Meet the doctor behind the vitamin D testing juggernaut

Dr Michael Holick’s enthusiasm for vitamin D can be fairly described as extreme.

The Boston University endocrinologist, who perhaps more than anyone else is responsible for creating a billion-dollar vitamin D sales and testing juggernaut, elevates his own levels of the stuff with supplements and fortified milk. When he bikes outdoors, he won’t put sunscreen on his limbs.

He has written book-length odes to vitamin D, and has warned in multiple scholarly articles about a