Bitter Melon Diabetes Treatment
Kathy Abascal, B.S., J.D., R.H. (A.H.G),
And
Eric Yarnell, N.D., R.H. (A.H.G.)
Abstract
Bitter Melon (Memordica charantia) has a long history of use as a food and as a hypoglycemic agent. This article reviews scientific evidence of its efficacy for treating diabetes mellitus and reviews studies on this plant’s effects on pregnancy and fertility, and use as an abortifacient, an understanding of which is important to bitter melon’s safe use.
Introduction
Bitter Melon (Memordica charantia) is a complex plant medicine that has a remarkably long history of use, both as a food and as a medicine. Many plants are used as foods and as medicines. Typically, such plants tend to be supportive, tonic, and nourishing in nature. They work effectively but seldom have strong hypoglycemic properties or strong effects on the reproductive tract. Bitter melon is unusual because it is widely consumed as food but also has a long history of use for conditions such as diabetes, psoriasis, and infections, as well as for menstrual cycle regulation, addressing infertility, and inducing abortions. Modern science is just beginning to investigate the plant’s many uses, and much remains to be learned about it.
The native habitat for bitter melon is not known. The plant is cultivated throughout the tropics, especially in China, India, East Africa, Central America, and South America. Bitter melon has many different common names, reflecting its widespread use in numerous cultures. The fruit has a bitter taste (as its name clearly conveys) and, for the most part, its palatability is said to be “an acquired taste.” In southern China, the melon is commonly eaten to cool the body.
There are many recipes for using bitter melon (see box entitled A Bitter Melon Recipe) but it is difficult to find data that shows how frequently the plant is eaten typically. Although it is common, bitter melon does not appear to be a daily staple. It does, however, seem to be eaten several times a week when it is in season (personal communication, James A. Duke, Ph.D., Fulton, Maryland, May 2005). This is important because plants that are widely consumed as foods have built-in safety testing by hundreds of generations of people. It seems that bitter melon is sufficiently common in the diet to provide some evidence of its safety for general use. When prepared as a food, only the fruit is eaten and the seeds are discarded.
The many uses of bitter melon include treating diabetes mellitus, and this article focuses on that use. Historically, bitter melon was used also variously as an aphrodisiac, and abortifacient, and emmenagogue, and a galactogogue. This article reviews the melon’s effects on the reproductive tract briefly because these effects may have significant implications on its appropriateness as a daily medicine for use in patients with diabetes.
Diabetes Mellitus
Diabetes is a complex disease that affects millions of people. It, of course, exists in two major forms: insulin-dependent diabetes mellitus (IDDM) and noninsulin-dependent diabetes mellitus (NIDDM). Bitter melon may have a valuable role to play in addressing both forms of the condition.
There are only a few clinical studies on bitter melon use for treating diabetes, and the studies are small and do not meet the criteria for reliability. Nonetheless, these studies appear to confirm consistently the widespread folk use of bitter melon for addressing diabetes.
In an open-label crossover trial, 27 patients with NIDDM were randomly assigned to two groups. One group drank 200 mL of dried fruit tea (with seeds) after each major meal while the other group drank black tea (Camellia sinensis). Crossover began at the end of 12 week without a washout period. Fasting blood sugar and elevated liver transaminase (serum, glutamic pyrovic traansaminase) levels decreased by those effects did not reach statistical significance. Glycosylated hemoglobin (HbA1C) decreased significantly in the active group. Adverse effects were increases in frequency and softness of stools.
In another study, 5 patients with DDM were given 15 g of powdered dried fruit in 3 equal doses per day and 7 were given 100 mL of decocted fresh fruit (100 g/100 mL) once daily for 21 days. The postprandial blood sugar levels of the patients on powdered fruit dropped 25 percent but this was without statistical significance.
The fall in blood sugar was 54 percent in the aqueous-extract treated group, a highly significant drop, and blood sugar levels were restored to normal within 3-7 weeks. Patients in this group had mild (fasting blood glucose (FBG) of 260 mg%) to severe (FBG of 433 mg%) diabetes at the start of the trial. The researchers noted that there appeared to be a time-related cululative response to the aqueous extract. Glycosylated hemoglobin decreased in both groups. The researchers stated that the hypoglycemic properties of bitter melon could not be attributed to a single principle.
Nine (9) patients whose diabetes was controlled by diet (n=1) or chlorproparride (n=3), tolubamide (n=3), glibenclamide (n=1), or glymidine (n=1) were given glucose tolerance tests. The first test was standard and the second was given after the subjects ate fried bitter melon (0,23 kg/day) for 7-11 weeks. Patients discontinued any drugs 48 hours before the test, fasted, and refrained from smoking the night before each test. In addition, two patients underwent a third test after taking bitter melon juice (0.9 kg fresh fruit, with the seeds removed, yielding 200-250 ML of fresh juice).
The study showed that the juice significantly improved glucose tolerance and the fried melon somewhat improved glucose tolerance. Serum insulin levels did not increase, suggesting that bitter melon may have influenced hepatic or peripheral glucose disposal directly. This is doubly important because any agents that stimulate insulin release (so-called insulin secretagogues) may worsen insulin resistance in patients with NIDDM and accelerate beta-cell loss in patients with IDDM. Glycosylated hemoglobin also decreased suggesting an extrapancreatic action.
In a study involving traditional Sri Lankan practitioners 18 patients recently diagnosed with NIDDM but not yet given prescriptions for conventional medication fasted overnight and drank 10 mL of water before taking a standard glucose tolerance test (50 g of glucose). The next day, again after an overnight fast, the patients drank 100 mL of homogenized bitter melon fruit juice prepared with seeds.
The patients were comprised of two groups: responders and nonresponders. The total data showed that the area under the glucose tolerance curves was significantly lower although complete data were not provided in the study report. The researchers concluded that the results, nonetheless, gave some scientific validity to using bitter melon as an oral hypoglycemic agent by traditional Sri Lankan practitioners.
The authors of an abstract reported that bitter melon seeds were investigated in the hope that they could be substituted for the fruit, which is seasonal. The seeds (dose not stated) reduced postprandial blood glucose levels (from approximately 350 mg% to approximately 150 mg%) in patients with IDDM (n=6) and NIDDM (n=20) but that the fasting blood glucose returned to normal by the next day. Adverse effects were minor and consisted of headaches.
Bitter melon contains a protein that is structurally and pharmacologically similar to bovine insulin. It is often referred to a “v-insulin” and research is ongoing to determine if this type of insulin may be suitable for patients who do not tolerate, or for philosophical reasons prefer not to use, animal sourced insulin. In a small study, 9 patients (6 with juvenile onset, 1 maturity onset, and 2 asymptomatic (IDDM) were given v-insulin subcutaneously. Five (5) healthy and 5 patients with overt diabetes served as controls and were given a placebo injection.
A hypoglycemic effect in the treatment group was observed that started 30-60 minutes after injection but peaked after 3-12 hours (compared to 2-3 hours for regular insulin).
In another study, subcutaneous v-protein produced a hypoglycemic effect in a small controlled study (n=19) of juvenile and maturity onset IDDM. One (1) juvenile patient who suffered side-effects when on bovine insulin (swelling, stomach pain, and bouts of hypoglycemia) was maintained on v-protein for 5 months, without experiencing and adverse effects.
Finally it was reported that a patient on chlorpropamide noticed a synergistic effect when consuming a curry made with bitter melon and garlic (Allium satiown). Bitter melon tea had a significant hypoglycemic effect in 2 small children (3 and 4 years’ old) who drank a tea of the leaves and vine on an empty stomach. An hour or two after ingestion, the children had convulsions followed by coma. Their blood sugar was approximately 1mM (normal is 3.8-5.5 mM); both children recovered.
PRECLINICAL STUDIES
There are many animal studies on bitter melon’s effect on the course of diabetes. These studies are usually of better design than the clinical studies. However, the animal studies also have certain flaws.
In the pharmacologic studies, bitter melon was also prepared and dispensed in a variety of ways. This reflects the fact that bitter melon was prepared in a variety of ways as a traditional diabetes medicine. In some cultures, the fruit was crushed and strained to produce a juice. Sometimes, the fruit was fried and consumed. In many cultures, the fruit was chopped and soaked in water, sometimes cold, sometimes decocted; sometimes with seeds, sometimes without. In other cultures, the whole plan was used in a similar manner. The heterogeneity in forms of bitter melon studied makes it difficult to draw firm conclusions about its mode of action, best form, and dose. However, the overwhelming majority of studies tended to confirm traditional wisdom regarding using bitter melon for addressing diabetes regardless of dose form.
These animal studies have shown, variously, that bitter melon inhibits glucose absorption, promotes glucose utilization in the liver, contains an insulin-like polypeptide, increases pancreatic insulin secretion, and may increase beta-cell production in the pancreas. However, an increase in blood levels of insulin has not been observed and the exact mechanism whereby bitter melon affects blood sugar remains unclear. Overall, the combined observations made traditionally, in clinical and animal studies, strongly suggest that bitter melon has a role to play in diabetes treatment.
Another facet of bitter melon is that it may mitigate diabetic complications Diabetes is associated with irreversible functional and structural changes in the kidneys, eyes, nerves, and blood vessels, and bitter melon appeared to, potentially, mitigate aspects of these complications. Nonetheless, although these studies are high preliminary, they are promising and additional research is definitely needed to investigate this aspect of bitter melon. It should also be noted these benefits may be secondary to improved blood glucose control.
For instance, diabetes is the leading cause of end-stage renal disease. Mice with streptozotocin-induced diabetes have elevated serum creatinine, urinary albumin, urine volume, and renal weight compared to normal mice. Mice treated with bitter melon had significantly improved, albeit not normalized, values for these parameters. Diabetic neuropathy causes limb pain, sexual dysfunction and other negative symptoms. Tail flick latency increases substantially (by 74 percent) in mice that have diabetes. A mouse study showed that an aqueous extract of bitter melon (200 mg/kg) significantly reduced this increase, raising the possibility that future research may someday reveal that bitter melon can provide a benefit for patients with diabetic neuropathy.
Another diabetic complication is diabetic enteropathy, which results in a syndrome of dyspepsia, heartburn, nausea, vomiting, abnormal pain, constipation, diarrhea, and fecal incontinence. Bitter melon was used in traditional medicines to improve gastrointestinal function, and it may provide some benefit for patients who have diabetic enteropathy.
The transit time with mice with diabetes was reduced by 83 percent compared to normal mice in one animal study. Aqueous bitter melon extract almost renormalized the animals’ transit time while also reducing their blood glucose levels. In a rat model of syndrome X (hyperglycemia, and obesity), aqueous bitter melon extract (400 mg/day) fed to rats on a fructose rich diet presented hyperinsulinmia and hyperglycemia compared to the effects experienced by control rats.
Finally, diabetes is an important risk factor for cataracts. In one experiment, aqueous bitter melon extract delayed somewhat the onset of cataracts in rats with alloxan-induced diabetes (12 days to onset compared to 100 days in controls). In a second study, high doses of bitter melon fruit (4g/kg) for 2 months also delayed the onset in rats that had diabetes (140-180 days compared to 90-100 days).
Reproductive Effects and Other Safety Issues
Bitter melon has been used in traditional medicine to treat a seemingly contradictory range of reproductive problems. The melon is reported to have been used as an aphrodisiac, to treat infertility, as an emmenagogue, as a galactogogue, and as an abortifacient. Often, the leaves, vine, and seeds were used for these purposes. In considering whether and how to use bitter melon in patients with diabetes, it is important to consider research showing that the plant has definite, although poorly elucidated, negative reproductive effects. These effects must also be evaluated in light of the fact that bitter melon is frequently consumed as a food but does not have a reputation for being an inappropriate food for pregnant women or in individuals planning to have children.
Mice fed bitter melon juice daily had a decline in fertility rate from 90 percent to 20 percent. Mice who did conceive bore normal litters and normal fertility rates returned when the bitter melon was not given to the mice. Bitter melon extract (1.75 g/day for 60 days) inhibited spermatogenesis in dogs and was associated with testicular lesions. After 60 days, the somniferous tubules were completely devoid of sperm.
Bitter Melon has been shown to contain several proteins (alpha-and beta momorcharins) that induce midterm abortion and terminate early pregnancy in mice. The early termination results from negative effects on embryo implantation and on the endometrium. Embryos that did implant had retarded development. Bitter melon juice (6 mL/kg by mouth) caused uterine hemorrhage and death in 2 pregnant female rabbits but did not have that effect on nonpregnant rabbits. However, the majority of rabbits fed bitter melon juice continuously died within 23 days, and rats given the juice intraperitoneally (15-40 mL/kg) died within 6-18 hours.
In patients using bitter melon for its antiviral properties in HIV, no apparent toxicity was observed even with long-term treatment (n=3). One (1) patient had no change in blood chemistry or any adverse symptoms after taking bitter melon daily for more than 3 years. These patients were taking a powder that combined the water and alcohol-soluble parts of the whole plant, with 1 g of powder being equal to 25 g of fresh plant. The actual dose taken by the patients was not disclosed.
Vicine is a compound that can induce favism in genetically susceptible individuals. Vicine is a compound that can induce favism in genetically susceptible individuals. Vicine (or a vicine-like) compound has been isolated from bitter melon seed and caution should be used in individuals who may be predisposed to favism. There are, however, no reports of favism induced by the ingestion of bitter melon.
Conclusions
There are strong indications that bitter melon may be highly useful in addressing diabetes. The seeded fruit has a long history of use as a food eaten with some frequency, and aquenous extracts of bitter melon appear to have a significant hypoglycemic effect. In addition, there are some (albeit very weak) indications that bitter melon extracts may protect patients against some of the complications of diabetes.
We feel comfortable recommending seeded bitter melon as a food or as a tea to older patients with NIDDM. A daily dose of bitter melon tea may be prepared by boiling 100 g of diced fruit in 200 ml of water until the liquid is reduced by half. However, given the plant’s potential abortifacient effects and ability to reduce fertility in animals, we would not, at this time, recommend daily use of bitter melon to younger patients or patients possibly interested in having children.
A Bitter Melon Recipe
Ingredients:
Bitter Melon – 1 lb
Sale – 2 tsp
Turmeric – 1 tsp fresh minced or ½ tsp dried
Mustard – ½ tsp
Red Chili Powder – 1 tsp
Asafoercida – ¾ tsp
Preparation:
Cut bitter melon into five pieces. Add salt,
tumeric powder; and let the mixture alone for
15 minutes. Heat 2 cup of oil in a frying pan.
Add mustard seeds, and when the mixture pops, add
¾ of a tsp of asafoercida. Squeeze the water
out from the bitter melon and add 1c to the oil.
Add red chili powder and fry well until fully
cooked.
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