Okinawan cuisine consists of smaller meal portions of green and yellow vegetables, fish, relatively smaller amounts of rice compared to mainland Japan, as well as pork, soy and other legumes. Pork and fish are often served in broth with a variety of ingredients and herbs. The center of the Okinawa diet is the Satsuma sweet potato. The sweet potato also contributes the self-sufficiency of the island. Contrary to the regular potato, the Okinawa sweet potato does not have a large effect on blood sugar. Not only is the potato used but so are the leaves from the plant. The leaves are used often in miso soup. The Okinawan bitter melon is proven to have some anti-diabetic effects. In Okinawa the bitter melon is called goyain and is served in the national dish, goya champuru. The bitter melon is effective in regulating blood sugar similar to the sweet potato.