The research is a follow-up study to one carried out in June last year by the School of Nutrition and Health Promotion at Arizona State University.
Long chain omega-3 fatty acids found in fish are known to combat the mood-altering effects of arachidonic acid (AA), an omega-6 fatty acid found in meat.
But while this suggests pescatarians should be in a much better mood than carnivores, those who eat fish are still not as contented as vegetarians, according to the ASU research.
This follow-up study saw 39 meat-eaters divided into three groups. The first continued to eat meat or fish daily, the second ditched the meat but ate fish three or four times a week; the last adopted a meat-free diet.
After two weeks the first two groups experienced no change in their mood, while the third group reported “significantly” better moods and less stress.
The conclusion of the researchers – that “restricting meat, fish and poultry improved short-terms mood state in modern ominvores” – bears out their 2011 findings.
Their conclusion was that the short-chain omega-3 fatty acids found in vegetables were responsible for a more optimistic outlook on life.