Objectives:

The objective of this evidence report was to conduct a search of the published literature on the use of Ayurvedic medicine/therapies for the treatment of health conditions and, on the basis of that search, to choose either a condition or a modality for a comprehensive review. Based on the results of initial searches, diabetes was chosen as the topic for the comprehensive review. The specific questions addressed in this project were: (1) What Ayurvedic therapies have been reported in the literature, for which conditions/body systems, and using what kinds of research designs? (2) What is the efficacy of Ayurvedic medicine/therapies, as reported in that literature, for the treatment of diabetes?

Search strategy:

Our research librarian performed an initial search of MEDLINE^®, HealthSTAR, EMBASE^®, Allied and Complementary Medicine^™, MANTIS^™, BIOSIS Previews^®, CAB HEALTH, and CINAHL^®. We used the MeSH terms “Ayurveda” or “Ayurvedic” combined with the botanical names of 16 herbs commonly used in Ayurvedic treatment. We also conducted a focused search using terms for Ayurvedic herbs that are used specifically to treat diabetes. In addition, a strategy was developed to identify and retrieve literature from India. This involved using an abstracting service in India to identify potentially relevant literature. The Indian search was limited to studies published in English.

Selection criteria:

The literature search was directed at any Ayurvedic therapy or at Ayurveda as a whole system. In practical terms, the primary Ayurvedic therapy that appeared in the literature was herbal treatment. In the initial search, studies were accepted as long as they were not veterinary or agricultural in nature. Those studies that focused on diabetes were then identified. Again, the main therapy tested was herbal therapy, with a much smaller number of dietary studies found.

Data collection and analysis:

All titles, abstracts, and articles were reviewed by two independent reviewers and entered into a database. Abstracts or full texts of articles were analyzed with a screening form used to collect a range of data, including Ayurvedic modality used in the study, body system/condition treated, subject population, and study design. An in-depth analysis was conducted on those studies that treated diabetes mellitus in human patients. We identified 54 articles containing the results of 62 clinical studies treating diabetes in humans with Ayurvedic therapy, primarily herbal therapy. Because of the degree of heterogeneity in study design and therapeutic intervention, we decided not to conduct a meta-analysis but to perform a qualitative synthesis. However, a number of studies that met specific criteria were subjected to further analysis; a common effect size was calculated to allow comparison among these studies.

Main results:

Our search of the Ayurvedic literature in the West found the largest number of studies for the following systems/disease states: diabetes mellitus, liver/hepatitis, hypercholesterolemia, central nervous system disorders (dementia/depression), infectious diseases, and cardiovascular diseases.

Botanical therapy was by far the most commonly studied treatment. Herbs were studied either singly or as formulas containing multiple herbs and sometimes minerals. For diabetes, 52 of the 54 articles focused on either single herbs or herbal formulas, while the remaining 2 articles focused primarily on diet. Although some of the Indian studies included Ayurvedic terms, these studies focused on Western diagnostic criteria and outcomes. The most commonly studied single herbs were Gymnema sylvestre, Coccinia indica, fenugreek (Trigonella foenum-graecum), and Eugenia jambolana. A number of herbal formulas were tested, but Ayush-82 and D-400 were the two most often studied.

The 54 articles contained the results of 62 studies. Thirty-five of the studies included in the comprehensive review came from the Western literature, and 27 came from the Indian literature. The designs of these studies were varied. There were 7 randomized controlled trials (RCTs) and 10 controlled clinical trials (CCTs). There were 38 case series, the most frequently used clinical design, and 7 cohort studies.

There is evidence to suggest that the single herbs Coccinia indica, holy basil, fenugreek, and Gymnema sylvestre and the herbal formulas Ayush-82 and D-400 have a glucose-lowering effect and deserve further study. Evidence of effectiveness of several other herbs is less extensive (C. tamala, Eugenia jambolana, and Momordica charantia).

Conclusions:

There is great heterogeneity in the available literature on Ayurvedic treatment for diabetes. The overwhelming majority of studies test herbal therapy. Heterogeneity exists in the herbs and formulas tested (more than 44 different interventions identified) and in the method of their preparation.

We observed significant methodological shortcomings, specifically: there were few RCTs and CCTs; studies in general were underpowered to determine even large effect sizes: many studies had an extremely small number of subjects; in a number of studies, appropriate statistical methods were not used in reporting the results. The majority of the studies tested non-insulin dependent diabetes mellitus (type 2) patients only. Therefore, no definitive conclusion can be drawn on the effect of these therapies on insulin dependent diabetes mellitus (type 1) patients.

Despite these limitations, there is sufficient data for several herbs or herbal formulas to warrant further studies.