What is the primary source of vitamin D?

• A. Fish oil
• B. Sunlight
• C. Milk
• D. Green vegetables

Answer: (B)

The primary source of vitamin D is sunlight. When the skin is exposed to ultraviolet B (UVB) rays from the sun, it synthesizes vitamin D through a biochemical process. This synthesis allows the body to maintain adequate levels of vitamin D, which is crucial for calcium absorption, bone health, and various other physiological functions.

While other options like fish oil, milk, and green vegetables can provide significant amounts of vitamin D, they are considered secondary sources. Fish oil is particularly rich in vitamin D, but it is not the body's primary means of obtaining this vital nutrient. Fortified milk also contributes to vitamin D intake, but again, it supplements rather than serves as the primary source. Green vegetables generally contain very little vitamin D, making them the least relevant option for this nutrient. Thus, sunlight's role in the synthesis of vitamin D highlights its importance as the primary source.