Vitamin D
What It Is: A fat-soluble vitamin created within the skin when exposed to sunlight; also present in cod liver oil, fortified milk and, in limited amounts, in butter and egg yolks
What It Does:
- Helps the body absorb and use calcium to strengthen bones and teeth
- Low levels have been associated with a higher risk of death; deficiencies may play a role in heart disease and several types of cancer
- Deficiencies have been linked to a number of other health conditions, including multiple sclerosis, Parkinson’s disease and depression
Usage Notes: Subclinical deficiencies are not uncommon; current RDA of 400 IU, thought by many scientists to be too low, is under official review; 5,000 IU believed to be more in line with actual need
