Endocrinologist Dr. Michael Holick, a leading vitamin D expert, tells The Epoch Times, "The body more effectively utilizes vitamin D when it's naturally synthesized from sunlight, compared to standard supplement doses." This difference is key to understanding vitamin D's health role and the complexities of supplementing a hormone. Unlike most nutrients, the hormonal nature of vitamin D means it has a broader systemic impact, influencing not just bone health but also immune function, cell growth, and inflammation control. This understanding is crucial in guiding medical approaches to its use, including the potential risks and benefits of supplementation.