More Vitamin D updates from Your Dietetic Diva!

Vitamin D

Chief functions

Regulates absorption and use of calcium and phosphorus for development of bones and teeth
Aids in maintenance of healthy nervous and muscular systems by regulating blood calcium levels
Aids in calcium absorption from intestines and deposition of calcium in bones/teeth
Prevents excessive urinary loss of calcium and phosphorus
Stimulates maturation of cells and proper formation of skeleton
Helps with maintenance of bones in ears for hearing
Essential for mineral homeostasis

Possible benefits

Insulin—may aid in function of insulin, therefore possibly aiding in regulation of blood glucose
Cancer—might aid in prevention or treatment of cancer by altering growth of cells
Immunity—might assist function, thereby helping defend against infection
Dialysis patients—might improve zinc status
Deficiency symptoms

Osteomalacia (adults)
Rickets (children)
Inadequate mineralization of the bone, leading to malformed bones
Deafness
Toxicity symptoms

Irreversible renal or heart damage
Causes calcium deposits in soft tissues—heart and lungs
Fragile bones
Hypertension
Kidney stones, stones in arteries, and excessive thirst
Mental and physical retardation
Constipation
Weight loss
Headaches
Loss of appetite
Irritability
Weakness
Nausea
Diarrhea
Dermatitis
Drowsiness
Stability

Stable to heat and oxidation
Destroyed by excess ultraviolet irradiation
Nutrient-nutrient reactions and absorption

Vitamin D is synthesized in the skin and also absorbed in the small intestine from foods containing vitamin D
For adequate absorption of vitamin D in the diet, at least 10% of calories must come from fat, because vitamin D is a fat-soluble vitamin
Conversion of active vitamin D takes place in the liver
Vitamin D is stored in the liver, skin, brain, bones, and other tissues
Cadmium can block the production of vitamin D in the skin
Sunblock with a SPF of 8 or higher prevents vitamin D synthesis
Clouds, smoke, smog, heavy clothing, window glass, and screens decrease vitamin D synthesis
Pantothenic acid (B5) is necessary for the synthesis of vitamin D in the skin
DRI
mcg
IU

Tolerable Upper Limits

0-1 year
5
200
25 mcg

1-50 years
5
200
50 mcg

51-70 years
10
400
50 mcg

71+ years
15
600
50 mcg

Pregnancy
5
200
50 mcg

Lactating
5
200
50 mcg


DRI=Dietary Reference Intakes
mcg=microgram
IU-international unit

Dietary sources

Fortified milk
Cheese
Cream
Butter and margarine
Oysters, salmon, and tuna
Fortified cereal
Liver
Cod-liver oil
Eggs

Groups at highest risk for deficiency

Dark-skinned children
Infants who are breastfed for a prolonged time with no supplementation
Children with inadequate intake of fortified vitamin D milk
Children on anticonvulsant therapy for epilepsy
Persons with intestinal malabsorption
Females who have had multiple pregnancies and have breastfed with little exposure to the sun
Women with a low calcium intake
Other facts

Vitamin D exists in two forms, D2 (ergocalciferol) and D3 (cholecalciferol)
D2 is the supplemental form of vitamin D
D3 is the naturally occurring form of vitamin D, found in foods and manufactured in the skin with exposure to sunlight
Light-skinned people require 10-15 minutes/day of sun exposure for complete vitamin synthesis
Dark-skinned people require 3 hours/day of sun exposure for complete vitamin synthesis
Persons with limited exposure to sunlight may require a vitamin D supplement
Toxicity can not occur from too much exposure to the sun
If an infant is breastfed and not exposed to sunlight, a daily supplement of 5-7.5 mcg or 200-300 IU is recommended
Fortified foods are the major dietary source of vitamin D
References
Sizer F, Whitney E. Nutrition Concepts and Controversies. 11th ed. Belmont, CA: Thomson & Wadsworth; 2008:219-259.

Somer E. The Essential Guide to Vitamins and Minerals. New York, NY: Harper Collins Publishers; 1992:1-65, 224-246, 287-293.

Schlenker E, Long S. Essentials of Nutrition and Diet Therapy. 9th ed. St Louis, MO: Mosby Elsevier; 2007:107-144.

US Dept of Agriculture, National Agricultural Library, Food and Nutrition Information Center. Dietary Reference Intakes: vitamins. Available at: http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=3&tax_subject=256&topic_id=1342&level3_id=5140. Accessed July 28, 2008.

Have a healthy and happy day!!