by Jacques Allou, PharmD student
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods. It is available as a dietary supplement, and is also produced inside the body when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis.1
In the past decade, wonderful claims has been made about the role of vitamin D in the prevention and treatment of conditions as varied as osteoporosis, heart disease, cancer, diabetes, dementia, neuromuscular and immune function, and reduction of inflammation.1 Reports from authoritative bodies and reviews show that there is good consensus on the role of Vitamin D in growth and development of bone. Adequate supply of vitamin D is required for efficient calcium absorption and for the maintenance of normal blood levels of calcium and phosphate that are needed for the normal mineralization of bone and bone health.1,2 Not only does vitamin D promote bone growth, it does also protect against cardiovascular disease. In a study published on June 23 in the Archives of Internal Medicine, a team of Austrian scientists revealed that low blood levels of vitamin D appear to have an increased risk of death overall and from cardiovascular.3 A recent consensus panel estimated that about 50 – 60 percent of older individuals in North America and the rest of the world do not have satisfactory vitamin D status, and the situation is similar for younger individuals. Blood levels of vitamin D lower than 20 to 30 nanograms per milliliter have been associated with falls, fractures, cancer, autoimmune dysfunction, cardiovascular disease and hypertension.3 Vitamin D was the leader in dietary supplement sales in 2009, recording 82% sales growth.4
In this recent article by Fox News, Researchers have indicated that Vitamin D may actually do very little to guard against osteoporosis, contrary to popular belief.5 The researchers from the University of Auckland in New Zealand analyzed data from 23 studies involving 4,082 healthy adults with an average age of 59.6 In these studies, bone mineral density – the measure of bone strength and the amount of bone mineral present – was examined at five different sites in the body: lumbar spine, femoral neck, total hip, total body and forearm. They found that adults who took supplements of vitamin D for an average period of two years did not see any improvements in their bone health, apart from a small increase in bone density around their femoral neck. However, the study authors believe such a small increase is unlikely to be clinically significant.6
I was surprised to learn that. I do not agree with the article because the study has some limitations. There could be a strong possibility that bone mineral density in middle-aged women is a poor predictor of who will eventually have osteoporosis as already suggested by Dr. Clifford.7 It could be that vitamin D and calcium need to be taken together, and that they help only when a person is really low on either or both. Researchers have shown that, even though calcium is the main bone health nutrient, its absorption in the gut and use by bone tissue is dependent on vitamin D. Therefore, regardless of the adequacy of calcium intake, poor vitamin D status will limit calcium absorption.8 This explains why interventions using combinations of calcium and vitamin D produce more consistent results than interventions based on calcium alone.9 The link between vitamin D and calcium has been known for decades, so studying vitamin D alone does not make it appropriate.
My self-care recommendation will not be changed, based on the above discussed limitations. When counseling patients, I will stress that calcium and vitamin D work synergistically, and that foods and supplements containing these nutrients should be eaten or taken regularly as part of a balanced diet.
Half of all people around the world are deficient in vitamin D and therefore at increased risk for serious and potentially fatal conditions.3 What will we do as pharmacists to protect the cardiovascular and bone health of our aging patients?
- Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010. http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D.aspx Assessed November 12, 2013
- European Food Safety Authority. Scientific Opinion of the Panel on Dietetic Products, Nutrition and Allergies on a request from the Association de la Transformation Laitière Française related to the scientific substantiation of a health claim on vitamin D and bone growth. The EFSA Journal (2008) 827, 1-10. http://www.efsa.europa.eu/en/efsajournal/doc/827.pdf Assessed November 12, 2013
- Dobnig H, Pilz S, Scharnagl H, et al. Independent Association of Low Serum 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Levels With All-Cause and Cardiovascular Mortality. Arch Intern Med. 2008;168(12):1340-1349. doi:10.1001/archinte.168.12.1340.
- Tousrounis C, Denneby C. Introduction to Dietary Supplements. Handbook of Nonprescription Drugs: An Interactive Approach to Self-Care, 17th Ed Washington DC, American Pharmacists Association Press; 2012: 955-956.
- Fox News. Vitamin D supplements do not improve bone health study finds. Fox News. http://www.foxnews.com/health/2013/10/14/vitamin-d-supplements-do-not-improve-bone-health-study-finds/ Published October 14, 2013. Assessed November 1, 2013
- Ian RR, Mark JB, Andrew G. Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysis. The Lancet. 2013; DOI: 10.1016/S0140-6736(13)61647-5.
- Shute N. More Evidence Against Vitamin D To Build Bones In Middle Age http://m.npr.org/news/Health/232028261. Published October 12, 2013. Assessed November 1, 2013
- Fleet JC, Schoch RD (2010) Molecular mechanisms for regulation of intestinal calcium absorption by vitamin D and other factors. Critical Reviews in Clinical Laboratory Sciences. 47, 4, 181-195
- Tang BM, Eslick GD, Nowson C, Smith C, Bensoussan A. Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis. The Lancet. 2007; 370, 9588, 657-666.