Vitamin D has long provided significant support for healthy bone density. Over the past year, however, scientists have validated the critical role that vitamin D plays in regulating cell division and differentiation. These new findings link a deficiency of vitamin D to a host of common age-related maladies. As a result of this new research and startling evidence of widespread vitamin D deficiency, prominent nutritional scientists are calling on Americans to increase their vitamin D intake to 1000 IU per day and higher. The current RDA, however, is only 400 IU.

Vitamin D3 is synthesized in the body from sunlight. However, the winter season, weather conditions, and sunblocks inhibit the body's ability to produce optimal levels of vitamin D. All of these factors point to the value of taking a daily supplement to ensure optimal vitamin D intake.

For those who need to take very high doses of vitamin D3 and are under a physician's supervision, Life Extension now makes available a 5000 IU vitamin D3 supplement.

Individuals consuming more than 2,000 IU/day of vitamin D (from diet and supplements) should periodically obtain a serum 25-hydroxy vitamin D measurement. Toxicity is very unlikely in healthy individuals at a dose of less than 10,000 IU. Vitamin D supplementation is contraindicated in individuals with hypercalcemia (high blood calcium levels). People with kidney disease, certain medical conditions (such as hyperparathyroidism, lymphoma, sarcoidosis), and those who use cardiac glycosides (digoxin) or thiazide diurectics should consult a physician before using supplemental vitamin D.