Gloria Y. Yeh

OBJECTIVE: To conduct a systematic review of the published literature on the efficacy and safety of herbal therapies and vitamin/mineral supplements for glucose control in patients with diabetes. RESEARCH DESIGN AND METHODS: We conducted an electronic literature search of MEDLINE, OLDMEDLINE, Cochrane Library Database, and HealthSTAR, from database inception to May 2002, in addition to performing hand searches and consulting with experts in the field. Available clinical studies published in the English language that used human participants and examined glycemic control were included. Data were extracted in a standardized manner, and two independent investigators assessed methodological quality of randomized controlled trials using the Jadad scale. RESULTS: A total of 108 trials examining 36 herbs (single or in combination) and 9 vitamin/mineral supplements, involving 4,565 patients with diabetes or impaired glucose tolerance, met the inclusion criteria and were analyzed. There were 58 controlled clinical trials involving individuals with diabetes or impaired glucose tolerance (42 randomized and 16 nonrandomized trials). Most studies involved patients with type 2 diabetes. Heterogeneity and the small number of studies per supplement precluded formal meta-analyses. Of these 58 trials, the direction of the evidence for improved glucose control was positive in 76% (44 of 58). Very few adverse effects were reported. CONCLUSIONS: There is still insufficient evidence to draw definitive conclusions about the efficacy of individual herbs and supplements for diabetes; however, they appear to be generally safe. The available data suggest that several supplements may warrant further study. The best evidence for efficacy from adequately designed randomized controlled trials (RCTs) is available for Coccinia indica and American ginseng. Chromium has been the most widely studied supplement. Other supplements with positive preliminary results include Gymnema sylvestre, Aloe vera, vanadium, Momordica charantia, and nopal.

OBJECTIVES: To summarize and critically evaluate research on the effects of Tai Chi on cognitive function in older adults. DESIGN: Systematic review with meta-analysis. SETTING: Community and residential care. PARTICIPANTS: Individuals aged 60 and older (with the exception of one study) with and without cognitive impairment. MEASUREMENTS: Cognitive ability using a variety of neuropsychological testing. RESULTS: Twenty eligible studies with a total of 2,553 participants were identified that met inclusion criteria for the systematic review; 11 of the 20 eligible studies were randomized controlled trials (RCTs), one was a prospective nonrandomized controlled study, four were prospective noncontrolled observational studies, and four were cross-sectional studies. Overall quality of RCTs was modest, with three of 11 trials categorized as high risk of bias. Meta-analyses of outcomes related to executive function in RCTs of cognitively healthy adults indicated a large effect size when Tai Chi participants were compared with nonintervention controls (Hedges' g = 0.90; P = .04) and a moderate effect size when compared with exercise controls (Hedges' g = 0.51; P = .003). Meta-analyses of outcomes related to global cognitive function in RCTs of cognitively impaired adults, ranging from mild cognitive impairment to dementia, showed smaller but statistically significant effects when Tai Chi was compared with nonintervention controls (Hedges' g = 0.35; P = .004) and other active interventions (Hedges' g = 0.30; P = .002). Findings from nonrandomized studies add further evidence that Tai Chi may positively affect these and other domains of cognitive function. CONCLUSION: Tai Chi shows potential to enhance cognitive function in older adults, particularly in the realm of executive functioning and in individuals without significant impairment. Larger and methodologically sound trials with longer follow-up periods are needed before more-definitive conclusions can be drawn.