Quote · The Diary Of A CEO with Steven Bartlett
Vitamin D Expert: The Supplement World Is Giving The WRONG Advice!
Where this was said
Why Vitamin D Isn't Actually A Vitamin
At 42:45 · chapter starts 40:36
This chapter delivers the episode's sharpest reframe. Dr. Gominak explains that vitamin D is not a dietary nutrient for humans in any meaningful biological sense — it is made on bald human skin exactly as it is on animal fur, where animals lick it off and absorb it orally. Humans can't lick their skin, so we absorb it directly through the skin. Eating salmon for vitamin D, she says, is like eating salmon to get a normal menstrual cycle from salmon oestrogen: it is that foreign. The classification error happened in the early twentieth century before the distinction between vitamins and hormones was well understood, and medicine doubled down on it in the 1980s when it decided vitamins were for 'lesser humans' and pushed vitamin D onto pharmacy shelves over the counter. She explains how this compares to oestrogen, testosterone, and thyroid — all managed via blood-level monitoring in tight bands because too much and too little are both harmful. She rejects the flat-dose approach used in virtually all vitamin D research (e.g. 4,000 IUs regardless of blood level) as fundamentally wrong for a hormone, which is exactly why that research keeps producing null or contradictory results. The Endocrine Society, she notes, acknowledged this flaw in 2004 but still chose to walk away from the question rather than fund better studies.
Vitamin D is synthesized on the skin like a hormone and acts on DNA receptors — calling it a vitamin was a historical mistake that shaped decades of bad medical guidance.
Vitamin D is synthesized on the skin exactly like a hormone, acts on DNA receptors inside cells, and should be managed like estrogen or testosterone with blood-level monitoring. Calling it a vitamin was a historical error that sent it to the over-the-counter shelf.
