When the topic of bone health arises, we often think of milk mustaches and calcium supplements. But what about visions of hitting the weights, jumping rope or doing pushups? It turns out there is more to bone health than consuming enough calcium and vitamin D.
Not only are there many other nutrients involved in developing and maintaining bone, but also exercise is imperative. People who exercise more have higher peak bone mass, and research suggests exercise plays just as important a role in bone health as nutrition.
Like muscles, bones are living tissue, and they require stress to stimulate growth and maintain integrity. Just as consuming extra protein without exercising will not result in strong muscles, consuming calcium without exercising will not result in optimal bone mass. Consider astronauts floating around in a spacecraft with little to no gravity — they experience significant bone mineral loss. But when astronauts participate in heavy resistance exercise, bone loss is reduced.
Exercise positively affects bone health in a number of ways. High-impact exercise has a site-specific effect on bones, meaning the area of the body worked in the exercise is where the most benefit is seen.
Stress in the form of a load stimulates calcium uptake and new bone formation, especially in children. Exercise also promotes stronger muscles and enhances coordination and balance, thus reducing the risk of falling and possibly fracturing a bone.
According to the National Osteoporosis Foundation's 2016 position statement on peak bone mass development and lifestyle factors, lifestyle behaviors affect 20 percent to 40 percent of adult peak bone mass, and only calcium intake and exercise received evidence with a grade A. All other lifestyle factors — including intakes of vitamin D, dairy and protein, and smoking — received lower grades, suggesting they do not have as significant an impact on bone health as calcium and exercise.
It's important to note that all forms of exercise are not equal when it comes to bone health. Weight-bearing exercise provides the stress load that bones need to stimulate mineral uptake. While this does occur in both children and adults, weight-bearing exercise is particularly important early in life as the most significant gains in bone mass are made during puberty. A 2014 meta-analysis found that weight-bearing activities in conjunction with high calcium intake resulted in optimal bone mineral content among prepubertal children.
Exercise is important for maintaining healthy mature bones, too. The impact of weight-bearing exercise on bone mineral density of premenopausal women is significant, and in healthy young men, even short-term exercise can boost bone mineral density. Analyses of National Health and Nutrition Examination Survey data found that the impact of physical activity on bone density and risk of osteoporosis is significant even when controlling for factors such as age, sex, race and ethnicity, body mass index, calcium and vitamin D intake, tobacco use and socioeconomic status.
Even postmenopausal women, who are at a particularly increased risk for osteoporosis, experience an increase in bone density from performing resistance exercises. Additionally, studies of osteopenia rehabilitation programs demonstrate feasibility and effectiveness of exercise on bone mineral density.
According to the National Institutes of Health, children between 6 and 17 should get 60 minutes of activity per day with bone-strengthening activities three days a week. Bone-strengthening activities for children include walking, jogging or running; playing tennis, racquetball, soccer, basketball or hockey; climbing stairs; jumping rope or other types of jumping; dancing; hiking; and lifting weights. While there are no specific recommendations for children younger than 6, the NIH recommends they play actively several times a day.
The National Osteoporosis Foundation recommends adults engage in weight-bearing exercise for 30 minutes most days of the week, with muscle-strengthening activities two to three days per week and balance, posture and functional exercises every day. Similarly, the surgeon general recommends daily physical activity with strength-building and balance-enhancing activities at least twice per week. Regarding type and duration, the surgeon general notes that five to 10 minutes of high-impact, load-bearing exercises may be sufficient, while 30 to 45 minutes of lower-impact exercises are needed to effectively impact bone health.
When discussing bone health with patients and clients, registered dietitian nutritionists should assess physical activity behaviors and reinforce physical activity recommendations to promote bone health. RDNs may find explaining cardiovascular and musculoskeletal benefits of exercise to clients while de-emphasizing weight and image-related motivations for exercising may increase clients' motivation and adherence.
While RDNs are qualified to communicate physical activity guidelines, clients interested in learning advanced exercises or starting new exercise regimens should consider working with a certified fitness professional, such as an American College of Sports Medicine-certified personal trainer or certified exercise physiologist. For specific guidance on balance, posture and functional exercises, a physical therapist should be consulted.