The correct answer is...

Vitamin D, often called the "sunshine vitamin," is produced in the skin when exposed to sunlight, specifically UVB rays. Just 10-30 minutes of sun exposure, depending on factors like skin type and geographic location, can produce 100% of your daily vitamin D needs. For most people, 15 minutes of sun exposure a few times a week is enough to maintain adequate levels of vitamin D.

However, factors like sunscreen use, skin color, age, and geographic location can influence how much vitamin D your body produces from the sun, which is why many people also rely on diet or supplements.