Last week's article reported on the connection between dieting and bone loss. In 1992 Dr. Henry C. Lukaski of the Grand Forks Human Nutrition Research Center in North Dakota conducted a five-month study of fourteen women in a weight reduction program. He found that the women lost one to two percent of their bone mass along with an average of eighteen pounds of weight.
Ballerinas and Osteoporosis
There have been epidemiological studies whose conclusions support Dr. Lukaski's clinical study correlating bone loss with weight loss. The New England Journal of Medicine published a study (5/22/86), which found that nearly a quarter of 75 female ballerinas surveyed at four major ballet companies had some degree of scoliosis, more than six time the normal rate of females in this age range. The study also found that dancers with scoliosis were more likely to have eating disorders (bulimia and anorexia) than others. It would appear that the curved spines and stress fractures of these young ballerinas are manifestations of the same osteoporosis that afflicts many postmenopausal women, taking a somewhat different form in youth than in middle age or old age.
It could be argued that it is the intense physical exercise involved in the training of young ballerinas rather than the intense dieting which often accompanies such exercise that is the real cause of the weakened bones. However, weight-bearing exercise is known to increase bone mass. It is more probable that the exercise is a compensating factor, which is not, however, sufficient to offset the deleterious effect of malnutrition. The authors of the study are of the opinion that: "the findings in the sample are especially surprising because extensive physical training of the type in which ballet dancers engage may have a protective effect on the skeleton and prevent bone loss. The studies suggest that the stress associated with regular strenuous exercise may not be sufficient to compensate for the loss in estrogen or dietary deficiencies at a crucial stage."
Anorexia Nervosa And Osteoporosis
To establish definitively whether the bones of the ballerinas were weakened by exercise or dietary deficiencies, a study of bone density in a population of anorexics who are not also ballerinas would be needed. Fortunately, such a study has been done. "Osteoporosis in Women With Anorexia Nervosa," also reported in The New England Journal of Medicine (12/20/84), involved a study of 18 anorexic women around the age of 25: "Our results demonstrate that women with anorexia nervosa have a significant reduction in critical bone density in comparison to controls of normal weightWe believe that the decreased bone density represents osteoporosis. The clinical consequence of decreased bone density was manifest in two patients who had multiple vertebrae compression fractures with back pain and loss of height before the age of 25." Their conclusions support the hypothesis of the ballerina study that it is malnutrition rather than strenuous exercise that is responsible for the loss of bone mass. In fact, their data confirm the protective effects of exercise on bone mass: "Patients reporting a high level of regular exercise had a significantly greater bone density than less active patientsFurthermore, the mean bone density of highly active patients did not differ from that of active or sedentary controls, suggesting that exercise may be protective."
The authors of the study go on to make the connection between malnutrition due to anorexia nervosa in adolescence and postmenopausal osteoporosis: "Young women who have an episode of anorexia nervosa during adolescence may not attain their potential peak skeletal mass and may have a lower bone density than age-matched normal subjects in early adulthood. Loss of bone mass may occur in addition to failure of bone development. After the menopause, when the rate of bone loss accelerates, women who have recovered from anorexia may be at an increased risk for osteoporotic fractures of the hip, vertebrae, and wrist."
It is reasonable to hypothesize, then, that the epidemic of osteoporosis in postmenopausal women in this country might very well be the result of chronic long term dieting, which though not as severe as that of anorexia nervosa, takes its toll over the years, finally manifesting its damage in the same symptoms at mid-life that afflict anorexic women in their mid-twenties. The studies reported in these articles were based upon a population of young girls at the start of their reproductive lives who yet displayed the brittle bones and curved spines of osteoporotic women at the end of theirs. The malnutrition brought about from dieting could well be the common cause of the brittle bones of the ballerinas and the elderly women in walkers.
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.