An essential amino acid (one the human body cannot synthesise from other compounds) involved in collagen synthesis and iron absorption. While L-Lysine is not itself a primary structural component of hair, dietary lysine status interacts with iron metabolism, which is required for hair follicle cycling.
The role of L-Lysine in hair-related nutrition has been reviewed in Almohanna et al. (2019) in Dermatology and Therapy and Guo and Katta (2017) in Dermatology Practical & Conceptual. Published clinical investigations of L-Lysine specifically for hair have used 1,000–1,500 mg daily, paired with iron supplementation in women with chronic telogen effluvium and low ferritin status.
The 450 mg daily dose in HR01.1 is below those trial levels. This is a deliberate formulation decision. A four-capsule daily dose carries a finite mass of actives; we have prioritised that capsule load toward the actives with the most direct evidence in hair-specific clinical research, Pumpkin Seed Oil, Saw Palmetto, Tocotrienol, Ashwagandha, and the regulated minerals, and dosed those at the levels investigated in the literature. L-Lysine is included to support the formulation's amino acid profile alongside L-Cystine, not as a standalone replacement for the iron-paired protocols described in the literature. Customers with diagnosed iron-related telogen effluvium should consult a healthcare professional, who can advise on iron supplementation and L-Lysine dosing appropriate to their ferritin status.