What is one of the primary functions of retinoids?

Retinoids, which are derivatives of vitamin A, play a critical role in regulating epithelial cell growth and differentiation. They are essential for normal growth and development, particularly in the skin and mucosal tissues. By influencing the expression of genes involved in these processes, retinoids help maintain healthy epithelial cells and support the overall integrity of the epithelial barrier. This regulation is crucial for functions such as wound healing and the proper functioning of the immune system.

The other options, while important for overall health and wellness, do not accurately represent the primary role of retinoids. Enhancing muscle recovery, improving cardiovascular health, and increasing bone density involve different mechanisms and nutrients, such as protein, omega-3 fatty acids, and vitamin D, respectively. Thus, the focus on epithelial cell regulation correctly identifies a foundational function of retinoids in human health.