Herbs are a commonly used treatment in Ayurveda. Ethnobotanical studies of traditional herbal remedies used for diabetes around the world have identified more than 1200 species of plants with hypoglycemic activity. These plants are broadly distributed throughout 725 different genera. The pharmacopoeia of India is especially rich in herbal treatments for diabetes. Eighty-five percent of the 20 antidiabetes plants most widely used around the world are prescribed in India.3 A few of the herbs commonly used by Ayurveda practitioners to treat diabetes are summarized in the TABLE.
In response to the increasing interest in Ayurveda and herbal treatments for diabetes in this country, the National Center for Complimentary and Alternative Medicine (NCCAM) requested we conduct a systematic review of Ayurvedic therapy for diabetes. This paper reports the results of that review, and is a condensation of an evidence report available at www.ahrq.gov/clinic/epcsums/ayurvsum.htm.
TABLE
Ayurvedic characteristics of herbs commonly used to treat diabetes
| HERB | TASTE (RASA) | INCREASES (AGGRAVATES) | DECREASES (PACIFIES) |
|---|---|---|---|
| Gymnema | Kasaya (astringent) | Kapha, Pitta | |
| Momordica | Tikta (bitter) | Kapha, Pitta | |
| Trigonella (fenugreek) | Tikta (bitter); Madhura (sweet) | Pitta | Kapha, Vata |
| Coccinia indica | Kasaya (astringent); Tikta (bitter) | Vata, Pitta | |
| Pterocarpus | Kasaya (astringent) | Vata | |
| Source: Kapoor, 1990;32 Dash, 198733 Mishra, Singh, and Dagenais, 2001.34 | |||
Methods
Identification of literature
We used the search term “Ayurveda” plus the names of 16 major botanicals characteristically used in Ayurveda for an initial search of the Western literature. The herbal terms were added to the search to increase its sensitivity, making it possible to find studies that used Ayurvedic herbal therapy without necessarily being directly identified as Ayurvedic studies.
We were concerned that a large body of literature existed in India that could not be obtained through the conventional search strategy outlined above. Hence, we decided to conduct a search for Ayurvedic literature from the Indian subcontinent. A physician member of the research team, fluent in English and Hindi and who had trained in India, went to India to identify Ayurvedic literature available there.
We therefore used several sources for our search:
- An initial “waterfront” search, which already had identified 120 articles on diabetes and Ayurveda (which was used by NCCAM to establish the rationale for selecting diabetes as the focus of this review).4 This search is detailed in our Evidence Report (available at www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat1.chapter.95372) and included Medline, HealthSTAR, Allied and Complementary Medicine, MANTIS, CAB HEALTH, BIOSIS Previews, and EMBASE.
- The in-person literature search in India—we obtained 16 volumes of abstracts from various Indian Ayurvedic journals, as compiled by the Central Council for Research in Ayurveda and Siddha (CCRAS) library. This yielded 318 titles.
- An additional online search of the previously mentioned databases for common botanicals used in the treatment of diabetes. This search yielded 773 additional articles.
- A search of the online CINAHL database, which yielded 70 articles.
- The reference lists of important articles in the Ayurveda/diabetes literature. We identified review articles of herbal treatment of diabetes and checked to see if they focused on any of the Ayurvedic herbal therapies we had identified for diabetes. Checking the bibliographies of all the articles we identified from any source, we found an additional 30 titles that were potentially relevant to our search.
- An RCT or a CCT or a natural experiment with a comparison arm that did not receive an herb or Ayurvedic therapy. RCTs of any size were included. For CCTs or natural experiments, the study had to have at least 1 treatment arm that contained at least 10 patients.
- Because of a paucity of studies meeting these design criteria, we also assessed cohort or case series data that used a “pre/post” method of analysis, if their sample included at least 10 subjects.
- The study had to test Ayurveda as a method or herbs used as a single agent, a formula acting as a single agent, or a limited combination of products (no more than 3) acting as a single agent. The agent had to be dispensed more than 1 time to the study patients (in other words, no single-dose studies).
- The study had to report on at least 1 of 3 outcome measures at 30 days minimum following the start of the study: glycosylated hemoglobin (Hb A1c), fasting blood glucose, or postprandial blood glucose at either 2 hours (preferred) or 1 hour (acceptable).
Data extraction
Detailed information from each study was extracted using a specialized form. The physician reviewers, working independently, extracted data in duplicate and resolved disagreements by consensus. A senior physician resolved any remaining disagreements. Information extracted from articles included the diagnostic criteria used to make the diagnosis (Ayurvedic or Western or both); the location in which the study was done; the subject population (age, gender, other demographics); the sample size in each arm of the study; the interventions used (primarily the names of the individual herbs or mineral and the manner of their preparation); the length of the study; and the outcomes. To evaluate the quality of the design and execution of trials, we collected information on the study design, appropriateness of randomization, blinding, description of withdrawals and dropouts, and concealment of allocation.5,6 A quality score was calculated for each trial using a system developed by Jadad.5 Empirical evidence has shown that studies scoring 2 or less on the Jadad scale report exaggerated results compared with studies scoring 3 or more.7 While other elements of the design and execution of controlled trials have been proposed as quality measures, empirical evidence supporting their use as generic quality measures is lacking.8