Diabetes has been likened to a car without its spark—the gas tank may be full, but the engine won’t start. Normally, the body’s spark is provided by insulin, a hormone that regulates the use of glucose, the body’s main source of energy. In diabetics, the body either lacks insulin or produces it but uses it ineffectively; meanwhile, glucose remains unused and circulating in the bloodstream. In some cases, untreated diabetes can be fatal.
More than sixteen million people are afflicted with diabetes in the United States, where it is the fifth leading cause of death, according to the American Diabetes Association. Records of its existence date to about 1500 b.c., but little is known about its cause, and a cure doesn’t exist. Most diabetics, however, can keep the disease in check through proper diet and regular exercise. Moreover, research has shown that some substances found in plants can contribute to this care, and other phytochemicals are under investigation.
What Diabetes Is
The body uses insulin to metabolize, or process, carbohydrates and to help tissues use glucose. Diabetics are generally grouped into two categories:
• Type I diabetics don’t produce insulin. This condition usually appears for the first time in people younger than age thirty. Although it is the more serious of the two types of diabetes, it accounts for only 8 percent of all cases of diabetes in the United States. Type I diabetics must take insulin orally or by injection to survive, but a healthful diet and exercise are also important to prevent complications stemming from the disease.
• In Type II diabetes, the body produces insulin but can’t use it to regulate glucose. The result is hyperglycemia, or high blood sugar, which over time can damage the eyes, kidneys, nerves, and/or heart. About 92 percent of American diabetics fall into this category, and most are middle-aged and overweight. Most Type II diabetics can be treated by following a low-fat, low- to moderate-carbohydrate, high-fiber diet and getting regular exercise, both of which increase the body’s ability to use insulin, and thus glucose, effectively.
The Role Plants Play
Antidiabetic medications have some unpleasant side effects, so researchers continue to search for safer alternatives. Test-tube screenings of 295 plants used in traditional herbal medicine showed that about 240 of them were potentially antidiabetic, and more than 200 of their constituents were found to be hypoglycemic, meaning that they lower blood sugar levels, and to improve the body’s ability to use insulin more effectively. Although as many as two-thirds of these plants may also be harmful, the herbs discussed below have been confirmed to be both safe and effective. Before trying any of these treatments, however, consult your health-care practitioner. Never give up insulin or other prescribed medication without advice from a specialist.
Four herbs have been shown to be safe and effective antidiabetics, consistently lowering blood glucose levels and improving the body’s ability to use insulin in specific tests. The fasting blood glucose test measures the glucose in a blood sample drawn from a person who has fasted overnight; a level of more than 140 mg of glucose per deciliter of blood is indicative of diabetes. The glucose tolerance test measures the body’s reaction to eating a large quantity of sugar. The herbs and their benefits are described below. For more details, consult the additional reading list on page 33.
Bitter melon (Momordica charantia): Bitter melon, also known as balsam pear, bitter gourd, bitter cucumber, or la-kwa, is the fruit of a climbing vine of the gourd family (Cucurbitaceae); it looks like a shriveled cucumber and is available throughout the West in Asian food stores. The unripe fruit is used traditionally in India, Africa, and Asia as both a diabetic remedy and “bitter tonic”, a food that is believed to restore normal tone to tissue. The components of bitter melon that lower blood sugar appear to be a mix of compounds called charantin and an unidentified insulinlike protein. Bitter melon’s effects are gradual and cumulative. A decoction, made by boiling chopped fruit in water, then simmering and straining, is more effective than the powdered, dried preparation.
Bitter melon preparations have been shown to significantly improve glucose tolerance without increasing blood insulin levels; to improve fasting blood glucose levels; and to decrease sugar levels in the blood and urine. In a 1991 study at a medical college in India, six Type II diabetics were given 100 ml of a bitter melon decoction once a day. After three weeks, their fasting blood glucose levels had dropped by an average of 54 percent. After seven weeks, the blood glucose levels of all six were at or near normal, and sugar was no longer detectable in their urine.
Gurmar (Gymnema sylvestre): The leaves of this climbing vine have long been used in the Ayurvedic medicine of India as a treatment for diabetes. Gurmar has been shown to enhance the ability of the pancreas to produce insulin in laboratory animals and to rejuvenate dysfunctional pancreatic cells in diabetic rats. It also lowers levels of blood cholesterol and triglycerides, high levels of which are associated with cardiovascular disease, without side effects.
In a 1990 study, twenty-two Type II diabetics in India who were taking unspecified oral antidiabetic medications were also given 400 mg of a standardized gurmar extract daily. After eighteen to twenty months, all were able to reduce their dosage of antidiabetic medication, and five participants were able to discontinue using it entirely. The researchers judged the gurmar extract to be superior to the medication for long-term blood sugar stabilization. In another study, 400 mg of the extract given to twenty-seven Type I diabetics lowered their insulin requirements by an average of nearly 50 percent, on the basis of their reduced fasting glucose levels.
Note: Because gurmar increases insulin secretion, it may not be appropriate for individuals with chronically high levels of circulating insulin.
Asian ginseng (Panax ginseng): For centuries, practitioners of traditional Chinese medicine have used ginseng to treat diabetes. In a 1995 Finnish study, thirty-six Type II diabetics who were receiving no other medication took 200 mg of ginseng daily. At the end of eight weeks, the fasting blood glucose measurements of the participants had decreased, and they reported that they felt better and were able to exercise more.
Onions and garlic (Allium cepa, A. sativum): Compounds as yet unidentified in these herbs are believed to protect insulin molecules by prolonging their life, thereby giving them more time to perform effectively. A 1989 review of the research on the antidiabetic effects of onions and garlic revealed that people who take a daily dose of 10 g of onion or garlic extract per kg of body weight showed lower fasting blood glucose levels and improved glucose tolerance tests. This is quite a lot of Allium—about 5 g per pound of body weight, or 11/2 pounds of onion or garlic per day per medium-sized adult. The recommended dose of garlic for a healthy person is 4 g, or one medium-sized clove, daily; eating more than five cloves a day may slow blood clotting. Onions and garlic, therefore, are best used as adjuncts to other herbal treatments. Consult your health-care provider for advice on dosage.
The Benefits of Fiber
Some herbs contain nutritional components that can be beneficial to diabetics as well. High-fiber diets are uniformly recommended for diabetics; of particular importance is soluble fiber, which increases the length of time it takes for food to be digested and thus for glucose to enter the bloodstream, which helps regulate blood-glucose levels; pectin and mucilage are beneficial soluble fibers.
Flax (Linum usitatissimum): Flaxseed meal is one of the richest sources of soluble fiber. In a 1991 University of Toronto study, six nondiabetics were given a glucose solution along with water containing a flaxseed extract, and six others were given the solution along with plain water. Glucose tolerance tests of the flaxseed group improved by 27 percent compared to those of the water group. Two other groups were given either bread containing 25 percent flaxseed meal or plain white bread. Glucose tolerance tests of subjects who ate the flaxseed bread improved by 28 percent compared with tests of those who ate plain bread.
Fenugreek (Trigonella foenum-graecum): Whole fenugreek seeds are another rich source of soluble fiber. Studies of their antidiabetic properties go back at least to 1982. In a double-blind study conducted by the Indian National Institute of Nutrition in 1990, ten Type I diabetics were given either 100 g of ground, defatted, and debittered fenugreek seeds to take each day with meals or no fenugreek. After ten days, fasting glucose levels of those who took the fenugreek had decreased by 30 percent, and their glucose tolerance improved. In double-blind studies of Type II diabetics, 15 to 25 g of fenugreek powder was similarly effective. Hypoglycemic agents in fenugreek seeds include coumarin, fenugreekine, nicotinic acid, phytic acid, scopoletin, and trigonelline, which may work together to bring down fasting blood glucose levels.
Nopal (prickly pear cactus) (Opuntia spp.): Nopal is widely eaten throughout Latin America. In a 1990 study in a Mexican hospital, eight diabetics were given 500 g of nopal on an empty stomach. After three hours, fasting glucose levels were lower by 22 to 25 percent. In a 1995 study, nopal improved rabbits’ tolerance of injected glucose by 33 percent. Although other cacti and succulents are also rich sources of pectin, many are not as tasty as nopal. Dried nopal preparations were not effective in either test.
Ivy gourd (Coccinia indica): Ivy gourd leaves, which are rich in pectin, have traditionally been used by Eastern herbalists to treat diabetes. In a 1980 double-blind study of thirty-two Pakistani diabetics, researchers testing this tradition found that six tablets of ivy gourd leaves per day for six weeks decreased fasting glucose and improved glucose tolerance tests by 20 percent. The mechanism for this effect has not been identified.
The wealth of anecdotal evidence supporting the efficacy of many plants traditionally used for diabetes has prompted their investigation in animal and test-tube studies. The more promising of these herbs include juniper berries, cumin, Siberian ginseng, and coriander, but they have not been tested in clinical studies. Test-tube studies by the U.S. Department of Agriculture have shown that extracts of cinnamon, cloves, turmeric, and bay leaf help insulin perform more effectively; investigation of cinnamon, the most promising of the four, is continuing.
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C. Leigh Broadhurst is a nutrition consultant and researcher for the USDA. She lives in Clovery, Maryland, and is currently researching antidiabetic herbs for the USDA.