All nutritional supplements undergo the same general process for digestion, with only times varying at each location depending on a wide variety of factors. In the stomach, acid will break down a substance into something the body can absorb. Some absorption can occur in the stomach lining, such as with alcohol, but the majority of what is consumed will be transferred to the small intestine.
In the small intestine, some substances will have already been prepared by the body for absorption. Others will need further break down by the gut microbiota, or will not be absorbed at all, such as some fibers. In the intestines, the body will absorb nutrients through villi. The absorbed nutrients will be taken by capillaries to the portal vein, that connects directly to the liver.
In the liver, everything will undergo something called first pass metabolism. Here enzymes will react with nutrients, making them better used by the body. They will then be passed into the circulation of the entire body, and transported to where they are most needed.
The kidneys will help filter out waste products generated by metabolism that the body no longer needs.