That is the opinion of the people at GcMAF.eu, but it is not shared by all docs who prescribe GcMAF. My D3 levels normalized (both 25 and 1,25) after a month on GcMAF. My doc didn't recommend supplementing with D3 while on GcMAF due to the possible risk of D 1,25 going too high. Before GcMAF my 1,25 was too high.