Vitamin D Benefits: Bone Health

The most critical way that vitamin D benefits the body is by ensuring proper bone health and preventing rickets, a disease that results from poor calcium absorption. An important thing to realize about bones is that they are not static, solid objects in your body-- they actually are constantly rebuilding and remodeling themselves. Adequate calcium, and therefore sufficient vitamin D, is critical for this process. As a result, vitamin D supplements have extensively benefited elderly patients who do not get out in the sun much and are prone to falls. This article covers the history, science, and clinical benefits of vitamin D for bone health.

Preventing Rickets: first among vitamin D benefits
Rickets first began showing up during the Industrial Revolution, when people started living in cities with dense smog cover (1). Children who played only in alleys, without direct sunlight, came down with symptoms of poor calcium absorption like deformed bones, muscle spasms, and seizures. In the early 19th century, a Polish physician realized that children from rural areas did not have this problem, and the connection to sunlight was made. A century of clever biochemistry later and most modern countries are fortifying milk with vitamin D to prevent this problem.

As we mentioned earlier , vitamin D orchestrates a broad response in the intestine to promote the uptake of the essential building blocks of bone: calcium and phosphate. This response includes ion channels, transport proteins and even feedback systems to avoid taking up too much calcium (2). Calcium uptake starts to maximize when serum concentrations of 25(OH)-D (the form in which vitamin D is stored in your body) hit 75-80 nmol/liter. These concentrations are actually quite difficult to achieve through supplements alone (3). Fortunately, rickets can largely be prevented by considerably lower levels of vitamin D (4).

Your Hollow Bones: Not as solid as you think
In adults, the rickets phenomenon is somewhat less severe, and is known as osteomalacia. Symptoms are similar: bone fragility, muscle weakness, and body pains. At first glance, one may be surprised that fully grown adult bones could require high levels of calcium. But if you have ever been given a bone scan to locate a stress fracture, you would have direct experience of drinking a cocktail of radioactive ions and literally watching the radioactivity incorporate into your bones. In fact, your bones exist in homeostasis, constantly balancing mineralization and resorption. We know that vitamin D plays a critical role in this process because when the vitamin D receptor or the protein that activates vitamin D are deleted in mice, bone remodelling is severely impaired (5). A well-controlled study on adolescent girls also showed quite convincingly that supplementation with vitamin D benefits users by increasing bone augmentation (6).

A number of studies in the last 10 years have precisely defined something that has been known for many decades: that vitamin D levels, from sunlight or supplementation improve the strength of bones and prevent fractures from falls (7,8). Unlike the situation with antioxidant like vitamin C or E, vitamin D benefits in basic health functions are very clear. It is very difficult to argue anything other than that supplementation is warranted to maximize your vitamin D benefits.

Supplementation levels prescribed in the USRDA as designed to prevent rickets. The last 30 years have pulled back the veil on a whole range of diseases that vitamin D helps us avoid. Learn about these different vitamin D benefits here.

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3. Vieth, R. "What is the optimal vitamin D status for health?" Progress Biophys Mol Biol. 92 (2006) 26-32.
4. Otten, JJ, Hellwig, JP, Meyers, LD, eds. National Institutes of Medicine. Dietary Reference Intakes. (2006) National Academies Press, Washington, DC. 225-233.
5. Panda, DK, Miao, D, Bolivar, I, et al. "Inactivation of the 25-hydroxyvitamin D 1alpha-hydroxylase and vitamin D receptor demonstrates independent effects of calcium and vitamin D on skeletal and mineral homeostasis." 279 (2004) 16754-66.
6. Viljakainen, HT, Natri, AM, Karkkainen, M, et al. "A putative dose-response effect of vitamin D supplementation on site-specific bone mineral augmentation in adolescent girls: a double-blind randomized placebo-controlled 1-year intervention." J Bone Miner Res 21 (2006) 836-44.
7. Bischoff-Ferrari, HA, Dietrich, T, Orav, J, Dawson-Hughes, B. "Positive association between 25-hydroxy vitamin D levels and bone mineral density: A population-based study of younger and older adults." Am J Med 116 (2004) 634-639.
8. Bischoff-Ferrari, HA, Willett, WC, Wong, JB, et al. "Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials." Arch Intern Med. 169 (2009) 551-561.