No funding

Vitamin D deficiency is common world wide. 25 OH vitamin D level is the best indicator of vitamin D status. The determination of the appropriate dose of vitamin D supplement is essential for management of vitamin D deficiency as well as for designing vitamin D fortification programs. The increments in 25 OH vitamin D levels following various doses of vitamin D supplement for different genders, body weights, and starting 25 OH vitamin D level have not been well defined. The time course of depletion of repleted vitamin D stores is also not known.

The investigators plan to conduct a double blind randomized study on 9 cohorts to determine levels of 25 OH vitamin D following supplementation with different doses of vitamin D3 for 5 months and their withdrawal for 3 months.

Inclusion Criteria:

• Adults living in Riyadh area who consume no more than one serving of milk/day, do not take vitamin supplement, habitually have less than 10 hr of sun exposure per week, don't suffer from granulomatous conditions, liver disease, or kidney disease, and don't take anticonvulsants, barbiturates, or steroids.
• Individuals with with total 25 OH vitamin D level exceeding 100 nmol/l will be excluded from the study. Individuals with 25 OH vitamin D levels less than 20 nmol/L will be excluded from the placebo arm.