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Symptoms, Causes, and Treatment of Vitamin D Deficiency
Vitamin D is a fat-soluble vitamin that can be synthesized in the human body through exposure to ultraviolet B (UVB) rays and can also be obtained through diet. It is a secosteroid hormone with receptors identified and functioning in over 30 tissues, including the small intestine, kidneys, endothelium, myocardium, skin, smooth muscle, lungs, brain, prostate, pancreatic β cells, colon, breast, monocytes, and macrophages. While the active form is 1,25(OH)2D, the form studied in biochemical tests is 25(OH)D, which has a longer half-life and can be present in the blood up to 1000 times more.
The most important effect of vitamin D is on calcium, phosphorus metabolism, and bone mineralization. However, in recent years, vitamin D deficiency and insufficiency have been found to be associated with various chronic diseases, including common cancers, cardiovascular diseases, metabolic syndrome, infectious and autoimmune diseases. The spectrum of these widespread diseases is particularly concerning because observational studies have shown that vitamin D deficiency is common in many northern regions of the world, including industrialized countries. Vitamin D deficiency can occur due to inadequate exposure to sunlight, inadequate intake through the diet, and absorption problems.
Vitamin D deficiency is now recognized as a global epidemic. In a recent study conducted in the United Kingdom, it was reported that more than 50% of the adult population had vitamin D insufficiency and 16% had severe vitamin D deficiency during the winter and spring seasons. In a study conducted in the Ankara region of Turkey by Uçar et al., a significantly high rate of vitamin D deficiency (51.8%) and vitamin D insufficiency (20.7%) was detected.
Adequate intake of vitamin D and maintaining optimal levels of vitamin D in the serum are not only important for bone, calcium, and phosphorus metabolism but also for overall health and well-being. Vitamin D deficiency and insufficiency as a global health problem are likely to pose a risk for a wide range of acute and chronic diseases.
Preventive And Therapeutic Health Policies To Prevent Vitamin D Deficiency Have Gained Importance Today.
To assess an individual's vitamin D level, the 25(OH)D level should be measured. Based on the findings of numerous studies conducted to identify vitamin D deficiency and insufficiency and determine the normal range of 25(OH)D levels, levels below 20 ng/mL indicate vitamin D deficiency, levels between 21 and 29 ng/mL indicate vitamin D insufficiency, levels above 30 ng/mL indicate sufficient levels (the preferred range is 40-60 ng/mL), and levels above 150 ng/mL indicate vitamin D intoxication.
Individuals at risk for low vitamin D levels include those with chronic kidney disease, liver failure, malabsorption syndromes (cystic fibrosis, inflammatory bowel disease, Crohn's disease, obesity surgery, radiation enteritis, hyperparathyroidism), medication use (antiepileptic drugs, glucocorticoids, AIDS treatment, antifungal, cholestyramine), pregnant and lactating women, older adults with a history of falls, older adults with a history of non-traumatic fractures, obese children and adults, and individuals with granulomatous diseases (sarcoidosis, tuberculosis, histoplasmosis), and certain lymphomas.
What Are The Symptoms Of Vitamin D Deficiency?
Vitamin D deficiency causes rickets in children and osteomalacia in adults, resulting in symptoms related to the musculoskeletal system such as bone pain, myalgia (muscle pain), and general weakness. It can also lead to insomnia, back pain, arthralgia (in wrists, ankles, shoulders, and fingers), proximal muscle weakness, headaches, and hair loss.
Vitamin D supports bone mineralization by maintaining physiological levels of parathyroid hormone and significantly reduces the risk of falls and fractures. Vitamin D deficiency is a defined risk factor for osteoporosis, falls, and fractures.
Approach to the Prevention and Treatment of Vitamin D Deficiency
Under normal conditions, 90-95% of the vitamin D present in the human body is synthesized in the skin through the effect of sunlight. Studies have shown that exposing the hands, face, and arms to the sun for 5-15 minutes, 2-3 times a week, is sufficient to meet the body's vitamin D needs. However, it should be noted that there are seasonal and geographical differences in vitamin D synthesis in the skin due to sunlight. In individuals living north or south of approximately 33° latitude, vitamin D synthesis is almost nonexistent during the winter months. Additionally, factors such as darker skin color, advanced age, and the use of topical sunscreens reduce this production in the skin. It is known that even SPF 30 sunscreens reduce vitamin D production in the skin by 95-98%. It has been reported that even SPF 8 sunscreens dramatically decrease blood levels of vitamin D. Evidence shows that the ability to produce vitamin D after UV exposure is one-fourth to one-fifth lower in the elderly compared to adults under 30 years old. The use of sunlight as a source of vitamin D is further complicated by factors such as cloudy weather, ozone density, air pollution, altitude, season, time of day, differences in skin color, and other similar factors that affect sunlight exposure.
To prevent vitamin D deficiency, the Institute of Medicine (IOM) recommends starting daily supplementation of 400 IU of vitamin D in infants during the first year, 600 IU/day for individuals aged 1-70, and 800 IU/day for those over 70 years old. These recommended doses by the IOM can increase 25-hydroxyvitamin D (25[OH]D) levels to 20 ng/mL, which is considered sufficient for bone health, but not for the target levels of 30 ng/mL recommended by the Endocrine Society. Therefore, to prevent vitamin D deficiency, the Endocrine Society suggests the following daily vitamin D supplementation in their practice guidelines: 400-1000 IU/day (up to 2000 IU is safe) for infants during the first year, 600-1000 IU/day (up to 4000 IU is safe) for children and adolescents aged 1-18, and 1500-2000 IU/day (up to 10,000 IU is safe) for adults aged 18 and above. However, higher doses may be required for obese individuals, those with malabsorption syndrome, and those using glucocorticoid and antiepileptic medications.
The Endocrine Society has recommended various treatment strategies for patients with vitamin D deficiency based on age and underlying medical conditions:
In infants (0-1 year) with vitamin D deficiency: 2000 IU/day or 50,000 IU/week of vitamin D2 or D3 for six weeks, followed by 400-1000 IU/day maintenance therapy to maintain 25(OH)D levels above 30 ng/mL.
In children (1-18 years) with vitamin D deficiency: 2000 IU/day or 50,000 IU/week of vitamin D2 or D3 for six weeks, followed by 600-1000 IU/day maintenance therapy to maintain 25(OH)D levels above 30 ng/mL.
In adults with vitamin D deficiency: 6000 IU/day or 50,000 IU/week of vitamin D2 or D3 for eight weeks, followed by 1500-2000 IU/day maintenance therapy to maintain 25(OH)D levels above 30 ng/mL.
Higher doses, at least 6000-10,000 IU/day of vitamin D, for initial treatment and 3000-6000 IU/day for maintenance therapy, are recommended for obese patients, those with malabsorption syndrome, and those using medications that affect vitamin D metabolism.
Vitamin D deficiency/insufficiency is widespread in Turkey and worldwide. It is evident that sunlight exposure is not sufficient for various reasons, emphasizing the importance of vitamin D-fortified foods or vitamin D supplementation in such cases.
Source:: Çağın Pandemisi: D Vitamini Eksikliği ve Yetersizliği. Fatma Fidan Berat Meryem Alkan Aliye Tosun. (Turk J Osteoporos 2014; 20: 71-74).
