Clay and earth in general, when clean and pure has an affinity for the improvement of the digestion.
Fired clay, such as would be found as the main structural component of an oven in ancient times was used by the Chinese as a remedy for bleeding due to deficiency cold, where the digestive fires are so weak that they fail to hold blood inside the vessels.
For most people, medicine this strong is not necessary and excessive use over a long period of time can lead to full fire however if there is major deficiency of the stomach and the spleen (meaning pancreas) such as might exist in cold type diabetes then this is useful. This refers to yellow clay however and white clay is likely to have other effects related to respiration, water metabolism and as stated, the skin which is ruled by the colour white and the metal element.
