The Energy Balance Podcast Vitamin D Still Low Despite Supplementing? RED FLAG
Feb 16, 2026
They explore why blood vitamin D can stay low despite taking supplements and how the body converts it. The role of parathyroid hormone in calcium balance and bone risk is discussed. Nutrients that regulate PTH like calcium, magnesium and vitamin K2 are highlighted. Practical food sources, daily intake targets, lab tests to check PTH, and supplement options are covered.
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Parathyroid Hormone Forces Vitamin D Conversion
- Elevated parathyroid hormone (PTH) drives conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D and frees calcium from bone.
- Feldman links this PTH-triggered conversion to the body's response when calcium is low.
Hidden PTH Elevation Threatens Bone Strength
- High PTH causes bone calcium release, increasing fracture risk and osteopenia/osteoporosis.
- Jay Feldman warns that chronic PTH-driven calcium leaching literally breaks down bone composition over time.
Vitamin D Conversion Impacts Immune Defense
- Immune cells (macrophages) need 25-hydroxyvitamin D to make 1,25-dihydroxyvitamin D locally during infection.
- If kidneys and PTH consume circulating 25-hydroxyvitamin D, macrophages lack substrate to mount defenses.