Cooked rehmannia root, also called Shu Di Huang in Pinyin, is produced throughout China. However, when it comes to medicinal uses, the herb from Huaiqing region in Henan province is thought to be the most "authentic" species. Thanks to its wide ranging medicinal properties, it has long been known as one of the 4 most famous Huai-medicines. Compared to raw or fresh rehmannia root, its tonic properties have been greatly enhanced by processing. By the way, the commercial rehmannia is ungraded and all items are usually sold at a single price. Medicinally the preferred one is bigger in size, heavier in weight, softer and oilier, and with blacker cross section and sweeter taste. So, what is rehmannia used for and how to get the most health benefits from it?

It was first appeared in Shen Nong Ben Cao Jing (Shen Nong’s Herbal Classic). Today there are there kinds of rehmannia available – prepared, fresh, and raw rehmannia root. All of them are capable of treating all diseases caused by deficiency of yin and body fluid since they can nourish Yin and produce saliva.

However, clinically they are not the same thing and with different healing properties. The fresh one is sweet-bitter in taste and extremely cold in nature. It is with weak yin-nourishing ability but a better performance on removing heat to cool blood, purging the pathogenic fire, and relieving restlessness. So, it is often used in patterns of blood heat due to exuberant pathogens and deficiency of yin and fluid; the dried one is of sweet taste and cold-moist nature. It is with less blood-cooling properties but a better ability on nourishing the yin of heart and kidney. Hence, it is the perfect option in the treatment of impaired yin caused by blood heat and fever due to yin deficiency; the cooked one is an important liver-kidney tonic that not only nourishes blood and yin, but also reinforces essence and marrow.

Tradition Chinese medicine believes that essence and blood are the most fundamental material basis of the body. That’s to say, adequate blood and essence is precondition of normal function of liver and kidney and healthy body. On the contrary, deficiency of blood and essence will result in light-headedness, sore aching low back and knees, deafness, Tinnitus, premature graying, premature aging, sexual dysfunction, and so on. In recent years, Liu Wei Di Huang Wan, a famous rehmannia-based Chinese patent medicine, has been found with promising effect on combating age-related diseases and anti-aging.