Dietary omega-3 DHA associated with 50%-70% reduced anxiety, depression risk

A new study by a collaboration of mental health, nutrition and metabolic researchers in Australia(1) aimed to determine if there is a link between levels of specific essential fatty acids - polyunsaturated fatty acids, or PUFAs - in a woman’s diet and risk of anxiety disorder and/or depression.

The researchers identified a random, community based cohort of 935 women, ages 20 to 93. They interviewed, surveyed and examined these women to:

• Profile the levels of omega-3 EPA & DHA and omega-6 essential fatty acids that their diets were providing. These types of fatty acids have long been termed ‘essential’ because the body requires them but must derive them, or their makings, from the diet. 

• And identify those subjects currently affected by depression or anxiety.

A number of careful measures were made. "A validated and comprehensive dietary questionnaire ascertained the consumption of omega-3 and omega-6 PUFA. Another assessed fish and energy intake and provided data for a dietary quality score. The General Health Questionnaire-12 (GHQ-12) measured psychological symptoms, and a clinical interview (Structured Clinical Interview for DSM-IV-TR Research Version, Non-patient edition) assessed depressive and anxiety disorders.”

The study’s key findings are that:

•  On average, the diets of the women studied supplied less than suggested target levels of omega-3 essential fatty acids.

•  The women whose diets placed them in the upper third (tertile) in terms of DHA intake were only half (50%) as likely to be currently affected by an anxiety disorder. DHA is the predominant essential fatty acid in oily fish/fish oil and in tiny water plants called micro-algae (where fish get it); and it is the dominant fatty acid in the brain.

•  This DHA-anxiety association was ‘linear’, meaning that as the amount of DHA the women were consuming increased, the less likely they were to have an anxiety disorder, and vice-versa.

•  There was also an association between DHA intake and depression risk, though this association was not linear. Apparently the average risk of depression was 70% lower in the second tertile group (moderate DHA intake) vs the lowest DHA group; but greater amounts did not correspond with further average reduction.

•  By comparison, dietary EPA levels (also found in fish oil, but in a lesser amount than DHA, and also plentiful in seeds and nuts and their oils) did not appear to be associated with different rates of either anxiety or depression – nor did any other PUFA except DHA.

•  As measured just by servings of fish per week, the women who ate fish less than once a week had higher GHQ-12 scores (more psychological symptoms).

The researchers suggest further research should examine dietary DHA’s potential as support for the anxiety-prone, and the most appropriate levels of DHA for support of the depression-prone.

Some Food Sources of DHA, EPA, Omega-6

Individual foods often offer a number of fatty acids. There are scores of them, including 11 omega-3’s and 10 omega-6's, for example, and they interact with each other in the body. But following are some basics:

•  As indicated, oily seafood such as tuna, wild salmon, herring & sardines is a rich source of DHA and EPA, the dominant one being DHA. Organ meat such as liver may be a rich DHA source too.

•  For non-fish-eaters, supplements made from the tiny water plants called micro algae are a rich source of DHA omega-3 (where fish get it), so these supplements are important for vegetarians & vegans. Dark green leaf vegetables such as kale, spinach and collard greens provide DHA and EPA also.

•  Animals and poultry that are able to eat pasture plants metabolize them to provide omega-3’s, including some EPA and DHA, in their meat and eggs. But the amount is far less than provided by oily fish or microalgae.

•  Some nuts such as walnuts, and flaxseed and tofu are rich sources of omega-3s - but not DHA omega-3.

•  ALA is another omega-3 (its richest source being flaxseed and other seed oils). As needed, a healthy metabolism will convert some ALA first to EPA and later to DHA – but this is “a process that is inefficient and varies.”

•  Sources of omega-6 (as well as omega-3 EPA) are seeds and nuts and their oils (flaxseed, sunflower seed, grapeseed, sesame seed, safflower, evening primrose, etc.).

•  Current thinking on the ideal dietary ratio of omega-3 to omega-6 essential fatty acids is between 1 to 1 and 4 to 1, though typically the modern diet is much heavier on the omega-6 side.

•  Omega-9 fatty acid is crucial for health, but in smaller amounts than the essential fatty acids. Omega-9 is not technically ‘essential’ because the body can manufacture it if need be. (This, however, requires dietary supplies of omega-3 and omega-6.) Rich sources of omega-9 are olive oil, avocados, nuts and seeds, though almost all animal and plant foods provide some.

___

1. Cited article: "Dietary intake of fish and PUFA, and clinical depressive and anxiety disorders in women", British Journal of Nutrition, Oct 10, 2012, by Felice N Jacka, et al. University of Melbourne, VIC; University of Wollongong, NSW, Australia.