Final answer:
Vitamin D is crucial for regulating calcium and phosphorus levels in the blood, which are vital for bone health and integrity. If ample sunlight exposure is provided, vitamin D is not considered an essential nutrient because the body can synthesize it.
Step-by-step explanation:
Vitamin D is not an essential nutrient if sufficient sunlight is met. We need vitamin D to help regulate blood calcium and phosphorus to maintain bone integrity. Vitamin D has a multifunctional role in the body, including support for the nervous system, aiding in blood clotting with Vitamin K, and combating bacterial, viral, and fungal infections through the maintenance of general immunity. The synthesis of vitamin D facilitates calcium absorption from the digestive system, calcium reabsorption from the kidneys, and the rebuilding of bone tissue. Additionally, vitamin D receptors found in most cells indicate its systemic importance, prompting some scientists to refer to it as a hormo