Vitamin D is one of the most debated topics in health: sunlight vs supplements, safe levels, deficiency risks, and whether it truly impacts conditions beyond bone health.

In this conversation with Professor Michael Holick, I explore:

• The difference between vitamin D from sunlight vs supplements

• Why 40–60 ng/ml (100–150 nmol/L) may be the true “optimal” range

• The role of vitamin D in bone health, pregnancy, immunity, and muscle • Why deficiency is linked to preeclampsia, diabetes, and autoimmune disorders

• The controversy around guidelines, testing, and “normal” ranges

• The evidence for and against megadosing in autoimmune conditions • How sunlight influences health beyond vitamin D (endorphins, nitric oxide, mood)

• What Professor Holick himself does daily - from supplementation to training for marathons at age 79

Whether you’re a coach or simply someone trying to make sense of vitamin D confusion, this episode will give you clarity from the world’s foremost expert.

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Sunlight vs Supplements: Vitamin D, Bone Health & Autoimmunity - with Professor Michael Holick