Ann Prentice

Vitamin D deficiency: a global perspective

The prevalence of clinical vitamin D deficiency (rickets and osteomalacia) is high in many parts of the world, and there is a resurgence of rickets among children of ethnic minority groups in Europe and Australasia. Plasma 25-hydroxyvitamin D concentration (25OHD) is a useful risk marker of clinical vitamin D deficiency. This review summarizes the factors that contribute to differences in 25OHD among populations and provides an overview of the prevalence of low vitamin D status worldwide. It discusses the controversies that surround the interpretation of 25OHD, other proposed indices of vitamin D adequacy and dietary reference values for vitamin D, and describes the emerging evidence that a very low calcium intake may contribute to the etiology of rickets in Africa and Asia. There is an urgent need for action to address the global burden of rickets and osteomalacia.

Whole body bone mineral content in healthy children and adolescents

Data from healthy children are needed to evaluate bone mineralisation during childhood. Whole body bone mineral content (BMC) and bone area were examined by dual energy x ray absorptiometry (Hologic 1000/W) in healthy girls (n=201) and boys (n=142) aged 5–19 years. Centile curves for bone area for age, BMC for age, bone area for height, and BMC for bone area were constructed using the LMS method. Bone mineral density calculated as BMC/bone area is not useful in children as it is significantly influenced by bone size. Instead, it is proposed that bone mineralisation is assessed in three steps: height for age, bone area for height, and BMC for bone area. These three steps correspond to three different causes of reduced bone mass: short bones, narrow bones, and light bones.

Vitamin D deficiency in Europe: pandemic?

Background: Vitamin D deficiency has been described as being pandemic, but serum 25-hydroxyvitamin D [25(OH)D] distribution data for the European Union are of very variable quality. The NIH-led international Vitamin D Standardization Program (VDSP) has developed protocols for standardizing existing 25(OH)D values from national health/nutrition surveys. Objective: This study applied VDSP protocols to serum 25(OH)D data from representative childhood/teenage and adult/older adult European populations, representing a sizable geographical footprint, to better quantify the prevalence of vitamin D deficiency in Europe. Design: The VDSP protocols were applied in 14 population studies [reanalysis of subsets of serum 25(OH)D in 11 studies and complete analysis of all samples from 3 studies that had not previously measured it] by using certified liquid chromatography–tandem mass spectrometry on biobanked sera. These data were combined with standardized serum 25(OH)D data from 4 previously standardized studies (for a total n = 55,844). Prevalence estimates of vitamin D deficiency [using various serum 25(OH)D thresholds] were generated on the basis of standardized 25(OH)D data. Results: An overall pooled estimate, irrespective of age group, ethnic mix, and latitude of study populations, showed that 13.0% of the 55,844 European individuals had serum 25(OH)D concentrations <30 nmol/L on average in the year, with 17.7% and 8.3% in those sampled during the extended winter (October–March) and summer (April–November) periods, respectively. According to an alternate suggested definition of vitamin D deficiency (<50 nmol/L), the prevalence was 40.4%. Dark-skinned ethnic subgroups had much higher (3- to 71-fold) prevalence of serum 25(OH)D <30 nmol/L than did white populations. Conclusions: Vitamin D deficiency is evident throughout the European population at prevalence rates that are concerning and that require action from a public health perspective. What direction these strategies take will depend on European policy but should aim to ensure vitamin D intakes that are protective against vitamin D deficiency in the majority of the European population.

Epidemiological study of hip fracture in Shenyang, People’s Republic of China

The aim of this study was to investigate the incidence and epidemiology in 1994 of hip fracture in Shenyang, a large city in the northeast of The Peoples Republic of China, using register information and medical records collected from the 36 hospitals in Shenyang. The hip fracture data were restricted to cervical or trochanteric types. A subset (59% of total) of medical records of hip fracture was used to investigate the causes of hip fracture. The causes were classified as simple fall, fall from a bicycle during cycling, bicycle accident, car accident, and fall from a height. There was a total of 453 hip fractures (206 in women and 247 in men) in the population over 50 years of age. The age-adjusted 1 year cumulative incidence rate was 67/100,000 (95% confidence interval [CI] = 58-76/100,000) for women and 81/100,000 (95% CI = 71-91/100,000) for men. The standardized incidence rate against the 1985 U.S. population was 87/100,000 (95% CI = 77-97/100,000) for women and 100/100,000 (95% CI = 89-111/100,000) for men. The mean (+/-standard deviation) age of patients with a hip fracture was 67.5+/-9.8 years for men and 66.9+/-9.0 years for women. The overall male-to-female ratio of hip fracture was 1.21:1 for age-adjusted hip fracture incidence and 1.15:1 for standardized incidence. Simple fall accounted for 70% hip fractures in women but caused only 49% in men (chi2 = 11.2, degrees of freedom [df] = 1,p = 0.0008). The frequency of hip fractures caused by a fall from a bicycle was higher in men (28%) than women (10%) (chi2 = 13.0, df = 1,p = 0.0003). The results of this study indicate (1) a low incidence of hip fracture in a Chinese population compared with more affluent countries, and (b) a higher incidence in men than women that is related in part to a higher incidence of accidents, especially bicycle-related ones.

Micronutrients and the Bone Mineral Content of the Mother, Fetus and Newborn

The fluxes of the primary bone-forming minerals, calcium, phosphorus, magnesium and zinc, across the placenta and through breast milk place considerable demands on maternal mineral economy. Increases in food consumption, elevated gastrointestinal absorption, decreased mineral excretion and mobilization of tissue stores are several possible biological strategies for meeting these extra mineral requirements. This paper presents a review of the evidence on the extent to which these strategies apply in the human situation, the mechanisms by which they occur, the limitations imposed by maternal diet and vitamin D status and the possible consequences for the growth of the infant and bone health of the mother. On the strength of current evidence it appears that pregnancy and lactation are associated with physiological adaptive changes in mineral metabolism that are independent of maternal mineral supply within the range of normal dietary intakes. These processes provide the minerals necessary for fetal growth and breast milk production without requiring an increase in maternal dietary intake or compromising maternal bone health in the long term. This may not apply to pregnant women whose mineral intakes or sunlight exposure are marginal. As a vehicle for promoting optimal growth and bone mineral content of infants, supplementation of lactating women with minerals or vitamin D is unlikely to prove effective. The situation in pregnancy is less certain. Until more studies have been conducted, a precautionary case can be made for targeted supplementation of pregnant women who have very low intakes of calcium or who are at risk of vitamin D deficiency.

Symposium on ‘Nutrition and health in children and adolescents’ Session 1: Nutrition in growth and development: Nutrition and bone growth and development

The growth and development of the human skeleton requires an adequate supply of many different nutritional factors. Classical nutrient deficiencies are associated with stunting (e.g. energy, protein, Zn), rickets (e.g. vitamin D) and other bone abnormalities (e.g. Cu, Zn, vitamin C). In recent years there has been interest in the role nutrition may play in bone growth at intakes above those required to prevent classical deficiencies, particularly in relation to optimising peak bone mass and minimising osteoporosis risk. There is evidence to suggest that peak bone mass and later fracture risk are influenced by the pattern of growth in childhood and by nutritional exposures in utero, in infancy and during childhood and adolescence. Of the individual nutrients, particular attention has been paid to Ca, vitamin D, protein and P. There has also been interest in several food groups, particularly dairy products, fruit and vegetables and foods contributing to acid–base balance. However, it is not possible at the present time to define dietary reference values using bone health as a criterion, and the question of what type of diet constitutes the best support for optimal bone growth and development remains open. Prudent recommendations (Department of Health, 1998; World Health Organization/Food and Agriculture Organization, 2003) are the same as those for adults, i.e. to consume a Ca intake close to the reference nutrient intake, optimise vitamin D status through adequate summer sunshine exposure (and diet supplementation where appropriate), be physically active, have a body weight in the healthy range, restrict salt intake and consume plenty of fruit and vegetables.

Bone mineral changes during and after lactation.

OBJECTIVE To assess bone mineral changes during and after lactation. METHODS Fifty-nine breast-feeding women, 11 formula-feeding women, and 22 nonpregnant, nonlactating women had dual-energy x-ray absorptiometry measurements of the whole body, spine, hip, and forearm at 0.5 (baseline), 3, 6, and 12 months postpartum, with an additional measurement at 3 months after lactation for women who had breast-fed for more than 9 months. RESULTS Lactation was associated with decreases in bone mineral at the whole body, spine, femoral neck, total hip, and radial wrist, which reversed as lactation declined and menstruation resumed. These changes were not seen in formula-feeding women. The magnitude and duration of the response were greater for women who breast-fed for a longer time. After lactation had stopped for at least 3 months, bone mineral, adjusted for bone area, had increased significantly above baseline at the whole body (+1.44%; 95% confidence interval [CI] +0.97%, +1.91%; P < .001), spine (+2.66%; 95% CI +1.60%, +3.72%; P < .001), and greater trochanter (+3.55%; 95% CI +2.53%, +4.57%; P < .001), was not different at the total hip and radial shaft, but was lower at the femoral neck (-2.07%; 95% CI -3.21%, -0.93%; P < .001) and radial wrist (-1.23%; 95% CI -1.99%, -0.47%; P < .01). Changes after lactation were largely independent of the duration of lactation or amenorrhea, and similar effects were observed in formula-feeding women. CONCLUSION Lactation was associated with temporary decreases in bone mineral. After lactation, there were significant residual effects on bone mineral that were unrelated to the duration of lactation and may be related to having been pregnant. The long-term effect of lactation on the femoral neck requires further investigation.

Energy and nutrient dietary reference values for children in Europe: methodological approaches and current nutritional recommendations.

The Expert Group on the Methodological Approaches and Current Nutritional Recommendations in Children and Adolescents was convened to consider the current situation across Europe with regard to dietary recommendations and reference values for children aged 2-18 years. Information was obtained for twenty-nine of the thirty-nine countries in Europe and a comprehensive compilation was made of the dietary recommendations current up to September 2002. This report presents a review of the concepts of dietary reference values and a comparison of the methodological approaches used in each country. Attention is drawn to the special considerations that are needed for establishing dietary reference values for children and adolescents. Tables are provided of the current dietary reference values for energy and for the macronutrients, vitamins, minerals, trace elements and water. Brief critiques are included to indicate the scientific foundations of the reference values for children and to offer, where possible, an explanation for the wide differences that exist between countries. This compilation demonstrated that there are considerable disparities in the perceived nutritional requirements of European children and adolescents. Although some of this diversity can be attributed to real physiological and environmental differences, most is due to differences in philosophy about the best methodological approach to use and in the way the theoretical approaches are applied. The report highlights the main methodological and technological issues that will need to be resolved before harmonization can be fully considered. Solving these issues may help to improve the quality and consistency of dietary reference values across Europe. However, there are also considerable scientific and political barriers that will need to be overcome and the question of whether harmonization of dietary reference values for children and adolescents is a desirable or achievable goal for Europe requires further consideration.

Maternal calcium metabolism and bone mineral status

Human pregnancy is associated with major changes in calcium and bone metabolism and in bone mineral status before and after gestation. The changes are compatible with the uptake and mobilization of calcium by the maternal skeleton to meet the high requirement for fetal growth and for breast-milk production. Breast-feeding is accompanied by decreases in bone mineral status, increases in bone turnover rate, and reductions in urinary calcium excretion. These effects are reversed during and after weaning, and, in several skeletal regions, bone mineral content ultimately exceeds that measured after delivery. By 3-6 mo after lactation, the postpartum changes in bone mineral status of women who breast-feed largely match those of women who do not, regardless of the duration of lactation. No consistent picture has emerged of the effect of pregnancy on bone mineral status, although increases in bone turnover, calcium absorption, and urinary calcium excretion are well recognized. Events before conception may modify the bone response, particularly if conception occurs within a few months of a previous pregnancy or lactation. There is no evidence that the changes observed during lactation reflect inadequacies in calcium intake. Supplementation studies have shown that neither the bone response nor breast-milk calcium secretion is modified by increases in calcium supply during lactation, even in women with a low calcium intake. The situation in pregnancy is less clear. Calcium nutrition may influence the health of the pregnant woman, her breast-milk calcium concentration, and the bone mineralization and blood pressure of her infant, but these possibilities require formal testing.

Breast-milk fat concentrations of rural African women: 2. Long-term variations within a community

1. Long-term variations in breast-milk fat concentration of mothers feeding on demand were studied in 120 rural West African women over a 12-month period. 2. The over-all mean 12 h breast-milk fat concentration was 39.3 g/l. 3. Mean breast-milk fat concentrations were affected by season in a manner which was correlated with seasonal changes in maternal subcutaneous fat stores (P less than 0.05) but which was unrelated to seasonal variations in maternal energy intake and breast-milk output. 4. Breast-milk fat concentrations were highest in early lactation, decreasing to a constant level during the first year. 5. There was significantly greater between-mother than within-mother variation in breast-milk fat concentrations measured in successive months, after correcting for season and stage of lactation (P less than 0.001). 6. Breast-milk fat concentrations were highest for primiparous mothers, decreasing to a constant level at parity 4 and higher. 7. A mothers relative breast-milk fat concentration was not correlated with her levels of dietary energy intake and breast-milk output but was positively correlated with her relative subcutaneous fat deposits (P less than 0.01).