One experimental double blind study of 22 severely disturbed hospitalized patients, including 16 paranoid schizophrenics, given a gluten free diet for six weeks showed initial improvement in five scores on a profile rating. Two of the paranoid schizophrenics who had shown improvement relapsed when gluten was reintroduced into their diet (Br J Psychiatry 1986; 148: 447-52).

Another study found that the blood of certain psychotic patients given gluten produced a substance (leukocyte migration inhibition factor) similar to that of celiac (gluten intolerant) patients, even though there was no evidence among the schizophrenics of malabsorption in the gut, as occurs in true celiac disease. The study concluded that gluten may be involved in the biological processes in the brain in certain psychotic individuals (Am J Psychiatry 1979; 136 (10): 1306-9).

Although not all experiments agree, and there is much we don't understand about "brain allergy", some studies in which wheat has been eliminated from the diet have shown improvement. In one, milk and cereal grains were eliminated from the diet of 14 patients, after which they were alternately given soy and wheat. The reintroduction of gluten arrested or reversed the improvement in 10 of them, particularly those with paranoia (Science, 1976; 191: 401-2).

Besides food allergies, a number of nutritional deficiencies can produce schizophrenic like psychoses or exacerbate the symptoms of the disorder.

The most common vitamin deficiency in schizophrenia may well be folic acid. It may even be a major cause of the schizophrenic syndrome. In a 1990 study in the Lancet (336: 392-95), more than a third of patients with schizophrenia had borderline or definite folate deficiency.

Supplementing with folic acid has also produced good results. In the above double blind study, 17 patients received either 15mg of methylfolate (a synthetic form of folic acid) or a placebo in addition to the standard antipsychotic drugs. After six months, there were significant behavioural improvements in the folic acid group.

Another survey of 36 patients with schizophrenia or depression found that almost all of the folate treated patients made a full recovery, compared with three quarters of controls (M I Botez and E N Reynolds, eds, Folic Acid in Neurology, Psychiatry and Internal Medicine, New York, Raven Press, 1979)

Although supplementation may be beneficial, bear in mind that excessively high blood levels of folic acid can exacerbate psychotic behaviour or even react with antipsychotic drugs.

Princeton's Dr Pfeiffer maintained that folic acid deficiency is more pronounced in patients with low histamine and high copper levels, compared with "pyroluric" schizophrenics those normal in copper but low in vitamin B6 and zinc (Botez and Reynolds, as above).

Dr Pfeiffer was possibly the first to discover the role of histamine in mental illness. In his investigations, half of his patients had high levels of histamine (histadelia), and tended to display phobic behaviour, with suicidal depression. In Pfeiffer's view, "histapenics" those with low levels of histamine demonstrated what we consider the classic symptoms of schizophrenia: delusions, paranoia and hallucinations. He believed this group would respond to high doses of niacin, niacinamide, B12, zinc and manganese, folic acid and a high protein diet.

Many of Pfeiffer's ideas were simply observational, based on his own good results. However, his theories have been borne out in some scientific tests. In their review book of folic acid, Botez and Reynolds include an experimental study of Pfeiffer's, which found that in addition to folic acid, vitamin B12, niacin (B3), vitamin C and zinc were effective in treating histapenic schizophrenics. After five to six months on this supplement regime, this group of schizophrenics had reduced blood copper and raised blood histamine, as well as general improvement in symptoms.