Biotin: Also known as B7, biotin is a water-soluble B-vitamin and perhaps the most popular ingredient we think of when we think of hair and nail health. “Biotin is a B-complex vitamin that helps convert nutrients into energy,” says Fazio. “It supports keratin production, a key structural protein in hair, skin, and nails, and low levels are linked to brittle nails and hair thinning.” It’s important to note that a true biotin deficiency is rare (save for congenital conditions). However, Dr. Tosti explains that there is emerging evidence that use of antibiotics, antiepileptics, isotretinoin, gastrointestinal disease, smoking, pregnancy, and lactation can all cause suboptimal biotin levels. “Up to 40% of patients with hair loss have marginal biotin levels and may benefit from supplementation,” she adds.

Collagen: Collagen is a structural protein that supports skin elasticity, nail strength, and hair health—it’s essential for healthy skin. It naturally declines with age. “When collagen breaks down, we develop skin laxity, wrinkles and sagging,” says Dr. Stern. When it comes to collagen supplementation, Fazio recommends hydrolyzed collagen peptides—Types I and III. “Clinical benefits are typically seen with 2.5 to 10 grams per day, taken consistently for at least 8–12 weeks,” she says.

Vitamin C: With potent antioxidant properties, there’s lots of research to support the benefits topical vitamin C has on skin. “It can improve the appearance of dark spots, wrinkles, prevent skin aging, and even protect against some UV and environmental induced damage,” says Dr. Stern. For oral or ingestible benefits, vitamin C helps support collagen production. “Vitamin C aids collagen synthesis which helps follicle integrity,” explains Tosti. “It protects against oxidative stress through its antioxidant properties, and enhances the absorption of iron—an essential mineral for healthy hair growth.”

Niacin/Niacinamide: Another form of Vitamin B3, niacinamide can also support hair and scalp health. “It can improve blood circulation to the follicles, helping deliver oxygen and nutrients, while also offering antioxidant protection against oxidative stress that can impair follicle function,” says Dr. Tosti.

Zinc: An essential micronutrient and trace mineral involved in cell repair, growth, and regeneration,, zinc supports a healthy scalp environment, helps reduce inflammation, and contributes to clearer skin and stronger nails, explains Dr. Amin. “Zinc deficiency can also lead to hair loss or thinning and poor skin healing,” adds Fazio.