Ethnic and racial differences in serum vitamin A levels of children aged 4-11 years

Establishing reference intervals of 20 biochemical markers for children in Southwestern Fujian, China based on the UniCel DxC 800 system

BACKGROUND

To date, China has no industry standard for reference intervals of paediatric blood biochemical markers. This study aimed to evaluate changes in biochemical markers in the venous blood of healthy children aged 29 days to 12 years, derived from the UniCel DxC 800 system, and establish appropriate reference intervals.

METHODS

We analysed venous blood from 1980 healthy children for 20 biochemical markers. Reference intervals were established according to the Clinical and Laboratory Standards Institute C28-A3c guideline and compared with those of adults in China.

RESULTS

All markers except for sodium and chlorine required partitioning by age, but not by sex. The reference intervals of total protein, albumin, globulin, carbon dioxide, urea nitrogen, creatinine and uric acid consistently increased with age in children, but were always lower than those of adults. Children aged 29 days to 12 years had a single combined RI for sodium and chloride, respectively; although the reference intervals in children were similar to those of adults, their upper limits were lower. The reference intervals of direct bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, potassium, calcium, magnesium, and phosphorus continued to decline with age. The reference intervals of total bilirubin, indirect bilirubin, and gamma-glutamyl transpeptidase initially declined followed by a slight rebound.

CONCLUSIONS

While establishing reference intervals, most markers required partitioning by age (aged 29 days to 12 years); the partitioning scheme differed for each marker, and paediatric reference intervals differed from those for adults. It is therefore necessary to establish separate paediatric reference intervals.

Relationship of NEFA concentrations to RBP4 and to RBP4/retinol in prepubertal children with and without obesity

BACKGROUND

The regulation of adipose tissue metabolism in early childhood obesity is not well understood. Insulin levels are higher and insulin resistance seems to be present in prepubertal children with obesity but, differing from their behavior in adults with obesity, non-esterified fatty acid (NEFA) concentrations are not increased. Retinol-binding protein (RBP)-4 concentration is associated with obesity and insulin resistance conditions, but the means of this relationship remain unclear, and few studies have taken retinol values into account to evaluate it.

OBJECTIVE

To analyze the relationship between RBP4 concentration and lipolytic products in plasma in 141 prepubertal children aged 6 to 8 years, with and without obesity.

METHODS

Plasma glucose, insulin, triacylglycerols, NEFA, glycerol, leptin, RBP4, and retinol were analyzed in obese and in their normal-weight counterparts. Homeostatic model assessment, quantitative insulin sensitivity check index, and fasting glucose to insulin ratio were calculated as indicators of insulin resistance.

RESULTS

Fasted plasma NEFA concentrations were lower in children with obesity than in their normal weight counterparts, despite leptin, insulin resistance indices, RBP4, retinol, and RBP4/retinol (an index of free-RBP4) being higher. NEFA and glycerol concentrations were inversely correlated with RBP4/retinol in children with obesity but not in those without obesity. In normal weight children, total RBP4 correlated negatively with NEFA and glycerol concentrations and positively with insulin and homeostasis model assessment for insulin resistance. These results indicate that a low saturation of RBP4 with retinol, which implies a higher concentration of free-RBP4, may preserve the antilipolytic function of insulin in adipose tissue in children with obesity.

CONCLUSION

Our findings suggest that, in prepubertal children with obesity and insulin resistance, the amount of RBP4/retinol correlates with the antilipolytic response of the adipose tissue to insulin rather than the total RBP4 concentration.

Race-ethnic, family income, and education differentials in nutritional and lipid biomarkers in US children and adolescents: NHANES 2003-2006

BACKGROUND

Children from ethnic minority and low-income families in the United States have higher rates of poor health and higher mortality rates. Diet, an acknowledged correlate of health, may mediate the known race-ethnic and socioeconomic differentials in the health of US children.

OBJECTIVE

The objective was to examine the independent association of race-ethnicity, family income, and education with nutritional and lipid biomarkers in US children.

DESIGN

We used data from the NHANES 2003-2006 to examine serum concentrations of vitamins A, D, E, C, B-6, and B-12; serum concentrations of folate, carotenoids, and lipids; and dietary intakes of corresponding nutrients for 2-19-y-old children (n = ~2700-7500). Multiple covariate-adjusted regression methods were used to examine the independent and joint associations of race-ethnicity, family income, and education with biomarker status.

RESULTS

Non-Hispanic blacks had lower mean serum concentrations of vitamins A, B-6, and E and α-carotene than did non-Hispanic whites. Both non-Hispanic blacks and Mexican Americans had higher mean serum vitamin C, β-cryptoxanthin, and lutein + zeaxanthin but lower folate and vitamin D concentrations compared with non-Hispanic whites. In comparison with non-Hispanic whites, non-Hispanic blacks were less likely to have low serum HDL cholesterol or high triglycerides. Family income and education predicted few biomarker or dietary outcomes, and the observed associations were weak. Moreover, modification of race-ethnic differentials by income or education (or vice versa) was noted for very few biomarkers.

CONCLUSION

Race-ethnicity, but not family income or education, was a strong independent predictor of serum nutrient concentrations and dietary micronutrient intakes in US children and adolescents.

Nutrition provided to Mexican-American preschool children on the Texas-Mexico border

The purpose of this study was to assess whether nutrients offered to border Mexican-American preschool children met the Recommended Dietary Allowances. Nutrient contents of two dietary patterns were examined in this study, one composed exclusively of home foods and one containing a combination of both home and school foods. The sample consisted of 198 Mexican-American preschoolers living on the Texas-Mexico border, who were recruited using a convenience sampling technique. A self-administered, precoded 24-hour recall questionnaire was used. Nutrient values of home foods were collected during a weekend day, and nutrient values containing a combination of both home and school foods were collected during a weekday. Fisher's exact test or chi2 test and t test were used for analyses. Mean nutrient contents of foods provided to the border Mexican-American children exceeded recommendations for total energy (P<0.001), total fat (P<0.001), saturated fat (P<0.001), carbohydrates (P<0.001), protein (P<0.001), sodium (P<0.001), and niacin (P<0.001). Foods offered were also significantly insufficient in fiber (P<0.001), vitamin A (P<0.001), and potassium (P<0.001). Nutrition interventions targeting low-income border Mexican-American families should emphasize the need and importance of providing children with diets that meet the Recommended Dietary Allowances.

Influence of apolipoprotein E genotype on fat-soluble plasma antioxidants in Spanish children

BACKGROUND

Apolipoprotein (apo) E is a major determinant of plasma lipid concentrations, which in turn influence the plasma concentrations of various fat-soluble vitamins.

OBJECTIVE

We aimed to analyze the effect of APOE genotype on fat-soluble antioxidant concentrations in children.

DESIGN

A total of 926 healthy boys and girls aged 6-8 y were selected from 4 cities in Spain. APOE genotyping was carried out, and plasma concentrations of lipids, apolipoproteins, and lipid-soluble antioxidants were measured.

RESULTS

Plasma lipid concentrations were strongly influenced by APOE genotype. The mean plasma concentration of alpha-tocopherol was 21.3 micromol/L, which is one of the highest values ever reported for a population of children. Although plasma concentrations of alpha-tocopherol, gamma-tocopherol, lycopene, and alpha-carotene varied significantly between subjects with different APOE genotypes, most of these differences disappeared after adjustment for lipoprotein-related covariates. Nevertheless, tocopherol concentrations remained elevated in individuals with the E2/2 genotype. Multivariate regression analysis showed interactions of APOE genotype with triacylglycerol and apo B in determining alpha-tocopherol concentrations. When subjects were stratified according to major apo E groups, apo B appeared to be the most important predictor of alpha-tocopherol concentrations in all groups, whereas triacylglycerol was identified only in carriers of the E2 allele.

CONCLUSIONS

The association between APOE genotype and lipophilic antioxidant concentrations is dependent mainly on the effect of the polymorphism on lipoprotein concentrations. However, triacylglycerol plays a role in determining the variability of alpha-tocopherol concentrations in E2 carriers only. This suggests that the alpha-tocopherol content in each lipoprotein class varies according to APOE genotype.

Intraindividual variation in serum retinol concentrations among participants in the third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

The biological variability in serum retinol concentrations has never been examined in a large sample, and its effect on population distribution estimates and the clinical assessment of vitamin A status is unknown.

OBJECTIVE

We evaluated the biological CV of serum retinol and examined the effect of the CV on both population distribution estimates and clinical assessments of vitamin A status by using data from the third National Health and Nutrition Examination Survey, 1988-1994.

DESIGN

We described the biological CV [(SD/x) x 100] and examined associations between the CV and other factors via multivariate analysis of variance and linear regression. We used linear regression to predict the mean retinol concentration from a single concentration and established 95% CIs for each participant. We estimated the adjusted prevalence of inadequate vitamin A status (retinol < 1.05 micromol/L) on the basis of the CIs. We estimated an uncertainty range for serum retinol concentrations for which the CIs included the established cutoff.

RESULTS

The mean biological CV across all strata was 6.45%. The biological CV varied significantly between racial-ethnic groups (P < 0.05). Prevalence estimates of inadequate serum retinol concentrations were reduced after adjustment for the total variation, with an adjusted overall prevalence of 0.62% compared with an unadjusted prevalence of 2.63%.

CONCLUSIONS

The actual population prevalence of inadequate vitamin A status may be 75% lower than the estimates previously reported. Confirmation of vitamin A status may be needed for persons in the United States with observed serum retinol concentrations near the recognized cutoff.

Vitamin A concentration in umbilical cord blood of infants from three separate regions of the province of Québec (Canada)

BACKGROUND

Inuit women from Northern Québec have been shown to consume inadequate quantities of vitamin A. This study was conducted to evaluate the prevalence of blood vitamin A deficiency in newborns from 3 distinct populations of the province of Québec.

METHODS

594 newborns were included in this study (375 Inuit newborns from northern Québec (Nunavik), 107 Caucasian and Native newborns from the Lower Northern Shore of the Saint-Lawrence River (LNS) and 112 newborns from Southern Québec where clinical vitamin A deficiency is uncommon). Mothers were recruited at delivery and vitamin A (retinol) was analyzed from umbilical cord blood samples by reversed-phase high-pressure liquid chromatography.

RESULTS

Nunavik and LNS newborns had significantly lower mean vitamin A concentrations in cord blood compared to Southern Québec participants (15.7 microg/dL, 16.8 microg/dL and 20.4 microg/dL respectively). The differences observed were similar when adjusted for sex and birthweight. Results also showed that 8.5% of Nunavik newborns and 12.2% of LNS newborns were below 10.0 microg/dL, a level thought to be indicative of blood vitamin A deficiency in neonates.

CONCLUSION

These data suggest that a carefully planned vitamin A supplementation program during pregnancy in Nunavik and LNS might be indicated to promote healthy infant development.

Serum concentrations of retinol, alpha-tocopherol and the carotenoids are influenced by diet, race and obesity in a sample of healthy adolescents

An important part of understanding the functions of vitamin A, vitamin E and the carotenoids in nutritional status assessment, health promotion and disease prevention is knowledge of factors that influence their distribution in human tissues. Our objective was to examine serum concentrations of these nutrients and compounds in a sample of 285 healthy participants, 12-17 y old, from three U. S. cities. Pearson correlations between diet measured with a food frequency questionnaire and serum nutrient concentrations among these adolescents (adjusted for total serum cholesterol, age, sex, race and body mass index) were as follows: retinol, 0.23; alpha-tocopherol, 0.16; alpha-carotene, 0.31; beta-carotene, 0.15; beta-cryptoxanthin, 0.38; lycopene, 0.08; and lutein + zeaxanthin, 0.25. Multivariate linear regression modeled associations of demographic, dietary and physiologic variables with serum concentrations of these nutrients. African-American participants had significantly lower concentrations of serum retinol (P < 0.001), alpha-tocopherol (P < 0.01) and alpha-carotene (P < 0.02), but higher concentrations of lutein + zeaxanthin (P = 0.001) compared with Caucasians. Obese participants had serum nutrient concentrations that were 2-10% (P < 0.05) lower than normal weight participants. Dietary intake was a significant predictor of all serum analytes (P < 0.01) except lycopene. These models explained 20% of the variability in serum retinol, 28% of the variability in serum alpha-tocopherol, and 14-24% of the variability in serum carotenoids.

Serum retinol distributions in residents of the United States: third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

Inadequate vitamin A status has been a potential nutritional problem for some segments of the US population, particularly children and the poor.

OBJECTIVE

We evaluated serum retinol concentration by using population-representative data from 16058 participants aged 4 to >/=90 y in the third National Health and Nutrition Examination Survey, 1988-1994.

DESIGN

We used multivariate regression to examine the simultaneous associations of sociodemographic, biologic, and behavioral factors with serum retinol concentration.

RESULTS

In children, serum retinol concentrations were greater with greater age, body mass index, serum lipids, and the use of supplements containing vitamin A. In adults, male sex, serum lipids, alcohol consumption, and age were positively associated with serum retinol concentration in most racial/ethnic strata. Household income was not associated with serum retinol concentration in children; associations were inconsistent in adults. The prevalence of serum retinol <0.70 micromol/L was very low in all strata; the prevalence of serum retinol <1.05 micromol/L was 16.7-33.9% in children aged 4-8 y and 3.6-14.2% in children aged 9-13 y, depending on sex and racial/ethnic group. The prevalence of serum retinol<1.05 micromol/L was higher in non-Hispanic black and Mexican American children than in non-Hispanic white children; these differences remained significant (P < 0.0001) after covariates were controlled for. Among adults, nonwhite women were significantly (P < 0.0001) more likely than white women to have serum retinol <1.05 micromol/L after covariates were controlled for.

CONCLUSIONS

Clinically low serum retinol concentration is uncommon in US residents aged > or = 4 y, although racial/ethnic and socioeconomic differences in serum retinol concentration still exist.

Serum retinol, the acute phase response, and the apparent misclassification of vitamin A status in the third National Health and Nutrition Examination Survey

BACKGROUND

Serum retinol decreases transiently during the acute phase response and can thus result in misclassification of vitamin A status.

OBJECTIVE

Our objective was to determine the prevalence of acute phase response activation in a representative sample of the US population, identify the factors associated with this activation, and determine whether persons with an active acute phase response have lower serum retinol concentrations.

DESIGN

Data from the third National Health and Nutrition Examination Survey (NHANES III) were analyzed. A serum C-reactive protein (CRP) concentration >/=10 mg/L indicated an active acute phase response.

RESULTS

Mean serum retinol was lowest in subjects aged <10 y and increased with age. Concentrations were higher in males than in females aged 20-59 y. The prevalence of a CRP concentration >/=10 mg/L was lowest in subjects aged <20 y (</=4%) and increased with age to a maximum of nearly 15%. An elevated CRP concentration was 2.4-fold greater in females than in males aged 20-59 y. Serum retinol was lower in subjects with elevated CRP concentrations.

CONCLUSIONS

Serum retinol increases with age and males have higher mean values than do females aged 20-59 y. The prevalence of a CRP concentration >/=10 mg/L also increases with age, is 2-fold greater in females than in males aged 20-69 y, and is associated with common inflammatory conditions. Thus, inflammation appeared to contribute to the misclassification of vitamin A status in the NHANES III population, and serum CRP is useful in identifying subjects who may be misclassified.

Blood retinol and beta-carotene levels in rural Guatemalan preschool children

Plasma retinol and beta-carotene levels were measured in 502 preschool Guatemalan children from five rural hamlets. Their ages ranged from 6 to 78 months (mean: 42.9 +/- 19.2 months); 45% males and 55% females. The mean retinol value in the whole group was 0.9 +/- 0.4 mumol/l (range: 0.1 to 8.4 mumol/l). There was no significant difference between sexes in retinol mean values nor in the incidence of retinol values less than 0.7 mumol/l (22% in males, 18% in females). When grouped by age and community, significant low retinol mean values were found in two hamlets in the youngest age group (12 to 23 months) as compared to the other age-groups (p < 0.05). In the other two hamlets, there were no significant differences among retinol means by age-group. The highest prevalence of deficient retinol values by age-group was in the 12 to 23 months group (40%), and decreased as age increased. The mean value for beta-carotene in the whole group was 0.13 +/- 0.18 mumol/l (range: 0.01 to 2.23 mumol/l). There were no significant differences in beta-carotene means between sexes in the whole group. Stratifying the beta-carotene data by age-groups and community, values were significantly higher in the 48-59 months and 72-83 months groups, as compared with the other age groups in two of the communities (p < 0.05). Significant differences across communities for beta-carotene were found only in the 12 to 23 months group.

Vitamin and mineral intakes of Anglo-American and Mexican-American preschoolers

OBJECTIVE

To assess vitamin and mineral intakes of Anglo-American and Mexican-American preschoolers.

DESIGN

By use of interview and observation methods, acquire food intake data, calculate total nutrient intake, and compare selected nutrients to the Recommended Dietary Allowances (RDAs) for ethnic and gender groups.

SUBJECTS

Low- to middle-income parents and their preschool children (N = 351) recruited from preschools in San Diego, Calif, consented to participate in the Study of Children's Activity and Nutrition conducted by researchers at the University of California, San Diego.

MAIN OUTCOME MEASURES

Data regarding 15 nutrients were summarized based on the average of two food intake records for each preschooler.

STATISTICAL ANALYSES PERFORMED

Means and standard deviations were used to describe micronutrient intakes for ethnic and gender groups; analyses of variance and t tests were performed to determine ethnic and gender differences.

RESULTS

Boys and Anglo-Americans had higher total nutrient intakes than girls and Mexican-Americans, respectively. Mexican-Americans had higher nutrient intakes per energy intake, which indicates a micronutrient-dense diet. When each nutrient was considered by the two thirds of the RDA criterion (66% of the RDA means adequate intake), the nutrients most likely to be inadequate were iron, zinc, vitamin D, vitamin C, and niacin. Mexican-American girls had significantly lower calcium intakes than the other gender and ethnic groups.

APPLICATION

Parents and day care providers must ensure that preschoolers, especially girls and Mexican-Americans, eat nutrient-rich foods in adequate quantities that will achieve the recommended intakes.

Health status by social class and/or minority status: implications for environmental equity research

Much of the epidemiologic research in the United States has been based only on the categories of age, sex and race; thus, race has often been used in health statistics as a surrogate for social and economic disadvantage. Few multivariate analyses distinguish effects of components of social class (such as economic level) from the relative, joint, and independent effects of sociocultural identifiers such as race or ethnicity. This paper reviews studies of social class and minority status differentials in health, with a particular emphasis on health status outcomes which are known or suspected to be related to environmental quality and conditions which increase susceptibility to environmental pollutants. Sociodemographic data are presented for the U.S. population, including blacks, Asian American/Pacific Islanders, American Indian/Alaska Natives, and Hispanics. Four areas of health status data are addressed: mortality, health of women of reproductive age, infant and child health, and adult morbidity. Conceptual and methodological issues surrounding various measures of position in the system of social strata are discussed, including the multidimensionality of social class, in the context of the importance of these issues to public health research. Whenever possible, multivariate studies that consider the role of socioeconomic status in explaining racial/ethnic disparities are discussed.

Epidemiologic studies utilizing surveys: accounting for the sampling design

BACKGROUND

Since large-scale health surveys usually have complicated sampling schemes, there is often a question as to whether the sampling design must be considered in the analysis of the data. A recent disagreement concerning the analysis of a body iron stores-cancer association found in the first National Health and Nutrition Examination Survey and its follow-up is used to highlight the issues.

METHODS

We explain and illustrate the importance of two aspects of the sampling design: clustering and weighting of observations. The body iron stores-cancer data are reanalyzed by utilizing or ignoring various aspects of the sampling design. Simple formulas are given to describe how using the sampling design of a survey in the analysis will affect the conclusions of that analysis.

RESULTS

The different analyses of the body iron stores-cancer data lead to very different conclusions. Application of the simple formulas suggests that utilization of the sample clustering in the analysis is appropriate, but that a standard utilization of the sample weights leads to an uninformative analysis. The recommended analysis incorporates the sampling weights in a nonstandard way and the sample clustering in the standard way.

CONCLUSIONS

Which particular aspects of the sampling design to use in the analysis of complex survey data and how to use them depend on certain features of the design. We give some guidelines for when to use the sample clustering and sample weights in the analysis.

Ethnic minorities, migration and risk of undernutrition in children

Well-controlled, comparative studies suggest that in "food rich" or "resource rich" environments, ethnic minority status is not an independent risk factor for malnutrition. In England, Australia, and the United States, nutrient intake, nutritional status measures and growth are comparable between children of ethnic minorities and non-minority children of similar economic status. Children of recent immigrants are an exception to this generalization, suggesting that recent arrival in a new environment is a risk factor for malnutrition. Family-level studies of intraethnic diversity are required to develop more sensitive and specific profiles of risk factors for malnutrition.

Derivation of retinoic acid and metabolites from a teratogenic dose of retinol (vitamin A) in mice

Megadose supplements of vitamin A are under suspicion as hazards to the developing embryo after the discovery that two vitamin A-related drugs, Accutane and Tigason, are human teratogens. Retinoic acid (all-trans-RA) is a natural metabolite of vitamin A which participates in many of the known functions of vitamin A and may be the active agent in teratogenesis. In this investigation we gave a single, high oral dose of retinol (vitamin A) to pregnant mice to assess its transplacental pharmacokinetics as well as to measure the formation and distribution of its metabolites in the embryo. Retinol was estimated to be 4-fold less active than retinoic acid in the whole animal teratogenesis and 20-fold less active in the in vitro bioassay. A fully teratogenic dose, 200 mg/kg, yielded considerable quantities of retinoic acid which were transferred to the embryo with kinetics similar to that of retinol. During the first 8 hr after administration of retinol, the metabolites (including all-trans-RA, 13-cis-RA, and 4-oxo-RA) constituted almost 50% of the quantity of all retinol derivatives found in the embryo. A comparison of combined peak concentrations of the metabolites (or their AUC values) with the extent of teratogenesis associated with them individually provided sufficient evidence to implicate the metabolites themselves as mediators of retinol-induced teratogenesis. However, since both retinol and retinoic acid were present in sufficient concentrations in the embryo to act as teratogens we cannot at present rule out the possibility that they may act independently. Further experimentation will be necessary to address whether retinoic acid detected in the embryo is the product of the embryo's own metabolic capability or is transferred from the maternal circulation.