Vitamin D Deficiency

Vitamin D deficiency, also known as hypovitaminosis D, happens when the level of vitamin D in the body is lower than normal. This often occurs when people don't get enough sunlight, especially UVB rays. When the body lacks vitamin D, it affects the keratinocytes, which are cells that help regulate the hair growth cycle. This can lead to slower hair growth and more hair shedding. With low vitamin D levels, the growth phase (anagen) of the hair cycle becomes shorter, while the resting phase (telogen) becomes longer.