Osteoporosis—A Primer on Bone Health

Osteoporosis is a condition of decreased bone mineral density (BMD) and increased fragility, predisposing one to fracture, even from seemingly minor impacts or bone stress.^[1][2]

It is most commonly associated with age, and is classically seen among postmenopausal women; however, men are also affected, and certain factors increase risk for bone loss even among younger people. For instance, individuals with celiac disease, inflammatory bowel disease, or other conditions characterized by nutrient malabsorption are at elevated risk; so are smokers, patients with hormonal conditions such as hyperthyroidism, patients on medications such as prednisone (a corticosteroid often used for autoimmune conditions) or antihormonal medications such as those used to treat breast cancer, or patients undergoing premature or early menopause.^[3] This article discusses some of the lifestyle- and nutrient-based strategies that are known to prevent bone loss and increase bone density.

Basic Bone Physiology

Bone density is the result of a constant flux in bone-remodelling processes. In the bone tissue, osteoblasts are cells that continually secrete new bone matrix, resulting in new bone tissue and increased bone strength. On the other hand, osteoclasts are cells responsible for breaking down existing bone tissue, releasing calcium and other minerals into the bloodstream. When the activity of osteoblasts outpaces that of osteoclasts, bone density increases; when osteoclasts outwork osteoblasts, bone is lost. Factors such as exercise; intake of key nutrients such as protein, calcium, vitamin D, etc.; and the presence of estrogen and androgens all increase osteoblast activity. On the other hand, poor diet, caffeine and alcohol intake, smoking, and excess levels of corticosteroids can increase osteoclast activity and result in accelerated bone loss.

Exercise

One of the most powerful interventions for maintaining and even increasing bone density as well as reducing fracture risk is exercise.^[1] The two single most important stimuli for bone and muscle growth are 1) the physical stress of exercise on these tissues, and 2) adequate protein intake.^[2] Exercise directly affects bone remodelling. In addition, improving balance and muscle strength through exercise will help prevent falls. A 2016 review on the bone effects of exercise reports that “multi-component training, including aerobic activity and other types of training (resistance and/or strength exercises), is the best kind of exercise in improving bone mass and bone metabolism in older adults.”^[1] Whole-body vibration training has also been shown to be effective. Other organizations simply recommend regular physical activity at least 3–5 times per week.^[2] The bottom line is that in our sedentary society, any form of getting active will be of benefit.

Protein Intake

Although there is a common perception that the main bone nutrient is calcium, protein intake is probably even more important. According to Heaney, protein makes up 50% of the volume of bone, and up to one-third of its mass.^[4] Protein provides the structural matrix for bone, and also stimulates growth factors such as insulin-like growth factor (IGF-⁠1) that promote new bone development.^[4] Although it has been argued that protein intake can increase urinary calcium excretion, it appears that it also increases intestinal calcium absorption, and that these two offset one another.^[4]

Current recommendations for optimal dietary protein intake in relation to bone health are approximately “1.0–1.2 g/kg body weight per day, with at least 20–25 g of high-quality protein at each main meal.”^[2]

Calcium and Micronutrients

As the main mineral component of bone, calcium supplementation is commonly recommended for maintaining bone density. It is not uncommon to see very high dosages often prescribed, up to 1500 mg calcium per day. Recently, evidence has suggested that such high intakes of calcium in isolation, apart from other micronutrients, may not be such a good idea. Data has emerged suggesting that excess calcium may be deposited in other tissues as well, such as blood vessels, which may contribute to atherosclerosis and increased risk of heart disease.^[5] It has been suggested that more modest doses of calcium (under 1000 mg), accompanied by other minerals and micronutrients, may be more appropriate. Indeed, there is much evidence to suggest that a type of synergy exists between these micronutrients, such that the addition of each may further increase the benefit of calcium on bone density.

For instance, the addition of vitamin D supplementation to calcium has been shown to reduce overall fractures by 15% and reduce hip fractures by 30%.^[6] Another study found that the addition of vitamin D supplementation to calcium and a bone medication resulted in an additional 25% decrease in markers of bone breakdown, compared to calcium plus the drug alone (without vitamin D) among women deficient in vitamin D.^[7] Similar results have been shown for other micronutrients as well, including magnesium, zinc, boron, silica, manganese, and vitamin K.^{[8][9][10][11][12][13]}

Finally, we consider the importance of calcium form. Evidence suggests that calcium hydroxyapatite may be preferable over other types of calcium, such as calcium carbonate or calcium citrate.^[14] Calcium hydroxyapatite is thought to be more bioavailable, and has been shown to result in greater increases in bone mineral density (almost double over a period of three years) compared to calcium carbonate.^[14]

1. Castrogiovanni, P., et al. “The importance of physical activity in osteoporosis. From the molecular pathways to the clinical evidence.” Histology and Histopathology. Vol. 31, No. 11 (2016): 1183–1194.
2. Rizzoli, R., et al.; ESCEO Task Force. “The role of dietary protein and vitamin D in maintaining musculoskeletal health in postmenopausal women: A consensus statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO).” Maturitas. Vol. 79, No. 1 (2014): 122–132.
3. Osteoporosis Canada. Checklist for risk of broken bones and osteoporosis. · http://www.osteoporosis.ca/osteoporosis-and-you/diagnosis/risk-factors/ · 2016
4. Heaney, R.P., and D.K. Layman. “Amount and type of protein influences bone health.” The American Journal of Clinical Nutrition. Vol. 87, No. 5 (2008): 1567S–1570S.
5. Reid, I.R., et al. “Cardiovascular effects of calcium supplementation.” Osteoporosis International. Vol. 22, No. 6 (2011): 1649–1658.
6. Weaver, C.M., et al. “Calcium plus vitamin D supplementation and risk of fractures: An updated meta-analysis from the National Osteoporosis Foundation.” Osteoporosis International. Vol. 27, No. 1 (2016): 367–376.
7. Olmos, J.M., et al. “Effects of 25-⁠hydroxyvitamin D₃ therapy on bone turnover markers and PTH levels in postmenopausal osteoporotic women treated with alendronate.” The Journal of Clinical Endocrinology and Metabolism. Vol. 97, No. 12 (2012): 4491–4497.
8. Aydin, H., et al. “Short-term oral magnesium supplementation suppresses bone turnover in postmenopausal osteoporotic women.” Biological Trace Element Research. Vol. 133, No. 2 (2010): 136–143.
9. Orchard, T.S., et al. “Magnesium intake, bone mineral density, and fractures: Results from the Women’s Health Initiative Observational Study.” The American Journal of Clinical Nutrition. Vol. 99, No. 4 (2014): 926–933.
10. Sato, Y., et al. “The prevention of hip fracture with menatetrenone and risedronate plus calcium supplementation in elderly patients with Alzheimer disease: A randomized controlled trial.” The Kurume Medical Journal. Vol. 57, No. 4 (2011): 117–124.
11. Hunt, C.D., J.L. Herbel, and F.H. Nielsen. “Metabolic responses of postmenopausal women to supplemental dietary boron and aluminum during usual and low magnesium intake: Boron, calcium, and magnesium absorption and retention and blood mineral concentrations.” The American Journal of Clinical Nutrition. Vol. 65, No. 3 (1997): 803–813.
12. Strause, L., et al. “Spinal bone loss in postmenopausal women supplemented with calcium and trace minerals.” The Journal of Nutrition. Vol. 124, No. 7 (1994): 1060–1064.
13. Spector, T.D., et al. “Choline-stabilized orthosilicic acid supplementation as an adjunct to calcium/vitamin D₃ stimulates markers of bone formation in osteopenic females: A randomized, placebo-controlled trial.” BMC Musculoskeletal Disorders. Vol. 9 (2008): 85.
14. Ciria-Recasens, M., et al. “Comparison of the effects of ossein-hydroxyapatite complex and calcium carbonate on bone metabolism in women with senile osteoporosis: A randomized, open-label, parallel-group, controlled, prospective study.” Clinical Drug Investigation. Vol. 31, No. 12 (2011): 817–824.