Dietary calcium and bone density among middle-aged and elderly women in China

Nutrition, genetics and skeletal development

From infancy through young adulthood the activity of bone formation predominates, resulting in a steady accumulation of bone mass. As the rate of growth changes with age, so skeletal modeling progresses through phases of different intensity with time. This is paralleled by concomitant changes in bone and calcium metabolism. Bone modeling and skeletal consolidation probably result from a complex sequence of hormonal changes in interaction with nutritional factors. However, current knowledge of the role, sequence, and genetic regulation of hormonal events during puberty, and of the response of bone tissue in interaction with nutrition is limited. This interaction is now beginning to be elucidated. The importance of this interaction with regard to fracture epidemiology in children and peak bone mass acquisition has been discussed.

The epidemiology of osteoporosis. The oriental perspective in a world context

In the past 3 decades, the incidence of osteoporotic hip fracture increased in Hong Kong Chinese by 2-fold to reach an incidence of approximately 10 per 1000 in women and men who are 70 years of age or older. It has been projected that 50% of all hip fractures in the world will occur in Asia by the next century. The bone mineral density of Asian populations is comparable to that of whites after adjusting for height and weight. Physical inactivity, a low dietary calcium intake, and falls have been found to be major risk factors for hip fractures in Asia. Other risk factors are cigarette smoking, heavy alcohol consumption, and multiparity. Population strategies to increase physical activity and calcium intake and to prevent falls in Oriental populations will be effective in the prevention of osteoporosis and hip fracture because of the high attributable risk for these factors.

Assessment of dietary intakes of cadets at the US Military Academy at West Point

OBJECTIVE

A study was conducted at the US Military Academy, West Point, NY, to assess the nutritional adequacy of menus and dietary intakes of the cadets and to determine the effect of the optional weekday evening meal policy on nutrient intakes.

METHODS

Dietary intakes were obtained over a 7-day period using a diary-interview technique. Volunteer cadets, 118 males and 86 females, recorded their own intakes and were interviewed by dietitians to verify food records. Cadets were categorized by gender and divided into three groups based on whether they consumed 0-1, 2-3, or 4-5 weekday evening meals in the Cadet Mess.

RESULTS

Multivariate methods were used to assess compliance with Military Recommended Dietary Allowances (MRDA) and nutrient densities as well as the role of gender, number of weekday evening meals consumed in the West Point Cadet Mess, and the use of nutritional supplements during the study week. The number of weekday evening meals consumed in the Cadet Mess, was positively correlated with the nutrient intakes of the cadet groups. The female 0-1 group had the highest proportion of individuals with mean intakes providing < 70% MRDA for vitamin B6, folate, vitamin A, magnesium, or zinc. Snacks provided from 24% to 32% of the energy intakes of the female groups and were often substituted for meals, particularly by cadets who ate the fewest meals in the Cadet Mess.

CONCLUSIONS

Diet counseling is recommended to help these cadets choose more nutritious meals and snacks. University and college students that choose not to purchase some of their meals from campus dining facilities could have similar dietary intake patterns and nutritional shortcomings.

Physical activity, nutrition, and chronic disease

Epidemiologic, animal, clinical, and metabolic studies demonstrate the independent roles of physical activity and nutrition in the prevention and treatment of several chronic diseases. Fewer data are available to describe the synergistic effects of exercise and diet, and questions remain as to whether and how these two lifestyle factors work together to promote health and prevent disease. This paper briefly reviews many of the known effects of physical activity and nutrition on the prevention and treatment of coronary heart disease, non-insulin-dependent diabetes mellitus, obesity, and osteoporosis as well as how exercise and diet may work together. A discussion of how to increase physical activity levels and how to improve dietary intake also is included. Finally, current exercise and dietary recommendations are summarized, as are directions for future research.

Dietary calcium intake, physical activity and the risk of vertebral fracture in Chinese

To study the relationship between dietary calcium intake, load-bearing activity, reproductive factors, anthropometric factors and vertebral fracture in Chinese, a case-control study was carried out on 481 women (aged 70-79 years) who lived in three housing blocks under the Geriatric Priority Housing Scheme in Shatin, Hong Kong. Lateral spine radiographs were taken from the T4 to L4 level. Definite and doubtful vertebral fractures were diagnosed when any of the three vertebral height (anterior to anterior, middle to posterior and posterior to posterior) ratios was 3 SD and 2-2.99 SD below the mean respectively. Women with one or more definite fractures were classified as definite cases, those with one or more doubtful fractures were classified as doubtful cases, and the rest as controls. The mean dietary calcium intake and load-bearing activities were obtained by interview, using a structured questionnaire. Detailed information on cigarette smoking, alcohol consumption and reproductive factors was also obtained. The grip strength, body weight and height were measured. Doubtful cases were found to differ little from the controls in their lifestyle and anthropometric factors. The odds ratio (OR) for being a definite case was 2.1 (95% CI = 1.1-3.9) when the dietary calcium intake was in the lowest quartile. The OR was 1.8 (95% CI = 0.8-4.4) for subjects who walked or exercised outdoors for less than an hour a day. Giving birth to or breast-feeding three children or more was protective against definite fracture. The definite cases were significantly lighter and shorter than controls; they also had a weaker grip strength. It is concluded that a low dietary calcium intake was significantly associated with an elevated risk of vertebral fracture, while the effect of infrequent load-bearing activity was uncertain. Giving birth to or breast-feeding three or more children was protective against vertebral fracture in our population.

Factors contributing to skeletal health of postmenopausal Mexican-American women

Incidence rates of hip fracture are lower in Hispanic (HC) than non-Hispanic Caucasians (NHC). To investigate factors that may affect skeletal health of Hispanics, we recruited 152 healthy community-dwelling Mexican-American Caucasian women into a 4-year longitudinal study that evaluates bone mass, nutritional status, muscle strength, mobility, falls, and other factors that may contribute to fracture risk. Results from the baseline component of the study are reported herein. Average bone mineral densities (BMD) evaluated by dual-energy X-ray absorptiometry (DXA) in this study group did not differ from BMDs in healthy, NHC women of similar age. Hip axis length (HAL), however, was significantly shorter than that reported for nonosteoporotic NHC. Factors independently associated with greater BMD and BMC at certain skeletal sites were lean body mass, fat mass, acculturation, years of estrogen use, sun exposure, hip adductor strength, grip strength, erythrocyte folate, and serum glucose concentrations. Factors independently associated with lower BMD and BMC at certain skeletal sites were age, parity, and vertebral deformities (all p < 0.05). Thus, the decreased risk of hip fracture in HC compared with NHC does not appear to be due to high bone mass. However, other factors such as HAL and body composition may play a role in maintenance of skeletal integrity.

Diet, bone mass, and osteocalcin: a cross-sectional study

To determine the relationships among nutrients intake, bone mass, and bone turnover in women we have investigated these issues in a population-based, cross-sectional, observational study in one county in central Sweden. A total of 175 women aged 28-74 at entry to the study were included. Dietary assessment was made by both a semiquantitative food frequency questionnaire and by four 1-week dietary records. Dual energy X-ray absorptiometry was performed at five sites: total body, L2-L4 region of the lumbar spine, and three regions of the proximal femur. Serum concentrations of osteocalcin (an osteoblast-specific protein reflecting bone turnover) were measured by a radioimmunoassay. Linear regression models, with adjustment for possible confounding factors were used for statistical analyses. A weak positive association was found between dietary calcium intake as calculated from the semiquantitative food frequency questionnaire and total body bone mineral density (BMD) among premenopausal women. No association emerged between dietary calcium intake and site-specific bone mass, i.e., lumbar spine and femoral neck, nor was an association found between dietary calcium intake and serum osteocalcin. BMD at some of the measured sites was positively associated with protein and carbohydrates and negatively associated with dietary fat. In no previous studies of diet and bone mass have dietary habits been ascertained so carefully and the results adjusted for possible confounding factors. Neither of the two methods of dietary assessment used in this study revealed any effect of calcium intake on BMD at fracture-relevant sites among these healthy, mostly middle-aged women.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized double-blind controlled calcium supplementation trial, and bone and height acquisition in children

There is limited information relating Ca intake to bone and height acquisition among Oriental children who consume little or even no milk. The present controlled study investigated the acquisition of bone mass and height of Chinese children with an initial Ca intake of approximately 567 mg/d who were supplemented to about 800 mg/d. Eighty-four 7-year-old Hong Kong Chinese children underwent an 18-month randomized, double-blind, controlled Ca-supplementation trial. The children were randomized to receive either 300 mg elemental Ca or a placebo tablet daily. Bone mass of the distal one-third radius was measured by single-photon absorptiometry, lumbar spine and femoral neck were determined using dual-energy X-ray absorptiometry. Measurements were repeated 6-monthly. Baseline serum 25-hydroxycholecalciferol concentration and physical activity were also assessed. Baseline Ca intakes of the study group and controls were respectively 571 (SD 326) and 563 (SD 337) mg/d. There were no significant differences in baseline serum 25-hydroxycholecalciferol concentration (P = 0.71) and physical activity (P = 0.36) between the study and control groups. After 18 months the study group had significantly greater increases in lumbar-spinal bone mineral content (20.9 v. 16.34%; P = 0.035), lumbar-spinal area (11.16 v. 8.71%; P = 0.049), and a moderately greater increment in areal bone mineral density of the radius (7.74 v. 6.00%; P = 0.081) when compared with the controls. The results confirm a positive effect of Ca on bone mass of the spine and radius but no effects on femoral-neck and height increase. A longer trial is warranted to confirm a positive Ca effect during childhood that may modify future peak bone mass.

Determinants of bone mass in the Chinese old-old population

One hundred and eighty-eight elderly men and women were included in a study of bone mass at the neck of femur and its related factors. The study subjects were a subsample of a Hong Kong wide study of the elderly population aged 70 years and above. The study variables included age, sex, body measurements of height, weight, body mass index, dietary calcium intake, grip strength, 16 feet (5 m) gait speed, smoking, drinking, and years since menopause among women. The neck of femur bone mineral density among elderly men was about 1 standard deviation higher than that of women. Subjects aged 85 years and above had about 20% lower bone mineral density at the neck of femur when compared with those in the age group 70-74 years. Mean dietary calcium intake ranged between 300 and 430 mg/day and was not associated with bone mass. Multiple regression analysis showed that body weight, 16 feet gait speed, sex and alcohol consumption explained 46% of the total variance of femoral neck bone mineral density. Body weight was the most significant predictor of bone mineral density, with a partial correlation coefficient of 0.5. The maintenance of body weight within the acceptable weight range and promotion of physical fitness may be important measures in reducing bone loss in the elderly population.

Bone density and lifestyle characteristics in premenopausal and postmenopausal Chinese women

The relationships between bone health and various lifestyle factors were examined in a cross-sectional study in 775 Chinese women aged 35-75 years. Bone mass was significantly positively associated with body weight, height, body mass index (BMI) and duration of breastfeeding, but was not significantly associated with other lifestyle variables, including alcohol consumption, parity, age at menarche and age at menopause after adjusting for age and body weight. A positive association was observed in premenopausal women (but not in postmenopausal women) for bone density with current cigarette smoking and plasma and urinary cotinine (the major metabolite of smoking). However, the confounding effects of other unknown factors present in this cross-sectional study may not be excluded. Daily physical activity, as indicated by time spent working in the fields, was found consistently to be positively associated with bone mass (p < 0.0001). When these women were grouped into three physical activity levels on the basis of occupation and daily work intensity, those undertaking heavy labor also had significantly higher radial bone mass than women undertaking light or medium labor. These results suggest a protective effect of daily physical activity on bone health in both pre- and postmenopausal women.