Omega 3 Fatty Acid Supplements and Autism Ranking: Insufficient/Mixed evidence

Key Features

What are fatty acids?

Fatty acids are components of fats in our food. Dietary fats not only provide a source of energy for our bodies, but also affect many different aspects of our health. Fatty acids are present in every cell in our bodies and play important roles in heart health, immunity and hormone responses.

Fatty acids are classified as saturated, monounsaturated or polyunsaturated depending on their molecular structure. Essential fatty acids (EFAs) are polyunsaturated fatty acids that cannot be created within the human body and must therefore be obtained from the diet.

There are 2 different families of EFAs – the omega-3 fatty acids and the omega-6 fatty acids.

Omega-3 fatty acids

There are a number of different forms of omega-3 fatty acid including alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

ALA is found in rapeseed, linseed (flaxseed) and soybean oils, and spreads made from these oils. It is also found in ground linseeds, soyabean products, walnuts, and dark green leafy vegetables.

EPA and DHA are found in the flesh of oily fish such as salmon, herring, mackerel, anchovies and sardines, and in fish oil supplements including cod liver oil.

Omega-3 enriched products such as bread, eggs and milk are also widely available.

Omega-6 fatty acids

There are a number of different forms of omega-6 fatty acid including linoleic acid (LA) and arachidonic acid (AA).

LA is found in safflower, sunflower, hemp and soybeans, and AA is abundant in typical Western diets in vegetable oils, nuts, cereals and animal fats.

The importance of balance

The typical Western diet contains much more omega-6 fatty acids than omega-3s. This fatty acid imbalance in our typical diet is thought to have many different negative health effects, including on our mental health and brain function. However, as Innes et al (2018) have noted “The interaction of omega-3 and omega 6 fatty acids … in the context of inflammation is complex and still not properly understood”

How can they be taken?

Fish oil supplements rich in the omega-3 fatty acids DHA and EPA are widely available from pharmacists, supermarkets and mail order companies. They are available as liquids, capsules and chewable tablets.

Omega-3 fatty acids can be incorporated into a normal diet by eating two portions of fish per week, one of which should be oily fish, and by eating more green leafy vegetables, soya beans and linseed.


Monounsaturated (fat molecules that have one unsaturated carbon bond in the molecule); polyunsaturated (fat molecules that have more than one unsaturated carbon bond in the molecule); saturated (fat molecules that have no double bonds between carbon molecules because they are saturated with hydrogen molecules).

14 Dec 2018
Last Review
01 Dec 2018
Next Review
01 Dec 2021