Showing papers by "Ian J. Griffin published in 2005"

Relationships among Vitamin D Levels, Parathyroid Hormone, and Calcium Absorption in Young Adolescents

Abstract: Background: Evidence suggests that vitamin D status in adults, as assessed by serum 25-hydroxyvitamin D (25-OHD), is positively associated with calcium absorption fraction and inversely associated with serum PTH. Few comparable pediatric data exist. Objectives: The objective of this study was to evaluate the relationships among vitamin D status, PTH, and calcium absorption in midpubertal boys and girls. Methods: Calcium absorption was measured as part of an evaluation of the effects of prebiotics (inulin-type fructans) using a stable isotope method in 93 young adolescents, 12.7 ± 1.0 yr of age, receiving diets averaging approximately 900 mg/d calcium. Results: A significant positive relation to calcium absorption was found for serum 1,25-dihydroxyvitamin D (P = 0.048) and PTH (P = 0.007), but not for 25-OHD (P = 0.77). PTH was significantly inversely related to 25-OHD and was positively related to serum 1,25-dihydroxyvitamin D and osteocalcin. PTH was marginally significantly inversely related to lumbar s...

Vitamin D receptor Fok1 polymorphisms affect calcium absorption, kinetics, and bone mineralization rates during puberty

Abstract: Few studies of the VDR polymorphisms have looked at calcium metabolism or long-term effects. We measured bone mineralization and calcium metabolic parameters longitudinally in a group of 99 adoles- cents. We found a significant relationship between calcium absorption and skeletal calcium accretion and the Fok1, but not other VDR or related, genetic polymorphisms. It seems that the Fok1 polymorphism directly affects bone mineralization during pubertal growth through an effect on calcium absorption. Introduction: There are few data regarding the relationship between genetic markers for low bone mass and changes in calcium metabolism in childhood or adolescence. We sought to identify the effects of polymor- phisms of the vitamin D receptor (VDR) on calcium and bone mineral metabolism in a longitudinal study of pubertal adolescents. Materials and Methods: Adolescents (n 99) received comprehensive stable isotope studies of calcium absorption, bone calcium kinetics, and bone mineralization. Studies were repeated 12 months later. Polymor- phisms of putative genetic markers were determined and related to bone mineralization and calcium metabolic finding. Results were analyzed by ANOVA in which changes over time were determined using the initial value as a covariate. Results: Polymorphisms of the Fok1 gene of the VDR were significantly related to calcium absorption (p 0.008) and whole body BMC (p 0.03) and BMD (p 0.006). The Fok1 effect on whole body BMD was significant for those with Ca intake >800 mg/day (p < 0.001), whereas for those with Ca intake 800 mg/day, the Fok1 genotype did not have a significant effect on whole body BMD (p 0.40). The Fok1 genotype was significantly related to the changes during the year in whole body calcium accretion, with the ff genotype having a 63 ± 20 mg/day deficit compared with the FF genotype (p 0.008). Conclusions: The Fok1 polymorphism of the VDR receptor seems to directly affect bone mineral accretion during pubertal growth through an effect on calcium absorption. The relationship between different genetic polymorphisms and bone mineral metabolism may vary by life stage as well as diet. J Bone Miner Res 2005;20:945-953. Published online on January 31, 2005; doi: 10.1359/JBMR.050114

Ferrous Sulfate Is More Bioavailable among Preschoolers than Other Forms of Iron in a Milk-Based Weaning Food Distributed by PROGRESA, a National Program in Mexico

Abstract: 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 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 + Na2EDTA. Iron absorption was measured using an established double-tracer isotopic methodology. Iron absorption from ferrous sulfate (7.9 ± 9.8% was greater than from either ferrous fumarate (2.43 ± 2.3%) or reduced iron + Na2EDTA (1.4 ± 1.3%) (P < 0.01). The absorption of log-(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-(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 (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 + Na2EDTA respectively. Ferrous sulfate was more bioavailable than either ferrous fumarate or reduced iron + Na2EDTA when added to the milk-based fortified food and more readily met the average daily iron requirements for children 2-3 y of age. (authors)

The Addition of Milk or Yogurt to a Plant-Based Diet Increases Zinc Bioavailability but Does Not Affect Iron Bioavailability in Women

Abstract: 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 +/- 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 (67)Zn and an i.v. dose of (70)Zn; iron absorption was measured by extrinsically labeling meals with (58)Fe and a reference oral dose of (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.

High Resolution Inductively Coupled Plasma Mass Spectrometry Allows Rapid Assessment of Iron Absorption in Infants and Children

Abstract: 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 58Fe and 57Fe 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 57Fe/54Fe and 58Fe/54Fe, 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-microL 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.

Methodological considerations in measuring human calcium absorption: relevance to study the effects of inulin-type fructans.

Abstract: During the last 50 years, a variety of methods have been developed to estimate Ca absorption in man. Mass balances were initially used, but these were unable to accurately measure fractional Ca absorption because they cannot distinguish unabsorbed dietary Ca from endogenous faecal Ca excretion (excretion of previously absorbed Ca back into the gut). A number of isotopic methods have been developed that can measure true fractional Ca absorption, employing radioisotopes, stable isotopes, or both. Different methods involve collection of urine, faecal or plasma samples. Of the currently available methods, the dual isotope tracer method with a timed urine collection is probably the most precise and reliable. It is also relatively straightforward to carry out and avoids the need for a faecal collection. The purpose of the present paper is to discuss the general advantages and disadvantages of the different methods of Ca absorption. In addition, the limitations the different methods have in examining the possible effects of non-digestible oligosaccharides on Ca absorption will be discussed.

Height and height Z-score are related to calcium absorption in five- to fifteen-year-old girls.

Abstract: Context: Understanding the relationship between calcium absorption and growth has been limited. We have developed a database of calcium absorption measurements in 315 girls aged 5.0–15.0 yr. Design: We have used this database to assess the relationship between height, its age- and gender-normalized value (height Z-score), and calcium absorptive efficiency. Results: Overall, height was significantly related to calcium absorption (corrected for calcium intake, age, Tanner, stage, and ethnicity) (P = 0.001). Similarly, height Z-score was significantly related to calcium absorption (P < 0.007). About 3–3.5% of the variability (η2) of absorption was associated with height or height Z-score. We found that calcium absorption was significantly lower in girls with height Z-score equal to or less than zero compared with those with a height Z-score more than zero (difference, 3.9 ± 1.4%, mean ± sem; P = 0.007). Limiting the analysis to those girls in which Tanner staging was performed or those age 9 yr or older did ...

Micronutrient Deficiencies: New solutions to a seemingly irresolvable problem

Abstract: Micronutrient deficiencies remain an enormous global problem constituting the ‘hidden hunger’ leading to poor growth, anemia, developmental delays, blindness and even death. Interventions have had some success in reducing the incidence of iodine and Vitamin A deficiency disorders. However, they have had little global impact on the prevalence of iron and zinc deficiencies. Furthermore, micronutrient deficiencies rarely occur in isolation. Multiple micronutrient deficiencies are relatively common, but most current interventions target only one or two micronutrients. In light of these ongoing problems, novel therapies are called for that provide multiple micronutrients in a form that is inexpensive, largely self-sustaining, economically viable and most importantly acceptable to the target population. We will review the global importance of micronutrient deficiencies and discuss some of the newer strategies to prevent or treat them.