Is Vitamin D an Enzyme? Unpacking the Truth
                                
                                
                                •
                                
                                
                        
                                    
                                    4 min read                                
                            
                                Vitamin D is often referred to as a vitamin, but it's a pro-hormone, not an enzyme. Approximately 1 billion people worldwide have vitamin D deficiency. Unlike enzymes, which act as catalysts, vitamin D functions as a signaling molecule throughout the body after being metabolized.