Eggs top our list of hair-healthy foods because they contain a lot of protein and biotin, as well as other nutrients like zinc and selenium. Hair follicles are mostly made of protein, and not enough protein in the diet is known to cause hair loss.
Biotin is an essential nutrient for the production of a particular kind of protein called keratin. If you have a biotin deficiency, consuming more may help improve hair growth. Many supplements that purport to improve hair quality contain biotin for this reason.