Stacy Sims on Vitamin D3
11 episodes · 15 references · 2025–2026
- Sims considers vitamin D3 essential for bone, muscle, immunity, and brain health, recommending 2,000–10,000 IU depending on location and season - Emphasizes post-training timing to reduce hepcidin and optimize iron absorption - No evidence of personal consumption or specific brand preference; one caution about overdosing without blood testing
Benefits
- Critical for osteoporosis prevention, maintaining bone density, muscle function, and brain health - Improves recovery, muscle function, lipid profile, and iron absorption - Supports immune function and preservation of lean mass (bone and muscle)
Best Practices
- Baseline dose of 2,000–5,000 IU daily, adjusted by latitude, skin color, and sun exposure - Up to 8,000–10,000 IU in winter if blood levels are at the low end of normal - Take after training to reduce hepcidin and optimize iron absorption
Cautions
- Requires baseline blood test before supplementing to avoid overdosing - Blood levels can spike dangerously high in some individuals who overdo it - Monitoring is especially important when using higher winter doses of 8,000–10,000 IU
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“Vitamin D is so essential for so many other different functions from building bone, maintaining bone, maintaining muscle, muscle function, brain health.”
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“Vitamin D3 is really important for osteoporosis prevention, muscle, immunity, and brain health.”
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“If you're in the low end of normal, then we see that dosing up to 8,000 to 10,000 international units is helpful in the winter time.”
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“Closer you get to the equator, the less you need. So basic is 2 to 5,000.”
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“It does vary between two and 5,000 depending on where the woman is, color of skin, sun advantageous exposure or not.”
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“You need to start dosing on some vitamin D because winter's coming your way.”
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“It works with a timing effect where we want to have it after training to help reduce hepcidin so that we can have optimal iron.”
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