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Vitamin D (Phytonadione)
Sunshine/Sunlight, sardines, button mushrooms, oysters, Cod-liver oil, Egg substitutes, Halibut-liver oil, Herring, Mackerel, Salmon, Tuna, Vitamin-D-fortified milk. (Breast-milk is low in vitamin D - exclusively breast-fed infants must be given a vitamin D supplement.)
What is known to be good for:
Essential for bone density & nervous system function. The main biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It promotes bone mineralization along with a number of other vitamins, minerals, and hormones. Without vitamin D, bones can become thin, brittle, soft, or misshapen. Vitamin D prevents rickets in children and osteomalacia in adults, skeletal diseases that result in defects that cause weak bones and muscles.
Other functions of Vitamin D:
- Formation of healthy teeth and cartilages.
Lack of Vitamin D can:
There has been increasing concern regarding possible vitamin D deficiency as a result of an increased use of sunscreens and UV-protective clothing. Symptoms include bone pain and tenderness and muscle weakness. In children, rickets may occur, in which bones lose calcium and become soft and curved. Without proper intake, there is an increased risk of osteoporosis, arthritis, and cancer.
Excess of Vitamin D can:
Habitual intake of excessive vitamin D is toxic. The symptoms include nausea, anorexia, polyuria, pruritis and calcification of soft tissues such as the kidney and heart. In infants, hypervitaminosis D can result in bossing of the skull, mental retardation and death. Mild vitamin D toxicity is manifested in elevated serum calcium levels. Skin cancer can develop if the source is from sun exposure (from 10 a.m. to 4 p.m.).
Do you know where you find Vitamin D in your body?
The provitamin D3 is found primarily in the skin of humans.
Storage and manipulation of suppliers of Vitamin D:
They are stable to heat, alkalis and oxidation.
Absorption, Storage and Excretion
Vitamin D occurs in 2 forms: Vitamin D2 (ergocalciferol), found in a small number of foods (plants), and vitamin D3 (cholecalciferol), which is synthesized by the skin when it is exposed to the sunlight. Both D2 and D3 are converted in an active form in the liver and kidneys. Kidneys convert vitamin D into its useful form (active form), which stimulates the intestine to increase the absorption of calcium and phosphorus. Intestinal absorption of vitamin D is analogous to that of vitamin A, in that, bile salts are required. (Please be aware that Dark-skinned people are protected from ultraviolet radiation by
melanin pigments so that less vitamin D3 is synthesized in them than in pale-skinned people.)
Sources: Nutrition for Life, The no-fad, no-nonsense approach to eating well and reaching your healthy weight, LisaHark, PhD, RD and Darwin Deen, MD
HEINZ HANDBOOK Of Nutrition, 9th EDITION, Edited by David L. Yeung, Ph.D. and Idamarie Laquatra, Ph.D., R.D.
Adapted by Editorial Department, May 2007
Last update, August 2008