Higher Level of Vitamin D Necessary

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol.

Vitamin D is essential for promoting calcium absorption in the gut and maintaining adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclast. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other roles in human health, including modulation of neuromuscular and immune function and reduction of inflammation. Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D. Many laboratory-cultured human cells have vitamin D receptors and some convert 25(OH)D to 1,25(OH)2D. It remains to be determined whether cells with vitamin D receptors in the intact human carry out this conversion.

Vitamin D deficiency is now recognized as a worldwide problem. Poor dietary intake and lack of moderate sun exposure have resulted in widespread vitamin D deficiencies throughout much of the world. Additionally, very few foods contain vitamin D naturally, and foods fortified with vitamin D are typically inadequate to satisfy adult vitamin D requirements.

Numerous recent scientific research papers and our own in-house clinical research suggests that higher vitamin D levels - much higher than previously thought - are needed for most people to attain optimal blood levels of vitamin D. USANA's recent change to the Mega AO formulation is a reflection of this recent research and an ongoing commitment to provide USANA customers with the most effective, scientifically valid, and up-to-date products possible.