Vitamins For Hair Growth: There are several hair care products in the market promising quick results but experts say real hair health begins from within. According to the National Institutes of Health (NIH) the most common reasons behind why people tend to experience hair thinning, breakage and slow growth are highly attributed to a deficiency of certain nutrients. The good news is that the US health agency highlights that adding the following vitamins plays a key role in supporting hair follicles, improving scalp health and promoting stronger, thicker hair over time.