What does it do?
Vitamin D increases intestinal absorption of calcium, which helps keep bones strong. It also has a protective effect against cancers, especially prostate cancer. It is also helpful with immunological diseases such as Multiple Sclerosis which is often associated with low levels of Vitamin D.
Vitamin D is the only one of 13 vitamins that can be made by the human body. Sunlight acts on a form of cholesterol in the skin resulting in Vitamin D3 that goes to the liver and kidneys to become an active vitamin D calcitrol.
What type of Vitamin D is best?
Either Vitamin D2 or D3 are good, as both must go to the liver to be activated. So either type is ok, and the proper dosage would be 1000IU of either or a combo of 500 IU. The recommended dosage for the 51-70 year old age range is 400 IU, however an individual over 71 years of age should increase their dosage to 600 IU. Dietary Vitamin D found in fish oil is better. If you are deficient, only supplementation will help you, as you would need 24 oz of fish to get 400 IU of Vitamin D.
Can I take too much?
The answer is yes. Do not take more than 5000 IU per day. The recommended dosage is 1000 IU.