Risk Factors for Vitamin D Deficiency
- Not enough exposure to sunshine when vitamin D producing UV-B rays are abundant.
- Dark pigmented skin without enough sun exposure.
- Daily use of sunscreens or sunblock (SPF 15 blocks 95% of UV-B rays)
- Living in northern latitudes (above San Francisco on the west coast; Richmond, Virginia on the east coast). Remember - the farther away from the equator, the fewer UV-B rays.
- Living in foggy and/or smoggy areas (Fog and smog reduce UV-B rays.)
- Indoor jobs or nightshift work that require sleeping during the day.
- Aging skin thins as we age and produces less vitamin D.
- A strict vegetarian diet, if no additional supplementation is added.
- Diets high in processed foods.
- Low-fat diets - vitamin D is fat-soluble.
- Digestion problems, especially fat malabsorption syndrome.
- Inflammatory bowel disease (IBD), including ulcerative colitis and Crohns disease.
- Cushingï¿½s syndrome.
- Surgical removal of segments of the small intestine.
- Kidney and liver disease.
- Excessive caffeine or salt.
- Cigarette smoking.
- Chronic use of antacids.
- Medications ï¿½ many medications interfere with vitamin D absorption and synthesis.
- Living and working where tall buildings or trees block the sun.
- Living in nursing homes, prisons, or other confined situations.
Vitamin D is a group of fat-soluble prohormones, the two major forms of which are vitamin D2 (or ergocalciferol) and vitamin D3 (or cholecalciferol). The term vitamin D also refers to metabolites and other analogues of these substances. Vitamin D3 is produced in skin exposed to sunlight, specifically ultraviolet B radiation.
Vitamin D plays an important role in the maintenance of several organ systems.
Vitamin D regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestines, and by promoting re-absorption of calcium in the kidneys.
It promotes bone formation and mineralization and is essential in the development of an intact and strong skeleton.
It inhibits parathyroid hormone secretion from the parathyroid gland.
Vitamin D affects the immune system by promoting immunosuppression, phagocytosis, and anti-tumor activity.
Several forms of vitamin D have been described. The two major forms are vitamin D2 or ergocalciferol, and vitamin D3 or cholecalciferol.
Vitamin D1: molecular compound of ergocalciferol with lumisterol, 1:1
Vitamin D2: ergocalciferol or calciferol (made from ergosterol)
Vitamin D3: cholecalciferol (made from 7-dehydrocholesterol in the skin).
Vitamin D4: dihydrotachysterol
Vitamin D5: sitocalciferol (made from 7-dehydrositosterol)
Chemically, the various forms of vitamin D are secosteroids; i.e. broken-open steroids. The structural difference between vitamin D2 and vitamin D3 is in their side chains. The side chain of D2 contains a double bond between carbons 22 and 23, and a methyl group on carbon 24.
Vitamin D2 is derived from fungal and plant sources, and is not produced by the human body. Vitamin D3 is derived from animal sources and is made in the skin when 7-dehydrocholesterol reacts with UVB ultraviolet light at wavelengths between 270ï¿½290 nm. These wavelengths are present in sunlight at sea level when the sun is more than 45ï¿½ above the horizon, or when the UV index is greater than 3. Adequate amounts of vitamin D3 can be made in the skin only after ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen. With longer exposure to UVB rays, an equilibrium is achieved in the skin, and the vitamin simply degrades as fast as it is generated.
Very few foods are naturally rich in vitamin D, and most vitamin D intake is in the form of fortified products including milk, soy milk and cereal grains.
A blood calcidiol (25-hydroxy-vitamin D) level is the accepted way to determine vitamin D nutritional status. The optimal level of serum 25-hydroxyvitamin D remains a point for debate among medical scientists. One recent consensus concluded that for optimal prevention of osteoporotic fracture the blood calcidiol concentration should be higher than 30 ng/mL (US units), which is equal to 75 nmol/L (System International units).
Season, geographic latitude, time of day, cloud cover, smog, and sunscreen affect UV ray exposure and vitamin D synthesis in the skin, and it is important for individuals with limited sun exposure to include good sources of vitamin D in their diet.
In some countries, foods such as milk, yoghurt, margarine, oil spreads, breakfast cereal, pastries, and bread are fortified with vitamin D2 and/or vitamin D3, to minimize the risk of vitamin D deficiency. In the United States and Canada, for example, fortified milk typically provides 100 IU per glass, or one quarter of the estimated adequate intake for adults over the age of 50.
Fatty fish, such as salmon, are natural sources of vitamin D.
Fortified foods represent the major dietary sources of vitamin D, as very few foods naturally contain significant amounts of vitamin D. Natural sources of vitamin D include:
- Fish liver oils, such as cod liver oil, 1 Tbs. (15 mL) provides 1,360 IU
- Fatty fish, such as:
- Salmon, cooked, 3.5 oz provides 360 IU
- Mackerel, cooked, 3.5 oz, 345 IU
- Sardines, canned in oil, drained, 1.75 oz, 250 IU
- Tuna, canned in oil, 3 oz, 200 IU
- Eel, cooked, 3.5 oz, 200 IU
- One whole egg, 20 IU
- Shiitake mushrooms, one of a few natural sources of vegan and kosher vitamin D (in the form of ergosterol vitamin D2)
Vitamin D deficiency can result from: inadequate intake coupled with inadequate sunlight exposure, disorders that limit its absorption, conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders, or, rarely, by a number of hereditary disorders. Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in children and osteomalacia in adults, and possibly contributes to osteoporosis.
Vitamin D testing at Home
Why test Vitamin D? Vitamin D deficiency is very common, particularly in northern climates with little sunshine. Vitamin D has been found to be important in protecting the body from a wide range of diseases, including cardiovascular disease, stroke, osteoporosis, osteomalacia, cancer, autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, diabetes (types 1 and 2), and schizophrenia.
Until now, venipuncture blood serum has been the standard medium for testing Vitamin D. To overcome the issues of inconvenience to the patient and practitioner, our new kit was developed and refined for Vitamin D testing with blood spots. A few drops of blood from a quick and nearly painless nick of the finger, placed on a filter paper to dry are all that is needed. This can be done at home, meaning no more painful venous needle sticks or the inconvenience of driving to a blood collection center.
How does the new blood spot Vitamin D assay compare with conventional venipuncture serum testing? This test method by liquid chromatography/tandem mass spectrometry (LC-MS/MS) has shown conclusively that this new blood spot testing method is quantitatively equivalent to conventional serum Vitamin D testing by LC-MS/MS.
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