Human Nutrition 3(3+0)
Lesson 21 : Vitamin D


  • Maintenance of proper calcium levels in the blood
    • Vitamin D, in the form of Calcitriol, the most metabolically active form of vitamin D, works with parathyroid hormone (PTH) to maintain proper levels of calcium in the blood.
    • When calcium levels in the blood are low, the parathyroid gland is stimulated to produce PTH and this hormone then stimulates the conversion of inactive forms of vitamin D to calcitriol.

  • Maintenance of proper phosphorus levels in the blood
    When vitamin D levels are low, the parathyroid gland becomes overactive (hyperparathyroidism), PTH levels rise, and blood levels of phosphorus drop. Without adequate phosphorus, bone cannot be properly mineralized, which contributes to the defects seen in osteomalacia. In addition, the new bone cells being laid down by the osteoblasts (the cells that create new bone) absorb more water and swell, causing the bone pain associated with osteomalacia.

  • Maintenance of normal cellular growth and function
    Vitamin D also plays a role in regulating cellular growth and function in our brain cells. Vitamin D has been found to have a significant effect on brain cell (neuronal) growth and division in mice.

  • Maintenance of healthy immune function and prevention of excessive inflammation
    Vitamin D helps to regulate immune system activity, preventing an excessive or prolonged inflammatory response. The immune cells, specifically active T-cells, have receptors for vitamin D. Autoimmune diseases-including multiple sclerosis, diabetes, rheumatoid arthritis, irritable bowel diseases (such as Crohn's and ulcerative colitis)all have a T-cell component of inflammation.
Last modified: Thursday, 9 February 2012, 11:34 AM