Q: Are vitamin D2 supplements potentially harmful as compared to D3?

Stasha Gominak, MD: "Absolutely. And because we've been giving them once a week, it's very difficult as a clinician to observe that. So once you know that D2 actually can bind to the receptor and block the D3 instead of actually being active, then you can actually interpret your patients saying things like, 'Oh, that's funny now you tell me that. I always wake up with a headache on Sunday morning. I always take my D on Saturday.'

"So giving D once a week is a ridiculous thing to do. It's not meant to be that way. And giving something that is not our natural hormone is crazy. I mean why would you give […] something that humans have never made, and no animal on the planet makes, to that animal, when we have D3 readily available? […]

"And there are plenty of articles that have explored the fact that D2 and D3 are different chemicals. We just have actually done very odd things with this particular hormone that we would never dream of doing in any other setting." —Stasha Gominak, MD @ 57:15 – 58:22 https://youtu.be/LbAXAvMEZX4&t=3435