Second in a two-part series. Part I: "Vitamin Boost" is available at Vitamin Boost.
A few minutes of sun exposure on a summer day can generate huge quantities of vitamin D in a person's body. A cholesterol-like substance in the skin absorbs ultraviolet (UV) energy and creates vitamin D. Then, a cascade of chemical reactions turns vitamin D into a surprisingly versatile hormone—one that has long been recognized to help the body absorb calcium from the diet to build strong bones. Recent work, however, indicates that vitamin D also bolsters muscle strength, insulin action, immune health, and the body's natural defenses against cancer.
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