A person can often maintain hair health by having a balanced diet.A 2019 review of studies found several that support a link between vitamin D deficiency and alopecia areata. This is a condition that can lead to severe hair loss.In many of the studies and surveys within the review, people with alopecia areata had lower levels of vitamin D in the blood.However, in a 2016 study on survey data from the Nurses' Health Study, which collected information from 55,929 women in the United States, researchers did not find a strong correlation between total vitamin D intake and hair loss. There is also little evidence to suggest that vitamin D can lead to hair regrowth.Therefore, more research is necessary to confirm the potential benefits of vitamin D for hair growth.Although vitamin D may not have direct links with hair growth, it may prevent the effects of low vitamin D levels.The Office of Dietary Supplements recommend that adults get 600 international units, or 15 micrograms (mcg), of vitamin D daily. However, many people fall below this requirement. In fact, statistics show that over 1 billion people worldwide have a vitamin D deficiency.