Two kinds of fats are ESSENTIAL NUTRIENTS - just like vitamins and minerals - because we need them, but can't make them for ourselves.

These essential fats are the OMEGA-3 and OMEGA-6 polyunsaturates.  And we need both kinds - but we need them IN THE RIGHT BALANCE.  However, most people's intake of omega-3 fats in particular is seriously sub-optimal.


Typical modern, western-type diets are very low in omega 3 fatty acids

• Our diet has been constantly changing over the centuries and so have our dietary sources of fatty acids. Research indicates that the diet of our ‘hunter-gatherer’ ancestors was relatively low in saturated fat but contained special kinds of polyunsaturated fats (omega-3 and omega-6) that are crucial to brain development and function.

• The ratio of omega-6 to omega-3 in the diet at that time is thought to have been between 1:1 and 4:1, and our physiology has not changed significantly since then.

• In contrast, modern diets are often high in saturated fat and trans fats (artificially saturated fats found in many processed foods), and they particularly lack omega-3 fatty acids.

• The current dietary ratio of total omega-6 to omega-3 fats in most western-type diets ranges from 6:1 to 20:1 or more - with higher ratios linked with diets high in 'ultra-processed', industrially-produced and packaged foods, rather than whole or minimally processed foods.

The long-chain omega-3 (EPA and DHA) are the biologically essential forms - and the most important to the brain. 

• The two most important omega-3 fatty acids for brain development and function are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These can be found in appreciable quantities only in fish and seafood (or some special forms of algae), or fortified foods.

• Oily fish contains more EPA and DHA than white fish - so sardines, pilchards, anchovies, mackerel, salmon or herring are particularly good sources.

• The UK Food Standards Agency recommends that we eat at least two portions of fish per week - one of which should be oily fish. This would provide around 1-2 grams per week of EPA and DHA combined.

Some plant and seed oils provide shorter-chain omega-3 fats - but conversion to of these into the long-chain omega-3 we really need (EPA and DHA) is poor, and NOT reliable in humans

• Vegans and vegetarians, who do not eat fish, have no direct source of EPA and DHA in their diet. So unless they supplement with these, they rely on the body converting shorter-chain omega-3 fatty acids - usually alpha-linolenic acid (ALA) - into EPA and DHA.

• Although some people may be able to obtain enough EPA and DHA without consuming these long-chain omega-3 pre-formed, all the evidence shows that most people simply cannot meet requirements this way - particularly if they are consuming a modern. western-type diet rich in omega-6 fats.

• On average, less than 5% of dietary ALA is converted to EPA, and less than 1% to DHA. For this reason, the established scientific consensus is that DHA is a dietary essential. (Brenna et al 2009)

• An excess of short-chain omega-6 from vegetable oils (found in most processed foods) is thought to be a major reason for the poor conversion of short-chain omega-3 from plant sources (ALA) into the omega-3 the brain needs (EPA and DHA).  

• Poor conversion of short- to long-chain omega-3 may occur for constitutional reasons - and/or owing to diet and 'lifestyle' factors.  For example:

• Conversion is also limited in young infants and in the elderly, compared with older children and younger adults
• Conversion is less efficient in males than females, for hormonal reasons
• Individual genetic differences in fatty acid metabolism are a powerful influence on the ability to make sufficient EPA and DHA from ALA, irrespective of age or sex.
• low levels of many vitamins and minerals prevent conversion as they are essential co-factors
• high levels of 'stress hormones' can impair conversion

• The long-chain omega-3 (DHA, and to a lesser extent EPA) can be derived from some special forms of algae - and these vegetarian forms are now available from supplements or fortified foods. 

• Algal-source supplements of DHA (+/- EPA), or foods fortified with these, are the best dietary sources of omega-3 for vegetarians, vegans and others unwilling or unable to eat fish and seafood, or to take supplements of oils from seafood sources.

• Some seed oils - particularly ahiflower - contain a short-chain omega-3 (SDA) that converts well to EPA, but not to DHA

Why a lack of long-chain omega 3 fatty acids in the diet matters

• Relative dietary deficiencies of omega-3 fatty acids (and high intakes of saturated and trans fats) are linked with numerous chronic physical health problems, including inflammatory conditions and auto-immune diseases, heart disease and stroke, many cancers. They are also linked with neurodegenerative diseases such as Alzheimers disease and other forms of dementia.  

• During pregnancy and infancy, a good supply of long-chain omega-3 (known as EPA and DHA) is essential for healthy brain development and function. Other things being equal, higher intakes of fish and seafood by mothers during pregnancy are associated with better verbal intelligence and other developmental outcomes in their children (see Hibbeln et al 2007)

• A relative lack of long-chain omega-3 in the diet is associated with child behaviour and learning problems such as ADHD, dyslexia, dyspraxia and autistic spectrum disorders. Controlled trials have shown that increasing dietary intakes of these special fats can improve behaviour, attention and concentration, and some aspects of learning such as reading and spelling:

• in children formally diagnosed with these conditions (Richardson and Montgomery 2005, Bloch and Qawasmi 2011)

• and in children from the general school population. (Richardson et al 2012)

• Research also shows that a lack of omega-3 may increase the risk of depression and other mental health conditions - and that increasing dietary intakes may help.

• Freeman et al 2006 - American Psychiatric Association guidlines (based on early meta-analyses of clinical trials)

• Guu et al 2019 International Society for Nutrition in Psychiatry Research (ISNPR) Guidelines

Because omega-3 fatty acids are so important for both physical and mental health, current advice from UK, US and other governments and health authorities is that we should try to increase our intake of omega-3 fatty acids (and reduce our intake of trans fats, and limit saturated fats).

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