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Calcium supplementation has been shown to increase bone mineralization in children and adolescents. However, catch-up mineralization later in puberty appears likely if intake is consistent with usual average intakes in the United States. Ultimately, individualized risk assessment will be developed based on genetic and lifestyle factors that can be used to guide optimal calcium intake during childhood. Key words: calcium absorption, dietary requirements, puberty, bone mass

Stable isotope absorption studies of iron have been limited by the high cost and limited availability of isotope ratio analysis using thermal ionization MS (TIMS). The development of high-resolution double focusing inductively coupled plasma MS (ICP-MS) may permit more cost-efficient sample analysis due to its high throughput, lower cost, easy sample pretreatment, and greater availability. Our objective was to develop an ICP-MS methodology for the measurement of iron isotope ratios using very small blood volumes. We developed a technique using multiple iron-nickel mixing standard solutions to adjust for nickel interference calibration. RBC samples from human subjects previously given [.sup.58]Fe and [.sup.5]7Fe were analyzed for iron isotope ratios and compared with our current methodology (TIMS). Reproducibility of iron isotope ratios provided external relative SD < 0.5 and 0.7% (1 SD) for [.sup.57]Fe/[.sup.54]Fe and [.sup.58]Fe/[.sup.54]Fe, respectively. Iron isotope ratios from ICP-MS analysis did not differ from those from TIMS based on statistical analyses, nor did the calculated iron absorption values. The mean and SD of iron absorption did not differ when measured by TIMS or ICP-MS. A 2-[mu]L RBC sample was sufficient for ICP-MS iron isotope ratio analysis with an internal relative SD < 0.5% and analytical time < 5 min. This technique may assist groups in increasing their use of stable isotope methods to assess iron absorption in infants and children. KEY WORDS: * inductively coupled plasma MS * iron absorption * isobaric interference * mass bias * stable isotopes

The addition of milk and milk-based products to the diets of individuals subsisting on plant-based diets was reported to have positive effects on nutritional status and functional outcomes such as growth, morbidity, and cognition. We examined the effect of the addition of milk or yogurt on the bioavailability of zinc and iron from a plant-based rural diet. The subjects were 48 Mexican women (30.9 [+ or -] 5.7 y) who habitually consumed a plant-based diet. The women were assigned to 1 of 3 groups: 1) the typical rural Mexican diet, 2) that diet with milk added, or 3) that diet with yogurt for 13 d. Zinc absorption was measured after extrinsically labeling meals with 87Zn and an i.v. dose of [sup.70]Zn; iron absorption was measured by extrinsically labeling meals with [sup.67]Fe and a reference oral dose of [sup.57]Fe. Including milk and yogurt in the diet increased zinc absorption by 50 and 68%, respectively (P < 0.05). The 3 groups did not differ in the percentage iron absorption. The total amount of zinc absorbed was increased (P < 0.05) by 70% when milk was added to the meal and 78% when yogurt was added. The total amount of iron absorbed did not differ among the groups. The addition of milk and yogurt to a plant-based diet high in phytate increases zinc bioavailability without affecting iron bioavailability. KEY WORDS: * nutrient bioavailability * zinc absorption * iron absorption * Mexican diets * stable isotopes

After 1 y of distributing a milk-based fortified weaning food provided by the Mexican social program PROGRESA, positive effects on physical growth, prevalence of anemia, and several vitamin deficiencies were observed. There was no effect on iron status, which we hypothesized was related to the poor bioavailability of the reduced iron used as a fortificant in PROGRESA. The objective of this study was to compare the iron bioavailability from different iron sources added as fortificants to the weaning food. Children (n 54) aged 2-4 y were randomly assigned to receive 44 g of the weaning food fortified with ferrous sulfate, ferrous fumarate, or reduced iron + [Na.sub.2]EDTA. Iron absorption was measured using an established double-tracer isotopic methodology. Iron absorption from ferrous sulfate (7.9 [+ or -] 9.8%) was greater than from either ferrous fumarate (2.43 [+ or -] 2.3%) or reduced iron + [Na.sub.2]EDTA (1.4 [+ or -] 1.3%) (P < 0.01). The absorption of [log-.sup.58] Fe sulfate given with the iron source correlated with serum ferritin (s-ferritin) concentration (n = 13, r = 0.63, P = 0.01) and [log-.sup.57] Fe absorption (reference dose) (n = 14, r = -0.52, P = 0.02). Absorption from ferrous fumarate and reduced iron + Na2EDTA did not correlate with s-ferritin or absorption of [sup.57] Fe. The recommended daily portion of the fortified complementary food provides an average of 0.256, 0.096, 0.046 mmol (1.44, 0.54, and 0.26 mg) of absorbed iron, if fortified with sulfate, fumarate and reduced iron + [Na.sub.2] EDTA, respectively. Ferrous sulfate was more bioavailable than either ferrous fumarate or reduced iron + [Na.sub.2]EDTA when added to the milk-based fortified food and more readily met the average daily iron requirements for children 2-3 y of age. KEY WORDS: * iron absorption * stable isotopes * fortification

For full-term infants in the first 6 months of life, exclusive breastfeeding remains the nutritional standard for calcium intake. However, unsupplemented human milk does not meet the nutritional requirements for growth of the very-low-birth-weight (< 1500 g) infant. Methods for human milk fortification have been evaluated, and recent studies have demonstrated the safety of these fortifiers. Key words: human milk, fortification, minerals, prematurity

Rice flour was proposed as a vehicle for iron and zinc fortification in Sri Lanka. Although widely consumed, rice flour has not been evaluated as a fortified food, and the absorption of minerals including iron and zinc from this flour is unknown. Determination of the bioavailability of these nutrients is a critical step before commencing a fortification program. We randomly divided 53 Sri Lankan schoolchildren ages 6-10 y into 4 groups that consumed a local dish prepared with 25 g of fortified rice flour labeled with one of the following: 1) [sup.58]FES[O.sub.4] 2) [sup.58]FES[O.sub.4] + [Na.sub.2]EDTA 3) [sup.58]FES[O.sub.4] + [sup.67].ZnO or, 4) [sup.58]FES[O.sub.4] + [Na.sub.2]EDTA + [sup.67]ZnO. The levels of iron and zinc were 60 mg/kg; the rice flour also contained folate at 2 mg/kg in each group. [Na.sub.2]EDTA was added at a Fe:[Na.sub.2]EDTA, 1:1 molar ratiO. A total of 48 children completed the trial. Absorption of [sup.58]Fe from a meal was significantly greater (P < 0.01) in the groups administered FeS[O.sub.4] + [Na.sub.2]EDTA (4.7 [+ or -] 3.6%) than in those administered FeS[O.sub.4] without [Na.sub.2]EDTA (2.2 [+ or -] 1.3%). Fractional absorption of Zinc was 13.5 [+ or -] 6.0% in the FeS[O.sub.4] + [Na.sub.2]EDTA group and 8.8 [+ or -] 2.0% in the FeS[O.sub.4] group (P = 0.037). Although zinc absorption was low, our results demonstrated a benefit in using [Na.sub.2]EDTA to improve both iron and zinc absorption. We conclude that the fortification of rice flour is feasible, although additional strategies such as dephytinization or an increase in the level of iron and zinc fortification should be considered to obtain a higher proportion of the daily requirement of total absorbed iron and zinc. KEY WORDS: * fortification * rice flour * Sri Lanka * iron absorption * zinc absorption

The search for a reliable, convenient indicator of Zn status was the focus of research for several decades. Plasma Zn concentration is still the most widely used clinical measurement, despite the known problems of interpretation. More recently, researchers suggested that isotopically determined kinetic parameters, such as the exchangeable Zn pool (EZP), may more accurately and reliably reflect body Zn status. The objective of this study was to examine the relationship between net body Zn loss and gain during acute changes in dietary Zn intake with biochemical and kinetic indices of Zn status. Five men participated in an 85-d Zn depletion/repletion study. Net body Zn loss and gain were determined from the difference between dietary plus intravenously administered Zn and Zn excretion. Biochemical indicators of Zn status included plasma Zn, plasma alkaline phosphatase activity, and plasma retinol binding protein concentration. Following intravenous administration of [sup.70]Zn or [sup.67]Zn, a compartmental model was used to determine EZP mass, fractional Zn absorption, endogenous zinc excretion (EZE), and plasma Zn flux. The changes in total body zinc correlated best with changes in plasma Zn ([r.sup.2] = 0.826, P < 0.001), EZE ([r.sup.2] = 0.773, P < 0.001), and plasma Zn flux ([r.sup.2] = 0.788, P < 0.001). This study confirms that plasma Zn concentration is a valid indicator of whole-body Zn status in the absence of confounding factors; however, further research is needed to determine how kinetic parameters respond to conditions where plasma Zn concentration is known to be unreliable. KEY WORDS: zinc status biochemical indices * stable isotopes * kinetic analysis * compartmental model

The most sustainable way to eradicate iron deficiency is through food fortification. Elemental iron powders are commonly utilized as fortificants due to their low cost and few sensory problems. However, their bioavailability is unknown. Our goals were to measure the bioavailability of elemental iron in Mexican style corn masa flour tortillas and to evaluate the effects of [Na.sub.2]EDTA. We used a stable isotope of [H.sub.2]-reduced iron powder, with and without [Na.sub.2]EDTA in tortillas prepared with corn masa flour. Two groups of 5- to 7-y-old children (n = 12/group) were fed tortillas to which was added 3 mg/100 g of [H.sub.2]-reduced [sup.58]Fe with a mean particle size of 15 [micro]m. In one group, [Na.sub.2]EDTA was incorporated at a ratio of 1:2 mol/mol. The next day, [sup.57]Fe ascorbate was given as a reference dose. After 14 d, blood samples were analyzed for isotopic enrichment. When normalized to 40% absorption of the reference dose, the geometric mean ([+ or -] range 1 SD) bioavailability of reduced iron in tortilla was 3.8% (2.7-5.3). The addition of [Na.sub.2]EDTA, tended to increase it (P = 0.18) to 5.1% (2.8-9.2). This observed low absorption was compounded by the use of iron isotopes with smaller particle size (mean diameter 15 [micro]m) than typical of commercial elemental iron powder ( KEY WORDS: * elemental iron * iron bioavailability * corn masa flour * disodium EDTA * stable isotopes

Provision of the bone minerals and vitamin D as fortificants in food or as dietary supplements designed for older infants and toddlers in Latin America is likely to be beneficial and safe. Currently available data are inadequate to establish the precise amounts of these nutrients that would be required for such a supplement. These amounts would vary according to the local base diet. However, reasonable estimates can be made on the basis of current dietary recommendations as well as existing data on bioavailability and customary intake. The strongest case can be made for calcium and vitamin D supplementation. Because excessive dietary calcium can reduce zinc absorption as a result of interactive effects within the intestine, an appropriate ratio of calcium to zinc should be used, even if this means adding zinc as a fortificant or supplement. Magnesium supplementation may be appropriate in some circumstances but it cannot be routinely advocated at present. It is unlikely that phosphorus supplementation is needed for most population groups because of the relatively high usual dietary phosphorus intakes, primarily from phosphate salts added to carbonated beverages and as food preservatives. KEY WORDS: * human nutrition * bone mineral metabolism * rickets * mineral fortification of foods * iron * zinc * infants * young children

Due to their widespread acceptability, multinutrient-fortified foods and beverages may be useful in reducing micronutrient deficiencies, especially in developing countries. We studied the efficacy of a new fortified beverage in improving the nutritional status of children in Botswana. We screened 311 lower income urban school children, ages 6-11 y, in two primary schools near Gaborone. Children were given seven 240-mL servings weekly of either an experimental beverage (EXP) fortified with 12 micronutrients or an isoenergetic placebo drink (CON) for 8 wk. Weight, mid-upper arm circumference, hemoglobin, retinol, ferritin, vitamin B-12, folate and riboflavin status were measured at baseline and at the end of the study. Plasma zinc and serum transferrin receptors also were measured at study end. A total of 145 children in the EXP group and 118 in the CON group completed the trial. Using multivariate analysis, the changes in mid-upper arm circumference, weight for age and total weight were significantly better in the EXP group than in the CON group (P < 0.01). Ferritin, riboflavin and folate status were significantly better in the EXP group than in the CON group at study end (P < 0.01), but serum vitamin B-12 was not. Zinc was significantly higher and transferrin receptors were significantly lower at the conclusion of the study in the EXP group than in the CON group (P < 0.001). Mean plasma retinol concentrations, which were low ( KEY WORDS: * Africa * fortified beverage * micronutrient deficiency * undernutrition

Introduction: The incidence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections in the Belgian community is mainly estimated based on test results of patients with coronavirus disease (COVID-19)-like symptoms. The aim of this study was to investigate the evolution of the SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) positivity ratio and distribution of viral loads within a cohort of asymptomatic patients screened prior hospitalization or surgery, stratified by age category. Materials/Methods: We retrospectively studied data on SARS-CoV-2 real-time RT-PCR detection in respiratory tract samples of asymptomatic patients screened pre-hospitalization or pre-surgery in nine Belgian hospitals located in Flanders over a 12-month period (1 April 2020–31 March 2021). Results: In total, 255925 SARS-CoV-2 RT-PCR test results and 2421 positive results for which a viral load was reported, were included in this study. An unweighted overall SARS-CoV-2 real-time RT-PCR positivity ratio of 1.27% was observed with strong spatiotemporal differences. SARS-CoV-2 circulated predominantly in 80+ year old individuals across all time periods except between the first and second COVID-19 wave and in 20–30 year old individuals before the second COVID-19 wave. In contrast to the first wave, a significantly higher positivity ratio was observed for the 20–40 age group in addition to the 80+ age group compared to the other age groups during the second wave. The median viral load follows a similar temporal evolution as the positivity rate with an increase ahead of the second wave and highest viral loads observed for 80+ year old individuals. Conclusion: There was a high SARS-CoV-2 circulation among asymptomatic patients with a predominance and highest viral loads observed in the elderly. Moreover, ahead of the second COVID-19 wave an increase in median viral load was noted with the highest overall positivity ratio observed in 20–30 year old individuals, indicating they could have been the hidden drivers of this wave. [ABSTRACT FROM AUTHOR]

Nutritional rickets, an ancient disease that was thought to have been cured in the early part of the 20th century, has made an unexpected comeback in recent years throughout the world. Although the frequency of its occurrence is poorly documented, increasing case reports of rickets are apparently related to low dietary intake of vitamin D and calcium and decreased sunshine exposure. Greater awareness of this problem is needed, as are further data regarding vitamin D status and incidence of rickets among infants and toddlers. Routine provision of supplemental vitamin D to all breastfed infants remains controversial, but may become more widely recommended. Key Words: rickets, vitamin D, calcium, sunshine

To assess the possibility of ethnic differences in mineral metabolism in prepubertal children, we compared measures of calcium metabolism in 7- and 8-y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorption, urinary calcium excretion, calcium kinetic values and total-body bone mineral content in the MA and CAU girls. In contrast, parathyroid hormone (PTH) concentrations were greater in MA girls (4.01 [+ or -] 0.47 vs. 1.96 [+ or -] 0.50 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentrations were lower in MA girls (68.9 [+ or -] 7.7 vs. 109.4 [+ or -] 8.4 nmol/L, P = 0.001) than in CAU girls, but 1,25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the girls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentrations between MA and CAU girls do not have a large effect on calcium absorption, excretion or bone calcium kinetics. These data do not provide evidence for adjusting dietary recommendations for mineral or vitamin D intake by MA girls. KEY WORDS: * human nutrition * calcium metabolism * stable isotopes * bone mineralization * puberty

The major components of calcium metabolism, as evaluated by a dual-tracer stable isotope method, were determined in 100 studies of 68 healthy girls, aged 5-18 y and analyzed from a developmental and regulatory viewpoint. Bone calcium deposition and removal rates were closely correlated with the size of the exchangeable bone calcium compartment. All three quantities, as well as intestinal calcium absorption, peaked at or near menarche. Both bone calcium deposition and removal rates were positively and linearly correlated with calcium absorption. However, in this correlation, because bone calcium deposition increased 70% faster than calcium absorption, most of the increase in the bone calcium compartment and its turnover must have occurred in response to something other than intestinal calcium input; presumably this occurred in response to developmental signals. Nevertheless, the constancy of the serum calcium in the face of a large intestinal calcium input and the modest way in which excretion overcame the calcium load in this population point to the importance of the exchangeable bone calcium compartment, in dynamic equilibrium with the bone mineral, as the site at which most of the load is taken up. In this population of girls, as in older women, this increase in the skeletal calcium balance resulted from a decrease in the bone calcium removal rate that was greater than the corresponding increase in the bone calcium deposition rate. KEY WORDS: calcium absorption rate in healthy girls bone calcium deposition rate bone calcium removal rate exchangeable bone calcium age-dependent changes

The determination of magnesium kinetics in adolescent girls and the effects of high and low calcium intake were analyzed using adolescent girls currently participating in a calcium balance study. Results of the research revealed that high calcium intake does not change or alter magnesium kinetics in adolescent girls. Furthermore, magnesium deficiency in humans can lead to low blood calcium and hypokalemia.