VITAMIN D

• Not just a vitamin; it is in face primarily considered a hormone.

• Skin cells can convert a cholesterol-like substance to the prohormone vitamin D, using sunlight

• Overall, sun exposure provides about 90% of our vitamin D needs

• Liver and kidney cells then convert the prohormone to its active hormone form

• The amount of sun exposure needed by individuals to produce vitamin D depends on their skin color, age, time of day, season, and location

• Experts recommend that people should expose their hands, face, and arms at least two to three times a week for 25% of the time it takes to turn ones skin pink (5-10 min) to make enough vitamin D

• Persons with dark skin would need additional exposure, about 3-5 times the amount just recommended

FUNCTIONS OF VITAMIN D

• Main function is to help regulate calcium and bone metabolism

• In concert with other hormones, especially parathyroid hormone, the vitamin D hormone closely regulates blood calcium to supply appropriate amounts of it to all cells

• The most obvious result of the vitamin D hormone action is increased calcium and phosphorous deposition in bones

• Without adequate calcium and phosphorus deposition during synthesis, bones weaken and bow under pressure (child with these symptoms-rickets)

• Osteomalacia (soft bones) is results from inefficient calcium absorption in the intestine or poor conservation of calcium by the kidneys

• This leads to fractures in the hip and other bones

VITAMIN D SOURCES AND NEEDS

• Few foods contain appreciable amounts of vitamin D

• Rich sources are fatty fish, fortified milk and yogurt, and some ready-to-eat breakfast cereals

UPPER LEVEL FOR VITAMIN D

• The upper level for vitamin D is 50 micrograms per day

• It’s based on the risk of overabsorption of calcium and eventual calcium deposits in the kidneys and other organs

Category: Biochemistry Notes