Schizophrenia: Nutritional Considerations

Among the sequelae of schizophrenia is an increased risk of cardiovascular disease. The greater risk results from several factors: patients' diets are often poor; smoking and physical inactivity are common; and antipsychotic medications may contribute to weight gain, hyperglycemia, and hypertriglyceridemia;^8-11 As a result, patients benefit from heart-healthy diets. Evidence indicates that behavioral interventions can improve weight control in persons with schizophrenia.^9,12

Aside from cardiovascular risk, there may be other reasons for patients with schizophrenia to avoid typical "Western" (ie, high-fat, high-sugar) diets. These diets reduce hippocampal expression of brain-derived neurotrophic factor (BDNF), an important growth and maintenance factor for dendrites, which is reduced in the prefrontal cortex of patients with schizophrenia. Low concentrations of BDNF have also been implicated in both coronary atherosclerosis and insulin-resistance syndrome.¹³ The latter is twice as common in schizophrenia patients as it is in the U.S. adult population, and helps explain the greater incidence of coronary heart disease in these patients.¹⁴ Clarification of these issues awaits further research.

Regarding the causation of schizophrenia, epidemiologic studies have adduced interesting but inconclusive links between schizophrenia and environmental factors, including diet. Some evidence indicates that maternal exposure to Toxoplasma gondii is a risk factor for schizophrenia in offspring.^15,16 Humans can become infected with T gondii in a variety of ways, including ingestion of animal tissues. T gondii can also be spread when cat litter is not promptly cleaned.

Researchers have speculated that Westernized diets may play a role, citing a lower prevalence of schizophrenia in unindustrialized cultures and Asian populations (although underreporting may contribute to this difference). During the Industrial Revolution, intakes of saturated fat, meat, dairy products, and refined sugars paralleled an increase in schizophrenia.⁸ Such possibilities remain speculative.

Several studies have suggested that individuals with schizophrenia have lower levels of certain polyunsaturated fats in the central nervous system, compared with other people, and that eicosapentanoic acid supplements may reduce symptoms of schizophrenia, as measured by the Positive and Negative Symptoms Scale (PANSS) (Peet, 2004). However, these studies were generally small and need to be repeated in larger, well-controlled studies.

One group of investigators has found a reduction in tardive dyskinesia symptoms with the use of branched-chain amino acid formulas.^18-20 Tardive dyskinesia is associated with deficient clearance of phenylalanine, an excess of which may increase production of catecholamines and indolamines, which may drive the hyperkinetic movements of tardive dyskinesia.¹⁸ Branched-chain amino acids compete with phenylalanine at the blood-brain barrier, reduce the entry of phenylalanine into the CNS, and subsequently reduce production of catecholamines and indolamines.

Orders

See Basic Diet Orders chapter.

What to Tell the Family

Schizophrenia is a lifelong illness that requires medication and support from both mental health professionals and family members. Persons with schizophrenia are at greater than average risk for cardiovascular disease from a combination of medication, sedentary lifestyle, poor diet, and smoking. Family members can support the affected member by providing a healthful diet and a smoke-free environment, and by encouraging participation in regular physical activity. The potential benefits of additional nutritional interventions is a matter of ongoing research.