Bone Health: What Works Now and What Looks Promising
by Thomas Incledon
Bone is living tissue that constantly undergoes remodeling - old bone is replaced by new bone. Osteoporosis is the most common human bone disease and is characterized by low bone mass or bone mineral density (BMD) and loss of bone tissue. Osteoporosis develops when bone that is lost is not replaced by new bone. This results in a decreased bone mass and the increased risk for fractures. The many common causes of osteoporosis range from lack of physical stress (exercise) on the bones, malnutrition, low hormone levels (ie estrogens, androgens, IGF-1), and old age. Secondary causes may be due to glucocorticoid therapy, where cortisol-like compounds, usually given to control inflammation, increase the rate of bone loss.
Osteoporosis was once viewed as a disease that primarily concerned older women due to decreasing levels of estrogen during the postmenopausal years. Estrogen causes increased osteoblastic (bone formation) activity and after menopause, minimal estrogen is secreted from the ovaries. However, since the recognition of The Female Athlete Triad, osteoporosis, osteopenia, and stress fractures are now a concern for much younger women. It is also evident that more and more men appear to be developing osteoporosis as well. According to the National Institutes of Health (NIH), 10 million people have osteoporosis and another 18 million have low bone mass, with the odds favoring that these people will also develop osteoporosis (1). This is very unfortunate because osteoporosis is largely preventable.
The NIH defines osteoporosis as a �skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture.� A common mistake is to think of osteoporosis simply as the result of bone loss. For individuals that never reach optimal bone mass, osteoporosis may develop without substantial bone loss. For further reading on osteoporosis, the NIH Consensus Statement at (INSERT URL HERE) is an excellent place to start. This article will cover more recent developments, address some ongoing concerns, and offer some practical interpretations.
Exercise: What Do We Need To Do?
To improve the quality of their bones, people need specific exercise programs and directions on how to do the exercises. In the case of young female athletes who may be over-exercising, an appropriate recommendation may be to reduce their training volume. This article will assume that the individual is older and lack of exercise is the problem. It�s clear that not all exercise protocols are effective, so the focus will be on what has been proven in research and what is applicable today. There is a strong relationship between muscle mass, strength and bone density (2, 3). A simple interpretation is that in general, stronger people have stronger bones. In controlled studies where subjects were strength-trained, bone density also increased, thus lending support to cross-sectional studies (4, 5). Recent research using rats even suggests that resistance exercise may be more beneficial than aerobic training for stimulating bone formation (6). While there is no guarantee the same results will be found in people, animal studies do allow researchers to exert greater control over the study as well as study mechanisms that may be difficult to study in people. Unlike pharmacological and nutritional approaches, strength training can influence multiple risk factors for osteoporosis and other diseases by increasing strength, balance and muscle mass simultaneously.
Strength training or resistance exercise is not simply going to the gym and �pumping iron.� A properly designed program can address balance, flexibility, cardiovascular conditioning and agility. These are often overlooked fitness components that can easily be incorporated into a program. Programs are designed based upon what a client has available to them (equipment, location, etc) and what they can actually do (physical limitations, contraindications, personal goals, etc). In previous research elderly subjects lifted food items (ie soup cans, bags of potatoes, milk containers, etc) and improved their strength, muscle mass, bone density, body composition and mental outlook.
Research in the past had older subjects lift weights in a very slow and controlled fashion because of the fear that fast or explosive movements may harm them. Today things are approached very differently. One of the consequences of aging is that there is a decrease in function in faster twitch motor units and hence muscle fibers. Observations so far indicate that power-type training in the elderly may be very beneficial in multiple areas, including improved speed, a decrease in medications for blood pressure, blood glucose control, and decrease in depression. It�s easy to get depressed when you can�t move around.
A properly designed exercise program is preceded by a doctor�s approval and a physical assessment to determine the individual�s functional capacity, joint integrity, and muscular strength. For example if a subject has weak legs and is without joint problems, single legged squats to a bed or chair can work well. Initially the range of motion is limited, and with improvements in strength and balance, the range of motion is increased. The chair or bed provide a safety measure so the subject does not squat too deep too fast. Push-ups and straight leg sit-ups (on a bed or carpet with the lower back pushing down against the bed/carpet) are also very effective movements. Try to select movements that make balance difficult, use primarily body weight (or some fraction) as resistance, use full range of motion unless contraindicated, and emphasize the lifting phase at a one or two tempo (subject says �one� or �one-two� and tries to complete the movement at the same time), with the lowering phase usually about twice as long. The main point here is that we know resistance exercise works to increase or prevent loss of bone mass (with many other positive benefits), now let�s see how we can make it fun, yet appropriate for the people we work with.
Diet: What Can We Recommend?
Recommending an increased intake of dairy products along with some sunlight will work with some people, but usually not most elderly clients. Other dietary factors be bone saving. Fruit and vegetable intake has a positive relationship with bone density (7, 8). While there may be other explanations for these positive relationships, there is overwhelming evidence that supports their prudent recommendation. The standard recommendations apply - five to nine servings each day for adults, with lots of variety. Results of the Framingham Osteoporosis Study indicated that even after controlling for multiple factors, a lower protein intake increased bone loss (9).
Studies on rats indicate that high protein diets do not adversely affect bone turnover and in support of the Framingham Study, show that low protein intake lowers IGF-1 and induces IGF-1 resistance in osteoblasts (10, 11). Given that most elderly people consume insufficient protein, a low protein intake appears to be more of a concern than a high protein intake when it comes to preventing osteoporosis. While terms such as high and low are often used based upon the relative percentage of calories contributed to the diet from protein, this can be very misleading. A better strategy to determine the adequacy of protein intake is relative to body mass and activity pattern of the individual. The RDA for protein is .8 g/kg of body mass. However, strength training increases the upper recommendation to as high as 1.8 g/kg of body mass.
Soybeans and flaxseed (oil or meal) are excellent sources of phytoestrogens. Phytoestrogens are plant chemicals that can modulate estrogen function. Many phytoestrogens have been implicated either indirectly or indirectly to have an impact on bone turnover. While there still isn�t enough evidence to say exactly how these foods may influence bone tissue, there is sufficient evidence to warrant recommending their consumption. Given the common problem that older people have of eating enough calories, the real trick is how to get this group to actually eat what may help them. For other groups, many people just don�t see the value in taking time to plan out and make all the healthy foods they know they should be eating. A practical example that has worked very well for some people is to make smoothies or some type of blended mixtures. A scoop of why protein mixed in with some frozen berries and flaxseed meal supplies lots of nutrients that can benefit bone. It is quick, convenient, can be stored for later consumption and transported to another location. For variety, switch between flaxseed oil and meal, use different fruits, and alternate between soy and whey proteins.
Supplementation: Do We Really Need Everything On The Market?
It�s clear that supplements (and drugs) can be effective when compared to a placebo. What is not so obvious is whether or not supplements to prevent bone loss work any better than eating a diet that provides similar nutrient values as in the supplements. Collectively most studies support the notion that if people get enough calcium, vitamin D, vitamin K, and boron from their diets and lead an active lifestyle, they will achieve and maintain healthy bone densities. The dilemma is that substantial portions of the population do not get the required amounts those nutrients. While counseling is often tried, this group is usually comprised of older adults who may have deeply established lifestyle patterns. Supplementation may be an appropriate recommendation as long as they remember to take the appropriate pills in the correct doses at the correct times.
Calcium is the most important specific nutrient for developing peak bone mass and preventing bone loss. Recommended intakes of calcium to prevent or treat osteoporosis are 1,000 - 1,500 mg per day for older adults. Calcium may displace or be displaced from being absorbed by other minerals. Calcium supplements should generally be taken at separate times from other mineral supplements or foods that contain minerals if one wants to maximize calcium absorption. They can be taken with juices and vitamins. Vitamin D is needed for optimal calcium absorption and has a recommended intake of 400-600 IUs per day. Vitamin D on its own has limited therapeutic value for people with normal vitamin D levels (12), but can increase bone density in people with depressed serum levels (13).
Since so much research has focused on calcium and vitamin D, other dietary constituents are often overlooked. Boron initially received attention for use as an intervention to treat and prevent arthritis. In parts of the world where boron intake are less than one milligram per day, arthritis incidence rates are 20-70%. In other places where boron intakes are three to ten milligrams per day, arthritis occurs in 10% or less of the population. A significant favorable response has been reported with 6 mg per day. The combination of 45 mg/d vitamin K2 and .75 micrograms of vitamin D3 increases bone density in post menopausal women with osteoporosis (14). Vitamin C is also correlated with increase bone density in postmenopausal women taking calcium and undergoing estrogen therapy (15). The supplement intake ranged from 100-5,000 mg/d with an average intake of 745 mg/d.
One supplement that has received lots of marketing attention is ipriflavone. Ipriflavone is a synthetic isoflavone sold over the counter. In some European countries it is considered to be one of the first and most effective treatment approaches to combating osteoporosis. Studies on ipriflavone however offer mixed results, with some indicating that it increases bone mineral density and others indicating that it does not. A recent study published in JAMA indicated that there was no effect on bone mineral density and that lymphocyte concentration decreased significantly (16).
Several companies have produced supplements marketed as anti-osteoporotic agents. Based upon the doses above, a supplement recipe for osteoporosis would consist of 1,000 - 1,500 mg/d of calcium, 400-600 IUs of vitamin D/d, 745 mg of vitamin C/d, 45 mg/d of vitamin K and 6 mg/d of boron. There is no research at this point in time that has examined the effects of simultaneously giving all of the above agents on bone density. Whether or not the combined use these supplements is more effective than some smaller combination is a matter of opinion. The most appropriate place to try this supplemention protocol is in clinical practice where a competent professional monitors patients. A greater concern is that individuals may self-prescribe these agents without monitoring and/or guidance from a competent professional.
Putting It Into Practice Today
One of the problems with research on preventing bone loss or increasing bone mineral density is that there are many variables to control for. Activity patterns can vary considerably and the results of a nutritional intervention may reflect the synergistic effects of nutrition plus exercise, even though only the nutritional component was carefully monitored. Another issue is that when bone mineral density has reached a certain critical point, significant interventions from a statistical perspective may mean little from a practical perspective. That is while the subject�s bone density increased, they may still fracture their bones at the same rate as before the study. This makes interpreting the results somewhat problematic.
A simple and prudent strategy is to get people to perform resistance exercise where balance is challenged (ie they work against gravity). The program should incorporate progression so as they get stronger, they will perform more challenging tasks. The diet should provide at least .8 g/kg body mass per day and not more than 1.8 g/kg per day if resistance training. It is generally understood that most nutrients can be obtained from the diet, however a substantial portion of the population has signs of low levels for one or more nutrients relating to bone health. While recommendations for lifestyle modifications are certainly warranted, compliance does not appear to be very high over the long-term. Supplementation of one or more of the following may be warranted: 1,000 - 1,500 mg/d of calcium, 400-600 IUs of vitamin D/d, 745 mg of vitamin C/d, 45 mg/d of vitamin K and 6 mg/d of boron. Ideally such strategies would occur under the guidance of a competent professional.
References
1. Anonymous, Osteoporosis prevention, diagnosis, and therapy. JAMA, 2001. 285(6): p. 785-95.
2. Huuskonen, J., et al., Determinants of bone mineral density in middle aged men: a population- based study. Osteoporos Int, 2000. 11(8): p. 702-8.
3. Proctor, D.N., et al., Relative influence of physical activity, muscle mass and strength on bone density. Osteoporos Int, 2000. 11(11): p. 944-52.
4. Kerr, D., et al., Resistance training over 2 years increases bone mass in calcium-replete postmenopausal women. J Bone Miner Res, 2001. 16(1): p. 175-81.
5. Ringsberg, K.A., et al., The impact of long-term moderate physical activity on functional performance, bone mineral density and fracture incidence in elderly women. Gerontology, 2001. 47(1): p. 15-20.
6. Notomi, T., et al., A comparison of resistance and aerobic training for mass, strength and turnover of bone in growing rats. Eur J Appl Physiol, 2000. 83(6): p. 469-74.
7. Tucker, K.L., et al., Potassium, magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women. Am J Clin Nutr, 1999. 69(4): p. 727-36.
8. New, S.A., et al., Dietary influences on bone mass and bone metabolism: further evidence of a positive link between fruit and vegetable consumption and bone health? Am J Clin Nutr, 2000. 71(1): p. 142-51.
9. Hannan, M.T., et al., Effect of dietary protein on bone loss in elderly men and women: the Framingham Osteoporosis Study. J Bone Miner Res, 2000. 15(12): p. 2504-12.
10. Bourrin, S., et al., Dietary protein restriction lowers plasma insulin-like growth factor I (IGF-I), impairs cortical bone formation, and induces osteoblastic resistance to IGF-I in adult female rats. Endocrinology, 2000. 141(9): p. 3149-55.
11. Creedon, A. and K.D. Cashman, The effect of high salt and high protein intake on calcium metabolism, bone composition and bone resorption in the rat. Br J Nutr, 2000. 84(1): p. 49-56.
12. Hunter, D., et al., A randomized controlled trial of vitamin D supplementation on preventing postmenopausal bone loss and modifying bone metabolism using identical twin pairs. J Bone Miner Res, 2000. 15(11): p. 2276-83.
13. Kantorovich, V., et al., Bone mineral density increases with vitamin D repletion in patients with coexistent vitamin D insufficiency and primary hyperparathyroidism. J Clin Endocrinol Metab, 2000. 85(10): p. 3541-3.
14. Iwamoto, J., T. Takeda, and S. Ichimura, Effect of combined administration of vitamin D3 and vitamin K2 on bone mineral density of the lumbar spine in postmenopausal women with osteoporosis. J Orthop Sci, 2000. 5(6): p. 546-51.
15. Morton, D.J., E.L. Barrett-Connor, and D.L. Schneider, Vitamin C supplement use and bone mineral density in postmenopausal women. J Bone Miner Res, 2001. 16(1): p. 135-40.
16. Alexandersen, P., et al., Ipriflavone in the treatment of postmenopausal osteoporosis: a randomized controlled trial. JAMA, 2001. 285(11): p. 1482-8.
Thomas Incledon, PhD(c), RD, LD/N, NSCA-CPT, CSCS, RPT has been involved in research on how to enhance health and human performance for over 17 years and is considered one of the worldwide leading experts on effective health and performance strategies. He is the Chief Executive Officer of Human Health Specialists. Tom can be reached at tom@thomasincledon.com or (480) 883-7240. Visit our websites at http://www.ThomasIncledon.com, http://www.HumanPerformanceSpecialists.com, http://www.HumanHealthSpecialists.com
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