Vitamin D Test
The Vitamin D Test is a serum or dried blood spot analysis that quantitates 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 metabolites. The metabolite 25-hydroxyvitamin D is the major circulating form of Vitamin D in the body and the best indicator of a patient’s true vitamin status. The major biologic function of Vitamin D is to maintain the normal blood levels of calcium and phosphorus involved in bone mineralization. Vitamin D also influences expression of more than 2,000 genes, including those responsible for regulation of cellular proliferation, cell differentiation, apoptosis, and angiogenesis. The immune-modulating effects of Vitamin D are profound, as evidenced by the many conditions that are associated with Vitamin D deficiency.
Vitamin D deficiency has been linked to increased risk for many common and serious diseases, including some common cancers, diabetes, cardiovascular disease, and osteoporosis. Deficiency is also prevalent in infants who are solely breastfed and who do not receive Vitamin D supplementation. Adults of all ages who have darker skin (increased skin melanin) or who always wear sun protection or limit their outdoor activities, such as homebound elderly persons, are also prone to Vitamin D deficits.
Studies suggest that exposure to sunlight enhances the production of Vitamin D in the skin and prevents many chronic diseases. Seasonal depression is also linked to low levels of Vitamin D, especially during the winter months when sunlight exposure is at a minimum. Vitamin D can also come from supplementation and diet, but there are very few foods (fatty fish, fish liver oil, and eggs) that naturally contain Vitamin D. Several foods claim to be fortified with Vitamin D, but the synthetic form isn’t as potent and doesn’t last as long in the body.
The Vitamin D Test can help to determine if sun exposure is adequate if dietary Vitamin D is sufficient and to assess the likelihood of malabsorption or liver disease.
RECOMMENDED FOR THE FOLLOWING DISORDERS AND DISEASES
- Cardiovascular disease including stroke & hypertension
- Cancer, especially prostate
- Low blood calcium levels
- Chronic bone/muscle/joint pain
- Periodontal disease
- Diabetes type I & II
- Inflammatory bowel diseases
- Rheumatoid arthritis
- Other autoimmune diseases (multiple sclerosis)
- Chronic fatigue
- Depression & mood disorders
- Cognitive impairment in seniors
- Birth defects
BIOLOGICAL FUNCTIONS OF VITAMIN D
The Vitamin D Receptor (VDR) is a nuclear hormone receptor that is activated by the active form of Vitamin D, calcitrol. VDR is expressed by most cells in every organ of the body. More than 2,000 genes are regulated by VDR activation.
The primary role of Vitamin D is to regulate blood levels of calcium and phosphorus by promoting absorption in the intestines and reabsorption in kidneys. Calcium and phosphorus levels are important for bone mineralization and growth as well as for the prevention of hypocalcemic tetany. Vitamin D is also an important immune regulator. It promotes phagocytosis, anti-tumor activity, and immunomodulary functions that play a role in autoimmune disease.
VITAMIN D DEFICIENCY BY POPULATION
The 2000-2004 NHANES provided the most recent data on the Vitamin D nutritional status of the U.S. population. Approximately 9 percent of the pediatric population, representing 7.6 million U.S. children and adolescents, were 25(OH)D deficient and 61 percent, representing 50.8 million U.S. children and adolescents, were 25(OH)D insufficient. Generally, younger people had higher Vitamin D levels than older people, males had higher levels than females, and non-Hispanic whites had higher levels than Mexican Americans, who in turn had higher levels than non-Hispanic blacks. Depending on the population group, 1-9 percent had levels <11 ng/mL , 8-36 percent had levels <20 ng/mL, and the majority (50-78 percent) had levels <30 ng/mL.
INDICATIONS FOR VITAMIN D TESTING
- Patients diagnosed with any of the Vitamin D related diseases (cancer, diabetes, hypertension, heart disease, multiple sclerosis, systemic lupus erythematosus, depression, Alzheimer’s, Parkinson’s, epilepsy, and other others)
- Patients with osteoporosis or rickets
- Persistent and nonspecific musculoskeletal pain
- Signs of depression or lack of energy
- Patients with gastrointestinal disease and/or who have had a cholecystectomy
- Elderly individuals
- Overweight individuals with a BMI >25
- Infants that are exclusively breastfed or children without a well-balanced diet
- Individuals taking Vitamin D supplementation greater than 50 mcg (2,000 IUs) per day
- Individuals that reside above 42 degrees north latitude (a line approximately between the northern border of California and Boston)
- Individuals with medium to dark complexions or who do not regularly receive 20 minutes of direct sunlight each day