Interaction of dietary calcium and protein in bone health in humans

Protein has both positive and negative effects on calcium balance, and the net effect of dietary protein on bone mass and fracture risk may be dependent on the dietary calcium intake. In addition to providing substrate for bone matrix, dietary protein stimulates the production of insulin-like growth factor-1 (IGF-1), a factor that promotes osteoblast-mediated bone formation. Protein also increases urinary calcium losses, by several proposed mechanisms. Increasing calcium intake may offset the negative impact of dietary protein on urinary calcium losses, allowing the favorable effect of protein on the IGF-1 axis to dominate. Several, although not all, studies are either compatible with or support this hypothesis. Protein supplements significantly reduced bone loss in elderly hip-fracture patients in a study in which both the protein and control groups received supplemental calcium. In an observational study, total protein intake was positively associated with favorable 3-y changes in femoral neck and total body bone mineral density in volunteers who received supplemental calcium citrate malate and vitamin D, but not in volunteers taking placebos. In conclusion, an adequate calcium intake may help promote a favorable effect of dietary protein on the skeleton in older individuals.     

Effect of dietary calcium deficiency on bone matrix-induced ectopic bone

The effect of dietary depletion of calcium on collagenous bone matrix-induced ectopic bone was studied, following thirty days of deficiency. While the molar ratio of phosphorus and calcium did not exhibit any significant differences between the control and experimental groups, individual concentrations of these minerals showed significant reduction in the ossicles derived from experimental rats. A concomitant decrease and increase in urinary excretion of calcium and phosphate was noted in the calcium deficient group; the serum levels of these parameters, however, were not affected. Both hexosamine and hydroxyproline levels appeared higher in calcium deficient ossicles. A significant elevation of alkaline and acid phosphatase as well as aryl sulfatase was observed in calcium deficient ossicles. There appeared to be no difference between control and experimental rats in the rate of calcification as measured by ⁴⁵Ca uptake. These results suggest that dietary deficiency induces significant resorption of ectopic bone without altering mineralization capacity. It is suggested that matrix-induced ectopic bone may be used as a suitable experimental model to study pathophysiology of bone loss under various experimental conditions.     

Children who avoid drinking cow milk have low dietary calcium intakes and poor bone health

BACKGROUND: Information concerning the adequacy of bone mineralization in children who customarily avoid drinking cow milk is sparse. OBJECTIVE: The objective was to evaluate dietary calcium intakes, anthropometric measures, and bone health in prepubertal children with a history of long-term milk avoidance. DESIGN: We recruited 50 milk avoiders (30 girls, 20 boys) aged 3-10 y by advertisement. We measured current dietary calcium intakes with a food-frequency questionnaire and body composition and bone mineral density with dual-energy X-ray absorptiometry and compared the results with those of 200 milk-drinking control children. RESULTS: The reasons for milk avoidance were intolerance (40%), bad taste (42%), and lifestyle choice (18%). Dietary calcium intakes were low (443 +/- 230 mg Ca/d), and few children consumed substitute calcium-rich drinks or mineral supplements. Although 9 children (18%) were obese, the milk avoiders were shorter (P < 0.01), had smaller skeletons (P < 0.01), had a lower total-body bone mineral content (P < 0.01), and had lower z scores (P < 0.05) for areal bone mineral density at the femoral neck, hip trochanter, lumbar spine, ultradistal radius, and 33% radius than did control children of the same age and sex from the same community. The z scores for volumetric (size-adjusted) bone mineral density (g/cm(3)) were -0.72 +/- 1.17 for the lumbar spine and -0.72 +/- 1.35 for the 33% radius (P < 0.001). Twelve children (24%) had previously broken bones. CONCLUSIONS: In growing children, long-term avoidance of cow milk is associated with small stature and poor bone health. This is a major concern that warrants further study.     

Role of calcium in bone health during childhood

A discussion of observational and longitudinal studies examining the effect of early-life calcium intake on bone health is provided. A critical analysis of pediatric calcium supplementation trials is conducted by determining annualized percent changes in bone mineral density (BMD). The focus of the analysis is to identify consistent findings at specific bone sites, determine whether effects differed by the age of children studied, and establish the relationship between bone changes and baseline calcium intake. We found that increases in BMD owing to higher calcium intake among children appear to occur primarily in cortical bone sites, are most apparent among populations with low baseline calcium intakes, and do not seem to persist beyond the calcium supplementation period. Older (e.g., pubertal) children appear to have greater annual increases in lumbar BMD than younger (e.g., prepubertal) children. The annual percent increase in midradius BMD appears to be greater at higher intakes among the older children, but such a relationship is less apparent among the younger children.     

The relationship of dietary and supplemental calcium intake to bone loss and osteoporosis

Calcium supplements have become big business in the United States. The sale of calcium supplements increased sevenfold from 1980 to 1985, with +130,000,000 being spent on calcium supplements during 1985. The median daily dietary calcium intake for women in the United States is 574 mg and for men is 826 mg. The average American diet contains 389 mg calcium per 1,000 kcal. The Recommended Dietary Allowance (RDA) of 800 mg calcium may be insufficient to meet the needs of women who are "poor absorbers" of calcium. Research linking calcium intake with bone density is confounded by the type of bone measured, the variation in efficiency of calcium absorption among individuals, and the methodology for measuring calcium intake. Although calcium supplements will retard cortical bone loss in some postmenopausal women and are generally safe, they are not so effective as estrogen.     

学龄期儿童膳食钙与骨密度的关系

目的 调查上海地区学龄期儿童膳食钙摄入现状及骨营养状况,分析膳食钙与骨密度(BMD)的关系.方法 以上海市杨浦区和宝山区10所小学二、三年级学生为研究对象,每个年级随机 抽取2个班级进行定量超声BMD测量,对宝山区6所小学所有二、三年级学生采用食物频率问卷法进行钙摄入量调查,分析调查人群膳食钙与BMD关系.结果 受试儿童平均钙摄入量为647 mg/d.不同年龄别BMD间差异无统计学意义(F=1.595,P=0.173),但不同年龄别间BMD的Z值差异有统计学意义(F16.02,P=0.000).总钙摄入量与BMD及其Z值无关.乳钙占总钙的百分比与BMD及其Z值均呈显著正相关(r=0.097,P=0.015;r=0.117,P=0.003),非乳钙占总钙的百分比和非乳钙摄入量与BMD及其Z值均呈显著负相关(r=-0.097,P=0.015;r=-0.110,P=0.006).当总钙摄入量≥600mg/d时,高乳钙组的BMD及其z值明显高于低乳钙组(P<0.05).当总钙摄入量<600mg/d时,高乳钙组的BMD及其Z值较低乳钙组虽有升高趋势,但差异无统计学意义(P>0.05).结论 高乳钙摄入对BMD有促进作用,当总钙摄入量≥600 mg/d时,该作用明显增强.     

Children's bone health and meeting calcium needs

One in two women and one in five men suffer from osteoporotic fractures after the age of 50. Enabling children and young people to develop strong bones and achieve their maximum potential bone mass will help prevent undue bone loss and osteoporosis in later life. Although 70-80% of peak bone mass is genetically determined, the remainder is determined by dietary and environmental factors. The most important dietary factor for bone health is calcium, which in the UK is obtained mainly from dairy foods (45%) and cereal-based foods (27%). In the UK one-quarter of teenage girls consume insufficient calcium to meet their minimum dietary requirements. The majority of teenage boys and girls fail to meet the UK Government's targets for calcium intakes. This is an important public health issue as 90% of peak bone mass is attained by the age of approximately 18 years in girls and 20 years in boys. Health professionals need to be aware of the importance of childhood and adolescence for building healthy bones and to work with this age group to promote the dietary and lifestyle factors that contribute to bone health and peak bone mass. They could usefully include advice on including three helpings of calcium in the diet each day, as highlighted in the current "3-a-Day" campaign.     

学龄期儿童膳食钙与骨密度的关系

Objective To investigate the prevalence of overweight and obesity and the nutritional status of dietary calcium intake in school-age children in Shanghai and to analyze the relationship between dietary calcium and bone mineral density (BMD).Methods A cross-sectional study was conducted in the second and third grade students of 10 primary schools in Yangpu District and Baoshan District in Shanghai. Food frequency questionnaire was used tu estimate the relative intake of dietary calcium of students in 6 primary schools in Baoshnn District. Quantitative ultrasound bone density examination was used to estimate the calcaneal BMD.The relation-ship between calcium intake and BMD was analyzed.Results The average calcium intake was 647 mg/d among ested students.BMD was not significantly different among different age groups (F=1.595,P=0.173),while Z-score was significantly different among different age groups (F=16.02,P=0.000).The total calcium intake was not correlated with BMD or Z-score.The percentage of dairy calcium intake was positively correlated with BMD (r=0.097,P=0.015)and Z-score (r=O.117,P=0.003),the percentage of non-dairy calcium intake and the non-dairy calcium intake were negatively correlated with BMD (r=-0.097,P=0.015) and Z-score(r=-0.110,P=0.006).When the total dietary calcium intake was ≥600 mg/d,BMD and Z-score significantly higherin students with high dairy calcium intake than those with low dairy calcium intake (P<0.05).When the total dietary calcium intake was <600mg/d,BMD and Z-score were higher in students with high dairy calcium in-take than in those with low dairy calcium intake,although no statistical significance was noted (P>0.05).Conclusions BMD and Z-score increase along with the increase of dairy calcium intake.Such effect becomes even more obvious when the total dietary calcium intake is ≥600 mg/d.     

Interactions between dietary caffeine and calcium on calcium and bone metabolism in older women.

Our purpose was to determine the effect of 2 weeks of caffeine abstinence on calcium (Ca) and bone metabolism in women habitually consuming caffeine and either low or moderate amounts of Ca.

Participants were 25 women, aged 39-76 years (mean 65 years, median 57 years) habitually consuming at least 200 mg caffeine daily. Three days of dietary records and 24-hour urine collections were made immediately prior to collection of fasting blood and 1-hour urine in a metabolic unit. Women were classified as low Ca consumers (414-584 mg daily) or moderate Ca consumers (662-1357 mg daily) based on 6 days of diet records.

Women in the low Ca group had higher levels of serum ultrafiltrable Ca (UFCa) after caffeine abstinence (1.40 mmol/L CAF+ vs 1.52 mmol/L CAF-, p < 0.01), while there were no differences between experimental periods for UFCa in the moderate Ca group (1.35 mmol/L CAF+ vs 1.38 mmol/L CAF-, ns). Women in the low Ca group also had lower serum bone isoenzyme alkaline phosphatase levels after caffeine abstinence (9.3 U/L CAF+ vs 8.8 U/L CAF-, p < 0.05), while no significant changes were seen in bone alkaline phosphatase in the moderate Ca consumers (8.7 U/L CAF+ vs 8.9 U/L CAF-, ns). Fasting total serum Ca, urinary hydroxyproline/creatinine, and Ca/creatinine ratios were unchanged in both dietary groups. Three-day mean 24-hour urinary Ca excretion decreased after caffeine abstinence in the moderate Ca group only. There were no differences in dietary intakes of Ca from dairy products between CAF+ and CAF- in either the low or moderate Ca groups.

Abstinence from moderate caffeine intake (mean 5.8 mg/kg lean body mass, 383 mg/day caffeine) raises ultrafiltrable Ca and decreases bone alkaline phosphatase in older women consuming < 600 mg Ca daily.     

Effects of dietary calcium compared with calcium supplements on estrogen metabolism and bone mineral density

BACKGROUND: High calcium intake has been associated with both high bone mineral density (BMD) and high urinary estrogen metabolites. However, the role of dietary calcium and calcium supplements on estrogen metabolism and BMD remains unknown. OBJECTIVE: The objective was to investigate the importance of the source of calcium intake on estrogen metabolism and BMD. DESIGN: The average total daily calcium intake from supplements and diet, urinary estrogen metabolites, and spine and proximal femur BMD were studied in 168 healthy postmenopausal white women. RESULTS: Women who obtained calcium primarily from the diet or from both the diet and supplements had significantly (P=0.03) lower ratios of nonestrogenic to estrogenic metabolites (2-hydroxyestrone 1/16 alpha-hydroxyestrone) than did those who obtained calcium primarily from supplements. Adjusted BMD z scores were significantly greater in the subjects who obtained calcium primarily from the diet or from both the diet and supplements than in those who obtained calcium primarily from calcium supplements at the spine (P=0.012), femoral neck (P=0.02), total femur (P=0.003), and intertrochanter (P=0.005). This difference was evident especially in those who obtained calcium primarily from the diet, whose total calcium intake was lower than that in those who obtained calcium primarily from supplements. CONCLUSION: Calcium from dietary sources is associated with a shift in estrogen metabolism toward the active 16 alpha-hydroxyl metabolic pathway and with greater BMD and thus may produce more favorable effects in bone health in postmenopausal women than will calcium from supplements.     

Calcium intake,calcium bioavailability and bone health

Calcium accounts for 1-2 % of adult human body weight. Over 99 % of total body Ca is found in the teeth and bones. Therefore, in addition to the obvious structural role of the skeleton, it also serves as a reservoir for Ca. Dietary Ca intake has an important impact on bone metabolism and bone health. Chronic Ca deficiency resulting from inadequate intake or poor intestinal absorption is one of several important causes of reduced bone mass and osteoporosis. It is vital, therefore, that adequate dietary Ca is consumed at all stages of life - in early life so that the genetically programmed peak bone mass can be reached and in later adulthood so that the skeletal mass can be maintained and age-related bone loss minimised. Unfortunately, there is wide variation in the estimates of daily Ca requirements made by different expert authorities. Furthermore, there is evidence that many individuals are not consuming these recommended levels. The consequence of this for bone health will be discussed in the present review. Besides the amount of Ca in the diet, the absorption of dietary Ca in foods is also a critical factor in determining the availability of Ca for bone development and maintenance. Thus, there is a need to identify food components and/or functional food ingredients that may positively influence Ca absorption in order to ensure that Ca bioavailability from foods can be optimised. This approach may be of particular value in individuals who fail to achieve the dietary recommended level of Ca.     

Osteoporosis health beliefs and knowledge in college students: The role of dietary restraint

This study investigated the relationship between dietary restraint (DR) and osteoporosis-related knowledge and beliefs in college women and men. A total of 517 university students completed measures of osteoporosis knowledge, perceived susceptibility to and severity of osteoporosis, barriers to and benefits of calcium and exercise, health motivation, exercise and calcium self-efficacy, and DR. Two MANOVAs were conducted to examine differences between high and low dietary restrainers on osteoporosis beliefs and knowledge. For women, HR scored higher on perceived susceptibility to, and severity of, osteoporosis, calcium barriers, and health motivation; for men, HR scored lower on exercise benefits. These results suggest that DR may be related to osteoporosis beliefs and knowledge differently for men and women.     

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.     

The effects of increased dietary calcium intake on bone mineral density in long-term lactating women, and recovery of bone loss caused by long-term lactation with low calcium diet

OBJECTIVES: The purpose of this study was to examine the efficacy of an increased calcium (Ca) diet for preventing bone mineral loss in long-term lactating women, considering bone metabolism, and recovery of bone loss caused by long-term lactation with low dietary Ca intake. SUBJECTS AND METHODS: Two groups of long-term (> 12 mon.) lactating women ... one with an enhanced Ca intake (Group M, n = 22) and the other with diet feeding no cow's milk and no milk products (Group N, n = 16) ... and a control group of 21 non-lactating postpartum women (Group C) were studied. Bone mineral density (BMD) was measured by ultrasonic bone densitometry. Stiffness calculated from the combined value of speed of sound and broadband ultrasound attenuation was used as an index of BMD. BMD and bone metabolic markers in urine and serum (only M and C groups) were assessed from 1 approximately 12 weeks postpartum (initial) at six-month intervals for a maximum of two years and changes were compared among the groups. RESULTS: 1. The mean (+/- SD) dietary Ca intake was 1032 (209) mg/day in the M group. 2. After lactating for one year, the N group demonstrated significant decrease in BMD, with both 1 and 2 babies, whereas the M group had no significant change. 3. The BMD in the N group returned to initial levels at 0.5 approximately 1 year post-weaning, 4. In the N group, compared with the M group, the urinary Hydroxyproline/creatinine ratio was significantly higher at the initial measurement and half a year thereafter, while urinary Ca/ creatinine ratio was significantly lower after a year. However, there were no significant differences between the M and C groups. 5. Serum bone alkaline phosphatase was significantly higher in the M group compared with the C group. CONCLUSIONS: Bone loss during long-term lactation can be prevented with adequate dietary Ca intake. Once lost, recovery to initial levels occurs 0.5 approximately 1 year post-weaning.     

The effects of a high calcium dairy food on bone health in pre-pubertal children in New Zealand

Childhood and adolescence is the period of most rapid skeletal growth in an individual's lifetime. A greater peak bone mass achieved in the first 2-3 decades of life, may protect against the risk of osteoporotic fracture in later life. The aim of this randomized, controlled study was to assess in pre-pubertal boys and girls (aged 8-10 years) the effect of 18 months of a calcium enriched, cocoa flavoured product on bone density, bone growth and bone size in New Zealand children. One hundred and fifty four pre-pubertal boys and girls (aged 8-10 years) were randomized to receive a high calcium dairy drink or a control drink reconstituted with water for 18 months. They were assessed at baseline and then every 6 months for the first 18 months, while they were having the supplement; they were then followed up 12 months after supplementation had finished. Bone mineral density and bone mineral content were assessed at the total body, hip and spine. Indicators of bone size (vertebral width and height) were also measured at the spine. Anthropometric data was collected, medical history questionnaires were administered (including the Tanner or pubertal stage questionnaire), dietary calcium intake was assessed with a calcium food frequency questionnaire and calcium supplement compliance was determined. There was no significant difference between the 2 groups for bone mineral density or bone mineral content at any time point. There was no difference in vertebral height or width at any stage of the study, indicating no additional influence on bone size at the lumbar vertebrae. There were no significant differences between height, weight, lean mass or fat mass at any time point. Both groups had higher habitual calcium intakes than recommended for this age group going into the study and throughout the study. In this 2(1/2) year study (18 months supplementation, 1 year follow-up) we did not observe a difference in bone mineral density in pre-pubertal children. This was probably due to their high habitual dietary calcium intake whereby minimal addition of calcium to the diet reached the threshold level where no further benefit was seen. There were no significant differences between the two groups in body composition. Growth and the mean height and weight remained between the 50th and 75th percentile for their age. We have shown calcium supplementation in children with high habitual dietary calcium intake appears not to have additional effects on bone mass. Calcium supplementation needs to be targeted in those children with low habitual dietary calcium intake.     

Vitamins and bone health: beyond calcium and vitamin D

Osteoporosis is a major health disorder associated with an increased risk of fracture. Nutrition is among the modifiable factors that influence the risk of osteoporosis and fracture. Calcium and vitamin D play important roles in improving bone mineral density and reducing the risk of fracture. Other vitamins appear to play a role in bone health as well. In this review, the findings of studies that related the intake and/or the status of vitamins other than vitamin D to bone health in animals and humans are summarized. Studies of vitamin A showed inconsistent results. Excessive, as well as insufficient, levels of retinol intake may be associated with compromised bone health. Deficiencies in vitamin B, along with the consequent elevated homocysteine level, are associated with bone loss, decreased bone strength, and increased risk of fracture. Deficiencies in vitamins C, E, and K are also associated with compromised bone health; this effect may be modified by smoking, estrogen use or hormonal therapy after menopause, calcium intake, and vitamin D. These findings highlight the importance of adequate nutrition in preserving bone mass and reducing the risk of osteoporosis and fractures.