From the Guidelines
Vitamin D plays a crucial role in maintaining overall health, particularly in supporting calcium absorption for bone health, and its deficiency can lead to severe health issues such as rickets in children and osteomalacia in adults. The effect of Vitamin D on health outcomes is complex and varies depending on the population and setting 1. Severe and prolonged Vitamin D deficiency can cause bone mineralization diseases, while more moderate decreases in Vitamin D levels have been associated with various health outcomes, including fractures, falls, cancer, cardiovascular disease, death, functional limitations, diabetes, and depression.
Key Findings
- Important sources of Vitamin D include diet and endogenous synthesis triggered by UVB exposure 1.
- Inadequate dietary Vitamin D intake, decreased Vitamin D absorption, and limited UVB exposure can all decrease Vitamin D levels 1.
- The association between Vitamin D status and health outcomes is unclear, with studies suggesting a decreased risk for colorectal cancer with higher 25-(OH)D levels and either an inverse or a U-shaped relationship with mortality 1.
- Studies on risk for fractures, falls, and cardiovascular disease have been less consistent, with most often white populations showing an increased risk for fractures and cardiovascular disease, and institutionalized populations showing an increased risk for falls 1.
Recommendations
- The recommended daily intake for most adults is 600-800 IU (15-20 mcg), though people with deficiencies may need higher doses of 1,000-4,000 IU daily as prescribed by a healthcare provider.
- Vitamin D can be obtained through sunlight exposure, consuming fatty fish, fortified foods, and supplements (vitamin D3 being more effective than D2) 1.
- Blood tests measuring 25-hydroxyvitamin D levels can determine if supplementation is needed, with levels below 20 ng/mL indicating deficiency 1.
- While Vitamin D is generally safe, excessive intake (typically above 4,000 IU daily long-term) can cause hypercalcemia with symptoms like nausea, kidney problems, and weakness 1.
From the Research
Effects of Vitamin D on the Body
- Vitamin D plays a crucial role in regulating calcium and phosphate metabolism, maintaining a healthy mineralized skeleton, and promoting intestinal calcium and phosphate absorption, renal tubular calcium reabsorption, and calcium mobilization from bone 2.
- It is essential for normal development and maintenance of the skeleton, and hypovitaminosis D can adversely affect calcium metabolism, osteoblastic activity, matrix ossification, bone remodeling, and bone density 3.
- Vitamin D deficiency can lead to rickets in children and osteomalacia in adults, and is also associated with chronic musculoskeletal pain, muscle weakness, and an increased risk of falling 2, 4, 3.
Role of Vitamin D in Bone Health
- Vitamin D is positively associated with bone mineral density (BMD) and is essential for calcium absorption and bone mineralization 5.
- It may influence fracture risk via its mediating effects on muscle function and inflammation, and vitamin D supplementation can improve muscle strength and decrease the incidence of falls 5.
- Vitamin D deficiency can result in secondary hyperparathyroidism, increasing bone resorption, and compromising the architectural integrity of bone, increasing the risk for fracture 6.
Importance of Vitamin D Sufficiency
- Vitamin D sufficiency is extremely important to maximize bone health throughout life, and helps to prevent bone loss, but it cannot restore bone loss due to increased bone resorption 6.
- The Endocrine Society Guidelines recommend maintaining a circulating concentration of 25-hydroxyvitamin D of at least 30 ng/mL for maximum bone health, and adequate vitamin D can be obtained from the sun, foods, and supplements 2, 6.
- Screening for vitamin D deficiency is recommended in individuals at risk, such as patients with diseases affecting vitamin D metabolism and absorption, osteoporosis, and older adults with a history of falls or nontraumatic fracture 2.