As you can see by the flowcharts I am not a medical professional and these charts are not complete. However, I have put these charts together from about 25 different medical abstracts I have read. It is meant as a way to understand how absorption is a complicated series of events. You need all the links working for the nutrition you take in to get to your cells where they are used to function correctly ie replicate and repair yourself.
As you can see Estriol is required to absorb B12, per the Utah University Physiology dept.
So if you have low estriol, which even men have in their bodies, then you will absorb less B12 required for DNA & Myelin Sheath synthesis.