FoundationFoundationsAnimal-derived
Vitamin D3
cholecalciferol · kolekalciferol
Correcting deficiency is clearly worthwhile for bone, muscle and immunity; “more is better” is not.
4/5· RCTs / large cohortsEstimated monthly cost: ≈ 3 €
Dose
1,000–2,000 IU (25–50 µg) daily; target 25(OH)D 30–50 ng/ml (75–125 nmol/l). Above 4,000 IU only for measured deficiency, with a doctor.
Timing
With a meal containing fat, any time of day.
⚠ Cautions
Talk to a doctor with hypercalcaemia, sarcoidosis or kidney-stone history. Don't stack with high-dose calcium without K2.
What it is
A fat-soluble prohormone the skin makes under UV-B. In Europe most people run low 25(OH)D from autumn to spring.
What the evidence shows
VITAL (25,871 people, 5 years, 2,000 IU/day) did not cut overall cancer or cardiovascular events in a replete population, but signalled lower cancer mortality and autoimmune disease. In deficient people, fall and fracture prevention is the strongest data.
Goals
Healthy yearsImmunityMuscle, strength
Related studies
Sources
Last reviewed: 6 September 2026
This site is educational and does not replace medical advice. Start any supplement or drug only after consulting a doctor or pharmacist.