Multivitamin blends are commonly used to support hair health and potentially address hair loss or thinning. Scientific evidence suggests that certain vitamins—particularly biotin (vitamin B7), vitamin D, vitamin E, and vitamin A—play roles in hair follicle function and growth. Deficiencies in these vitamins have been associated with hair thinning or loss in both observational studies and clinical reports. For example, biotin deficiency is known to cause hair loss, and supplementation can reverse this in deficient individuals. Vitamin D has also been linked to hair follicle cycling, with low levels sometimes observed in those with hair disorders like telogen effluvium or alopecia areata.

However, for individuals without demonstrated deficiencies, high-quality studies supporting the efficacy of multivitamin blends for preventing or treating hair loss are limited. Most randomized controlled trials have focused on specific populations or on individuals with diagnosed deficiencies rather than the general population. While some small studies and anecdotal evidence suggest modest improvements, the overall quality of evidence is moderate. Excessive intake of certain vitamins (like vitamin A) may actually worsen hair loss.

In summary, while there is a scientific basis for using vitamin blends to correct deficiencies that may contribute to hair loss, the evidence for benefit in those without deficiencies is less robust. Clinical guidelines generally recommend targeted supplementation only when a deficiency is identified.