Diet may not fully explain cardiometabolic problems in bipolar disorder

Dec 19 2013

By Eleanor McDermid, Senior medwireNews Reporter

The diet of patients with bipolar disorder or schizophrenia seems to be no worse than that of mentally healthy people, a study suggests.

This indicates that researchers should look elsewhere to determine why these patients are so prone to developing the metabolic syndrome and its resultant cardiovascular complications, say study author Vicki Ellingrod (University of Michigan, Ann Arbor, USA) and colleagues.

“While these findings should not be taken to imply that dietary and lifestyle factors are not important in the development of metabolic syndrome in the general population, they do suggest that the mechanisms behind metabolic complications in individuals with serious mental illness are more complicated,” they write in Bipolar Disorders.

The team ascertained the diets of 116 patients with bipolar disorder and 143 with schizophrenia through 24-hour recall during a standardized interview, repeated at least once within 10 days. The methodology was identical to that used in the National Health And Nutrition Examination Survey (NHANES; 1999–2000), from which the researchers obtained data of 259 age-, race-, and gender-matched mentally healthy controls.

In all, 33% of the bipolar disorder patients had the metabolic syndrome, compared with 17% of their matched controls. The corresponding rates for schizophrenia patients and controls were 47% and 11%.

“It is widely assumed that metabolic syndrome is largely associated with poor dietary habits, and while the literature shows ample support for this thesis in the population at large, this has been remarkably under-investigated in those with serious mental illness,” say Ellingrod et al.

However, the significantly increased metabolic syndrome rates among the psychiatric patients in their study were not explained by their diet. Indeed, the patients consumed significantly fewer calories than controls (1896 vs 2309 kcal/day for bipolar patients vs controls, for example), as well as less carbohydrate and more fiber.

Furthermore, dietary intake among the patients was not significantly different in those with and without the metabolic syndrome.

“Thus, these data directly contradict the theory that a poor diet is primarily responsible for the increased metabolic syndrome risk seen in those with mental illness,” say the researchers.

The only factor associated with the metabolic syndrome was use of antidepressants, despite these reportedly having variable effects on weight. The team says that related factors such as residual depressive or vegetative symptoms could underlie the association, and that more research is necessary.

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