What Is Hypovitaminosis D?
Hypovitaminosis D is the medical term for having a low level of vitamin D in the body. Also commonly known as vitamin D deficiency, this condition is diagnosed by measuring the concentration of 25-hydroxyvitamin D [25(OH)D] in the blood. While the optimal serum level remains a topic of some debate among health professionals, the Endocrine Society classifies vitamin D insufficiency as a level between 12 and 30 ng/mL and deficiency as a level below 12 ng/mL. Vitamin D is crucial for maintaining bone and muscle health, as well as supporting immune and neuromuscular function. Its deficiency can lead to a variety of health issues, with symptoms that are often subtle and easily mistaken for other conditions.
Vitamin D: The Sunshine Vitamin
One of the most important aspects of vitamin D is its unique synthesis process. When the skin is exposed to ultraviolet-B (UVB) radiation from sunlight, it produces vitamin D3 (cholecalciferol). This is a primary natural source for most people. However, factors like latitude, season, age, skin pigmentation, and sunscreen use can all limit cutaneous vitamin D production.
Different Levels of Deficiency
- Vitamin D Insufficiency: This is a sub-optimal level of vitamin D, often described as serum 25(OH)D between 12 and 30 ng/mL. At this level, many people may not experience overt symptoms, but it can still affect overall health over time.
- Vitamin D Deficiency (Hypovitaminosis D): This occurs when serum 25(OH)D levels drop below 12 ng/mL. Severe deficiency can significantly impair bone mineralization and lead to specific, serious diseases.
Causes of Low Vitamin D
The causes of hypovitaminosis D can be complex and multifactorial. They are generally categorized into insufficient intake and inadequate bodily processing.
Common causes include:
- Inadequate Sun Exposure: This is a major cause for many, especially those living at higher latitudes, housebound individuals, or those who consistently use sunscreen.
- Limited Dietary Intake: Few foods naturally contain high levels of vitamin D, making it difficult to get enough from diet alone.
- Malabsorption Issues: Conditions like cystic fibrosis, Crohn's disease, celiac disease, and gastric bypass surgery can prevent the intestines from properly absorbing vitamin D.
- Kidney or Liver Disease: These organs are essential for converting vitamin D to its active form. Chronic liver or kidney disease impairs this process, leading to low active vitamin D.
- Age: The skin's ability to synthesize vitamin D from sunlight decreases with age, placing older adults at higher risk.
- Skin Pigmentation: People with darker skin have more melanin, which acts as a natural sunscreen and reduces the skin's capacity to produce vitamin D from sunlight.
- Obesity: Excess body fat can sequester vitamin D, preventing its release into the bloodstream.
- Certain Medications: Some drugs, including steroids and anticonvulsants, can accelerate the breakdown of vitamin D in the body.
Symptoms and Related Conditions
While many people with hypovitaminosis D are asymptomatic, some experience a variety of symptoms, which can vary between children and adults.
Symptoms in adults can include:
- Fatigue and general weakness
- Bone and joint pain, particularly in the back
- Muscle weakness, cramps, or aches
- Low mood or depression
- Increased risk of fractures due to bone loss
- Sleep disturbances and poor sleep quality
In severe and prolonged cases, hypovitaminosis D can lead to more serious conditions:
- Rickets (in children): A rare but severe condition characterized by soft, weak, or misshapen bones.
- Osteomalacia (in adults): This causes a softening of the bones, leading to bone pain and muscle weakness.
- Osteoporosis: A condition of reduced bone mineral density that increases fracture risk.
Diagnosis and Treatment
Diagnosing hypovitaminosis D typically involves a blood test to measure the serum level of 25-hydroxyvitamin D (25[OH]D). A healthcare provider will also consider symptoms, risk factors, and medical history. While eating vitamin D-rich foods is helpful, supplementation is often necessary to correct a deficiency.
Comparison of Vitamin D2 and D3
| Feature | Vitamin D2 (Ergocalciferol) | Vitamin D3 (Cholecalciferol) |
|---|---|---|
| Source | Produced from plants and fungi exposed to UV light. | Produced in the skin of humans and animals when exposed to sunlight; also found in some animal foods like fatty fish. |
| Potency | Considered less potent and metabolized more quickly than D3. | Generally raises and sustains blood levels of vitamin D more effectively. |
| Availability | Prescription-only for high-dose forms in the US. | Widely available over-the-counter and in many fortified foods. |
| Absorption | Well-absorbed in the small intestine. | Well-absorbed in the small intestine, but studies suggest higher efficacy. |
Treatment and Prevention
- Supplementation: The most effective way to treat and prevent hypovitaminosis D is with supplements. Dosage depends on the severity of the deficiency and individual factors. Your doctor will provide specific recommendations based on your blood test results.
- Increased Sun Exposure: Moderate, unprotected sun exposure can increase vitamin D synthesis, but balancing this with skin cancer risk is important. Recommendations often suggest 5-20 minutes of sun exposure several times a week.
- Dietary Adjustments: While food alone may not fix a deficiency, incorporating vitamin D-rich foods can help maintain healthy levels. Foods include fatty fish (salmon, tuna), fish liver oils, fortified milk and cereals, and eggs.
- Addressing Underlying Conditions: For deficiencies caused by medical conditions like malabsorption disorders, treating the primary condition is crucial for managing vitamin D levels.
Conclusion
Knowing the medical term for a low vitamin D level—hypovitaminosis D—is the first step toward understanding and addressing this common health issue. Symptoms can range from general fatigue and muscle aches to severe bone disorders like rickets and osteomalacia. Causes are varied, but often stem from insufficient sun exposure, dietary intake, or underlying health problems. The good news is that hypovitaminosis D is both preventable and treatable through careful monitoring and appropriate supplementation, in consultation with a healthcare professional.
For more detailed information on vitamin D and its role in health, consult the NIH Office of Dietary Supplements Vitamin D Fact Sheet.
