Vitamin D Deficiency

Vitamin D deficiency occurs when the body lacks sufficient vitamin D, a fat-soluble nutrient essential for calcium homeostasis, bone metabolism, and overall health. Without adequate vitamin D, bones become thin, brittle, bent, or bowed—causing nutritional rickets in children and osteomalacia in adults.

Common symptoms include fatigue, poor sleep, bone pain or achiness, depression, hair loss, muscle weakness, loss of appetite, frequent illness, and pale skin. Many individuals remain asymptomatic until complications develop. Classic manifestations include symmetric low back pain, proximal muscle weakness, and throbbing bone pain when pressing the sternum or tibia.

Key risk factors include limited sun exposure, darker skin (reduces vitamin D synthesis), obesity, age over 65, breastfeeding infants without supplements, inflammatory bowel disease, malabsorption disorders (celiac disease), and diets lacking vitamin D. Nearly 1 in 4 U.S. adults has low vitamin D levels.

The recommended daily intake is 600 IU for adults through age 70, increasing to 800 IU after age 70, and 400 IU for infants up to 12 months. Best sources include fatty fish (salmon, trout), fortified milk/yogurt, fortified cereals, plant milks, and UV-treated mushrooms. Moderate sunlight exposure also helps synthesis.

Treatment involves vitamin D3 supplements (more effective than D2), which raise levels more effectively. Severely low levels may require prescription-strength doses (50,000 IU weekly for eight weeks), followed by maintenance dosages of 800–1,000 IU daily. Untreated deficiency increases fracture, fall, osteoporosis, cardiovascular disease, and diabetes risks.