Friday 7 December 2018

Diet and depression

One in seven people will experience depression at some point in their lifetime. Researchers at the James Cook University in Australia researched the effects of fish or fast food on depression and found a clear correlation.

One in seven people will experience depression at some point in their lifetime. Depression appears to be linked to certain dietary habits, but is also associated with social and environmental factors, making this a complex area of research.


Researchers at the James Cook University in Australia investigated the link between depression and the quantity of fish and fast food eaten. They investigated the inhabitants of two different Torres Strait islands, one where fast food is available and a smaller island where no fast food chains are located. 
One hundred inhabitants of each island were asked about their diets, their level of depression was screened and blood samples were analysed. People on the smallest island reported, as expected, a significantly higher consumption of seafood and lower consumption of fast food. 


The study revealed that nineteen participants suffered from moderate to serious symptoms of depression: sixteen of these participants lived on the island with fast food chains. The participants with symptoms of depression were not only found to be younger, but also reported a higher consumption of fast food.

Analysis of the blood samples showed that there were differences between the fatty acid levels in the people who lived on the different islands and a higher omega 6/3 ratio was found in the blood of the inhabitants of the fast food island. On both islands, a higher omega-6/3 ratio was associated with moderate to severe depression scores. 

Omega 6/3 ratio

Polyunsaturated fatty acids are essential nutrients. They consist of omega-3 fatty acids (alpha-linolenic acid in linseed oil and rapeseed oil and metabolites that form from these oils, such as EPA and DHA in seafood) and omega-6 fatty acid (linolenic acid from vegetable oils and fats, arachidonic acid from meat and GLA). In today’s Western diet, the ratio between omega-6 and omega-3 fatty acids is approximately 15-25:1, whilst a ratio of approx. 5:1 to 1:1, as is the case in a traditional diet, is desirable.


The inhabitants of the smallest island, with no fast food chains, consumed more fish and have a lower omega-6/3 ratio in the blood. This means a more traditional division of the fats in the food, where omega-3 is more proportionately consumed with omega-6. These participants had significantly fewer symptoms of depression than the inhabitants of the larger island. The aforementioned data suggests that a diet high in omega-3, provided by seafood, that is not as high in omega-6, can be effective in the fight against depression. Supplementation with omega-3 fatty acids (EPA and/or DHA) may have a restorative effect.


Berger M, Taylor S, Harriss L, Campbell S, Thompson F, Jones S, Makrides M, Gibson R, Amminger G.P, Sarnyai Z & McDermott R (2018) Cross-sectional association of seafood consumption, polyunsaturated fatty acids and depressive symptoms in two Torres Strait communities, Nutritional Neuroscience, DOI: 10.1080/1028415X.2018.1504429

Sánchez-Villegas A, Verberne L, De Irala J, Ruíz-Canela M, Toledo E, Serra-Majem L, et al. (2011) Dietary Fat Intake and the Risk of Depression: The SUN Project. PLoS ONE 6(1): e16268.