Your body manufactures vitamin D when exposed to sunlight. Dietary sources include foods that naturally contain or are fortified with vitamin D, and nutritional supplements. Vitamin D is essential for a healthy bones and muscles, supports immune system function, regulates cell growth and participates in a variety of cellular functions. Vitamin D deficiency in adults is often clinically silent, meaning it frequently causes no symptoms. A longstanding deficiency, however, might lead to symptoms primarily involving the bones and muscles. Similarly, observable signs of a vitamin D deficiency in adults usually involve the skeletal system.
From a medical perspective, a symptom is something an individual experiences in association with a disease or condition. Among adults who develop symptoms related to a vitamin D deficiency, these symptoms almost exclusively affect the musculoskeletal system -- the bones and muscles. These symptoms may include:
- Gradually developing bone pain and tenderness, especially of the low back and hips
- Weakness of the proximal muscles, meaning those of thighs, pelvis and shoulders
- Spasms of the muscles of the hands and/or feet
- Difficulty walking or a waddling walking pattern
- Lack of energy and fatigue
These symptoms arise primarily because a vitamin D deficiency disrupts normal calcium and phosphorus metabolism, which weakens the bones and interferes with normal muscle function.
Medically speaking, a sign is an observable consequence of a disease or condition. Signs associated with a vitamin D deficiency in adults develop when the condition is longstanding. Signs associated with vitamin D deficiency involve the bones, which become weak due to poor incorporation of calcium and phosphorus. Signs of a vitamin D deficiency in adults include:
- Decreased bone mineral density seen with dual-energy x-ray absorptiometry (DEXA) testing
- Areas of demineralized bone (Looser zones) on routine x-rays, most often involving the thigh and shin bones, pelvis, shoulder and ribs
- Nontraumatic bone fractures, especially of the spine, hip and ribs
- Spinal curvature leading to a forward leaning posture
- Reduced muscle reflexes
- Low blood levels of vitamin D
Causes and Risk Factors
Several factors can lead to a vitamin D deficiency in adults. Inadequate dietary intake and lack of sun exposure are primary causes, but other factors can contribute to or increase your risk for this nutritional deficiency, including:
- People with black or brown skin (due to decreased vitamin D production with sun exposure)
- Chronic kidney disease
- Obesity or prior gastric bypass surgery
- Chronic liver disease, Crohn disease, pancreatic disease and cystic fibrosis
- Advanced age (seniors)
- Reduced parathyroid gland function
The potential role of a reduced vitamin D level in a variety of diseases and conditions is an active area of research interest. Diseases and conditions that might be influenced by vitamin D levels include diabetes, heart disease, high blood pressure, cancer, autoimmune diseases and mental health disorders. Ongoing and future research may lead to further clarification of the potential preventative or treatment-related role of vitamin D for one or more of these conditions.
If you are concerned that you might have a vitamin D deficiency, talk with your doctor -- especially if you have risk factors for this vitamin deficiency.
Reviewed and revised by: Tina M. St. John, M.D.