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This week we consider some new findings regarding the use of inositol as a therapeutic agent in psychiatric conditions.
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Arbor Clinical Nutrition Updates
NUTRITION RESEARCH REVIEW
Study one: Eating disorders
Inositol is therapeutic in bulimia nervosa and binge eating, according to researchers in Israel.
Subjects: 24 patients with the above conditions who were NOT suffering from anorexia nervosa.
Method: Randomised, double-blind, placebo-controlled, crossover design with 6 week period on 18 gm/day inositol or placebo.
Results: Half the patients dropped out (8/12 were during the placebo arm) despite the low level of side-effects (some mild abdominal pain, flatulence and soft stools which responded to lowering of the dose of inositol). There were significant effects on two of the parameters measured, whilst two other measures showed changes of marginal or no statistical significance. See Table.
Table: Measures of eating disorder after 6 weeks treatment
Inositol Placebo Signif.
Visual Analogue Scale 42.5 65.8 p< 0.05
Clinical Global Impression 3.3 4.6 p< 0.05
Eating Disorders Inventory 66.8 79.8 p= 0.06
Eating Attitude Test 32.1 36.3 NS
Reference: International J of Eating Disorders 2001;29:345-348
Study two: panic disorder
Inositol is just as effective, if not more so, than conventional medication for the management of panic disorders, according to another recent trial from the same research centre in Israel.
Subjects: 20 patients with panic disorder.
Method: Randomised, double-blind, crossover study comparing with one month of inositol (up to 18g/day) with one month of fluvoxamine (up to 150g/day).
Results: The reduction in scores for Hamilton Rating Scale for Anxiety, agoraphobia and Clinical Global Impressions Scale were similar for both treatments. Inositol produced a greater reduction in the number of panic attacks than fluvoxamine (4.0/week c.f. 2.4/week for fluvoxamine (p = 0.049).
Side effects of nausea and tiredness were more common with fluvoxamine than inositol (p = 0.02 and p = 0.01 respectively).
Reference: J Clin Psychopharmacol 2001 Jun;21(3):335-9
Study three: depression
A non-significant trend towards improved clinical status was seen in 22 out of 24 patients with bipolar depression who completed a randomised, placebo-controlled trial of inositol (12g/day) or placebo for 6 weeks. The patients were continued on their regular medication during this period. The inositol had minimal side-effects, and blood levels of the active regular medication for depression were not changed.
Reference: Bipolar Disord 2000 Mar;2(1):47-55
Comments: Inositol is a sugar alcohol the essentiality of which has been debated. However, it does appear to play an essential role in phospholipids and hence it has a well established role in the maturation of the lungs and production of surfactant in the neonate. A few trials of inositol supplementation in premature infants have found it to be useful in countering respiratory distress syndrome and improving neonatal outcome (ref.1).
Inositol also has a role as a `second messenger', releasing calcium in the process of neuromuscular nerve transmission (ref.2.). Some have speculated that interaction with inositol may be part of the mechanism of action of lithium in bipolar disorders (ref.3).
The suggestion that inositol supplementation may be useful in psychiatric conditions actually has quite a reasonable basis on theoretical grounds, animal studies and some small clinical trials (ref. 4), many of which have been conducted by the Israeli group involved in two of the new studies. The conditions for which it has been most feasibly suggested are depression, panic disorder and obsessive compulsion - disorders which interestingly are also responsive to serotonin selective reuptake inhibitors (ref.4).
The three trials summarised in this issue are thus representative of the current state of our knowledge of inositol in psychiatry. All found results of enough interest to suggest that further studies are warranted, but none can be regarded as conclusive because of their small sample sizes and significant drop-out rates. Some earlier trials have not found significant improvements (ref.5).
Although some have raised the question of its safety when given to patients with diabetes or renal disease (ref.6), none of these trials had other than minor side-effects.
WHAT DOES IT MEAN FOR THE CLINICIAN?
Inositol is an interesting possible nutritional therapy for certain psychiatric disorders, both as alternative and an additive to conventional therapy. At this point the clinical evidence is based on small scale trials only.
1. Cochrane Database Syst Rev 2000;(4):CD000366
2. Clin Exp Pharmacol Physiol 2000 Sep;27(9):734-7
3. Biol Psychiatry 1999 Dec 15;46(12):1634-41
4. J Affect Disord 2001 Jan;62(1-2):113-21
5.Biol Psychiatry 1999 Feb 1;45(3):270-3
6. Bender A. Quasi-vitamins. Definition and examples. Chapter in: Sadler MJ and Strain JJ (eds.). Encyclopedia of Human Nutrition. Academic Press, 1999, p.1682.
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