The red loin and white loin correspond to the kidneys and testicles of sheep, respectively. Red waist and white waist are the common names for both of them (kidneys and testicles of sheep) when eating lamb kebabs. The white waist is the outer kidney, which in Chinese medicine is Yang, and therefore is the reason why the white waist of sheep has the medicinal and nutritional value of tonifying the kidneys and aphrodisiacs. The red loin is the inner kidney, which has some medicinal and therapeutic value, mainly for kidney deficiency and strain, and is also recorded in ancient Chinese medical texts as being warm and sweet in nature, tonifying kidney energy and benefiting the essence. The two are the same in that they both nourish the kidneys and can be used as food therapy and medicine, and both are gourmet food. The difference is that the former tonifies kidney yin while the latter strengthens kidney yang.