Bitter Melon（苦瓜）

Momordica charantia is a tropical and subtropical vine of the family Cucurbitaceae, widely grown for edible fruit, which is among the most bitter of all vegetables. English names for the plant and its fruit include bitter melon or bitter gourd (translated from Chinese: 苦瓜; pinyin: kǔguā), and goya from Japanese).

The original home of the species is not known, other than that it is a native of the tropics. It is widely grown in India and other parts of the Indian subcontinent, Southeast Asia, China, Africa, and the Caribbean.

The herbaceous, tendril-bearing vine grows to 5 m. It bears simple, alternate leaves 4–12 cm across, with 3–7 deeply separated lobes. Each plant bears separate yellow male and female flowers.

The fruit has a distinct warty looking exterior and an oblong shape. It is hollow in cross-section, with a relatively thin layer of flesh surrounding a central seed cavity filled with large flat seeds and pith. Seeds and pith appear white in unripe fruits, ripening to red; they are not intensely bitter and can be removed before cooking. However, the pith will become sweet when the fruit is fully ripe, and the pith's color will turn red. The pith can be eaten uncooked in this state, but the flesh of the melon will be far too tough to be eaten anymore. Red and sweet bitter melon pith is a popular ingredient in some southeast Asian salads. The flesh is crunchy and watery in texture, similar to cucumber, chayote or green bell pepper. The skin is tender and edible. The fruit is most often eaten green. Although it can also be eaten when it has started to ripen and turn yellowish, it becomes more bitter as it ripens. The fully ripe fruit turns orange and mushy, is too bitter to eat, and splits into segments which curl back dramatically to expose seeds covered in bright red pulp.

Bitter melon comes in a variety of shapes and sizes. The typical Chinese phenotype is 20–30 cm long, oblong with bluntly tapering ends and pale green in color, with a gently undulating, warty surface. The bitter melon more typical of India has a narrower shape with pointed ends, and a surface covered with jagged, triangular "teeth" and ridges. Coloration is green or white. Between these two extremes are any number of intermediate forms. Some bear miniature fruit of only 6–10 cm in length, which may be served individually as stuffed vegetables. These miniature fruit are popular in Southeast Asia as well as India.

Bitter melon contains a bitter compound called momordicin that is said to have a stomachic effect.

Bitter melon has been used in various Asian traditional medicine systems for a long time. Like most bitter-tasting foods, bitter melon stimulates digestion. While this can be helpful in people with sluggish digestion, dyspepsia, and constipation, it can sometimes make heartburn and ulcers worse. The fact that bitter melon is also a demulcent and at least mild inflammation modulator, however, means that it rarely does have these negative effects, based on clinical experience and traditional reports.

Though it has been claimed that bitter melon’s bitterness comes from quinine, no evidence could be located supporting this claim. Bitter melon is traditionally regarded by Asians, as well as Panamanians and Colombians, as useful for preventing and treating malaria. Laboratory studies have confirmed that various species of bitter melon have anti-malarial activity, though human studies have not yet been published.

In Panama bitter melon is known as Balsamino. The pods are smaller and bright orange when ripe with very sweet red seeds, but only the leaves of the plant are brewed in hot water to create a tea to treat malaria and diabetes. The leaves are allowed to steep in hot water before being strained thoroughly so that only the remaining liquid is used for the tea.

Laboratory tests suggest that compounds in bitter melon might be effective for treating HIV infection. As most compounds isolated from bitter melon that impact HIV have either been proteins or glycoproteins lectins), neither of which are well-absorbed, it is unlikely that oral intake of bitter melon will slow HIV in infected people. It is possible oral ingestion of bitter melon could offset negative effects of anti-HIV drugs, if a test tube study can be shown to be applicable to people. In one preliminary clinical trial, an enema form of a bitter melon extract showed some benefits in people infected with HIV (Zhang 1992). Clearly more research is necessary before this could be recommended.

The other realm showing the most promise related to bitter melon is as an immunomodulator. One clinical trial found very limited evidence that bitter melon might improve immune cell function in people with cancer, but this needs to be verified and amplified in other research. If proven correct this is another way bitter melon could help people infected with HIV.

Folk wisdom has it that bitter melon helps to prevent or counteract type-II diabetes. A recent scientific study at JIPMER, India has proved that bitter melon increases insulin sensitivity. Also, in 2007, the Philippine Department of Health issued a circular stating that bitter melon, as a scientifically validated herbal medicinal plant, can lower elevated blood sugar levels. The study revealed that a 100 milligram per kilo dose per day is comparable to 2.5 milligrams of the anti-diabetes drug Glibenclamide taken twice per day. Bitter melon is sold in the Philippines as a food supplement and marketed under the trade name Charantia. Charantia capsules and tea are being exported to the United States, Canada, Europe, Mexico, Japan, Korea, and parts of the Middle East.

Bitter Melon contains four very promising bioactive compounds. These compounds activate a protein called AMPK, which is well known for regulating fuel metabolism and enabling glucose uptake, processes which are impaired in diabetics. "We can now understand at a molecular level why bitter melon works as a treatment for diabetes," said David James, director of the diabetes and obesity program at the Garvan Institute of Medical Research in Sydney. "By isolating the compounds we believe to be therapeutic, we can investigate how they work together in our cells."

Bitter melon contains a lectin that has insulin-like activity. The insulin-like bioactivity of this lectin is due to its linking together 2 insulin receptors. This lectin lowers blood glucose concentrations by acting on peripheral tissues and, similar to insulin's effects in the brain, suppressing appetite. This lectin is likely a major contributor to the hypoglycemic effect that develops after eating bitter melon and why it may be a way of managing adult-onset diabetes. Lectin binding is non-protein specific, and this is likely why bitter melon has been credited with immunostimulatory activity - by linking receptors that modulate the immune system, thereby stimulating said receptors.

Various cautions are indicated. The seeds contains vicine and therefore can trigger symptoms of favism in susceptible individuals. In addition, the red arils of the seeds are reported to be toxic to children, and the fruit is contraindicated during pregnancy.

Bitter melon is often used in Chinese cooking for its bitter flavor, typically in stir-fries (often with pork and douchi), soups, and also as tea.

It is very popular throughout India, where it is often prepared with potatoes and served with yogurt on the side to offset the bitterness, or used in sabji. It is stuffed with spices and then fried in oil, which is very popular in Punjabi cuisine. It is a popular food in Tamil Nadu and in the South Indian state of Kerala. They use it for making a dish called thoran mixed with grated coconut, theeyal and pachadi. This is one common medicinal food for diabetics. Popular recipes include curry, deep fry with peanuts (ground nuts), and 'Pachi Pulusu' (కాకరకాయ పచ్చి పులుసు), a kind of soup made up of boiled Bitter Melon, fried onions and other spices.

In Pakistan bitter melon is available in the summertime, and is cooked with lots of onions. A traditional way to cook bitter melon curry is to peel off the skin and cut into thin slices. It is salted and exposed to direct sunlight for few hours to reduce its bitterness. After a few hours, its salty, bitter water is reduced by squeezing out the excess by hand. Then it's rinsed with water a few times. Then fried in cooking oil, with onions also fried in another pan. When the onions have turned a little pink in color, the fried bitter melon is added to them. After some further frying of both the onions and bitter melon, red chili powder, turmeric powder, salt, coriander powder, and a pinch of cumin seeds are also added. A little water can be sprinkled while frying the spices to prevent burning. Then a good amount of tomato is added to the curry, with green chillies, according to taste. Now the pan is covered with a lid, heat reduced to minimum, the tomatoes reduce, and all the flavors blend together. The curry is stirred a few times (at intervals) during this covering period. After half an hour or so, the curry is ready to serve, with soft hot flatbreads (chappatis, چپاتی) and yogurt chutney. Another dish in Pakistan calls for whole, unpeeled bitter melon to be boiled and then stuffed with cooked ground beef. In this dish, it is recommended that the bitter melon be left 'debittered'. It is served with either hot tandoori bread, naan, chappati, or with khichri (a mixture of lentils and rice).

Bitter melon is rarely used in mainland Japan, but is a significant component of Okinawan cuisine, and is credited with Okinawan life expectancies being higher than already long Japanese ones.
In Indonesia, bitter melon is prepared in various dishes, such as stir fry, cooked in coconut milk, or steamed.

In Vietnam, raw bitter melon slices consumed with dried meat floss and stuffed to make bitter melon soup with shrimp are popular dishes. Bitter melons stuffed with ground pork are served as a popular summer soup in the South. It is also used as the main ingredient of "stewed bitter melon". This dish is usually cooked for the Tết holiday as its name: "bitter" reminds people not to forget or disrespect to poor living condition experienced in the past.

It is prepared in various dishes in the Philippines, where it is known as Ampalaya. Ampalaya may also be stir-fried with ground beef and oyster sauce, or with eggs and diced tomato. A very popular dish from the Ilocos region of the Philippines, pinakbet, consists mainly of bitter melons, eggplant, okra, string beans, tomatoes, lima beans, and other various regional vegetables stewed with a little bagoong-based stock. The young shoots and leaves may also be eaten as greens; in the Philippines, where bitter melon leaves are commonly consumed, they are called dahon (leaves) ng ampalaya.

In Nepal bitter melon is prepared in various ways. Most prepare it as fresh achar (a type of pickle). For this the bitter gourd is cut into cubes or slices and sautéed covered in little oil and a sprinkle of water. When it is softened and reduced, it is minced in a mortar with a few cloves of garlic, salt and a red or green pepper. Another way is the sautéed version. In this, bitter gourd is cut in thin round slices or cubes and fried (sauteed) with much less oil and some salt, cumin and red chili. It is fried until the vegetable softens with hints of golden brown. It is even prepared as a curry on its own, or with potato; and made as stuffed vegetables.