Abundant rice and vegetables are produced from the fertile Sichuan Basin, whereas a wide variety of herbs, mushrooms and other fungi prosper in the highland regions. Pork is overwhelmingly the most common type of meat consumed. Beef is somewhat more common in Sichuan cuisine than it is in other Chinese cuisines, perhaps due to the prevalence of oxen in the region. Sichuan cuisine also uses various bovine and porcine organs as ingredients, such as intestine, arteries, head, tongue, skin and liver, in addition to other commonly used portions of the meat. Rabbit meat is also much more popular in Sichuan than elsewhere in China. It is estimated that the Sichuan Basin and Chongqing area are responsible for about 70 percent of China's total rabbit meat consumption. Yoghurt, which probably spread from India through Tibet in medieval times, is consumed among the Han Chinese. This is an unusual custom in other parts of the country. The salt produced from Sichuan salt springs and wells, unlike sea salt, does not contain iodine, which led to goiter problems before the 20th century.