Botanical products for diabetes treatment
Allium sativum (garlic). Found in many kitchens, allium sativum (garlic), has also been used for medicinal purposes around the world. A majority of contemporary medical use and research for garlic has focused on treatment of cardiovascular-related diseases.
In clinical trials, garlic supplementation among patients with dyslipidemia produced modest reduction in total cholesterol with no significant changes in LDL or HDL cholesterol levels.10,11 Pooled data from clinical trials of patients with hypertension have shown significant decreases in systolic (8.4 ± 2.8mmHg) and diastolic (7.3 ± 1.5mmHg) blood pressure levels in patients using garlic treatment compared to control groups.12 Less research has been conducted among patients with diabetes. Limited animal studies have suggested that the chemical components of garlic may increase insulin secretion or decrease degradation.10,11 Clinical trials of oral garlic in patients with type 2 diabetes have not demonstrated significant changes in blood glucose or insulin levels.12,13
Aloe vera. This desert plant is the source of the common gel used topically for dermatological conditions. In the Arabian peninsula, parts of the aloe plant have been used orally as a traditional treatment for diabetes. The gel derived from the meaty pulp of the leaf, taken orally, may produce hypoglycemic effects through β-cell stimulation.13,14
Two controlled, nonrandomized trials in patients with type 2 diabetes who were given aloe gel juice reported decreases in fasting blood glucose during 6 weeks.15,16 However, these studies lacked sufficient details in reporting, including study design and results, leading to inconclusive evidence. In contrast to the gel, aloe latex from the inner lining of the leaf contains a harsh anthroquinone laxative that may be unsafe.17
Coccinia indica (ivy gourd). Ayurveda is a traditional medical system from the Indian subcontinent that often uses herbs for treatment. The creeper plant coccinia indica is prescribed in Ayurveda for the treatment of diabetes. Coccinia may produce hypoglycemia in a mechanism similar to insulin.18 Two randomized, controlled trials (RCTs)19,20 and one controlled, nonrandomized trial18 have suggested decreases in fasting blood glucose without adverse effects among type 2 diabetes patients after administration of coccinia. In one of these studies,20 60 subjects were randomized to coccinia or placebo. Patients who received the herb had a 16% decrease in fasting blood glucose.
Although data are suggestive of a therapeutic effect for coccinia, further research is necessary to determine optimal preparations, dose, mechanisms, and safety.
Gymnema sylvestre (gymnema). This botanical has also been used for two centuries in Ayurveda for the treatment of diabetes. Traditionally, the leaves of the plant are chewed, which can suppress the sweet taste sensation, giving rise to its Hindi name gurmar, or “sugar destroyer.” In addition to affecting taste, the herb has demonstrated hypoglycemic effects in animal and human studies, perhaps functioning as an insulin secretagogue.21,22
An extract of gymnema leaf, called GS4, has been studied as an adjuvant therapy to conventional care in two controlled, nonrandomized trials of patients with type 1 and type 2 diabetes, respectively.23,24 Both studies reported significant before-to-after improvements in fasting blood glucose and A1C levels among patients receiving GS4. No significant before-to-after changes were reported in the control groups. These studies lacked between-group comparisons and randomization, precluding definitive evidence for gymnema for the treatment of diabetes.
Momordica charantia (bitter melon). This tropical vegetable, grown in Africa, Asia, and South America, is known as bitter melon, or “vegetable insulin.” It may reduce blood glucose in patients with diabetes.25,26 Potential mechanisms of action for bitter melon are decreased hepatic glucose production, increased hepatic glycogen synthesis,27 and insulin-mimetic activity.28,29 Most clinical trials of bitter melon among patients with diabetes have lacked adequate design to determine clinical effectiveness.26,30
Opuntia streptacantha (prickly pear cactus, nopal). Found in desert regions of North America, nopal is used in Mexican cuisine and indigenous medicine. Mexican-American patients with diabetes have reported using nopal for glucose control.31 Few studies of nopal have been published in English, and these have explored acute metabolic effects rather than clinical outcomes.32,33
Panex ginseng, P. quiquefolius (ginseng). The panex genus contains multiple species described as ginseng, with two varieties most frequently used and studied: panex ginseng (Asian ginseng, Chinese ginseng, Korean ginseng) and panex quinquefolius (American ginseng). The root of this herb traditionally has been used in Asia and is one of the most popular botanicals in the United States.3
Ginseng has many proposed health benefits, including improved general well-being, increased concentration, and treatment of cardiovascular disease and diabetes (panex is cognate to panacea). Ginseng can cause hypoglycemia, perhaps through activity similar to insulin or by altering hepatic glucose metabolism.34
Buettner et al., in a systematic review,35 found conflicting clinical data of ginseng’s effect on blood glucose in diabetic and nondiabetic populations. Variations in response may reflect chemical heterogeneity of different ginseng batches used in studies.36,37
Trigonella foenum graecum (fenugreek). Fenugreek is grown in North America and Asia and often flavors Indian food. It has been used as medicine for diabetes in India and China. Mechanisms proposed for fenugreek in diabetes are decreased carbohydrate absorption and increased insulin secretion.