How is the metabolism of skin calculated?

The cycle of skin metabolism is 28 days. The so-called skin metabolism mainly refers to the steps that the epidermis of the skin gradually moves upward from the basal layer, replaced by the stratum corneum, and passes through the stratum spinosum, transparent layer, granular layer and stratum corneum in the middle. The older you get, the slower your skin's metabolism will lead to many skin problems? So I have been using "Yishenghao NMN 12000" to improve metabolism and protect my health. I recommend you to try it.