A recent Nordic study indicates that psychotic conditions are much more common among women who do not eat fish, as compared to those who do.
“Our research strengthens the hypothesis that a shortage in vitamin D and some fatty acids may contribute to the emergence of psychotic conditions”, says Maria Hedelin of Karolinska Institutet, The Nobel Prize-awarding institution in Solna near Stockholm.
“However, more research is needed to prove that the correlation is really causal”, she added in an interview with Upsala Nya Tidning, a local newspaper.
The study performed by seven scientists in Sweden, Finland and Norway and published in BMC Psychiatry, a trade journal, involved almost 34,000 women in the Uppsala region. The women first answered a comprehensive questionnaire describing their eating habits, then again eleven years later a similar battery of questions on if, and if so to what extent, they had suffered from psychotic symptoms.
Such problems were not uncommon per se – more than 40 percent of those asked said they had had such isolated incidents – but only two percent experienced them often, or close to permanently.
When the researchers tried to find out if there was a difference in eating habits for those suffering from frequent occurrences, they actually saw a marked correlation with the consumption of fish.
The high level of psychotic symptoms was twice as common among those who seldom or never ate fish, compared to those who had fish three or four times a week.
Based on the eating habits, the scientists then calculated the intake of vitamin D and the omega-3 and omega-6 fatty acids, all substances of whom fish is an important source.
Here, as well, the study found a clear correlation – the lower were the consumption level of those substances, the more common was the occurrence of psychotic symptoms.
“We know that omega-3 and omega-6 are important for the nerve cells in the brain membranes, and we know that vitamin D plays an important role for the growth and specialisation of the cells”, explained Dr. Hedelin. “So it’s possible to imagine that low levels of them may lead to disturbances in the functions of the nerve cells.”
“Still, even though we can’t tell for sure if increased consumption of fish really protects against psychotic symptoms, we do know that eating fish has many other positive health effects. The strongest evidence is for fish working against cardiovascular disease”, she added.