Ten million Americans over the age of 50 experience osteoporosis, and about 44 million more have bone mass below normal. Many people mistakenly believe these are all women, but of those with osteoporosis, two million are men and another 12 million men are in the at-risk group! Yet, half of all women over 50 who have low bone mass will suffer a fracture of their hip, spine, or wrist sometime during their lifetime. Indeed one out of two women and one out of four men will break a bone due to osteoporosis. 1 Many of those who sustain hip fractures die within a year, while a great number of the survivors are unable to walk without assistance. Spinal compression fractures are the frequent cause of severe back pain. The stakes are obviously high.
Research demonstrates that a whole spectrum of nutrients is necessary for bone health. The bones are constantly remodeling themselves and a number of lifestyle factors determine their integrity.
Contributors to Osteoporosis (O.P.)
Both genetics and lifestyle play an important role in osteoporosis. Age increases the risks. Unhealthy lifestyle habits include smoking, low calcium and vitamin D intake, sedentary life, inadequate sun exposure, high caffeine, soft drink, alcohol, or salt consumption. Regular use of certain medications, such as glucocorticoids (“steroids”) can cause osteoporosis. Low levels of testosterone in men and menopause in woman accelerate it. Chronic diseases that affect the lungs, kidneys, stomach, neck glands (thyroid and parathyroid) and intestines increase one’s risk for O.P. Also, certain conditions, such as hyperthyroidism, rheumatoid arthritis, and chronic kidney disease may also lead to increased bone loss.
The Calcium Balance: Bone Builders
Calcium is essential in building strong bones. Low fat dairy products are not the only choices to obtain an adequate calcium intake. Many dark green leafy vegetables, dried fruits, legumes, tofu, and fortified soy beverages also contain modest levels of calcium. Nonetheless, for adequate use of the calcium in food, the body needs enough vitamin D, the sunshine vitamin, to be able to absorb it in the intestines.
The Calcium Balance: Bone Robbers
Some additional dietary factors may also alter the calcium balance. Phosphoric acid in soft drinks decreases calcium absorption but increases fecal calcium losses. The levels of calcium excreted in the urine are increased with a high sodium intake. The ingestion of caffeine-containing foods and beverages also poses a risk. In a prospective study of middle-aged women, risk of hip fracture in high-caffeine users was three times that of the non-caffeine users, and the use of only one ounce of alcohol per day more than doubled the risk of hip fractures compared to non-drinkers.2 Calcium excretion is actually a more important determinant of the calcium status than is calcium absorption. On the average, for every gram of sodium ingested, an additional 25 mg of calcium are lost.3
Just a Little Slide
The long-term consequence of even a small change in calcium balance can prove quite substantial. On the average, a 30-mg increase in urinary calcium loss per day will result in an 11-gram loss per year. This corresponds to about 22% and 30% of a typical male and female skeleton, respectively, over a 20-year period.4
But Calcium is Not the Whole Story
Animal protein diets lead to increases in urinary calcium loss. In one study, postmenopausal lacto-ovo-vegetarian women lost only half as much bone mineral mass after age 5o compared with a similar group of non-vegetarian women, even though both groups consumed similar levels of calcium. 5 Calcium loss is, overall, less in vegetarians.
Reported by Dr. Hegsted, hip fractures around the world occur more frequently in populations that consume higher intakes of protein and higher levels of calcium derived mainly from dairy products. 6,7
As mentioned, adequate vitamin D is essential for the utilization of calcium. The elderly enjoy significantly stronger bone density and fewer fractures when they consume adequate levels of vitamin D as well as calcium. However, marginal vitamin D status or even deficiency is fairly common among the elderly due to poor synthesis of vitamin D from sunlight and inadequate food sources.
A satisfactory intake of the trace mineral boron may also help to reduce the risk of osteoporosis. Postmenopausal women fed a diet supplemented with 3 mg of boron excreted about 20% less calcium in their urine than did those receiving no supplement.8 Soy, almonds, peanuts, raisins, prunes, and hazel nuts also have high levels of boron.
A number of intervention studies have established the benefit to bone health of an increased calcium intake among women in late menopause.9 Calcium supplements appear to exert beneficial effects on bone density in these women, particularly when their calcium intake is low. Bone loss in the immediate postmenopausal period is usually precipitated by decreases in the estrogen level, resulting in a lower benefit on bone mass during the first five years after menopause from calcium intake and regular weight-bearing exercise.
Dangers of Supplements
But supplements have their limitations. For example, large calcium intakes may produce urinary tract stones in susceptible persons. Calcium carbonate, as found in some antacids, may cause constipation, while calcium gluconate may produce diarrhea. Furthermore, some supplemental sources of calcium such as bone meal, dolomite, and oyster shells are often contaminated with lead and other toxic heavy metals. In addition, iron absorption may be reduced by calcium supplements by as much as 50%! Large doses of calcium appear to interfere with the blood-clotting action of vitamin K, while the chronic use of calcium supplements may cause the body to adapt to high levels of calcium and suppress vitamin D activity. While total daily calcium intake should be about 1200 mg to 1300 mg during adolescence, pregnancy, and lactation, clearly supplementation exceeding total calcium intake of 1000 mg per day at other times is not recommended.
Normal, healthy persons who are bedridden for periods of time lose substantial bone mass. In those who engage in weight-bearing exercise, such as walking or other vigorous activities that require exertion against gravity, bone loss occurs slowly as they age.
Finnish women aged 50 to 60 who participated in physical activity for four or more hours per week had significantly higher bone mineral density than the women who were much less active.10 Scientists at Tufts Research Center on Aging showed that spinal bone density in sedentary postmenopausal women decreased 7% over one year while similar women who walked one hour a day, four times a week, had no loss of bone density.11
For postmenopausal women, an adequate level of serum estrogen also helps to maintain bone density. Low dose estrogen replacement therapy has proven very effective in reducing bone loss. The major drawback with such therapy is that there is a substantial increase for endometrial cancer and thrombosis. Doctors usually reserve this therapy for persons at high risk for osteoporosis.
Osteoporosis is a lifestyle problem that cannot be simply cured with a pill. It is also not just a “woman’s disease”. The best defense against osteoporosis is to maximize bone mass before maturity and minimize the rate of bone loss during aging. A lifetime of adequate calcium intake absorption and incorporation ensures the development of peak bone mass by age 35. This is useful to know not only for you but also to sensibly guide your spouse, your children, and your grandchildren.
The risk of osteoporosis can be greatly reduced by the maintenance of appropriate body weight, regular exercise, moderate exposure to sunshine, avoidance of smoking and alcohol, and ingestion of adequate calcium over a lifetime. Your bone bank is like a regular bank. If you deposit more than you withdraw, your balance grows. Conversely, when withdrawals exceed deposits, the balance diminishes. A good diet and healthful lifestyle will help to keep your bone bank in rich condition.
- Osteoporosis Fast Facts↩
- Hernandez-Avila,M., et al. Caffeine, Moderate Alcohol Intake, and Risk of Fractures of the Hip and Forearm in Middle-aged Women. Am J Clin Nutrition, 54:157-63, 1991↩
- McBean, L.D., et al. Osteoporosis: Visions for Care and Prevention. A Conference Report. J AM Diet Assoc, 94:668-71, 1994↩
- Brazel, US., et al. Excess Dietary Protein Can Adversely Affect Bone. J Nutr, 128: 1051-53, 1998↩
- Ibid, Braze↩
- Hegsted, D.M. Calcium and Osteoporosis. J Nutr, 116:2316-2319, 1986↩
- Linkswiler, H.M., Joyce, C.L., et al. Calcium retention of young adult males as affected by level of protein and of calcium intake. Tran New York Acad. Sci, series ll, 36:333-349, 1974↩
- Nielsen, F. H., et al. Effect of Boron Depletion and Repletion on Blood Indicators of Calcium Status in Humans Fed a Magnesium-Low Diet. J Trace Elem Exp Med, 3:45-54, 1990↩
- Heaney, R.P., Nutritional Factors in Osteoporosis, Ann Rev Nutri, 13:287-316, 1993↩
- Ceng, S., et al. Bone Mineral Density and Physical Activity in 50-60 Year Old Women. Bone and MIneral, 12:123-132, 1991↩
- Nelson, M.E., Fisher, E.C., et al. A 1-year Walking Program and Increase↩