What is bitter melon

Bitter melon (Momordica charantia) is a commonly consumed vegetable that is found throughout the sub-tropical world (China, India, Thailand, East Africa, The Caribbean, Central and South America) and is known by various names, such as balsam pear, bitter gourd, bitter squash, carilla, cerasee (wild variety), cundeamor, goo-fah, African cucumber and Karela 1). All parts of the plant, including the fruit, taste bitter 2). Hence, the fruits are usually cooked with different vegetables, stir-fried, stuffed or used in small quantities in soups or beans to give a slightly bitter flavor and taste. Several parts of bitter melon, including fruits, flowers, and young shoots, are used in various Asian dishes as a flavoring agent. The shoots and leaves of bitter melon are also cooked and consumed as vegetables and fruit extracts are also used in tea preparations 3). Bitter melon is also used as a vegetable in India and other Asian countries and as an ingredient in some kinds of curries.

Bitter melon is used traditionally for various stomach and intestinal disorders including gastrointestinal (GI) upset, ulcers, colitis, constipation, and intestinal worms 4), 5). Bitter melon is also used for diabetes, kidney stones, fever, a skin condition called psoriasis, and liver disease; to start menstruation; and as supportive treatment for people with HIV/AIDS 6), 7).

Topically, bitter melon is used for deep skin infections (abscesses) and wounds.

Figure 1. Bitter melon

bitter melon

Bitter melon nutritional facts

The nutritional analysis has revealed that bitter melon fruits are a rich source of carbohydrates, proteins, vitamins, and minerals. Bitter melon possesses the highest nutritive value among cucurbits 8). The vitamin C content of Chinese bitter melon varies significantly (440–780 mg/kg edible portion), while variation in nutrient contents has been observed in bitter melon including carbohydrates, proteins, zinc, iron, calcium, magnesium, phosphorous, and ascorbic acid 9). The crude protein content of bitter melon fruits (11.4–20.9 g/kg) is higher than that of tomato and cucumber 10). The pulp around the seeds of the mature ripe fruit is a rich source of the carotenoid lycopene 11).

Table 1. Bitter melon nutritional facts

[Source 12)]

Bitter melon extract

At latest count, approximately 228 different compounds with possible medicinal properties, acting alone or in combination, have been isolated from bitter melon fruit, seeds, leaves, stems, pericaps, endosperm, callus tissues, and cotyledons 13). Among these, the most actively studied constituents shown to improve glycemic control include charatin, polypeptide-p, vicine, momordin, and similar derivatives (e.g., momordinol, momordicilin, momorcharin, momordicin) 14), 15). The medicinal value of bitter melon has been attributed to its high antioxidant properties due in part to phenols, flavonoids, isoflavones, terpenes, anthroquinones, and glucosinolates, all of which confer a bitter taste 16).

Bitter melon health benefits

Bitter melon has been studied for several decades because of its use as a food product and several traditional medical uses. Various extracts of bitter melon are studied for biological activities, including anti-oxidant 17), anti-diabetic 18), anti-cancer 19), anti-inflammatory 20), anti-bacterial 21), antifungal 22), anti-viral 23), anti-HIV 24), anti-helminthic 25), anti-mycobacterial 26), hypotensive 27), anti-obesity 28), immunomodulatory 29), anti-hyperlipidemic 30), hepatoprotective 31), and neuropro-tective 32) activities. Several chemical constituents such as cucurbitane type triterpenoids, cucurbitane type glycosides, triterpene saponins, phenolic, and flavonoid compounds, and some protein fractions have been isolated from bitter melon 33).

The effectiveness ratings for bitter melon (Momordica charantia) are as follows:

Insufficient evidence to rate effectiveness for:

  • Diabetes. Research results so far are conflicting and inconclusive. Some studies show that bitter melon fruit, fruit juice, or extract improves glucose tolerance, reduces blood sugar levels, and lowers HbA1c (a measure of blood sugar control over time) in people with type 2 diabetes. However, these studies have some flaws. Other research has not been positive.
  • Psoriasis.
  • Stomach and intestinal disorders.
  • Kidney stones.
  • Liver disease.
  • Skin abscesses and wounds.
  • Other conditions.

Clinical studies reported mostly lack appropriate study design and are inconclusive. More evidence is needed to rate the effectiveness of bitter melon for these uses.

Bitter melon and diabetes

The public have used different parts of bitter melon (Momordica charantia) including the leaves, the stem and mainly the green fruits or seeds to treat diabetes. Figure 2 shows the chemical structures of momocharin (1) and momordicin (2) which is believed to possess insulin-like chemical structure and properties. People eat the fruit raw, boil or cook the different parts or drink the pulp of the fruit as a juice. Over the years several scientists have tried to isolate the various active ingredient of bitter melon for commercial purpose.

Over the past 50 years, both basic and clinical studies have been done to determine the effect of bitter melon on the management of diabetes mellitus. Table 2 shows the effect of oral administration of bitter melon on human type 2 diabetes mellitus. They were administered with a hot water extract, concoction, the fruit, the fruit juice or the seeds 34). Of the five studies presented in Table 2, only two studies show no effect on type 2 diabetes mellitus patient 35), 36). However, overall, it remains controversial whether bitter melon has proven benefits in lowering blood sugar among pre-diabetics or aids in slowing the progression to diabetes 37). While the evidence to date, when examined as a whole, is suggestive of a possible beneficial effect, future clinical studies that meet rigorous methodological standards are warranted before attempts to establish clinical recommendations regarding the use of bitter melon for pre-diabetics and diabetics.

Figure 2. Chemical Structure of Bitter melon’s Momorcharin and Momorcidin

bitter melon - momorcharin
bitter melon - momordicin

Table 2. Effects of Oral Administration of Bitter Melon on Type 2 Diabetes Mellitus

Experimental ModelsParts of Plant usedEffectsReferences
Human (Type 2 Diabetes Mellitus)Fruit juice/leavesBeneficial38); 39)
Human (Type 2 Diabetes Mellitus)Fruit juiceNo effect40), 41)
Human (Type 2 Diabetes Mellitus)Fruit powderBeneficial42)
[Source 43)]

What dose is used ?

The appropriate dose of bitter melon depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for bitter melon. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Bitter melon side effects

Bitter melon fruit is POSSIBLY SAFE for most people when taken by mouth in the short-term 44). The safety of long-term use (beyond 3 months) is not known – the risk associated with the long-term use of bitter melon supplements have not been studied. There also is not enough information about the safety of consuming other parts of the bitter melon or applying bitter melon to the skin.

The most commonly observed adverse effects include mild diarrhea and abdominal pain, which subside after discontinuing use 45). However, bitter melon has been shown to potentiate the effect of certain drugs used to treat diabetes, possibly resulting in hypoglycemia 46). Rare cases of hypoglycemic coma and convulsions have been reported in children drinking bitter melon tea 47). A single case report has suggested that bitter melon may induce paroxysmal atrial fibrillation, based on a Naranjo adverse drug reaction score of 6 (corresponding to a probable causal association) 48). Bitter melon use also is contraindicated during pregnancy because of its abortifacient properties 49).

Special precautions & warnings

Pregnancy and breast-feeding: Bitter melon is LIKELY UNSAFE when taken by mouth during pregnancy. Traditionally, bitter melon has also been used as an abortifacient agent used to induce abortions. Therefore, pregnant women are advised to avoid consumption of the plant 50). Certain chemicals in bitter melon fruit, juice, and seeds can start menstrual bleeding and have caused abortion in animals. Not enough is known about the safety of using bitter melon during breast-feeding. Stay on the safe side and avoid use.

Diabetes: Bitter melon can lower blood sugar levels. If you have diabetes and take medications to lower your blood sugar, adding bitter melon might make your blood sugar drop too low. Monitor your blood sugar carefully.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency: People with G6PD deficiency might develop “favism” after eating bitter melon seeds. Favism is a condition named after the fava bean, which is thought to cause “tired blood” (anemia), headache, fever, stomach pain, and coma in certain people. A chemical found in bitter melon seeds is related to chemicals in fava beans. If you have G6PD deficiency, avoid bitter melon.

Surgery: There is a concern that bitter melon might interfere with blood sugar control during and after surgery. Stop using bitter melon at least 2 weeks before a scheduled surgery.

Interactions with medications

Moderate – Be cautious with this combination.

Medications for diabetes (Antidiabetes drugs)

Bitter melon can decrease blood sugar levels. Diabetes medications are also used to lower blood sugar. Taking bitter melon along with diabetes medications might cause your blood sugar to be too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.

Are there interactions with herbs and supplements ?

Herbs and supplements that might lower blood sugar

Bitter melon can lower blood glucose levels. Using it with other herbs or supplements that have the same effect might cause blood sugar levels to drop too low. Some herbs and supplements that can lower blood sugar include alpha-lipoic acid, chromium, devil’s claw, fenugreek, garlic, guar gum, horse chestnut, Panax ginseng, psyllium, Siberian ginseng, and others.

References   [ + ]

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