The vitamin primarily involved in the absorption of calcium is vitamin D. This crucial vitamin facilitates the intestinal absorption of calcium, making it essential for maintaining strong and healthy bones. Without sufficient vitamin D, the body cannot efficiently absorb calcium from dietary sources, which can lead to bone density loss and conditions such as osteoporosis or rickets. Vitamin D also plays a role in overall immune function and muscle health. Therefore, both adequate sunlight exposure and the consumption of vitamin D-rich foods, such as fatty fish or fortified dairy products, are critical for calcium absorption and bone health.