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

An Algorithm to Assess Calcium Bioavailability from Foods

BACKGROUND

The recommended calcium intakes to meet calcium requirements at various ages are based on average population absorption values. Absorption is altered by physiology, the calcium load, and type of food. The calcium intake necessary, therefore, to meet requirements depends upon diet composition, through bioavailability.

OBJECTIVE

The objectives of this study was to improve predictions of calcium bioavailability on the basis of the food matrix.

METHODS

We modeled calcium absorption data from individual foods, beverages, and fortified foods that were determined with calcium isotopic tracers and compared with milk as a referent to adjust for physiologic differences of the host.

RESULTS

Data from 496 observations were modeled to develop a predictive algorithm for calcium bioavailability in adults on the basis of calcium load and oxalate and phytate loads, which represent the 2 main inhibitors of calcium absorption.

CONCLUSIONS

This algorithm will be helpful in assessing calcium availability from the food supply, for developing diets for individuals and research cohorts, and for designing policies and interventions to address inadequate calcium intake for populations.

Effects of Hard Water Boiling on Chalky Rice in Terms of Texture Improvement and Ca Fortification

In the present paper, we investigated the characteristics of chalky rice grains generated by ripening under high temperature and compared them with whole grains. We evaluated 14 unpolished Japonica rice grains harvested in Japan in 2021, and these samples (original grains) were divided into two groups (a whole grain group and a chalky grain one). We found that not only activities of endogenous amylase and proteinase, but also cell wall-degrading enzymes, such as xylanase and cellulase, changed markedly between chalky grains and whole grains. Using rice grains blended with 30% of chalky grains as the material, we compared the sugar and mineral contents and textural properties of the rice grains soaked and boiled in either ordinary water or hard water, such as Evian or Contrex. It was shown that xylanase, in addition to amylase and proteinase, may play an important role in changing the texture of the boiled chalky rice grains. For the sake of preventing the above-mentioned deterioration in the texture of boiled grains of chalky rice, we tried to use hard water, such as Evian or Contrex, to soak and cook the chalky rice grains. It was shown that the hard water was useful for the prevention of texture deterioration of the boiled rice grains due to inhibition of the activities of endogenous hydrolytic enzymes, such as α-amylase, β-amylase, proteinase, and xylanase. Furthermore, we found that the hard water was useful in increasing the calcium absorption through the meal by 2.6 to 16.5 times.

Comparison of physicochemical properties of different tissues from China climbing perch Anabas testudineus and crucian carp Carassius auratus

This study aimed to investigate nutrition in climbing perch Anabas testudineus which is an important nutritious economic freshwater fish in Asia and compare with Carassius auratus (crucian carp). Three kinds of tissues, including muscle, livers, and eggs, were isolated, respectively. Physicochemical properties including moisture, ash, protein, amino acids, fat, vitamins, and calcium contents in those tissues were determined. The results showed climbing perch muscle and liver contained less moisture, but more protein, amino acids, and vitamins than crucian carp muscle and liver. While moisture, ash, protein, and total amino acids contents of climbing perch egg were lower than those of crucian carp egg. Climbing perch egg had more fat, vitamins, and calcium than crucian carp egg. The amino acid profile was also performed, and 16 amino acids were identified and quantified in muscle, liver, and egg. Among tissues, the highest and lowest concentration of total amino acid content was found in crucian carp eggs and livers, respectively. Glutamic acid (Glu) and histidine (His) were the most and least amino acids in climbing perch and crucian carp tissues, respectively. Sixteen amino acids in climbing perch egg were less than those in crucian carp egg while it is an opposite case in muscle and liver, which amino acids of climbing perch tissues were more than those of crucian carp muscle and liver. Vitamin A of climbing perch was more than crucian carp in all three tissues, but vitamin E content in climbing perch liver was lower than that of crucian carp liver. Calcium content of muscle had no difference between two species. The abovementioned comparison of physicochemical properties of different tissues from China climbing perch and crucian carp will provide a necessary supplementary of freshwater muscle nutrition research, also was helpful for application of climbing perch.

Fortified Milk Supplementation Improves Vitamin D Status, Grip Strength, and Maintains Bone Density in Chinese Premenopausal Women Living in Malaysia

This study compared the effects of a high-calcium vitamin D fortified milk with added FOS-Inulin versus regular milk on serum parathyroid hormone (PTH), vitamin D status, grip strength (GS), as well as bone density in Chinese premenopausal women over 52 weeks. Premenopausal women (n = 133), mean age 41 (±5.1) years were randomized into control (n = 66; regular milk at 500 mg calcium per day) or intervention (Int; n = 67; fortified milk at 1200 mg calcium, 15 μg vitamin D, and 4 g FOS-Inulin per day) groups. Assessments were at baseline, weeks 12, 24, 36, and 52 for changes in vitamin D status, levels of PTH, and GS. Bone mineral densities (BMDs) of the lumbar spine (LS), femoral neck (FN), and whole body (WB) were assessed at baseline and week 52 using GE Lunar iDEXA (GE Healthcare, Madison, WI). At baseline, WB lean mass was positively associated with LS BMD (r = 0.30, p < 0.001) and FN BMD (r = 0.33, p = 0.003). Baseline 25(OH) vitamin D3 levels were 48.6 and 53.2 nmol/L (p = 0.57), respectively, and after the 12 months at 60.8 nmol/L (Int) versus 55.0 nmol/L (controls; p < 0.05 for change from baseline for both groups; no difference between groups at week 52). PTH levels decreased in both groups compared to baseline (p < 0.001), with no significant difference between groups. WB bone mineral content (BMC) and FN Z-score increased significantly in the Int group (p = 0.024 and p = 0.008). GS was positively associated with body weight, increasing in both groups over 52 weeks. Fortified milk improved vitamin D status, WB BMC, and Z-score of the FN, while regular milk maintained BMD. In addition, vitamin D status and GS improved.

Evaluation of the Relationship Between Height and Zinc, Copper, Iron, Calcium, and Magnesium Levels in Healthy Young Children in Beijing, China

We evaluated the relationship between child (aged 6-36 months) height and blood zinc, copper, iron, calcium, and magnesium concentrations. We selected 840 children following a physical examination. Weight and supine length or standing height were measured according to the World Health Organization guidelines. Polarographic analysis was used to measure zinc, copper, iron, magnesium, and calcium levels. Differences in heights between groups with low vs. high mineral concentrations, stratified by sex and age, were compared by analysis of variance. Relationships between these five elements and heights were tested by multiple regression analysis. Zinc levels in the shorter group (height for age (HAZ) ≤ -0.3) were 135.84 ± 39.76 and 134.83 ± 37.57 μmol/L in boys and girls, respectively. Zinc concentrations in the taller group (HAZ > -0.3) were 142.50 ± 35.85 and 140.52 ± 35.80 μmol/L in boys and girls, respectively. The difference between the two height groups in boys and girls was statistically significant. Compared with those (143.06 ± 33.76 μmol/L) in the taller group, zinc concentration (131.30 ± 40.75 μmol/L) in the shorter group was significantly lower (p = 0.04) at age 6-12 months. Height was positively correlated with zinc level in children aged 6-12 months (p < 0.05). Zinc levels were positively correlated with calcium, magnesium, and iron concentrations in children aged 6-36 months (p < 0.05). Our results indicated that zinc levels and height are correlated, and zinc levels were related to calcium, magnesium, copper, and iron concentrations. Therefore, to ensure healthy development in children, blood levels of these five elements should be balanced.

Short-Term Effects of Kefir-Fermented Milk Consumption on Bone Mineral Density and Bone Metabolism in a Randomized Clinical Trial of Osteoporotic Patients

Milk products are good sources of calcium that may reduce bone resorption and help prevent bone loss as well as promote bone remodeling and increase bone formation. Kefir is a product made by kefir grains that degrade milk proteins into various peptides with health-promoting effects, including antithrombotic, antimicrobial and calcium-absorption enhancing bioactivities. In a controlled, parallel, double-blind intervention study over 6 months, we investigated the effects of kefir-fermented milk (1,600 mg) supplemented with calcium bicarbonate (CaCO3, 1,500 mg) and bone metabolism in 40 osteoporosis patients, and compared them with CaCO3 alone without kefir supplements. Bone turnover markers were measured in fasting blood samples collected before therapy and at 1, 3, and 6 months. Bone mineral density (BMD) values at the spine, total hip, and hip femoral neck were assessed by dual-energy x-ray absorptiometry (DXA) at baseline and at 6 months. Among patients treated with kefir-fermented milk, the relationships between baseline turnover and 6 months changes in DXA-determined BMD were significantly improved. The serum β C-terminal telopeptide of type I collagen (β-CTX) in those with T-scores > -1 patients significantly decreased after three months treatment. The formation marker serum osteocalcin (OC) turned from negative to positive after 6 months, representing the effect of kefir treatment. Serum parathyroid hormone (PTH) increased significantly after treatment with kefir, but decreased significantly in the control group. PTH may promote bone remodeling after treatment with kefir for 6 months. In this pilot study, we concluded that kefir-fermented milk therapy was associated with short-term changes in turnover and greater 6-month increases in hip BMD among osteoporotic patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02361372.

Differential effects of calcium- and vitamin D-fortified milk with FOS-inulin compared to regular milk, on bone biomarkers in Chinese pre- and postmenopausal women

PURPOSE

To compare the effects of a high-calcium vitamin D-fortified milk with added FOS-inulin versus regular milk on serum parathyroid hormone, and bone turnover markers in premenopausal (Pre-M) and postmenopausal (PM) women over 12 weeks.

METHODS

Premenopausal women (n = 136, mean age 41 (±5) years) and postmenopausal women [n = 121, mean age 59 (±4) years] were recruited, and each age group randomised into two groups to take two glasses per day of control = regular milk (500 mg calcium per day) or intervention (Int) = fortified milk (1000 mg calcium for pre-M women and 1200 mg calcium for PM women, 96 mg magnesium, 2.4 mg zinc, 15 µg vitamin D, 4 g FOS-inulin per day). At baseline, week 4 and week 12 serum minerals and bone biochemical markers were measured and bone density was measured at baseline.

RESULTS

Mean 25-hydroxyvitamin D [25(OH) vitamin D3] levels among groups were between 49 and 65 nmol/L at baseline, and over the 12 weeks of supplementation, the fortified milk improved vitamin D status in both Int groups. CTx-1 and PINP reduced significantly in both Pre-M and PM groups over the 12 weeks, with the changes in CTx-1 being significantly different (P < 0.035) between PM control and PM Int groups at week 12. Parathyroid hormone levels were significantly reduced in all groups over time, except for control PM group where levels increased at 12 weeks.

CONCLUSION

The overall pattern of responses indicates that while both regular milk and fortified milk reduce bone resorption in young and older women, fortified milk is measurably more effective.

Greater milk intake is associated with lower bone turnover, higher bone density, and higher bone microarchitecture index in a population of elderly Japanese men with relatively low dietary calcium intake: Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) Study

The effects of milk intake on bone health are not clear in elderly Asian men with low dietary calcium intake. This study showed that greater milk intake is associated with lower bone turnover, higher bone density, and higher bone microarchitecture index in community-dwelling elderly Japanese men.

INTRODUCTION

The consumption of milk or dairy products is widely recommended for maintaining bone health regardless of gender or age. However, little evidence exists on the beneficial effects of milk intake on bone health in elderly Japanese men characterized with relatively low dietary calcium intake. Here we examined whether or not greater milk intake was associated with lower bone turnover, higher bone density, and stronger bone microarchitecture in community-dwelling elderly Japanese men.

METHODS

Interviews were conducted to obtain information on medical history and lifestyle, including the amount of habitual milk intake, nutrient intake calculations based on a 1-week food diary, and measurements of areal bone mineral density (aBMD) at the lumbar spine (LS), total hip (TH), and femoral neck (FN) by dual-energy x-ray absorptiometry (DXA), trabecular bone score (TBS) using DXA images at LS, and biochemical markers of bone turnover in sera. Participants with a history of diseases or medications that affect bone metabolism, or with missing data, were excluded from the analysis.

RESULTS

The median intake of milk in the 1479 participants (mean age, 73.0 ± 5.1 years) was one glass of milk per day. Bone turnover markers showed a decreasing trend (p < 0.05) and aBMD at TH (p = 0.0019) and FN (p = 0.0057) and TBS (p = 0.0017) showed increasing trends with greater milk intake after adjusting for demographic and behavioral confounding factors. This association was attenuated after further adjusting for nutrient intake, in particular, calcium intake.

CONCLUSIONS

Greater milk intake was associated with lower bone turnover, higher aBMD, and higher TBS in community-dwelling elderly Japanese men.

A descriptive study of knowledge, beliefs and practices regarding osteoporosis among female medical school entrants in Sri Lanka

BACKGROUND

Osteoporosis is a significant problem in rapidly ageing populations in Asian regions. It causes a significant personal and societal impact and increases the burden on health care services.

OBJECTIVES

Aim of this study is to determine the knowledge, beliefs and practices regarding osteoporosis among young females entering medical schools in Sri Lanka.

METHODS

This is a descriptive cross sectional study conducted amongst 186 female medical school entrants of the Faculties of Medicine, Universities of Colombo and Kelaniya from September to December 2010. A self administered questionnaire was used to assess knowledge, beliefs and practices on osteoporosis, including a food frequency chart to assess the calcium intake.

RESULTS

The mean age was 20.7 +/- 2.1 years. Majority of the participants (51.6%, n = 96) had an average score (40-60) on the knowledge test, while 40.8% (n = 76) had a poor score (<40). However, in depth knowledge on risk factors, and protective factors was lacking. Perceived susceptibility for osteoporosis was low with only 13.9% (n = 26) of women agreeing that their chances of getting osteoporosis are high. The mean calcium intake was 528 mg/day and only 18.8% (n = 35) of the participants achieved the Recommended Daily Allowances (RDA) for Calcium. Exercise was grossly inadequate in the majority and only 13.6%( n = 23) engaged in the recommended exercises. Only 3.8% (n =7) of the participants currently engaged in specific behaviours to improve bone health while 10.8% (n = 20) had thought of routinely engaging in such behaviours.

CONCLUSIONS

Although majority of participants had a modest level of knowledge on osteoporosis, there were gaps in their knowledge in relation to risk factors, protective factors and on the insidious nature of osteoporosis. Perceived susceptibility for osteoporosis was low. Practices towards preventing Osteoporosis were inadequate.

Ethnic differences in calcium, phosphate and bone metabolism

The prevalence of osteoporosis and the incidence of age-related fragility fracture vary by ethnicity. There is greater than 10-fold variation in fracture probabilities between countries across the world. Mineral and bone metabolism are intimately interlinked, and both are known to exhibit patterns of daily variation, known as the diurnal rhythm (DR). Ethnic differences are described for Ca and P metabolism. The importance of these differences is described in detail between select ethnic groups, within the USA between African-Americans and White-Americans, between the Gambia and the UK and between China and the UK. Dietary Ca intake is higher in White-Americans compared with African-Americans, and is higher in White-British compared with Gambian and Chinese adults. Differences are observed also for plasma 25-hydroxy vitamin D, related to lifestyle differences, skin pigmentation and skin exposure to UVB-containing sunshine. Higher plasma 1,25-dihydroxy vitamin D and parathyroid hormone are observed in African-American compared with White-American adults. Plasma parathyroid hormone is also higher in Gambian adults and, in winter, in Chinese compared with White-British adults. There may be ethnic differences in the bone resorptive effects of parathyroid hormone, with a relative skeletal resistance to parathyroid hormone observed in some, but not all ethnic groups. Renal mineral excretion is also influenced by ethnicity; urinary Ca (uCa) and urinary P (uP) excretions are lower in African-Americans compared with White-Americans, and in Gambians compared with their White-British counterparts. Little is known about ethnic differences in the DR of Ca and P metabolism, but differences may be expected due to known differences in lifestyle factors, such as dietary intake and sleep/wake pattern. The ethnic-specific DR of Ca and P metabolism may influence the net balance of Ca and P conservation and bone remodelling. These ethnic differences in Ca, P and the bone metabolism may be important factors in the variation in skeletal health.

High-calcium, vitamin D fortified milk is effective in improving bone turnover markers and vitamin D status in healthy postmenopausal Chinese women

BACKGROUND/OBJECTIVES

Risk for developing osteoporosis increases in Asia. The purpose of the study was to evaluate the impact of a high-calcium vitamin D fortified milk (HCM) intervention on parathyroid hormone (PTH) levels, vitamin D status and markers of bone turnover in postmenopausal Chinese women.

SUBJECTS/METHODS

Sixty three women (>55 years) were assigned to receive two servings of either a calcium/vitamin D fortified milk or a control drink for 12 weeks. PTH, serum 25 (OH)D levels, C-telopeptide of type I collagen (CTX) levels and procollagen type I N-terminal propeptide (PINP) were measured at baseline, 2, 8 and 12 weeks of supplementation.

RESULTS

Daily calcium intake at baseline ranged between 260 and 482 mg for the HCM, and 252 and 692 mg for the control group. HCM improved serum 25 (OH)D levels significantly (33.13-39.49 nmol/l), while remaining similar in the control group (29.27-28.21 nmol/l). The difference between the groups were significant at week 2, 8 and 12. The percentage change in PTH levels in the HCM group was significant from week 2 onwards compared to the control drink (P<0.017, P<0.05 and P<0.001 at weeks 2, 8 and 12, respectively). Plasma CTX of the HCM group reduced by 25% between weeks 0 and 2, remaining significantly lower and at similar levels up to week 12. The difference between the HCM and control group for PINP reached significance at weeks 8 (P=0.011) and 12 (P=0.003).

CONCLUSIONS

The HCM intervention significantly improved vitamin D status and reduced bone turnover over 12 weeks in postmenopausal Chinese women.

Dietary habit and bone mineral density in Korean postmenopausal women

SUMMARY

Postmenopausal women were assessed to determine the association between dietary intake of various food groups and low bone mineral density. Among dietary factors, high consumption of protein-containing food and dairy products was associated with a reduced risk for low bone mineral density.

INTRODUCTION

There have been several studies regarding the correlation between bone mineral density and dietary intake. In this study, we assessed the association between dietary habit and low bone mineral density among Korean postmenopausal women.

METHODS

Bone mineral density of the lumbar spine was measured by dual energy X-ray absorptiometry in 2,501 subjects. A brief food frequency questionnaire, which included 16 food items, was used in this cross-sectional survey.

RESULTS

After adjusting for other risk factors related to low bone mineral density, a high intake frequency of protein-source food was associated with a lower risk for osteopenia (odds ratio (OR), 0.68; 95% confidence interval (CI), 0.54-0.87 for high vs. low intake frequency; p for trend, 0.02) and osteoporosis (OR, 0.76; 95% CI, 0.39-0.83 for high vs. low intake frequency; p for trend, 0.003), and a high intake frequency of dairy food was associated with a decreased risk for osteopenia (OR, 0.73; 95% CI, 0.57-0.94 for high vs. low intake frequency; p for trend, 0.018).

CONCLUSION

These results suggest that adequate nutrient intake is essential to maintain bone health in postmenopausal women.

Role of dairy beverages in the diet

The U.S. Dietary Guidelines for Americans recommends 3 cups of low fat milk or equivalent daily for most calorie levels [1]. Milk provides over 10% of the requirement for calcium, vitamin D, magnesium, phosphorus, potassium, riboflavin, protein, and carbohydrates for most people. Obtaining adequate intakes of calcium, potassium, and magnesium without milk in the diet requires effort. Milk has bioactive ingredients that may play unique roles in health. Benefits of dairy consumption are associated with reduced risk of low bone mass, stroke, metabolic syndrome, and some cancers. Concerns over milk consumption have focused on saturated fats historically. More research is needed to resolve potential concerns of milk consumption and risk of several disorders including ovarian cancer and soft tissue calcification.

Should dairy be recommended as part of a healthy vegetarian diet? Point

A benefit-risk evaluation of the evidence for including dairy foods in the diet is presented. For many persons dairy products provide a substantial portion of essential nutrients, but especially calcium, potassium, and magnesium. Dietary supplements and fortified foods can be alternative sources of these nutrients, although other components of dairy foods such as amino acid composition and conjugated linoleic acid may be instrumental in the benefits associated with dairy product consumption for bone health and reduced risk of stroke, metabolic syndrome, and some cancers. Newer evidence shows that protein-induced calciuria does not have a detrimental effect on net calcium retention, and the concentrations of hormones in milk are not outside of the range of endogenous concentrations. Increased dietary protein, including from milk, can elevate serum concentrations of insulin-like growth factor I, which has an unknown relation to cancer. The concern over consumption of milk leading to increased risk of prostate cancer through reduction of serum 1,25-dihydroxyvitamin D, a potent anti-prostate cancer hormone, has been resolved with new evidence that local production of this hormone is independent of diet. Overall, evidence suggests that being a lactovegetarian has greater health benefits and reduced health risks than being a vegan.

Change in bone mineral density and its determinants in pre- and perimenopausal Chinese women: the Hong Kong Perimenopausal Women Osteoporosis Study

This 30-month study investigating bone change and its determinants in 438 perimenopausal Chinese women revealed that the fastest bone loss occurred in women undergoing menopausal transition but maintenance of body weight and physical fitness were beneficial for bone health. Soy protein intake also seemed to exert a protective effect.

INTRODUCTION

This 30-month follow-up study aims to investigate change in bone mineral density and its determinants in Hong Kong Chinese perimenopausal women.

METHODS

Four hundred and thirty-eight women aged 45 to 55 years were recruited through random telephone dialing and primary care clinic. Bone mass, body composition, lifestyle measurements were obtained at baseline and at 9-, 18- and 30-month follow-ups. Univariate and stepwise multiple regression analyses were performed with the regression coefficients of BMD/C (derived from baseline and follow-up measurements) as the outcome variables. Menopausal status was classified as pre- or postmenopausal or transitional.

RESULTS

Menopausal status was the strongest determinant of bone changes. An annual bone loss of about 0.5% was observed among premenopausal, 2% to 2.5% among transitional, and about 1.5% in postmenopausal women. Multiple regression analyses, revealed that a positive regression slope of body weight was protective for follow-up bone loss at all sites. Number of pregnancy, soy protein intake and walking were protective for total body BMC. Higher baseline LM was also protective for neck of femur BMD.

CONCLUSION

Maintenance of body weight and physical fitness were observed to have a protective effect on for bone loss in Chinese perimenopausal women.

Vitamin D status of apparently healthy schoolgirls from two different socioeconomic strata in Delhi: relation to nutrition and lifestyle

Forty to fifty per cent of skeletal mass, accumulated during childhood and adolescence, is influenced by sunlight exposure, physical activity, lifestyle, endocrine status, nutrition and gender. In view of scarce data on association of nutrition and lifestyle with hypovitaminosis D in Indian children and adolescents, an in-depth study on 3,127 apparently healthy Delhi schoolgirls (6-18 years) from the lower (LSES, n 1,477) and upper socioeconomic strata (USES, n 1650) was carried out. These girls were subjected to anthropometry and clinical examination for hypovitaminosis D. Girls randomly selected from the two strata (LSES, n 193; USES, n 211) underwent detailed lifestyle, dietary, biochemical and hormonal assessment. Clinical vitamin D deficiency was noted in 11.5 % girls (12.4 % LSES, 10.7 % USES). USES girls had significantly higher BMI than LSES counterparts. Prevalence of biochemical hypovitaminosis D (serum 25-hydroxyvitamin D < 50 nmol/l) was seen in 90.8 % of girls (89.6 % LSES, 91.9 % USES, NS). Mean intake of energy, protein, fat, Ca, vitamin D and milk/milk products was significantly higher in USES than LSES girls. Conversely, carbohydrate, fibre, phytate and cereal intakes were higher in LSES than USES girls. Physical activity and time spent outdoors was significantly higher in LSES girls (92.8 v. 64 %, P = 0.000). Significant correlation between serum 25-hydroxyvitamin D and estimated sun exposure (r 0.185, P = 0.001) and percentage body surface area exposed (r 0.146, P = 0.004) suggests that these lifestyle-related factors may contribute significantly to the vitamin D status of the apparently healthy schoolgirls. Hence, in the absence of vitamin D fortification of foods, diet alone appears to have an insignificant role.

Differences in bone mineral status between urban and rural Chinese men and women

BACKGROUND

Few studies have investigated differences in bone health and associated lifestyle factors between urban and rural populations in countries, such as China, undergoing rapid nutrition transition. Such a study may help to identify risk factors of osteoporosis and provide evidence for future preventive strategies.

OBJECTIVE

To determine primarily whether differences in bone mineral content (BMC) and bone mineral density (BMD) exist between urban and rural Chinese men and women and secondly whether any urban-rural differences could be explained by body size or lifestyle factors.

METHODS

In total, 490 men and 689 women aged 50-70 were included in the study. 535 of them were from urban Shanghai and 644 from surrounding rural areas. Anthropometric measurements were conducted and spine lumber 1-4 BMC measurements were determined by dual-energy X-ray absorptiometry (DEXA). Information on socioeconomic status, medical history, smoking and drinking habits and physical activity were collected.

RESULTS

Urban men and women had significantly higher spine BMC, BMD and bone area than their rural counterparts (P<0.01). After controlling body size, the differences between urban-rural spine BMC and BMD remained in women (P<0.001), but were no longer significant in men. The urban and rural differences of BMC and BMD in women could not be explained by including the lifestyle factors such as income, intake of milk, vitamin D and calcium, total physical activity level, walking and social activity.

CONCLUSION

This study found the significant differences in both spine BMC and BMD between urban and rural men and women in Shanghai, China. This difference could be explained by the body size in men; however, it remained unexplained in women after adjusting for body size and certain lifestyle risk factors.

Milk Supplementation and Bone Health in Young Adult Chinese Women

BACKGROUND

Milk is potentially beneficial for bone health, particularly for Chinese populations where consumption of dairy products is low. There are few data about milk consumption by Chinese women aged 20-35 years. This study examines whether milk supplement over 2 years caused increased bone mineral density (BMD) in Chinese women aged 20-35 years.

METHODS

Four hundred forty-one community-living women living in Hong Kong SAR (221) and Beijing (220) China were randomized to receive milk supplement or nothing. The supplement consisted of two sachets of milk powder (1000 mg calcium, 80 microg vitamin K(1)), for 24 months. BMD at total hip, total spine, and whole body was measured at baseline and at 6, 12, 18, and 24 months; blood specimens were analyzed at baseline and at 3 and 24 months for biochemical indices of bone turnover and vitamin K. Urine samples also were collected. Analysis was by intention to treat as well as per protocol. Differences in change from baseline between the milk and control groups were analyzed using the mixed models approach to repeated measures, including the baseline value as a covariate.

RESULTS

Both groups had an increase in BMD and a decrease in bone turnover markers over time, as an indicator of the process of attainment of peak bone mass during this period. Apart from a higher total spine BMD at 6 months in the milk group using per protocol analysis, there was little significant difference observed between the milk group and the control group.

CONCLUSIONS

Age-related bone metabolism and lack of compliance most likely explain the lack of consistent changes in BMD or bone biochemical measures in response to milk supplementation for 2 years in Chinese women aged 20-35 years.

Effect of nutrition and physical activity on bone health of children and young adults

The development and maturation of the skeletal system starts in utero. The bone-growth process starts with the addition of cells; these cells grow and incorporate materials that increase bone strength. During puberty, this process is accelerated to the degree that approximately 25% of the total bone mass is accumulated. Failure to meet the increased demand for bone-building materials during an accelerated growth period may increase fracture tendency. The greater is the bone mass at the start of puberty; the better is the final outcome at full maturity. This is in accordance with the tracking theory (keeping bone growth along a steady percentile). Nutrition and physical activity will facilitate bone accumulation from an early age. Therefore, a program for bone health that includes physical activity and nutrition should be introduced early in the prepubertal age. There are differences in the timing and rate of bone-mass accumulation of different parts of the skeleton so that measurement of one bone may not represent the whole skeleton. In addition, bone measurements using different devices cannot be compared. Therefore, until a universal standard is reached, repeated measurements of one individual should be done using the same apparatus. The choice of the apparatus should be made so that the relevant part of the skeleton is measured. Repeated measurements of bone may detect bone mass loss much earlier than the osteoporosis line is reached. This suggests that a dynamic measure of bone growth rate similar to height velocity should be adopted, since both parameters in an optimal setting follow a steady percentile and falling of the percentile in both parameters needs an etiological diagnosis.

Major Scientific Advances with Dairy Foods in Nutrition and Health

A large body of scientific evidence collected in recent decades demonstrates that an adequate intake of calcium and other nutrients from dairy foods reduces the risk of osteoporosis by increasing bone acquisition during growth, slowing age-related bone loss, and reducing osteoporotic fractures. These results have culminated in the new (2005) Dietary Guidelines for Americans that now recommend 3 servings of milk products per day to reduce the risk of low bone mass and contribute important amounts of many nutrients that may have additional health attributes beyond bone health. A number of animal, observational, and clinical studies have shown that dairy food consumption can help reduce the risk of hypertension. Clinical trials indicate that the consumption of recommended levels of dairy products, as part of a healthy diet, can contribute to lower blood pressure in individuals with normal and elevated blood pressure. Emerging data also indicate that specific peptides associated with casein and whey proteins can significantly lower blood pressure. In addition, a growing body of evidence has provided support for a beneficial effect of dairy foods on body weight and fat loss. Clinical studies have demonstrated that during caloric restriction, body weight and body fat loss occurs when adequate calcium is provided by supplements and that this effect is further augmented by an equivalent amount of calcium supplied from dairy foods. Several studies support a role for calcium, vitamin D, and dairy foods against colon cancer. Additionally, conjugated linoleic acid, a fatty acid found naturally in dairy fat, confers a wide range of anticarcinogenic benefits in experimental animal models and is especially consistent for protection against breast cancer.

Caloric restriction and calcium's effect on bone metabolism and body composition in overweight and obese premenopausal women

Obesity results in numerous preventable deaths and comorbidities. Unfortunately, a reduction of body weight has been correlated with a reduction in bone mass, the reasons for which have not been fully elucidated. The importance of maximizing peak bone mass during premenopausal years is well known. Most studies demonstrate a positive relationship between calcium intake and bone mass. However, during caloric restriction, which is commonly used for weight loss, calcium intake has shown mixed results. Calcium from dairy sources has received additional attention, beyond its importance to bone, for its role in regulating body weight and composition. Dairy foods are perceived as high fat, and therefore, are generally minimized or avoided during caloric restriction. The current calcium intake for premenopausal women is significantly below recommendations, and even if met during caloric restriction, may not be adequate. This review underscores the need for maintaining at least adequate intake levels of calcium, if not more, during weight loss regimens to minimize potential long-term detrimental effects on bone metabolism.

Calcium supplementation and bone mineral density in females from childhood to young adulthood: a randomized controlled trial

BACKGROUND

Short-term studies established that calcium influences bone accretion during growth. Whether long-term supplementation influences bone accretion in young adults is not known.

OBJECTIVE

This study evaluated the long-term effects of calcium supplementation on bone accretion among females from childhood to young adulthood.

DESIGN

A 4-y randomized clinical trial recruited 354 females in pubertal stage 2 and optionally was extended for an additional 3 y. The mean dietary calcium intake of the participants over 7 y was approximately 830 mg/d; calcium-supplemented persons received an additional approximately 670 mg/d. Primary outcome variables were distal and proximal radius bone mineral density (BMD), total-body BMD (TBBMD), and metacarpal cortical indexes.

RESULTS

Multivariate analyses of the primary outcomes indicated that calcium-supplementation effects vary over time. Follow-up univariate analyses indicated that all primary outcomes were significantly larger in the supplemented group than in the placebo group at the year 4 endpoint. However, at the year 7 endpoint, this effect vanished for TBBMD and distal radius BMD. Longitudinal models for TBBMD and proximal radius BMD, according to the time since menarche, showed a highly significant effect of supplementation during the pubertal growth spurt and a diminishing effect thereafter. Post hoc stratifications by compliance-adjusted total calcium intake and by final stature or metacarpal total cross-sectional area showed that calcium effects depend on compliance and body frame.

CONCLUSIONS

Calcium supplementation significantly influenced bone accretion in young females during the pubertal growth spurt. By young adulthood, significant effects remained at metacarpals and at the forearm of tall persons, which indicated that the calcium requirement for growth is associated with skeletal size. These results may be important for both primary prevention of osteoporosis and prevention of bone fragility fractures during growth.

Iron deficiency negatively affects vertebrae and femurs of rats independently of energy intake and body weight

The question of whether iron deficiency has direct adverse effects on vertebral trabecular bone and long bones was answered by this study. Four groups of female weanling rats were fed for 5 wk diets that were 1) control; 2) calcium restricted, 1.0 g Ca/kg diet; 3) iron deficient, <8 mg Fe/kg diet; or 4) control, pair-fed to the iron-deficient group. Whole body and femur DEXA analysis revealed that calcium-restricted and iron-deficient rats had lower bone mineral density (BMD) and content (BMC) than pair-fed and control rats. However, pair-fed rats also had decreased BMD and BMC compared to control rats. The third lumbar trabecular bone microarchitecture in both diet-restricted groups had decreased bone volume fraction (BV/TV) and trabecular number and thickness, a less favorable structural model index, and increased trabecular separation compared with the controls and the pair-fed groups as determined by microcomputer tomography. The control and pair-fed groups did not differ from one another, suggesting that iron deficiency and calcium restriction affected vertebrae independently of food intake and body weight. Finite element analysis revealed lower force to compress the vertebrae and lower stiffness but greater von Mises stress in calcium-restricted and iron-deficient groups compared to the control and pair-fed groups. Urinary deoxypyridinium crosslinks, serum osteocalcin, and cholcalciferol were increased in calcium-restricted rats compared to the other 3 groups. Using micro-CT imaging technology, this study demonstrated microarchitectural pathology due to iron deficiency upon vertebral trabecular bone compared to the control and pair-fed rats, although not to the same extent as severe calcium restriction.

Dairy intakes affect bone density in the elderly

BACKGROUND

Race and sex differences in the effect of diet on bone mineral density (BMD) at the hip in the elderly are unknown.

OBJECTIVES

This study related cross-sectional nutrient and dairy product consumption to hip BMD in white and black men and women aged >60 y and evaluated the influence of nutrient and dairy product consumption on changes in BMD in a white cohort participating in a calcium, vitamin D, or placebo trial.

DESIGN

The Health Habits and History Questionnaire was used in 289 white women and 116 white men who participated in the trial and in 265 black women and 75 black men to predict total hip and femoral neck BMD or changes in BMD.

RESULTS

Blacks had higher calcium intakes than did whites (700 and 654 mg/d, respectively; P = 0.0094), and men had higher calcium intakes than did women (735 and 655 mg/d, respectively; P = 0.0007). For men, the correlation between total hip BMD and dairy calcium intake after adjustment for age, race, and weight was 0.23 (P < 0.005); this relation was not significant in women (r = 0.02, P = 0.12). Similar results were found for femoral neck BMD. In the longitudinal study, calcium supplementation reduced bone loss from the total hip and femoral neck in those who consumed <1.5 servings of dairy products/d and were <72 y old.

CONCLUSIONS

Cross-sectional results indicated that higher dairy product consumption is associated with greater hip BMD in men, but not in women. Calcium supplementation protected both men and women from bone loss in the longitudinal study of whites.

Reliability and validity of a food-frequency questionnaire for Chinese postmenopausal women

OBJECTIVES

(1). To determine the reliability and validity of a food-frequency questionnaire (FFQ) for use in epidemiological research in postmenopausal women; and (2). to compare the volume estimation (VE) and weight estimation (WE) method of administration of this questionnaire.

DESIGN

An initial list of foods was derived and modified after pre-testing in 22 subjects. Test-retest reliability was assessed in 21 subjects who had repeat administrations of the questionnaire 14 days apart (FFQ1, FFQ2). The validity of the FFQ was assessed by comparing nutrient intakes with those from a 4-day food record.

SETTING

Chengdu, People's Republic of China.

SUBJECTS

Twenty-two postmenopausal women (50-70 years) were recruited from The Second University Hospital, West China University of Medical Sciences, Chengdu and participated in the pre-test. Another 21 women (50-70 years) were randomly selected from the general population of all five districts of Chengdu and participated in the reliability and validity sub-studies.

RESULTS

Energy, protein, carbohydrate, magnesium and sodium intakes in this sample were less than the Recommended Dietary Allowances (RDAs) for 45-70-year-old women in China. Intake of non-cooking fat was higher than the Chinese RDA. Pearson correlation coefficients and intra-class correlation coefficients (ICCs) for reliability of the VE FFQ ranged from 0.51 to 0.85 and from 0.51 to 0.81, respectively; for the WE FFQ, they ranged from 0.22 to 0.86 and from 0.21 to 0.81. Correlation coefficients and ICCs for validity of the WE FFQ ranged from 0.36 to 0.69 and from 0.34 to 0.57, respectively; corresponding values for the VE FFQ were -0.30 to 0.65 and -0.14 to 0.65.

CONCLUSIONS

Both the VE and WE FFQs were reliable and valid except for sodium intake. The VE FFQ provided more valid estimates of nutrient intakes than did the WE FFQ.

Position of the American Dietetic Association and Dietitians of Canada: vegetarian diets

It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Approximately 2.5% of adults in the United States and 4% of adults in Canada follow vegetarian diets. A vegetarian diet is defined as one that does not include meat, fish, or fowl. Interest in vegetarianism appears to be increasing, with many restaurants and college foodservices offering vegetarian meals routinely. Substantial growth in sales of foods attractive to vegetarians has occurred and these foods appear in many supermarkets. This position paper reviews the current scientific data related to key nutrients for vegetarians including protein, iron, zinc, calcium, vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and iodine. A vegetarian, including vegan, diet can meet current recommendations for all of these nutrients. In some cases, use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life-cycle including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fibre, magnesium, potassium, folate, antioxidants such as vitamins C and E, and phytochemicals. Vegetarians have been reported to have lower body mass indices than non-vegetarians, as well as lower rates of death from ischemic heart disease, lower blood cholesterol levels, lower blood pressure, and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer. While a number of federally funded and institutional feeding programs can accommodate vegetarians, few have foods suitable for vegans at this time. Because of the variability of dietary practices among vegetarians, individual assessment of dietary intakes of vegetarians is required. Dietetics professionals have a responsibility to support and encourage those who express an interest in consuming a vegetarian diet. They can play key roles in educating vegetarian clients about food sources of specific nutrients, food purchase and preparation, and any dietary modifications that may be necessary to meet individual needs. Menu planning for vegetarians can be simplified by use of a food guide that specifies food groups and serving sizes.

Hormone replacement therapy and menopause: a review of randomized, double-blind, placebo-controlled trials

Hormone replacement therapy (HRT) is frequently prescribed to healthy women to ameliorate menopausal symptoms. HRT is used long term (> or = 1 year) to prevent chronic disease in older women. The objective of this study was to review the benefits and risks of HRT and studies of menopause or HRT in Taiwan via a MEDLINE search. Recommendations are provided for future HRT research in Taiwan. Randomized, double-blind, placebo-controlled clinical trials are considered the gold standard of scientific evidence. A MEDLINE literature search (January 1966-July 2002) identified 23 papers on trials (> or = 1 year) that met the inclusion criteria. The results showed that various HRT regimens used for more than 1 year caused more harm than good in healthy menopausal women and that there was no benefit for women with coronary artery disease, Alzheimer's disease, hysterectomy, hysterosalpingo-oophorectomy, and ischemic stroke. None of this research was conducted in Taiwan. A MEDLINE search using the key words "estrogen replacement therapy and menopause in Taiwan" identified 16 studies. There was only one, short-term, HRT trial. No evidence suggested benefits from long-term HRT in menopausal women in Taiwan.

Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets

It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Approximately 2.5% of adults in the United States and 4% of adults in Canada follow vegetarian diets. A vegetarian diet is defined as one that does not include meat, fish, or fowl. Interest in vegetarianism appears to be increasing, with many restaurants and college foodservices offering vegetarian meals routinely. Substantial growth in sales of foods attractive to vegetarians has occurred, and these foods appear in many supermarkets. This position paper reviews the current scientific data related to key nutrients for vegetarians, including protein, iron, zinc, calcium, vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and iodine. A vegetarian, including vegan, diet can meet current recommendations for all of these nutrients. In some cases, use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits, including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fiber, magnesium, potassium, folate, and antioxidants such as vitamins C and E and phytochemicals. Vegetarians have been reported to have lower body mass indices than nonvegetarians, as well as lower rates of death from ischemic heart disease; vegetarians also show lower blood cholesterol levels; lower blood pressure; and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer. Although a number of federally funded and institutional feeding programs can accommodate vegetarians, few have foods suitable for vegans at this time. Because of the variability of dietary practices among vegetarians, individual assessment of dietary intakes of vegetarians is required. Dietetics professionals have a responsibility to support and encourage those who express an interest in consuming a vegetarian diet. They can play key roles in educating vegetarian clients about food sources of specific nutrients, food purchase and preparation, and any dietary modifications that may be necessary to meet individual needs. Menu planning for vegetarians can be simplified by use of a food guide that specifies food groups and serving sizes.

Bone morphology, strength and density are compromised in iron-deficient rats and exacerbated by calcium restriction

Rats fed an iron-deficient diet develop decreased bone mass and increased fragility. This study documents that rats fed two minerals likely to be low in American diets, calcium and iron, had dramatic changes in bone density and morphometry. Weanling male Long-Evans rats were fed a diet that was either deficient in iron (5-8 mg/kg or 89-143 micro mol/kg diet), low in calcium (1.0 g/kg Ca or 0.025 mol/kg diet) or deficient in both minerals or a control diet with adequate iron and calcium. Eight rats in each of the four groups were fed their respective diets for 5 wk. Total femur and tibia widths were decreased in all experimental groups and iron-deficient rats had decreased medullary widths compared with the other three groups. Cortical width was decreased in all experimental groups, with either the calcium-restricted group or the iron-deficient + calcium-restricted group showing the greatest impact. Both calcium restriction and iron deficiency, either singly or in combination with one another, had reduced cortical bone area. Analysis by dual-energy X-ray absorptiometry revealed a pattern of significant reductions in bone density for iron-deficient, calcium-restricted and the combination of calcium-restricted+ iron-deficient rats, respectively, as compared with controls. These data suggest that a commonly deficient trace element in American diets, iron, has a negative impact upon bone health, and this impact is exacerbated by a calcium-restricted diet.

Milk consumption and bone mineral content in Chinese adolescent girls

A cross-sectional study of a random sample of 649 girls, aged 12-14 years (mean +/- SD: 12.9 +/- 0.6 years), in the Beijing area examined the relationship between diet and bone mineral status. Food and nutrient intakes over the past year were estimated by means of a semiquantitative food frequency questionnaire. Bone mineral content (BMC) and bone width (BW) at the distal one-third and one-tenth radius and ulna were measured by single-photon absorptiometry. Results showed Beijing pubertal girls had a low mean milk consumption (fresh and powdered milk, vitamin D-fortified milk, and yogurt) at 50 g/day (95% confidence interval [CI] 44-55 g/day whereas one-third consumed no milk at all. Mean calcium intake was 356 +/- 97 mg/day of which only 21% was provided by milk and milk products. Milk intake varied by region (rural, suburban, and urban: 9, 36, and 83 g/day, respectively, p < 0.0005) as did the proportion of milk consumers in the three areas (30%, 64%, and 91%, p < 0.0005). Bone mineral density (BMD) at the distal one-third and one-tenth radius and one-tenth ulna was positively associated with milk consumption (p < 0.05). Multiple regression analysis of BMC on foods and nutrients as well as confounding factors, including weight, bone age, Tanner stage, and School Physical Activity Score (SPAS), showed that milk intake was the only dietary factor included in the models for BMC at the four bone sites measured. The model explained 54%-65% of the variation in BMC, and milk alone accounted for up to 3.2% of the variation. Milk was the only food group with significant partial correlation with BMC. SPAS, weight, bone age, and Tanner stage each accounted for a smaller variation in BMC (<1.8%). The results indicate that milk (presumably as an integrated source of nutrients) had a beneficial effect on bone mass of Beijing pubertal girls and was a better nutritional determinant of BMC than intake of any milk nutrient alone. Promotion of milk consumption should be considered for achieving optimal bone mass in this population group.

Reducing the personal risk of perceived disease: the chiropractic patients' self-care endeavor

OBJECTIVE

It has been suggested that clinicians should be looking at new ways to enhance the self-care of their patients. Patient education is one strategy that primary providers may use. This study investigates the behavior of chiropractic patients to identify whether they are using widely published community health information messages to reduce their personally perceived risk of various diseases.

METHODS

An exploratory study of chiropractic patients was undertaken to investigate the health-relevant behaviors of patients. Purposive sampling of 9 Australian chiropractic clinics was undertaken. Convenience sampling of patients attending these clinics resulted in the participation of 102 patients. All participants completed a questionnaire, and data were collected and collated into a series of case studies that described some behaviors of participants that might have influenced their risk of acquiring disease. The study was limited to diseases for which participants believed they were at risk.

RESULTS

A substantial number of participants had undergone a screening procedure as recommended by health authorities. The 67 participants who believed they were at risk for one or more of the conditions listed were more likely to have complied. In addition, all participants made certain healthy lifestyle choices. However, implementation of those lifestyle choices that would reduce the personal risk of perceived diseases was sporadic.

CONCLUSION

The behavior of participants in this study suggests that many chiropractic patients would benefit from additional personalized health information messages. The use of information brochures in chiropractic clinics may not alone lead to a lifestyle change.

Nutrition in bone health revisited: a story beyond calcium

Osteoporosis is a complex, multi-factorial condition characterized by reduced bone mass and impaired micro-architectural structure, leading to an increased susceptibility to fractures. Although most of the bone strength (including bone mass and quality) is genetically determined, many other factors (nutritional, environmental and life-style) also influence bone. Nutrition is important modifiable factor in the development and maintenance of bone mass and the prevention and treatment of osteoporosis. Approximately 80-90% of bone mineral content is comprised of calcium and phosphorus. Other dietary components, such as protein, magnesium, zinc, copper, iron, fluoride, vitamins D, A, C, and K are required for normal bone metabolism, while other ingested compounds not usually categorized as nutrients (e.g. caffeine, alcohol, phytoestrogens) may also impact bone health. Unraveling the interaction between different factors; nutritional, environmental, life style, and heredity help us to understand the complexity of the development of osteoporosis and subsequent fractures. This paper reviews the role of dietary components on bone health throughout different stages of life. Each nutrient is discussed separately, however the fact that many nutrients are co-dependent and simultaneously interact with genetic and environmental factors should not be neglected. The complexity of the interactions is probably the reason why there are controversial or inconsistent findings regarding the contribution of a single or a group of nutrients in bone health.

Dairy foods and bone health: examination of the evidence

It is unclear whether dairy foods promote bone health in all populations and whether all dairy foods are equally beneficial. The objective of this review was to determine whether scientific evidence supports the recommendation that dairy foods be consumed daily for improved bone health in the general US population. Studies were reviewed that examined the relation of dairy foods to bone health in all age, sex, and race groups. Outcomes were classified according to the strength of the evidence by using a priori guidelines and were categorized as favorable, unfavorable, or not statistically significant. Of 57 outcomes of the effects of dairy foods on bone health, 53% were not significant, 42% were favorable, and 5% were unfavorable. Of 21 stronger-evidence studies, 57% were not significant, 29% were favorable, and 14% were unfavorable. The overall ratio of favorable to unfavorable effects in the stronger studies was 2.0 (4.0 in <30-y-olds, 1.0 in 30-50-y-olds, and 1.0 in >50-y-olds). Males and ethnic minorities were severely underrepresented. Dairy foods varied widely in their content of nutrients known to affect calcium excretion and skeletal mass. Foods such as milk and yogurt are likely to be beneficial; others, such as cottage cheese, may adversely affect bone health. Of the few stronger-evidence studies of dairy foods and bone health, most had outcomes that were not significant. However, white women <30 y old are most likely to benefit. There are too few studies in males and minority ethnic groups to determine whether dairy foods promote bone health in most of the US population.

The bioavailability of dietary calcium

This update focuses on the bioavailability of dietary calcium for humans. Fundamentals of calcium metabolism, intestinal absorption, urinary excretion and balance are recalled. Dietary factors, especially lactose and other milk components, influencing calcium bioavailability at intestinal and renal levels are reviewed. A critical examination of all the methods used for evaluating calcium bioavailability is made. This includes in vitro assays, classical and isotopic balances, urinary excretion, isotope labeling in the urine, plasma and bones, long term evaluation of bone mineralization and the use of biological bone markers. Importance and advantages of animal models are discussed. The state of the art in the comparative bioavailability of calcium in foods is detailed including a comparison of sources of calcium (dairy products and calcium salts) in human studies and in some animal studies, casein phosphopeptides, proteins, lactose and lactase and their relation with calcium bioavailability (in humans and rats). An update on the consumption of dairy products and bone mass is presented. Emphasis on peculiarities and advantages of calcium in milk and dairy products is given.

Calcium, dairy products and osteoporosis

Osteoporosis is a multifactorial disorder in which nutrition plays a role but does not account for the totality of the problem. 139 papers published since 1975 and describing studies of the relationship of calcium intake and bone health are briefly analyzed. Of 52 investigator-controlled calcium intervention studies, all but two showed better bone balance at high intakes, or greater bone gain during growth, or reduced bone loss in the elderly, or reduced fracture risk. This evidence firmly establishes that high calcium intakes promote bone health. Additionally, three-fourths of 86 observational studies were also positive, indicating that the causal link established in investigator-controlled trials can be found in free-living subjects as well. The principal reason for failure to find an association in observational studies is the weakness of the methods available for estimating long-term calcium intake. While most of the investigator-controlled studies used calcium supplements, six used dairy sources of calcium; all were positive. Most of the observational studies were based on dairy calcium also, since at the time the studies were done, higher calcium intakes meant higher dairy intakes. All studies evaluating the issue reported substantial augmentation of the osteoprotective effect of estrogen by high calcium intakes. Discussion is provided in regard to the multifactorial complexity of osteoporotic response to interventions and to the perturbing effect in controlled trials of the bone remodeling transient, as well as about how inferences can validly be drawn from the various study types represented in this compilation.

Development and validation of a calcium intake questionnaire for postmenopausal women in China

PURPOSE

Develop and evaluate a food frequency questionnaire (FFQ) for assessing calcium intake in Chinese postmenopausal women.

METHODS

An interviewer-conducted FFQ that asks respondents about their consumption of 110 calcium-containing foods over the previous week was developed and administered to 21 randomly selected postmenopausal women from Chengdu. This FFQ uses both the traditional weight-estimation method of assessing portion size in China and a new volume-estimation method. Test-retest reliability was assessed by re-administering the questionnaire two weeks later and validity was assessed by comparing the computed daily calcium intake to that obtained by a researcher-conducted 4-day food record.

RESULTS

Estimates of calcium intake derived from the volume-estimation method were significantly lower than estimates derived from the traditional weight-estimation method (median calcium intakes = 270 mg/day versus 570 mg/day), but were quite similar to those obtained from the 4-day food record (median calcium intake = 275 mg/day). The test-retest reliability and validity of the volume-estimation method (intraclass correlation coefficient (ICC) = 0.73 and 0.86, respectively) were better than those of the weight-estimation method (ICC = 0.58 and 0.39, respectively).

CONCLUSIONS

The reliability and validity of the traditional weight-estimation FFQ method of assessing dietary intake of nutrients in China is poor; this method may significantly overestimate dietary intakes. The proposed volume-estimation FFQ method for assessing calcium intake is a simple, interviewer-conducted method that is both reliable and valid. The calcium intake of postmenopausal women in urban China is much lower than the recommended daily allowance of 800 mg.

Choices for achieving adequate dietary calcium with a vegetarian diet

To achieve adequate dietary calcium intake, several choices are available that accommodate a variety of lifestyles and tastes. Liberal consumption of dairy products in the diet is the approach of most Americans. Some plants provide absorbable calcium, but the quantity of vegetables required to reach sufficient calcium intake make an exclusively plant-based diet impractical for most individuals unless fortified foods or supplements are included. Also, dietary constituents that decrease calcium retention, such as salt, protein, and caffeine, can be high in the vegetarian diet. Although it is possible to obtain calcium balance from a plant-based diet in a Western lifestyle, it may be more convenient to achieve calcium balance by increasing calcium consumption than by limiting other dietary factors.

Excess retinol intake may explain the high incidence of osteoporosis in northern Europe

An epidemiologic study of postmenopausal women in Sweden revealed that a chronic excess of retinol intake (> 1.5 mg/day) decreased bone mineral density and increased hip fracture risk. These data provide one explanation for the higher incidence of osteoporosis in Sweden and Norway compared with other European countries. Retinol in fortified milk could explain also the association of high calcium intake and hip fracture incidence in northern Europe because milk is an important source of both nutrients.

China: the soyabean-pork dilemma

In 1996 the population of China reached 1.23 billion, 22% of the world population, and is expected to increase to 1.5 billion by 2020. As China has only 7% of the world's arable land such population increases are likely to have an important impact on food supply in China and the world. Projections of the potential impact are discussed. The restructuring of Chinese agriculture at the end of the 1970s has led to dramatic increases in agricultural production and food consumption, in particular of animal products, fruit and vegetables. Along with these rapid changes there is evidence of a nutrition transition in which diseases associated with affluence are becoming more prevalent than deficiency diseases. This transition has led to concern about the evolving dietary pattern. The replacement of legumes, including soyabean, by meat and other animal products as rich sources of protein and other nutrients has been controversially argued on grounds of nutritional health, ecological impact, economic effects and world food supply. These arguments are reviewed and the pressures internal and external to China concerning the production and consumption of animal v. legume products are presented. It is concluded that nutritional policies to promote the consumption of soyabean are unlikely to be effective in the context of an increasingly free and global market.

Determinants of plasma retinol concentrations of middle-aged women in rural China

The purpose of this study was to assess the correlates and possible determinants of plasma vitamin A among middle-aged women in rural China. The vitamin A adequacy of the different diets at the five widely varying survey sites was also assessed. Patterns of correlations among dietary and biochemical measurements were strikingly different from previous studies in Western subjects. Plasma beta-carotene was uncorrelated with beta-carotene intake even after adjusting for potential confounders. In counties with low preformed vitamin A intake, plasma retinol correlated with plasma copper (P = 0.007), which in turn was correlated with dietary intake of copper (P = 0.007). In these counties plasma retinol was correlated with plasma beta-carotene (P = 0.001) and was increased 10% in women in the first 2 y of menopause (P = 0.028). Plasma retinol and C-reactive protein levels are inversely correlated (r = -0.15, P < 0.001), indicating that vitamin A status and inflammatory response may be related but the causal direction is unknown. Despite low intake of vitamin A (county averages of 13-78% of recommended daily allowance [RDA]), and particularly of preformed vitamin A, only 3% of these women had plasma retinol levels below 0.7 mumol/L, considered to indicate possible marginal deficiency. Plasma levels of retinol and beta-carotene were more influenced by intrinsic factors such as menopause, lipid status, retinol requirements, and possibly copper status and inflammation than by extrinsic factors such as diet and lifestyle.

Place of birth and dietary intake in Ontario. II. Protein and selected micronutrients

BACKGROUND

Because of the importance of dietary intake on health, this study investigated the relationship between place of birth and nutrient intake in Ontario, using cross-sectional data from the 1990 Ontario Health Survey.

METHODS

Adults (age = 18) were categorized as nonimmigrants (born in Canada; n = 29,458) or immigrants (born outside of Canada, classified by countries of birth; n = 7,158). Protein, calcium, iron, vitamin C, thiamin, riboflavin, and niacin intakes were studied (a companion article describes energy and other nutrient intakes). Multiple linear and logistic regression analyses investigated the association of place of birth with nutrient intakes, adjusting for sociodemographic factors and ethnicity.

RESULTS

The proportions of subjects at an increased risk of "inadequate" nutrient intakes were relatively low. However, immigrants (particularly from Asian countries) were at a higher risk of inadequate intakes of protein (OR = 1.51, P = 0.001), calcium (OR = 1.41, P < 0.0001), and iron (OR = 1.44, P = 0.002) compared with nonimmigrants. Immigrants from various Asian countries were more likely to report inadequate thiamin, riboflavin, and niacin intakes.

CONCLUSION

Some immigrants groups in Ontario display higher risks of inadequate protein and micronutrient intakes compared with nonimmigrants. More research on the nutritional status of these subgroups is needed to develop culturally sensitive health and nutrition promotion programs.

Milk, dietary calcium, and bone fractures in women: a 12-year prospective study

OBJECTIVES

This study examined whether higher intakes of milk and other calcium-rich foods during adult years can reduce the risk of osteoporotic fractures.

METHODS

This was a 12-year prospective study among 77761 women, aged 34 through 59 years in 1980, who had never used calcium supplements. Dietary intake was assessed with a food-frequency questionnaire in 1980, 1984, and 1986. Fractures of the proximal femur (n = 133) and distal radius (n = 1046) from low or moderate trauma were self-reported on biennial questionnaires.

RESULTS

We found no evidence that higher intakes of milk or calcium from food sources reduce fracture incidence. Women who drank two or more glasses of milk per day had relative risks of 1.45 for hip fracture (95% confidence interval [CI] = 0.87, 2.43) and 1.05 for forearm fracture (95% CI = 0.88, 1.25) when compared with women consuming one glass or less per week. Likewise, higher intakes of total dietary calcium or calcium from dairy foods were not associated with decreased risk of hip or forearm fracture.

CONCLUSIONS

These data do not support the hypothesis that higher consumption of milk or other food sources of calcium by adult women protects against hip or forearm fractures.