Best Study | Bone and Soy

Bone and Soy

A review of the current research is confusing regarding the effect of soy on bone. What we do know is that soy contains phytoestrogens or plant estrogens. During menopause estrogen levels drop in women and so does their bone density. The soy phytoestrogens called isoflavones act like a weak form of estrogen and may help to preserve bone. In several studies, soy isoflavones' influence on bone has been investigated.

The scientific results presented at the Fourth International Symposium on the Role of Soy in Preventing and Treating Chronic Disease are conflicting. Eva Lydeking-Olsen, from the Institute for Optimal Nutrition in Denmark, found that postmenopausal women eating a diet with a high isoflavone soymilk had an increase in spinal bone mineral density (BMD) whereas, the spine BMD of women eating a soymilk low in isoflavones decreased. However, Mara Vitolins, from Wake Forest University, found no differences in BMD at any bone site when women ate soy protein. Lisa Spence, from Purdue University, also showed no differences in BMD between women who ate a low and women who ate a high isoflavone diet. However, epidemiological studies do suggest that a higher isoflavone intake is associated with a higher BMD. So why all the conflicting information? The study designs, the age of the subjects, the number of subjects, and the length of the studies all contribute to conflicting results regarding soy. Research studies are only beginning to determine the effects of soy on bone health.

Apart from the possible beneficial effects of soy isoflavones on bone, substituting soy protein for animal protein may reduce the loss of calcium in the urine. Since 99% of the body's calcium is stored in the bones, eating soy may preserve calcium thus, may preserve bone. On a gram basis, soy protein causes less calcium to be lost in the urine than animal protein. In addition, soy foods provide high quality protein, are low in saturated fat, and are a good source of essential fatty acids. The Food and Drug Administration announced diets low in saturated fat and cholesterol that include 25g of soy protein a day may reduce the risk of heart disease.

The relationship between soy and bone is unclear at this time. However, adding soy to any diet will add variety. Variety, balance and moderation are the keys to a healthy diet

Bone, Estrogen, Strength Training (BEST) Study

Osteoporosis and cardiovascular disease account for the majority of deaths and health care costs in older women in the United States. The BEST (Bone, Estrogen, Strength Training) research study at the University of Arizona was designed to evaluate the effectiveness of exercise on bone and cardiovascular health in postmenopausal women.

BEST Study Design
The BEST study was designed to examine the effects of exercise in two populations of inactive, non-smoking, postmenopausal women, with no history of bone fractures or osteoporosis. The women were assigned to two groups: those on Hormone Replacement Therapy (HRT) and those not on HRT (noHRT). Within each of these two groups (HRT and noHRT) the women were randomly assigned to the intervention (exercise) group or the control group (no exercise). All participants were provided with calcium supplements containing 800 milligrams of calcium (calcium citrate) per day. (first part on home page and link to complete article on

The Exercise Program
The exercise program included six parts: warm up, progressive weight bearing movement, resistance exercises, abdominal strengthening, stretching, and balance exercises. The program follows the exercise guidelines from the American College of Sports Medicine and was designed to improve cardiorespiratory endurance, muscle strength, flexibility, and balance, along with bone mineral density. The program was carried out in local exercise facilities with trainers three times a week. A total of 266 women completed the one-year exercise program, making it the largest study to date investigating the effects of exercise in a clinical trial.

Selected Preliminary Results
1. The combination of HRT, exercise, and calcium intake increased bone mineral density the most.

2. Those who lifted more weight had the most gains in bone- especially at the hip location.

3. The exercise program had less effect on bone for those who lost 5 lbs or more of body weight, as compared to those who did not lose weight or those who gained weight.

4. The exercise program had less effect on bone for those who had higher scores of depression at the beginning of the study.

5. Large increases in body strength were found for all subjects who participated in the exercise program. Increases were also found in body image, self-concept, and quality of life.

This research is important because we found that consistent weight lifting and weight-bearing exercise with HRT and calcium citrate supplementation has an advantage over other combinations. In addition, if participants continue to follow this comprehensive program for several years, further benefits to fracture risk may be obtained in post-menopausal women.

Sponsors
Sponsors of the BEST study include: the National Institute for Arthritis and Musculoskeletal and Skin Diseases, of the National Institutes of Health, University of Arizona Departments of Physiology and Nutritional Sciences, and Mission Pharmacal. The study was conducted by the University of Arizona's Departments of Physiology and Nutritional Sciences, which are in the colleges of Medicine and Agriculture and Life Sciences. The following community fitness facilities provided facilities for the BEST study: The Fitness and Health Institute of Tucson, University Medical Center Health and Wellness Center, Naturally Women Fitness Centers, and Metro Fitness.

Contact Information
Nuris Finkenthal
BEST Program Coordinator
nuris@email.arizona.edu
520-621-4391

Published article:

Metcalfe L, Lohman T, Going S, Houtkooper L, et al. Postmenopausal Women and Exercise for Prevention of Osteoporosis. ACSM"S Health and Fitness Journal May/June 2001.

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