Hair Growth Supplements: What Actually Works (And What's a Waste of Money)

Separating Marketing from Medicine

The global hair supplement market is worth billions of dollars, and the marketing claims are often far ahead of the science. As a registered dietitian, I spend a significant amount of time helping women navigate this landscape — figuring out which supplements have genuine clinical support and which are expensive placebos.

The most important principle to understand is this: supplements are most effective when they address a genuine deficiency or insufficiency. If your hair loss is driven by low ferritin, iron supplementation can be transformative. If your ferritin is already optimal, iron supplementation will do nothing for your hair. This sounds obvious, but it's frequently overlooked in the supplement marketing world.

Ingredients With Genuine Evidence

Iron (as ferritin optimization): The strongest evidence for any nutritional intervention in hair loss. Correcting ferritin deficiency has been shown to reduce shedding and support regrowth in multiple studies.

Zinc: Zinc deficiency is associated with hair loss, and supplementation has been shown to improve hair loss in zinc-deficient individuals. The evidence is less clear in those with normal zinc levels.

Vitamin D: Vitamin D receptors are present in hair follicles, and deficiency has been associated with alopecia areata and telogen effluvium. Correcting deficiency is warranted, but supraphysiological supplementation in those with normal levels is not supported.

Marine-based collagen peptides: Some evidence suggests that marine collagen peptides may support hair shaft strength and reduce breakage, though the evidence for stimulating new growth is less robust.

Ingredients With Weak or No Evidence

Biotin: Despite being the most marketed hair supplement ingredient, biotin supplementation has no clinical evidence for improving hair growth in women with normal biotin levels. Save your money unless you have a documented deficiency.

Keratin supplements: Keratin is the structural protein of hair, but oral keratin supplements are largely broken down into amino acids during digestion. The evidence for keratin supplementation specifically improving hair growth is weak.