Vitamin D: Bones & Joints need Vitamin D
Vitamin D, a fat-soluble vitamin, has the noteworthy distinction as the only vitamin that the human body manufactures both efficiently and abundantly if given the right environment. And what is that environment? Sun, plenty of sun.
Mother Nature, borrowing from her photosynthesis playbook, has co-opted the Sun, specifically Ultra-Violet B (UVB) radiation, to optimize vitamin D production.
In the top layer of skin, referred to as the epidermis, UVB triggers the synthesis of vitamin D from a substance that is a derivative of cholesterol. However, vitamin D in this form is biologically inactive and must undergo two additional modifications, one in the liver (25 OH Vitamin D) and one in the kidney (1,25 OH Vitamin D), before it is considered functional.
Vitamin D’s notoriety in the popular press usually stems from its role in bone health, specifically osteoporosis. However, vitamin D is a versatile vitamin materially contributing to a broad scope of physiologic and biologic processes. Some research estimates vitamin D influences close to 1250 genes. That’s huge!
3 Musculoskeletal Health Benefits
1. Vitamin D Promotes Joint Health
Chronic unhealthy inflammation drives degenerative joint disease. Research demonstrates that vitamin D has a positive influence on the immune system’s response to chronic injury. Vitamin D mitigates uncontrolled inflammation by blocking the production of key proteins that magnify the inflammatory response. Additionally, scientific investigation implies that vitamin D enhances the production of cartilage extracellular proteoglycans, thus boosting the joint’s shock-absorbing properties. Moreover, vitamin D has been shown to curb the synthesis of matrix metalloproteinases, the tissue-destroying enzymes responsible for considerable cartilage damage. Finally, vitamin D promotes the ideal calcium mineralization and density of subchondral bone. Subchondral bone, as its name implies, is the area of bone just below cartilage. The subchondral bone provides cartilage with the strong structural support needed to counteract daily wear and tear.
Boston researchers found that individuals with similar characteristics who were deficient in vitamin D and who were assessed radiographically for osteoarthritis had an increased risk for osteoarthritis of the knee. (Zhang FF, Driban JB, Lo GH, et al. Vitamin D deficiency is associated with progression of knee osteoarthritis. J Nutr. 2014;144: 2002-2008)
Population studies have shown people with insufficient vitamin D levels are at increased risk for both developing osteoarthritis and for osteoarthritis progression. Some data indicate a 3-fold increase in both incidence and progression in the setting of inadequate vitamin D. (McAlindon et al. Ann Intern Med. 1996;125:353-359.)
2. Vitamin D Boosts Bone Health
Calcium is stored in bones. Optimal amounts of calcium make bones strong. If bone has insufficient calcium, then it is weaker and at risk for breaking. Vitamin D stimulates calcium absorption from the gut. If vitamin D levels are suboptimal, then less calcium is absorbed and there is less calcium in bones. Calcium deficiency makes osteoporosis and fractures more likely.
Additionally, vitamin D has been shown to promote a healthy immune response to injury and to constrain excessive inflammation, underscoring another mechanism in which vitamin D supports bone health. Chronic inflammation and free radical damage stimulate the activity of cells, called osteoclasts, that actively resorb bone. Increased bone resorption further decreases the strength and density of bone.
Boston researchers demonstrated epidemiological evidence that higher serum vitamin D levels are associated with greater bone mineral density in both young and old populations (Bischoff-Ferrari HA, Dietrich T, Orav EJ, et al. Positive association between 25-hydroxy vitamin D levels and bone mineral density: a population-based study of younger and older adults. Am J Med 2004; 116: 634–639.)
3. Vitamin D Supports Muscle Health
As individuals age, they are at risk for a muscle condition called sarcopenia. Sarcopenia manifests as loss of muscle mass, weakness, decreased function, and infiltration of fat into muscle. Unhealthy inflammation is thought to contribute to sarcopenia. Research implies that vitamin D discourages a disproportionate immune response to muscle injury.
Additionally, muscle cells have receptors that are sensitive to vitamin D stimulation. Scientific investigation has demonstrated an association between healthy vitamin D levels and healthy amounts of type II muscle fiber. Type II muscle fibers are important for strength, muscle mass, and power.
Dutch researchers showed that older adults who had low serum vitamin D concentrations were twice as likely to have sarcopenia over a 3-year follow-up period when compared with participants who had higher vitamin D concentrations. (Visser M, Deeg DJH, Lips P. Low vitamin D and high parathyroid hormone levels as determinants of loss of muscle strength and muscle mass (sarcopenia): the longitudinal aging study Amsterdam. J Clin Endocrinol Metab 2003;88:5766e72. http://dx.doi.org/10.1210/jc.2003-030604.)
Precautions
Vitamin D from natural foods is generally well tolerated. RDA amounts can be obtained from a balanced, healthful diet and moderate sun exposure. The National Institutes for Science has published an upper limit value of 100 mcg or 4000 IU/day.
Excessive intake of vitamin D may cause blood calcium to reach levels that are dangerous. This high blood calcium level is known as hypercalcemia. The excess calcium is deposited in blood vessels, the heart, and the kidneys, potentially increasing the risk of cardiovascular disease and kidney stones.
Any consideration of supplementation should be discussed with a qualified health professional familiar with your unique medical history.
References
- Bergink, A. P., Zillikens, M. C., Van Leeuwen, J. P., Hofman, A., Uitterlinden, A. G., & Van Meurs, J. B. (2016). 25-hydroxyvitamin D and osteoarthritis: A meta-analysis including new data. Seminars in Arthritis and Rheumatism, 45(5), 539-546. https://doi.org/10.1016/j.semarthrit.2015.09.010
- Felson, D. T., Niu, J., Clancy, M., Aliabadi, P., Sack, B., Guermazi, A., & Booth, S. L. (2007). Low levels of vitamin D and worsening of knee osteoarthritis: Results of two longitudinal studies. Arthritis & Rheumatism, 56(1), 129–136. https://doi.org/10.1002/art.22292
- Heidari, B., Javadian, Y., Babaei, M., & Yousef-Ghahari, B. (2015). Restorative effect of vitamin D deficiency on knee pain and quadriceps muscle strength in knee osteoarthritis. Acta Medica Iranica, 53(8), 466-470.
- Hunter, D. J., Hart, D., Snieder, H., Bettica, P., Swaminathan, R., & Spector, T. D. (2003). Evidence of altered bone turnover, vitamin D and calcium regulation with knee osteoarthritis in female twins. Rheumatology, 42, 1311–1316. https://doi.org/10.1093/rheumatology/keg373
- Keen, R. W., Hart, D. J., Lanchbury, J. S., & Spector, T. D. (1997). Association of early osteoarthritis of the knee with a Taq I polymorphism of the vitamin D receptor gene. Arthritis & Rheumatism, 40(8), 1444-1449. https://doi.org/10.1002/art.1780400812
- McAlindon, T. E., Felson, D. T., Zhang, Y., Hannan, M. T., Aliabadi, P., Weissman, B., & Jacques, P. (1996). Relation of dietary intake and serum levels of vitamin D to progression of osteoarthritis of the knee among participants in the Framingham study. Annals of Internal Medicine, 125(5), 353-359.
- McAlindon, T., LaValley, M., Schneider, E., Nuite, M., Lee, J. Y., Price, L. L., & Dawson-Hughes, B. (2013). Effect of vitamin D supplementation on progression of knee pain and cartilage volume loss in patients with symptomatic osteoarthritis: A randomized controlled trial. JAMA, 309(2), 155-162. https://doi.org/10.1001/jama.2012.164487
- Neve, A., Cantatore, F. P., Corrado, A., Gaudio, A., Ruggieri, S., & Ribatti, D. (2013). In vitro and in vivo angiogenic activity of osteoarthritic and osteoporotic osteoblasts is modulated by VEGF and vitamin D3 treatment. Regulatory Peptides, 184, 81-84. https://doi.org/10.1016/j.regpep.2013.03.014
- National Institutes of Health. (2016). Vitamin D fact sheet for health professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- Micronutrient Information Center. (2017). Vitamin D. Linus Pauling Institute, Oregon State University. http://lpi.oregonstate.edu/mic/vitamins/vitamin-D
- The World’s Healthiest Foods. (2017). Vitamin D. http://www.whfoods.com/genpage.php?tname=nutrient&dbid=110
- Otten, J. J., Hellwig, J. P., & Meyers, L. D. (Eds.). (2006). Dietary reference intakes: The essential guide to nutrient requirements. National Academy of Sciences.
