Short answer: 25(OH)D is 1000 times weaker at activating the VDR than 1,25(OH)D, but 1000 times more abundant. This is why I advocate measuring both, and ultimately believe we need to create a calculated index of "biological vitamin D activity" from them.

This is a clip from a live Q&A session open to CMJ Masterpass members. In addition to this episode, you can access five other free samples using this link: https://chrismasterjohnphd.substack.com/p/questions-on-vitamin-d-fatty-liver In that batch of free episodes you will also find the answers to these questions:

• What's the difference between 25(OH)D and 1,25(OH)2D when it comes to the VDR?
• Reversing Fatty Liver: How Long Does It Take?
• What if my A1C says I'm diabetic but my CGM says I'm fine?
• Will reishi, turmeric, or curcumin tank my testosterone?
• The 3 Phases of Fasting: And How to Get Kicked Out of Each One

If you want to become a Masterpass member so you can participate in the next live Q&A, or so you can have access to the complete recording and transcript of each Q&A session, you can save 10% off the subscription price for as long as you remain a member by using this link to sign up: https://chrismasterjohnphd.substack.com/qanda Learn more about the Masterpass here: https://chrismasterjohnphd.substack.com/about This snippet is from the April 13, 2022 AMA. The full recording and transcript is reserved for Masterpass members. Here is a preview of what's included:

• How to balance vitamins E and K
• What prenatal vitamin do I recommend?
• Why does my smoothie make my hands cold?
• What type of choline to use?
• Is there an interaction between glycine and aspirin?
• What supplements can be used in the fasting state?
• How to manage protein intake within a small eating window on an intermittent fasting regimen?
• Looking at a study on calcium alpha-ketoglutarate supplementation.
• Should I take vitamin D for COVID if I easily get hypercalcemia from it?
• What to do about nausea in pregnancy?
• Brief questions on restless legs, exercise during fasting, puffy eyes, and health effects of spicy foods. Here's a link to the full AMA: https://chrismasterjohnphd.substack.com/p/ask-me-anything-april-13-2022

Access the show notes, transcript, and comments here.

Chris Masterjohn, PhD, is the Founder and Scientific Director of the mitochondria test Mitome.