Bovine-derived ingredients, particularly bovine collagen, are used in supplements marketed for hair health. The scientific rationale primarily centers on collagen's role as a structural protein in the body. Collagen provides building blocks for hair, skin, and nails, and bovine collagen supplements are promoted to support hair strength and growth. Some limited scientific studies suggest that oral collagen peptides may improve hair thickness and strength by providing amino acids necessary for keratin production, the primary protein in hair. For example, a few small clinical trials and in vitro studies have shown improvements in hair parameters after collagen supplementation, although these studies often have small sample sizes and potential funding biases.

However, the overall quality and quantity of scientific evidence is limited. Most research is preliminary, and definitive, large-scale clinical trials are lacking. Furthermore, since collagen is broken down into amino acids during digestion, it is not certain that bovine collagen specifically confers unique benefits over other dietary protein sources for hair health. While anecdotal reports and some small studies are promising, the current consensus is that bovine collagen may modestly support hair health, but more robust research is needed for stronger recommendations.