Have you ever eaten Goya (bitter melon)? It's a famous Okinawan vegetable, a green Godzilla-looking squash with dimples. You eat them before they ripen, which is about 15 - 20 days after they bloom. Waiting any longer than that and they lose their bitterness and become sweet.
Many people don't like Goya because of its bitterness, and indeed in ancient China, it was regarded as a food "only fit for a famine". A Chinese survival book written in 1406 says that Goya was one of the last desirable foods to eat during a famine, among the other total of 414 items, such as figs.
The "Goya champuru" dish is representative of Okinawan cuisine. Historically, it came from India via China in the 15th century.
Goya need at least 20C of warmth to grow, and they are a natural Uminanchu (Okinawan) plant. Goya are rich in Vitamin C, double or triple that of lemons. Also the bitterness is caused by enzymes that also happen to be effective in lowering blood pressure, and thus they can beused as a diabetes medicine.
It's not very hot yet, but I recommend you try Goya champuru with a beer to beat the summer.