Along with calcium, vitamin D is the nutrient that most people recognize as important for bone health (Holick 2007). But, even today, few people understand the powerful and complex ways that vitamin D acts to promote not only bone health, but the way the entire body handles calcium, both in healthy and in undesirable ways (Holick 2007). Vitamin D triggers absorption of calcium from the intestine and deposition of calcium in bone — and also removal of calcium from blood vessel walls. Conversely, insufficient vitamin D intake results in depletion of calcium from bones — and increased deposition of calcium in arterial walls, contributing to atherosclerosis (Celik 2010, Tremollieres 2010).
Vitamin D deficiency (or insufficiency) also causes muscle weakness and neurological deficits, increasing the risk of falling, which of course makes fractures still more likely (Bischoff-Ferrari 2009, Pfeifer 2009, Janssen 2010). The dose of vitamin D required to achieve the neuroprotective and other non-bone related effects are substantially higher than those required simply to achieve good calcium absorption (Bischoff-Ferrari 2007).
A validated measure of total body vitamin D status in blood is serum 25-hydroxy vitamin D (also known as 25(OH)D, or calcidiol). Note that this measure is reported in two different units, nmol/L and ng/dL, so it is vital to check which set of units a lab is using. Vitamin D deficiency is defined as a serum 25(OH)D level of less than 50 nmol/L, or less than 20 ng/dL. Experts recommend a higher level of 75 nmol/L, or 30 ng/dL (Bischoff-Ferrari 2007, 2009). To obtain the many health benefits of Vitamin D, current scientific evidence suggests a minimum target threshold for optimal health is over 50 ng/ mL or 125 nmol/L (Aloia 2008, Dawson-Hughes 2005, Heaney 2008).
The optimal dose of vitamin D has been hotly debated in recent years. More than 13,000 Life Extension® members have had their vitamin D level checked. The results from these tests provides important information about achieved vitamin D blood levels in a large group of dedicated, health-focused individuals. Vitamin D dosage as high as 5000 to 8000 IU per day may be required to achieve a minimum target level for optimal health in aging individuals (Life Extension Magazine January 2010).
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These supplements should be taken in conjunction with a healthy diet and regular exercise program. Results may vary.