The time when China ate yam can be traced back to 2000 BC. Among the historical materials unearthed in Dunhuang Mogao grottoes a few years ago, there is a record of "fairy porridge": "A catty of yam, steamed and peeled; Half a catty of chicken head, cooked, shelled and mashed into rice, half a catty of japonica rice, cooked into porridge with slow fire and eaten on an empty stomach. " In order to be called fairy porridge, Lu You, a poet in Song Dynasty, once wrote a poem to express: "Everyone in the world is an elder, but I don't know for many years. At present, I try my best to make porridge immortal. " Eating yam porridge can live forever. Of course, this is the poet's exaggeration, but yam porridge does have the effect of regulating appetite, keeping healthy and prolonging life, and it is also well known. There are many poems praising yam in history. "Chen Da Search" Yu Yanzan said: "There is a panacea in the mountains, because it is fairy, innocent and fragrant." Zhu Shi said, "If you want to give Yu Yanzhi, you have nothing to say, and you are ashamed to talk about honey mutton soup." They praised yam as jade in color, fragrant as flowers, sweet as honey and better in taste than mutton soup.
"Shennong's Classic of Materia Medica" contains: "Dioscorea is sweet in taste and warm in nature, which mainly tonifies middle energizer, tonifies deficiency, eliminates cold and heat, tonifies middle energizer and promotes granulation". Can play a role that ginseng can't play. Ginseng is not suitable for young people because it is hot after eating, but it is mild and nutritious, and can be taken by the elderly, young people, women, children and infants.