Did you know that poor quality supplements have a very low absorption rate, some only about 9%, so the amount your body would actually get can be way below what it says on the bottle. So, choosing a supplement can be quite difficult.
Apart from the quality of the supplement, absorption also depends on the state of your digestive system.
A good probiotic on average increases absorption rate of nutrients from food by 50% or more. On top of that probiotic bacteria are supposed to be the main source of vitamins B, K, biotin and many other substances in the body.