Scientists confirm that Vitamin D functions as a steroid hormone, not a typical dietary vitamin. It is synthesized in the skin via sunlight, then converted into its active hormonal form, which binds to vitamin D receptors present in nearly every cell type. Once activated, Vitamin D regulates gene expression, immune response, calcium absorption, muscle function, inflammation, and even brain activity. Its mechanism of action is more similar to hormones like testosterone than to nutrients obtained

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