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Biomedical subjects

Kenneth H Brown

Publications and source records attributed to Kenneth H Brown.

29 records · Page 2Linked to original sources
PubMed2003

Population-based plasma kinetics of an oral dose of [2H4]retinyl acetate among preschool-aged, Peruvian children.

BACKGROUND: The deuterated-retinol-dilution technique provides a quantitative estimate of total-body vitamin A (TBVA) stores in adults. To apply the technique to children, information on plasma retinol kinetics in this age group is needed. OBJECTIVES: We described the plasma retinol kinetics of an oral dose of [(2)H(4)]retinyl acetate in a population of Peruvian children (12-24 mo of age) in order to examine the relation between TBVA stores and individual plasma isotopic ratios 3 d after the dose and to estimate 1) the time required for the isotope dose to mix with endogenous vitamin A, 2) the fractional catabolic rate for retinol, and 3) TBVA stores. DESIGN: An oral dose of [(2)H(4)]retinyl acetate (14 micromol retinol equivalents) was administered to children (n = 107) to construct a population-level kinetic curve of the plasma ratio of [(2)H(4)]retinol to retinol to estimate equilibration time and the fractional catabolic rate. TBVA stores were estimated by using a modification of the isotope dilution equation for adults. RESULTS: The dose of [(2)H(4)]retinyl acetate fully mixed with endogenous vitamin A 8 d after the dose. The fractional catabolic rate was 0.022/d (95% CI: 0.014, 0.030/d). Mean (+/- SD) TBVA stores were estimated as 0.097 +/- 0.081 mmol (range: 0.016-0.392 mmol). Plasma ratios of [(2)H(4)]retinol to retinol 3 d after the dose were correlated with the inverse of estimated TBVA stores (r = -0.74, P < 0.0001). CONCLUSIONS: Compared with previous results in adults, the equilibration time occurred earlier and the estimated system fractional catabolic rate was higher in this population of children. The modified isotope dilution equation provided estimates of hepatic vitamin A concentration that are similar to values reported in US children at autopsy.

Administration, Oral↗
PubMed2003

Absorption of zinc from wheat products fortified with iron and either zinc sulfate or zinc oxide.

BACKGROUND: Several chemical forms of zinc have been proposed for food fortification, but information is needed on their absorption from common cereals having varied phytate content. OBJECTIVE: The goal was to measure zinc absorption from wheat products fortified with iron sulfate and either zinc sulfate or zinc oxide. DESIGN: Adult volunteers received either low-phytate bread (n = 11) or higher-phytate porridge (n = 11) once weekly on 2 or 3 occasions. The foods were fortified with 1 of the 2 zinc salts (60 mg elemental Zn/kg wheat flour) during week 1 and with the other during week 2, in random order. (65)Zn in the same chemical form as the fortificant was incorporated in each food to assess zinc absorption with the use of whole-body counting. The porridge group received an additional test meal fortified with zinc oxide during week 3, but the (65)Zn tracer was given as an oral solution of (65)ZnCl(2). RESULTS: Zinc absorption from bread (13.8%; 95% CI: 11.8%, 16.2%) was significantly (P < 0.001) greater than from porridge (6.4%; 5.5%, 7.6%), presumably because of the greater phytate content of the porridge. With control for food type, there were no significant differences in zinc absorption from meals fortified with zinc sulfate or zinc oxide (P = 0.24). When the porridge was fortified with zinc oxide and labeled with (65)ZnCl(2), absorption of the tracer (8.9%; 7.1%, 11.0%) was significantly (P = 0.007) greater than when (65)ZnO was incorporated in the porridge (5.6%; 4.5%, 6.9%). CONCLUSIONS: Either zinc oxide or zinc sulfate can be used to fortify wheat products consumed by presumably healthy persons. Isotopic tracers used to assess the absorption of mineral fortificants should have the same chemical form as the fortificant.

Adult↗
PubMed2003

Suggested lower cutoffs of serum zinc concentrations for assessing zinc status: reanalysis of the second National Health and Nutrition Examination Survey data (1976-1980).

BACKGROUND: The risk of zinc deficiency in populations can be estimated by comparing serum zinc data with statistically defined lower cutoffs derived from a presumably healthy population. Serum zinc data are available from a large sample of the US population assessed during the second National Health and Nutrition Examination Survey (NHANES II). Although the original analysis of these data considered fasting status and the time of day of blood sampling, it did not account for potentially confounding variables that may affect the serum zinc concentration, such as age, sex, and health status. OBJECTIVE: The objective was to describe variations in serum zinc concentration by age, sex, and other characteristics and to recommend lower cutoffs for presumably healthy persons. DESIGN: Serum zinc data from NHANES II were analyzed by using analysis of variance and covariance models to identify and describe variables significantly associated with serum zinc concentration; 2.5th percentile curves were produced and used to establish age- and sex-based lower cutoffs. RESULTS: Age and sex were significant confounders of serum zinc concentration, so separate lower cutoffs were derived for children and adolescent and adult males and females. Other minor confounding variables were identified. Tentative lower cutoffs for pregnancy and oral contraceptive use were also derived. CONCLUSIONS: The interpretation of population serum zinc data with the use of lower cutoffs should account for the age and sex of the subjects, pregnancy and oral contraceptive use, and fasting status and time of day of blood collection.

Adolescent↗
PubMed2003

Zinc intake of US preschool children exceeds new dietary reference intakes.

BACKGROUND: The recent dietary reference intakes publication provides updated information on the physiologic and dietary requirements for zinc and proposes new tolerable upper intake levels. OBJECTIVE: We analyzed dietary intake data of US preschool children to determine the prevalence of inadequate and excessive intakes of zinc. DESIGN: Diets of 7474 nonbreastfeeding preschool children in the Continuing Survey of Food Intakes by Individuals (1994-1996 and 1998) were analyzed for the intakes of zinc and other dietary components, and factors associated with zinc intake were examined. RESULTS: The mean intakes of zinc by children aged < 1 y, 1-3 y, and 4-5 y were 6.6, 7.6, and 9.1 mg/d, respectively. Less than 1% of children had usual zinc intakes below the adequate intake or estimated average requirement. The percentages of children with intakes exceeding the tolerable upper intake level were 92% (0-6 mo), 86% (7-12 mo), 51% (1-3 y), and 3% (4-5 y). Controlling for age and energy intake, zinc intake was greater in 1998 than in 1994 (P < 0.0001) and was positively associated with participation in the Women, Infants, and Children Program (P < 0.001) and with the lowest income category (P < 0.001). CONCLUSIONS: Preschool children in the United States have dietary zinc intakes that exceed the new dietary reference intakes. Zinc intakes increased during the 4 y of the study. The present level of intake does not seem to pose a health problem, but if zinc intake continues to increase because of the greater availability of zinc-fortified foods in the US food supply, the amount of zinc consumed by children may become excessive.

Aging↗
PubMed2003

Diarrhea and malnutrition.

Publication of the WHO monograph, "Interactions of Nutrition and Infection," in 1968 by Scrimshaw, Taylor and Gordon stimulated many scientists to pursue further research on these issues. With regard to the relationships between diarrhea and malnutrition, the research conducted since 1968 can be categorized in one of three major areas: 1) the impact of diarrhea on nutritional status, particularly in young children; 2) nutritional risk factors for diarrhea; and 3) appropriate dietary therapy for patients during and after enteric infections. The results of these studies have prompted a number of changes in the clinical treatment of patients with diarrhea and in public health policies regarding its prevention.

Child, Preschool↗
PubMed2003

Assessment of the trace element status of individuals and populations: the example of zinc and copper.

This paper describes the proceedings of a workshop that was convened at the 11th International Symposium on Trace Elements in Man and Animals (TEMA-11) symposium to review recent advances concerning the assessment of the trace element status of individuals and populations, using zinc and copper as the primary examples to illustrate basic principles and recent advances in assessment methods. The workshop was initiated with a brief review of the importance of zinc nutriture for human health and a discussion of the likely common occurrence of zinc deficiency worldwide. This overview was followed by presentations on selected issues concerning the assessment of zinc status, with particular attention devoted to dietary assessment techniques, the use of isotopic tracers to assess zinc homeostasis and the relationship of these methods to biochemical indicators of zinc status. Because relatively little information is available on zinc toxicity, the discussion concerning the definition of excess intake of trace elements focused primarily on recent work concerning risk assessment of copper toxicity.

Animals↗
PubMed2003

Update on technical issues concerning complementary feeding of young children in developing countries and implications for intervention programs.

This paper provides an update to the 1998 WHO/UNICEF report on complementary feeding. New research findings are generally consistent with the guidelines in that report, but the adoption of new energy and micronutrient requirements for infants and young children will result in lower recommendations regarding minimum meal frequency and energy density of complementary foods, and will alter the list of "problem nutrients." Without fortification, the densities of iron, zinc, and vitamin B6 in complementary foods are often inadequate, and the intake of other nutrients may also be low in some populations. Strategies for obtaining the needed amounts of problem nutrients, as well as optimizing breastmilk intake when other foods are added to the diet, are discussed. The impact of complementary feeding interventions on child growth has been variable, which calls attention to the need for more comprehensive programs. A six-step approach to planning, implementing, and evaluating such programs is recommended.

Breast Feeding↗
PubMed2002

Effect of supplemental zinc on the growth and serum zinc concentrations of prepubertal children: a meta-analysis of randomized controlled trials.

BACKGROUND: Multiple studies have been carried out to assess the effect of zinc supplementation on children's growth. The results of these studies are inconsistent, and the factors responsible for these varied outcomes are unknown. OBJECTIVE: Meta-analyses of randomized controlled intervention trials were therefore completed to assess the effect of zinc supplementation on the physical growth and serum zinc concentrations of prepubertal children. DESIGN: A total of 33 acceptable studies with appropriate data were identified by MEDLINE (National Library of Medicine, Bethesda, MD) searches and other methods. Weighted mean effect sizes (expressed in SD units) were calculated for changes in height, weight, weight-for-height, and serum zinc concentration by using random-effects models; factors associated with effect sizes were explored by meta-regression techniques. RESULTS: Zinc supplementation produced highly significant, positive responses in height and weight increments, with effect sizes of 0.350 (95% CI: 0.189, 0.511) and 0.309 (0.178, 0.439), respectively. There was no significant effect of zinc on weight-for-height indexes [weighted mean effect size: -0.018 (-0.132, 0.097)]. Zinc supplementation caused a large increase in the children's serum zinc concentrations, with an effect size of 0.820 (0.499, 1.14). Growth responses were greater in children with low initial weight-for-age z scores and in those aged >6 mo with low initial height-for-age z scores. CONCLUSIONS: Interventions to improve children's zinc nutriture should be considered in populations at risk of zinc deficiency, especially where there are elevated rates of underweight or stunting. The population mean serum zinc concentration is a useful indicator of the successful delivery and absorption of zinc supplements in children.

Adolescent↗