#GBites: Considerations for Bone Health: Do Calcium Supplements Live Up To The Hype?

by Dan Goldstein and Natalie Gentile, MD

Following up on our last article on dietary supplements, we wanted to take this week to hone in on one of the most commonly taken supplements—calcium. Typically encouraged for prevention of osteoporosis or osteopenia and for individuals who may lack calcium in their diet, one in five Americans took a calcium supplement in 2019, according to one survey.1

Calcium is a mineral and an essential nutrient implicated in bone density, muscular contraction and nervous function. It is primarily stored in bones and teeth, giving them their rigidity. 

While dietary calcium supplements would appear to be the quickest and most convenient solution for osteoporosis, they are not the most effective treatment. Before we look into the efficacy of calcium supplements, let us peer into the condition that osteoporosis is and why it comes about.

Of note, this GBites is referring to primary prevention of bone disease, not treatment of known osteopenia or osteoporosis.

Overview of Osteoporosis

Osteoporosis is a disease of the bones, classified by thinning, impaired strength and increased susceptibility to fractures.2 Osteopenia refers to decreased bone density, but not to the extent of osteoporosis.3 These conditions typically develop over the course of decades and tend to affect older adults,2 especially women, but are also common among younger female athletes.4 

Bone development primarily takes place early in life and by the age of 30, most people have reached their peak bone density.2 After this point, bone density tends to decline with age, especially in post-menopausal women.5 When a person is diagnosed with osteopenia or osteoporosis, it becomes a race against time to maintain bone strength before a potentially debilitating fracture. 

Is a Calcium Supplement Your Best Bet?

The first thing a physician would advise to somebody with low bone density is to make sure they are consuming enough dietary calcium. It is commonplace for individuals to address this by taking calcium in a pill. A calcium supplement seems like the most direct, straightforward treatment, but this strategy may not be as fruitful as one may assume. 

While these recommendations are well intentioned, unfortunately, calcium supplements do not seem to provide the benefits to bone density that one would hope. There is actually evidence to suggest that supplementing with calcium can actually increase one’s hip fracture risk.11 

Dietary Sources of Calcium

Getting adequate calcium through diet is absolutely essential for maintaining bone strength as we age, however it is best consumed through whole food sources. Calcium is readily available in green leafy vegetables like kale, collard greens, mustard greens and swiss chard as well as broccoli and Brussels sprouts. Spinach, however, is not a good source of calcium. Although calcium is present in spinach, the leaves contain oxalic acid, which binds up the calcium making it hard to absorb when eaten. Beans such as chickpeas, baked beans and tofu (made from soybeans) are also great sources. 

Greens and beans? you may ask. Perhaps these are not the foods that come to mind when you think about calcium. To many, milk and other dairy products are basically synonymous with calcium. While dairy does certainly contain calcium, it is not a source I would recommend. The calcium in milk is less well-absorbed in the gut compared to many plant-based sources. Additionally, milk and other foods made from it induce acidosis in the body, forcing a person to recruit calcium from their bone reserves to offset the acidity. For adults who have reached peak bone density, this mechanism presents a bleak feedback loop, potentially undermining already weak bones. You read that correctly. Drinking milk may actually force your body to pull more calcium from your diminishing bone reserves, opposite of the outcome one hopes for when drinking the stuff. Many may find this counterintuitive considering that milk products have long been touted as good for bone health. Studies have shown that dairy is not associated with greater bone strength,6–8 and worse, its consumption is actually linked to higher rates of hip fracture in women.8,9

It should be noted that salt may have a similar acidosis-inducing effect within the body. Limiting sodium intake is important for bone health, especially for those who have low bone density.10

Get Moving and Eat Well!

When it comes to healthy bones, calcium intake is only part of the story. Surprisingly, total calcium intake is not associated with greater bone density.7,8,11 This is not to say that calcium is not important—it is a primary building block of bones. But as long as a person’s diet contains a reasonable amount of whole food calcium sources, they need not be concerned with taking additional calcium in a pill. When it comes to building strong bones, the most important consideration is exercise, especially weight-bearing exercise. Lacing up your sneakers and getting moving is the best step a person can take to build or maintain bone density.

The right time to think about bone health is when a person is young. Adolescence is likely the best window to build up bone density.12 Being physically active and making sure to eat plant-based sources of calcium during this critical age is the best preventive measure against osteoporosis later in life. 

For those who have been diagnosed with osteoporosis, do not lose hope! Weight-bearing exercise can still increase the bone mineral density of those with osteoporosis, well past the point of peak bone density.13 

For all individuals young and old, maintaining bone health involves the same general principles: engage in daily weight-bearing exercise, eat lots of greens and beans, avoid dairy and other animal products, and limit salt intake. 

1. Dietary Supplement Use Reaches All Time High — Available-for-purchase consumer survey reaffirms the vital role supplementation plays in the lives of most Americans | Council for Responsible Nutrition. https://www.crnusa.org/newsroom/dietary-supplement-use-reaches-all-time-high-available-purchase-consumer-survey-reaffirms. Accessed December 18, 2019.

2. Sunyecz JA. The use of calcium and vitamin D in the management of osteoporosis. Ther Clin Risk Manag. 2008;4(4):827-836.

3. Karaguzel G, Holick MF. Diagnosis and treatment of osteopenia. Rev Endocr Metab Disord. 2010;11(4):237-251. doi:10.1007/s11154-010-9154-0

4. MacKnight JM. Osteopenia and Osteoporosis in Female Athletes. Clin Sports Med. 2017;36(4):687-702. doi:10.1016/j.csm.2017.05.006

5. Menopause & Osteoporosis. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/10091-menopause--osteoporosis. Accessed January 3, 2020.

6. Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, et al. Milk intake and risk of hip fracture in men and women: a meta-analysis of prospective cohort studies. J Bone Miner Res Off J Am Soc Bone Miner Res. 2011;26(4):833-839. doi:10.1002/jbmr.279

7. Feskanich D, Willett WC, Colditz GA. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr. 2003;77(2):504-511. doi:10.1093/ajcn/77.2.504

8. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. Am J Public Health. 1997;87(6):992-997. doi:10.2105/ajph.87.6.992

9. Michaëlsson K, Wolk A, Langenskiöld S, et al. Milk intake and risk of mortality and fractures in women and men: cohort studies. BMJ. 2014;349:g6015. doi:10.1136/bmj.g6015

10. Preventing and Reversing Osteoporosis. Physicians Committee for Responsible Medicine. https://www.pcrm.org/good-nutrition/nutrition-information/health-concerns-about-dairy/preventing-and-reversing-osteoporosis. Accessed January 3, 2020.

11. Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, et al. Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials. Am J Clin Nutr. 2007;86(6):1780-1790. doi:10.1093/ajcn/86.5.1780

12. Ackerman KE, Misra M. Bone Health in Adolescent Athletes with a Focus on Female Athlete Triad. Phys Sportsmed. 2011;39(1):131-141. doi:10.3810/psm.2011.02.1871

13. Shanb AA, Youssef EF. The impact of adding weight-bearing exercise versus nonweight bearing programs to the medical treatment of elderly patients with osteoporosis. J Fam Community Med. 2014;21(3):176-181. doi:10.4103/2230-8229.142972