Biotin2500–5000 mcg · morning
Thickens the nail plate by improving how keratin knits together — about 25% thicker in trials.
Mixed · 3 of 4 studies positiveResearch →
skin hair nails · symptom
Brittle Nails
Nails that split, peel or break easily.
Might help
Real research, but thin or split. Worth knowing, not worth counting on.2Real research, but thin or split. Worth knowing, not worth counting on.
Collagen2.5–5 g · any
Supplies the building blocks nails are made from, and speeds how fast they grow.
Evidence · 1 study, positiveResearch →
No research yet
People take these for it. We haven’t found trials we would stand behind.4People take these for it. We haven’t found trials we would stand behind.
Manganese2–5 mg · any
Needed to build collagen and the ground substance the nail grows from.
No trials we can vouch forResearch →
Iron18–36 mg · empty_stomach
Nail cells need oxygen to grow, and low iron starves them of it.
No trials we can vouch forResearch →
Calcium1000 mg · split
No trials we can vouch forResearch →
Zinc15–30 mg · empty_stomach
Nail cells divide fast and need zinc to do it, and to build keratin.
No trials we can vouch forResearch →