Exercise and Bone Health

The term weight-bearing exercise often confuses people. The National Osteoporosis Foundation defines weight-bearing as exercise in which bones and muscles work against gravity as the feet and legs bear the body's weight. Examples of weight bearing activities include walking, jogging, stair climbing, dancing, racquet sports and weight training. However, over exercising can actually decrease bone density and for women, loss of menses may be a signal that a female may be participating in too much physical activity.
Resistance training is also an excellent way to help increase or maintain bone density due to the stress placed upon the bone as the muscles shorten during contraction. The contraction causes a slight "bending" of the bone where the muscle is attached and stimulates increases in bone density. As well, resistance training strengthens back muscles, which can help to improve and maintain posture of an osteoporotic spine that has rounded over. A qualified profession who works with special populations will be able to correctly diagnose a spinal irregularity.

Osteoporosis

Osteoporosis is defined as a loss of calcium from the skeleton resulting in weaker bones that are more susceptible to fracture, or compression in the spinal vertebrae. Osteoporosis causes an imbalance in the cycle of bone re-building and like many tissues in the body, bone is continually removed and re-built. Osteoporosis occurs when the balance of removal and renewal shift towards removal, and the bones lose their density. Listed below are risk factors for osteoporosis that can and cannot be modified. Fortunately, diet and exercise are factors that can be modified and together create healthy bones.

Risk Factors for Osteoporosis

Factors that CANNOT be modified:
· Caucasian or Asian ancestry
· Female gender
· Family history of osteoporosis
· Early menopause
· Small body (skeletal) frame
· Advanced age

Factors that CAN be modified:
· A poorly balanced diet
· Low dietary intake of calcium and vitamin D
· Smoking
· Lack of exercise
· Excessive alcohol
· Certain medications

Other Factors Affecting Bone Health: Fact or Fiction

1. Drinking soda pop weakens bones: Up until 2000, there was a strong theory stating that the phosphoric acid (5) or the carbonation in soft drinks was depleting the calcium in children's bones. After more research, it has been concluded that it is not the actual ingredients in soft drinks that weaken bones, but the replacement of milk from a child’s diet with other beverages such as soda pop. Therefore, the decreased level of milk intake is the concern.

2. Caffeine weakens bones: The effect of caffeine consumption on indices of bone health, both in terms of bone mass and fracture risk, remains inconclusive (3,4). There is research that supports that caffeine consumption either has no effect on bone health or has a negative effect - with the most harmful outcomes resulting from a combination of high caffeine intake coupled with low calcium intake. Therefore, adequate calcium intake combined moderate caffeine consumption appears to be an acceptable conclusion at this point in time.

3. Severe dieting can weaken bones: It is true that severe dieting can weaken bones. Not only do severe dieters consume too little calcium, restricted caloric intake in females results in very low body weight or disordered eating behaviors. These behaviors can cause a female to have irregular periods or no periods at all. Irregular and the non-occurrence of periods is extremely damaging to bone health. In the short term, severe dieters have an increased risk for stress fractures and in extreme eating disorders cases, premature osteoporosis can occur.

4. Excess animal protein leads to bone loss: Excess protein in the diet can cause bones to leach calcium. However, this type of excess is rare. Moderation and a balanced diet is key and a recent study made claims against the intake of animal protein (6), but the study has since been criticized for poor design. Interestingly, a more recent study (7) showed that vegetable protein was linked to low bone density. All in all, adequate protein from a variety of sources seems to be the best approach for a healthy diet. Further, if a higher protein diet is matched with high calcium intake, the increased protein intake most likely will not adversely affect bone health.

Lifting weights is good for your bones:

Lifting weights is definitely important for healthy bones. The stress placed on the bone when lifting weights is a valuable stimulus. The stimulus signals the deposition of more calcium into the bones and increases the bone's structural integrity and density.

Should calcium pills be taken in split does?

If you are taking more than 500 mg of a calcium supplement to meet your daily requirements, the dose should be split, and taken in the morning and evening. The body can only absorb a maximum of about 500 mg at one time. So for example; if your goal is 1000 mg/day, and your diet includes 300 mg a day, then 700 mg must be supplemented. The supplement would then be split into two 350 mg doses, morning and evening.

In Summary:

Positive Tips for Healthy Bones at Any Age
· Eat a well balanced diet with ample fruits, vegetables and adequate, but not excessive amounts of protein
· Vegetarians or individuals following a special diet should consult a
nutritionist about food sources of calcium and the possible need for supplements
· Ensure adequate calcium and vitamin D in the diet
· Limit alcohol and caffeinated beverages
· Don't use tobacco products
· Participate in regular weight bearing exercise such as walking, dancing, sports
· Participate in resistance training exercise (weight lifting, power yoga, etc.) to stress the bones and increase bone density

References

1. National Osteoporosis Foundation. : America’s Bone Health: The State of Osteoporosis and Low Bone Mass in Our Nation. 2001 report.

2. New SA, Robins SP, Campbell MK, 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;71:142-151.

3. Ilich JZ, Brownbill RA. More evidence for the beneficial effects of moderate alcohol intake and adverse effects of caffeine consumption on bone mass in postmenopausal women.J Bone Miner Res. 2001;16(suppl 1):S273.

4. Homan MC, McGovern PG, Bowman PJ, et al. Caffeine consumption, rates of hip bone loss and risk of hip fracture. J Bone Miner Res. 2001;16(suppl 1):S386.

5. Heaney et al. American Journal of Clinical Nutrition. 1999, vol. 69, pp.727 – 36
6. Sellmeyer, D.E., et al. A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk of fracture in postmenopausal women. American Journal of Clinical Nutrition 73(January):118. 2001.

7. Barrett-Connor, E et al. Animal protein consumption associated with bone density in elderly women. Am J Epidemiol 2002;155:636-644.

Nanci S. Guest is a certified personal trainer & nutritionist, and is completing her Master of Science degree in nutrition this June. She owns "Power Play: Nutrition, Fitness, Performance" in Vancouver, BC, and for the past 8 years she has been providing individuals, sports teams & the community with nutritional consulting & personal training services, as well as research services, seminars and article writing for local & national publications.