Vitamin D contributes significantly to maintaining normal bone density. Vitamin D has been shown to play a role in regulating healthy cell proliferation and the immune system. Vitamin D3 can be synthesized through the skin when exposed to the sun's rays. Research results link vitamin D deficiency to common problems of aging. For most people, this 1,000 IU potency is insufficient to achieve optimal blood levels of the vitamin. For smaller individuals (and children) already getting 2,000-3,000 IU in their multinutrient formulas, this vitamin D strength may be adequate. It is recommended to take 1 capsule a day or follow a medical prescription. People consuming more than 2,000 IU/day of vitamin D (between diet and supplements) should have a serum 25-hydroxy-vitamin D measurement periodically. No more than 10,000 IU per day should be taken without prescription. Vitamin D supplements are not recommended for people who have high levels of calcium in their blood. Do not exceed the recommended dose. Do not buy the product if the outer seal is broken or damaged. If you are undergoing medical treatment, are pregnant or lactating, consult your doctor first. Keep out of the reach of children.