Why do we need omega-3 fats and how much?

Why do we need fish oil?

Fish oil supplements are taken for their omega-3 fatty acid content.

Omega-3 fatty acids form an important component of cell membranes. More specifically, DHA is reported to play a role in visual acuity, preventing neurological and cardiovascular diseases. EPA is the important fatty acid in terms of allergic diseases due to it’s anti-inflammatory action as it acts as a precursor for Prostaglandin E3 and Leukotrine B5.

The human body can produce the fatty acids it needs apart from omega-6 and omega-3 fatty acids (referred to as essential fatty acids -EFAs). Omega-6 fatty acids are converted to Arachidonic acid (AA). Omega-3 fatty acids (alpha-linolenic acid) are converted to docosahexanoic acid (DHA) and eicosapentanoic acid (EPA). There is however some evidence that this conversion of alpha-linolenic acid to DHA and EPA may be impaired in some people, which means that they are unable to produce DHA and EPA or sufficient amounts of it. This could lead to negative effects on cardiovascular, neurological and immunological processes.

The EFAs (AA, DHA and EPA) are important components of cell membranes and form substrates for immunological signaling molecules.

How much omega-6 and omega-3 fatty acids do we need?

The omega-3 recommendations differ across the globe. I have summarized guidance from the USA, UK, Australia and Europe.

United States

The 2002 report from the Institute of Medicine, recommends the following adequate intake (AI)* for alpha-linolenic acid. No specific intakes were set for DHA and EPA.

Age Male Female
Infants and children
0 to 12 months 0.5 grams/day 0.5 grams/day
1 to 3 years 0.7 grams/day 0.7 grams/day
4 to 8 years 0.9 grams/day 0.9 grams/day
9 to 13 years 1.2 grams/day 1.0 grams/day
14 to 18 years 1.6 grams/day 1.1 grams/day
19 – 30 years 1.6 grams/day 1.1 grams/day
31 – 50 years 1.6 grams/day 1.1 grams/day
51 – 70 years 1.6 grams/day 1.1 grams/day
>70 years 1.6 grams/day 1.1 grams/day
14 to 18 years 1.4 grams/day
19 – 30 years 1.4 grams/day
31 – 50 years 1.4 grams/day
14 to 18 years 1.3 grams/day
19 – 30 years 1.3 grams/day
31 – 50 years 1.3 grams/day

* If sufficient information is not available to establish a Estimated Average Requirement (EAR) and then calculate an RDA, an adequate intake (AI) is recommended.

The ratio of omega-6 to omega-3 intake is also important for human health and disease prevention as higher levels of omega-6 can lead to chronic low grade inflammation seen in e.g. in allergic diseases. The Institute of Medicine recommends an AI of 4.4 g omega-6 fatty acids per day for infants at the age of 0-6 months, and 4.6 g per day for infants 7-12 months. The omega-3 fatty acid AI for 0-12 month olds is 0.5 mg/day. For adults, the omega 6 is 17/g per day for young men and 12g/day for young females. The omega-3 fatty acids AI is 1.6 g/day and 1.1 g/day for young males and females. This roughly translates to a ratio of 8-10:1 (omega-6 fatty acids:omega-3 fatty acids),

 United Kingdom

In the UK the omega-3 recommendations** state a minimum intake for individuals, as 0.2% of food energy coming from omega-3 fatty acids (i.e. alpha linolenic, DHA, EPA and DPA [docosapentanoic acid]).

Age Male Female
Children 0.2% of total energy intake – amounts will vary according to age and weight
Adults 0.55 g/day – based on 0.2% of total energy intake 0.45 g/day – 0.2% of total energy intake

 ** Committee on Medical Aspects of Food Policy (COMA), Department of Health. Nutritional Aspects of Cardiovascular Disease. Report on Health and Social Subjects No 46. S.3.7.3 P:17 London: HMSO 1994.


Australia and New Zealand

The nutrient reference values from the Australian & New Zealand Health Authorities (Department of Health & Aging, National Health & Medical Research Council) state the following AIs for fatty acid intake.

Age Male Female
Omega-3 fatty acid intake (i.e. alpha linolenic, DHA, EPA and DPA)
0-6 months 0.5 g per day 0.5 g per day
7-12 months 0.5 g per day 0.5 g per day
Alpha-linolenic acid
1-3 years 0.5 g per day 0.5 g per day
4-8 years 0.8 g per day 0.8 g per day
9-13 years 1.0 g per day 0.8 g per day
14 – 18 years 1.2 g per day 0.8 g per day
Adults 1.3 g per day 0.8 g per day
14- 18 years 1.0 g per day
19 – 50 years 1.0 g per day
14- 18 years 1.2 g per day
19 – 50 years 1.2 g per day

Additional AIs for DPA, DHA + EPA recommend a range of 40 – 125 mg per day for boys and 40 mg per day – 85 mg per day for girls. AIs for these fatty acids of 160 mg per day are suggested for males and 90 mg per day for females.

European food safety authority

The European Food Safety Authority (EFSA) set recommendations for EPA and DHA based on an intake of approximately 250 mg of EPA+DHA per day for adults and children; DHA intake of approximately 100 mg per day for infants 7 to 24 months and 250 mg DHA and EPA per day during pregnancy and lactation with an additional 100 – 200 mg per day of DHA.

Can I take too much omega-3 fatty acids?

It is debatable if too much omega-3 fatty acids increase the risk of bleeding (stroke, gastric bleeding) with a recent systematic review concluding that omega-3 fatty acids “do not produce clinically significant bleeding episodes” but no clear upper level of safety was set by this paper – although an upper level of 3000 mg per day has been suggested and a period of 12 – 20 weeks may be required for EPA and DHA levels in mononuclear cells to return to baseline values post supplementation.

Which foods contain omega-6 and omega-3 fatty acids?

Sources of omega-6 fatty acids

  • Meat (especially pork and the dark meat from chicken and turkey) and in oily fish
  • Poultry
  • Eggs
  • Nuts
  • Durum wheat
  • Most vegetable oils

Sources of omega-3 fatty acids

  • Meat or eggs of animals fed omega 3 (n-3) fatty acid-enriched diets
  • Flaxseed, canola oil, English walnuts, specialty eggs are particularly good sources of alpha-linolenic acid

I have excluded fatty fish from my list – if you do have a fish or shell fish allergy, please see my question covering these allergies and always consult your physician. If you wish to eat fatty fish, please look at the following recommendations:

The Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) are advising women who may become pregnant, pregnant women, nursing mothers, and young children to avoid some types of fish and eat fish and shellfish that are lower in mercury. This is because mercury has been implicated in impaired child neuropsychological development.

Specific advice from the UK food standards agency and from Food Standards Australia and New Zealand can be accessed on their websites.

NOT allergic to salmon – try this delicious recipe by Priya Tew RD

Finally, just a few definitions

The Estimated Average Requirement (EAR) is the intake level for a nutrient at which the needs of 50 percent of the population will be met.

 Recommended Dietary Allowance (RDA): average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%-98%) healthy people.

 Adequate Intake (AI): The recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate-used when an RDA cannot be determined.

REMEMBER: If you have an allergy to fish or shell fish, do consult your physician