In researching the benefits of ghrelin, I came across a study that doubled the amount in patients by a traditional Chinese herb concoction that blocked its degradation and stimulated production. They investigated it and found the primary cause of the increase in ghrelin to be from about 4 or 5 specific compounds. It turned out they were all from one of the "herbs" which turned out to be aged dried mandarin peel. The compounds are hesperidin, tangeretin, nobiletin, and heptamethoxyflavone. These are also in tangerine peel extract, which can be found in China. Surprisingly, each one of these compounds had 1 or 2 studies on PD in mice or rats and they all worked, but by mechanisms that seem different from an increase in ghrelin. If something works by two different routes, it is more significant. To simulate they gave the mice, you would have to eat about 2 pounds of fresh tangerine peel per day. There are 10:1 concentrations of tangerine peel, getting it down to about 1/3 cup of a brownish powder per day. It is possible to obtain them in isolated form, getting it down to a few pills per day.