How does the presence of melanin in the skin affect the production of vitamin D?

Melanin in the skin acts as a natural sunscreen, which can reduce the skin's ability to produce vitamin D when exposed to sunlight. This is because melanin absorbs and blocks some of the UVB rays needed for vitamin D synthesis. As a result, individuals with darker skin tones may require more sun exposure to produce an adequate amount of vitamin D compared to those with lighter skin tones.