Effect of Large Oral and Intravenous Doses of Vitamins D2 and D3 on Vitamin D in Milk

Abstract

Vitamins D2 and D3 were measured in milk after high performance liquid chromatography of unsaponifiable lipids first on a silica column and then on a reverse-phase column. Milk from cows kept indoors contained barely detectable vitamin (less than 2 IU/100ml) predominantly in the form of vitamin D3. When cows were given 5 or 10million IU vitamin D3, maximums were in milk 3 to 7 days after oral doses and up to 10 days after intravenous injections. Maximums ranged from 7 to 90 IU/100ml. Two cows were given a mixture of 1million IU vitamin D2 and 1million IU vitamin D3 orally, and of the vitamins were maximum 2 to 3 days after the dose in blood plasma and a day later in milk. Equal amounts of the two forms of the vitamins were in milk, but vitamin D3 in plasma was double vitamin D2. Different mechanisms control concentrations of vitamins D2 and D3 in blood and milk after large doses.