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D3
Vitamins
Vitamin D3 (Cholecalciferol)
Supports calcium absorption and bone mineralization; UL is 4,000 IU/day for adults.
What it is
Vitamin D is best established for bone health and correcting low vitamin D status; many other claimed benefits are more inconsistent.
How it works
Converted to active metabolites that regulate calcium/phosphate handling and gene transcription via vitamin D receptors.
What the evidence says
Strong for bone and deficiency correction; broader benefits are more variable across trials.
Safety Notes
- Adult UL is 4,000 IU/day; toxicity is typically from excessive supplementation.
- Use caution with: hypercalcemia, granulomatous disease (caution), severe kidney disease (caution).
- orlistat: Reduces absorption of fat-soluble vitamins.
- thiazide diuretics: May increase hypercalcemia risk when combined with vitamin D.
Timing With Other Supplements
- Calcium (Supplemental): Useful for bone, but combined high intakes can raise hypercalcemia/hypercalciuria risk.