Which vitamin is essential for intestinal calcium absorption?

• A. Vitamin A
• B. Vitamin B12
• C. Vitamin D
• D. Vitamin K

Answer: (C)

Vitamin D enables intestinal calcium absorption. When activated in the body to calcitriol, it acts on the lining of the gut to raise the amount of calcium that gets absorbed from food. It does this by upregulating calcium-handling proteins in intestinal cells, such as calbindin, and by enhancing the activity of calcium transport pathways. This helps keep blood calcium levels adequate for bone mineralization and other bodily functions. If vitamin D is deficient, even with calcium in the diet, absorption is impaired, which can contribute to weaker bones. The other vitamins listed don’t play the primary role in promoting intestinal calcium uptake.