Dietary Soy Supplement on Fibromyalgia Symptoms : A Randomized, Double-Blind, Placebo-Controlled, Early Phase Trial

الملخص EN

Most patients with fibromyalgia use complementary and alternative medicine (CAM).

Properly designed controlled trials are necessary to assess the effectiveness of these practices.

This study was a randomized, double-blind, placebo-controlled, early phase trial.

Fifty patients seen at a fibromyalgia outpatient treatment program were randomly assigned to a daily soy or placebo (casein) shake.

Outcome measures were scores of the Fibromyalgia Impact Questionnaire (FIQ) and the Center for Epidemiologic Studies Depression Scale (CES-D) at baseline and after 6 weeks of intervention.

Analysis was with standard statistics based on the null hypothesis, and separation test for early phase CAM comparative trials.

Twenty-eight patients completed the study.

Use of standard statistics with intent-to-treat analysis showed that total FIQ scores decreased by 14% in the soy group (P = .02) and by 18% in the placebo group (P < .001).

The difference in change in scores between the groups was not significant (P = .16).

With the same analysis, CES-D scores decreased in the soy group by 16% (P = .004) and in the placebo group by 15% (P = .05).

The change in scores was similar in the groups (P = .83).

Results of statistical analysis using the separation test and intent-to-treat analysis revealed no benefit of soy compared with placebo.

Shakes that contain soy and shakes that contain casein, when combined with a multidisciplinary fibromyalgia treatment program, provide a decrease in fibromyalgia symptoms.

Separation between the effects of soy and casein (control) shakes did not favor the intervention.

Therefore, large-sample studies using soy for patients with fibromyalgia are probably not indicated.