What Is Vitamin D?
Vitamin D is an essential nutrient that plays a role in the balance of calcium and bone health in our body. It is a prohormone, or precursor of a hormone, that is made in the skin after the exposure to ultraviolet radiation. Vitamin D is derived from foods such as fatty fishes or fortified products, such as milk and cereals. However, it is important to note that less than 10% of vitamin D comes from dietary sources in the absence of fortified foods or supplements.
Vitamin D is converted to a metabolically active form in the liver and kidneys, and is stored as calcidiol. It is recommended to have calcidiol concentrations between 30 to 40 ng/mL, and to have levels lower than 20 ng/mL is undesired. In the kidneys, the calcidiol is activated to become calcitriol which plays a role in regulating calcium and phosphorus levels in your body. Therefore vitamin D deficiency can be characterized by low calcium or phosphate levels.
Why Is Vitamin D Important?
Vitamin D is a necessary nutrient in your body because you must have it in order to absorb calcium and promote bone growth. If you have too little vitamin D, it can cause rickets in growing children and osteomalacia in older adolescents and adults. Rickets refers to the failure of mineralization of growing bone and cartilage. Osteomalacia (the softening of bones) refers to impaired mineralization which main be manifest as isolated or generalized muscle and bone pain.
What Can Cause Vitamin D Deficiency?
Vitamin D deficiency can occur as a result of decreased intake or absorption, reduced sun exposure, increased degradation of the liver, or decreased synthesis in the body. Associated symptoms of vitamin D deficiency include bone pain and tenderness, muscle weakness, fracture, and difficulty walking.
Vitamin D deficiency should especially be considered for the following specific populations:
- Older Adults: Vitamin D intake, production and storage declines with age
- The Obese: an inverse association exists between obesity and vitamin D due to the sequestration of vitamin D in fat. Low levels of vitamin D are found in individuals with larger amounts of belly fat or visceral obesity, therefore vitamin D requirements are thus higher in obese individuals
- Healthy Adults in the Winter: Changes in vitamin D are common in healthy, young adults and are most prominent at the end of winter.
- Immigrants to Cold Climates from Warm Climates: Vitamin D deficiency has been reported in dark-skinned immigrants from warm climates to cold climates in North America and Europe.
- Osteoporosis: Vitamin D deficiency is also common in postmenopausal women who are seeking advice or receiving therapy for osteoporosis.
- Children: Dietary vitamin D deficiency can also occur in children, and it is also a concern for lactating mothers and breast-fed infants
- Dark skinned: An increase in skin pigmentation is associated with less vitamin D production. A racial difference exists in the association of calcidiol levels and bone fracture risks.
- Hospitalized Patients: Inadequate vitamin D intake, winter season, and housebound status are independent predictors of vitamin D deficiency. The prevalence of vitamin D deficiency in hospitalized patients may also be dependent on the age of patients in hospital wards.
- Malabsorption: Conditions that impair fat absorption, such as irritable bowel disease (IBD) and celiac disease, are associated with inadequate vitamin D absorption from the gut for this process is chylomicron dependent. Chylomicrons are particles that transport dietary fats from the intestines to other places in the body.
- Medications: Certain antiretroviral drugs used to treat HIV, glucocorticoids, and antifungal agents can precipitate vitamin D deficiency
Therefore, make sure you are getting your daily dose of vitamin D everyday either through fortified foods, a dietary supplement, or by being outdoors in the lovely sunshine!
Consult your physician if you have questions or concerns about vitamin D deficiency.
M. Jensen Horan ASU (Pre-Med)
David Carfagno, D.O., C.A.Q.S.M.
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