limit their intake of tuna and other deep sea fish such as shark, swordfish and marlin. Pregnant women should also avoid having more than two portions of oily fish per week because these fish can contain pollutants such as dioxins and PCBsi. Fish oil supplements are screened to ensure they are free of these pollutants. Select a supplement that supplies DHA and which is especially designed for pregnancy.

Cardiovascular Disease

Omega-3 fish oils have a beneficial effect on blood pressure, blood stickiness and blood fat levels. Results from 34 studies found that people with the highest intakes of EPA and DHA had a 6% lower risk of heart attack or stroke than those with low intakes. Among people with the most risk factors for cardiovascular disease, the protective effect was significantly greater with a 16% reduced risk.ii

Brain Health

Omega-3 fish oils play an important structural role within brain cell membranes, improving their fluidity so that messages are passed on more rapidly from one cell to another. There is growing evidence that good intakes of omega-3 may help to protect against dementia by reducing inflammation within the brain iii,iv . Omega-3s also have a beneficial effect against depression, especially those that are enriched with EPAv.

Joint Health

Omega-3 fish oils have a pain-killing effect similar to that of non-steroidal anti-inflammatory drugs and have an equivalent effect in reducing arthritis painvi. By reducing inflammation, they help to reduce joint pain and swelling. Results from 22 trials show that fish oil supplement can significantly improve joint symptoms due to rheumatoid arthritisvii. Surprisingly, the effects against osteoarthritis are less well studied. Laboratory studies involving cartilage cells have shown that EPA and DHA reduce the production of inflammatory substances and can increase joint lubrication.viii Many people with osteoarthritis do find omega-3 supplements helpful.

Getting omega-3 from your diet

Good dietary sources of omega-3 include oily fish such as mackerel, herring, salmon, sardines, pilchards and fresh (not tinned) tuna, nuts, seeds and fortified foods. Omega-3s are also found in grass-fed wild game meats such as venison and buffalo.

A minimum intake of 450mcg omega-3 per day is recommended from dietary sources (equivalent to eating two portions of fish, once of which is oily, per week). Higher doses are needed for therapeutic effects.

Correct Dosage

Typical doses for omega-3 supplements are 1g to 3g per day.

Sources include:

  • Omega-3 fish oils from the flesh of oily fish.
  • Krill oil – from a shrimp-like, Antarctic crustacean.
  • Cod liver oil – from the liver of cod.
  • Algae oil – from marine algae.
  • Flaxseed oil – from mature linseed.


Because of concerns about pollutants in sea fish, government guidelines suggest limiting intakes of fresh fish to no more than two portions (140g each) of oily fish a week for girls and women who might have a baby in the future, and up to four portions for other women, men and boys.ix

Fish oil supplements are screened to ensure they are free from pollutants.
Do not exceed a supplemental daily intake of 5 g of EPA and DHA combined.
Pregnant women should avoid cod liver oil as a source of omega-3 as it also contains vitamin A.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn’t possible supplements can help. This article isn’t intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.




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