Strong evidenceGeneral health

Vitamin D3

Essential for bone health, muscle function, and immunity. Supplementation is clearly beneficial for people who are deficient — a very common condition worldwide.

What the science says

Correcting deficiency and bone health Strong evidence
Vitamin D deficiency impairs bone mineralization (osteomalacia, rickets), and supplementation corrects deficiency effectively. Together with calcium, it reduces fracture risk in older adults with low levels.
Immune support Moderate evidence
A meta-analysis of randomized trials suggests a modest reduction in the risk of acute respiratory infections, with the greatest benefit in people with marked deficiency.
Preventing chronic disease in people with normal levels Limited evidence
Large trials (such as VITAL) showed no reduction in cardiovascular events or cancer with supplementation in people who are not deficient.

Dosage & safety

Studied dose1,000–2,000 IU/day is common for maintenance; deficiency requires higher doses under medical supervision with blood testing (25-OH-vitamin D).

SafetySafe at usual doses. Very high doses over long periods can cause hypercalcemia. It is fat-soluble: taking it with a meal improves absorption.

Scientific references

Vitamin D deficiency
Holick MF — New England Journal of Medicine, 2007
Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data
Martineau AR et al. — BMJ, 2017
Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL)
Manson JE et al. — New England Journal of Medicine, 2019

Where to buy

California Gold Nutrition, Vitamin D3, 125 mcg (5,000 IU), 90 Fish Gelatin Softgels

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Related in General health

Omega-3 (EPA/DHA) Moderate evidence
Vitamin B12 Strong evidence
Multivitamin Limited evidence
Iron Strong evidence
Iodine Moderate evidence
NAC (N-Acetylcysteine) Moderate evidence