Fish fats and the oils extracted from them contain two main biologically active fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These are sometimes called Omega3 fatty acids. There are good theoretical reasons why both might be important in the brain. However, with regard to schizophrenia evidence is accumulating that it is the EPA which is really helpful whereas DHA may not be beneficial in this context. The strongest evidence comes from a study at Sheffield University by Dr. Malcolm Peet and his colleagues.
They did a study in patients with chronic, partially treatment-resistant schizophrenia (3). These patients continued on their existing medications. They were then randomized on a double-blind basis to receive either a placebo (corn oil), or a high EPA fish oil from sardines or anchovies, or a high DHA fish oil from tuna.
The words ‘randomization’ and ‘double-blind’ mean that all the treatments were coded so that neither the patients nor the doctors know which patient was receiving which treatment until the trial had been completed and the code is broken. When the code was broken, the results were very clear. The placebo patients, as always happens, showed a small improvement. The DHA patients also showed a small improvement but this was actually less than in the placebo group, raising the possibility that DHA may not be helpful. In contrast, the patients on EPA showed a significant improvement which was comparable to that seen with the newer antipsychotic drugs but without the side effects.
Other studies have also shown that the same EPA-rich oil as was used in the Sheffield study is very helpful in improving symptoms even in those who have a shorter history of schizophrenia (4,5). It, therefore, seems that the best fish oils to use are those which are both HIGH in EPA and LOW in DHA.
An ordinary can of sardines or pilchards a day will usually provide about as much EPA as is found in eight capsules of the EPA rich fish oil. Other types of fish oil usually tend not to contain as much EPA or to contain more DHA which may not be helpful for people with schizophrenia. One useful source of fish oil which has an EPA/DHA ratio of around 3:2 is available from the Schizophrenia Association of Great Britain. Alternatively, with an EPA/DHA ratio of over 3:1, the same oil as was used in the clinical trials, Kirunal, is now available by mail order from the USA by phoning 001-617-556-8414 or by writing to Fincastle LLC,PO Box 55, Leominster, MA 01453, USA, or from The Schizophrenia Association of Great Britain.
The recommended dose for long term use is eight capsules a day. If this is going to produce beneficial effects they will take between 6 and 12 weeks to appear. A higher dose of 16 capsules a day may produce results more quickly but this is too many capsules for some people. Neither dose has been associated with side effects other than mild gastrointestinal upsets in about 5% of people. These can almost always be avoided by breaking up the daily dose. It is important to note that cod liver and halibut liver oils are unsuitable for this purpose. They contain only low levels of EPA and DHA.
It cannot be emphasized too strongly that nutrition should never be considered a substitute for other social, psychological, or drug treatments and management programmes in schizophrenia. Nutrition is not a replacement for those other approaches. Nutrition is a way of putting the biochemistry of the brain in the best possible shape to allow other treatments to work. Nutrition is a partner in the therapeutic alliance, not the only player. When looked on in this way, many people can be helped to manage their schizophrenia better.