From the Guidelines
Vitamin D increases calcium in the body through two primary mechanisms: enhancing intestinal absorption and interacting with parathyroid hormone to maintain calcium homeostasis between the blood and bones. These mechanisms are crucial for maintaining proper calcium levels in the body, which is essential for various bodily functions such as bone growth, muscle strength, and nerve transmission. In the intestines, vitamin D controls calcium absorption, and insufficient levels of vitamin D can lead to impaired dietary calcium absorption, resulting in the body using calcium from skeletal stores, which can weaken existing bones 1. Key aspects of vitamin D's role in calcium metabolism include:
- Enhancing intestinal absorption of calcium
- Interacting with parathyroid hormone to maintain calcium homeostasis
- Maintaining bone density and growth
- Preventing impaired dietary calcium absorption due to insufficient vitamin D levels. Given the importance of vitamin D in calcium metabolism, it is essential to ensure adequate vitamin D levels, either through diet, sun exposure, or supplementation, to maintain optimal bone health and prevent conditions such as osteoporosis and fractures 1.
From the FDA Drug Label
Health Claims DIETARY SUPPLEMENT Vitamin D3 50,000 IU is essential for absorption of calcium and necessary for healthy bones and a healthy immune system. Caution Adequate dietary calcium is necessary for response to vitamin D therapy.
The two ways vitamin D increases calcium are:
- Absorption: Vitamin D is essential for the absorption of calcium 2
- Utilization: Vitamin D requires adequate dietary calcium to be effective, implying it helps with calcium utilization 3
From the Research
Vitamin D and Calcium Homeostasis
Vitamin D plays a crucial role in maintaining calcium homeostasis in the body. Two ways vitamin D increases calcium are:
- Increasing the efficiency of intestinal absorption of dietary calcium 4, 5
- Reducing calcium losses in urine and mobilizing calcium stored in the skeleton 4
Mechanisms of Vitamin D
The molecular actions of vitamin D on calcium-regulating target tissues are mediated predominantly by transcription controlled by the vitamin D receptor 5. Vitamin D also has specific actions on the kidney and bone, highlighting its importance in maintaining calcium homeostasis 5.
Importance of Vitamin D
Vitamin D is essential for gastrointestinal calcium absorption, mineralization of osteoid tissue, and maintenance of serum ionized calcium level 6. Its deficiency can lead to various health problems, including rickets, osteomalacia, and osteoporosis 4, 7.