Vitamin D comes in several forms, the two most popular are D2 (ergocalciferol) and D3 (cholecalciferol). D2 is produced by plants, fungus and invertebrates as a response to sunlight. D3 is created by human and animal skin in response to sunlight, specifically UVB rays. Vitamin D3's function in humans and animals mainly is to maintain proper levels of phosphorus and calcium in the blood. Recent studies show that vitamin D3 aids in prevention of various autoimmune diseases, hypertension and osteoporosis. Aside from sunlight, most people get vitamin D3 from natural foods or supplements.
Who Needs Vitamin D?
As humans spent more time indoors, and immigrated away from the equator to more northern latitudes with less sunlight, the increased need for supplemental vitamin D3 began. The vitamin is found as an additive in most commercial milks, fish, eggs, green vegetables and cod liver oil. People that are elderly or obese, breastfed infants, as well as those with limited exposure to the sun, are advised to increase their consumption of vitamin D3.
How Much Do You Need?
The National Osteoporosis Foundation and The National Academy of Sciences' Institute of Medicine differ in the upper limits of vitamin D intake for normal, healthy people. The National Osteoporosis Foundation states that adults (no lowest age specified) under age 50 need 400 to 800iu of vitamin D and adults over 50 need 800 to 1,000iu daily.
The National Academy of Sciences' Institute of Medicine finds that infants to twelve months should take 1,000iu per day; 2,000iu is recommended for children and adults; and adults aged 50 and over should take 1,000iu. Specific dosage should be recommended only by a personal physician or health care professional since an individual's medical condition, daily exposure to sunlight and other health complications could vary the recommended dosage.
Sun, Food and Supplements
A 2000 study by the Journal of the American Medical Association found that proper servings of fruits, vegetables and alkaline forming foods taken throughout the day may lead to better absorption than supplements. Supplements do not absorb well in an acidic enviroment (foods such as soft drinks, coffee, meat and eggs). If one is taking supplements such as Citracal, then it is recommended to take it on an empty stomach (preferably bedtime). Certain medications block absorption of vitamin D3 such as barbiturates, many cholesterol-lowering drugs and cortisone. A doctor should be consulted how to balance taking both vitamin D3 and one of these. Studies cited in the May 1999 American Journal of Clinical Nutrition found that full body exposure to sunlight for less than an hour could provide more than the recommended daily allowance. Generally it is recommend not to expose oneself to the sun without sunscreen for extended periods of time, and particularly during the hottest times of the day (generally 11:00 a.m. to 2:00 p.m.).
"The Best Time" Is Relative
In summation, if one spends some time outside, and eats meals at various times throughout the day, including items such as fortified milk, fish, eggs, green vegetables and cod liver oil, they should be getting enough vitamin D3 absorbed properly. It is always best to confer with a doctor to determine your exact needs.