Life Extension, Vitamin D3, 1000 IU 250 Caps
(LEF-00251)

Vitamin D is necessary for utilization of calcium and phosphorus and in many ways acts as a hormone. The two most important forms of vitamin D are cholecalciferol (D3), which is derived from our own cholesterol and ergocalciferol (D2), a plant analogue derived from the diet. The cholecalciferol supplied by the Life Extension Foundation is synthetic, but its form is identical to that which is derived from cholesterol and synthesized by sunlight on the skin. Cholecalciferol is essential for bone growth and maintenance of bone density.

A dietary deficiency of vitamin D inhibits the production of the protein that binds calcium in the intestines, so that calcium cannot be absorbed, even if there is adequate intake. Deficiencies of vitamin D are often found in the elderly and in women who have low intake of milk and receive inadequate exposure to sunlight. Vitamin D is potent in minute quantities, one microgram of cholecalciferol has 40 IU of vitamin D activity.

Large doses (1400-2000 IU/day) may cause hypercalcemia, a decrease in renal function, and nephrocalcinosis. Monthly blood tests to monitor serum calcium and parathyroid hormone levels should be done to protect against vitamin D3 toxicity. Underlying kidney disease precludes high-dose vitamin D3 supplementation. Although some research indicates that dosages up to 10,000 IU/day are safe, healthy people should stay below 2000 IU/day.