How consideration of population variance and individuality affects our understanding of nutritional requirements in human health and disease

Biomarkers of nutrition for development--iodine review

The objective of the Biomarkers of Nutrition for Development (BOND) project is to provide state-of-the-art information and service with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect. Specifically, the BOND project seeks to develop consensus on accurate assessment methodologies that are applicable to researchers (laboratory/clinical/surveillance), clinicians, programmers, and policy makers (data consumers). The BOND project is also intended to develop targeted research agendas to support the discovery and development of biomarkers through improved understanding of nutrient biology within relevant biologic systems. In phase I of the BOND project, 6 nutrients (iodine, vitamin A, iron, zinc, folate, and vitamin B-12) were selected for their high public health importance because they typify the challenges faced by users in the selection, use, and interpretation of biomarkers. For each nutrient, an expert panel was constituted and charged with the development of a comprehensive review covering the respective nutrient's biology, existing biomarkers, and specific issues of use with particular reference to the needs of the individual user groups. In addition to the publication of these reviews, materials from each will be extracted to support the BOND interactive Web site (http://www.nichd.nih.gov/global_nutrition/programs/bond/pages/index.aspx). This review represents the first in the series of reviews and covers all relevant aspects of iodine biology and biomarkers. The article is organized to provide the reader with a full appreciation of iodine's background history as a public health issue, its biology, and an overview of available biomarkers and specific considerations for the use and interpretation of iodine biomarkers across a range of clinical and population-based uses. The review also includes a detailed research agenda to address priority gaps in our understanding of iodine biology and assessment.

Assessment of iodine nutrition in populations: past, present, and future

Iodine status has been historically assessed by palpation of the thyroid and reported as goiter rates. Goiter is a functional biomarker that can be applied to both individuals and populations, but it is subjective. Iodine status is now assessed using an objective biomarker of exposure, i.e., urinary iodine concentrations (UICs) in spot samples and comparison of the median UIC to UIC cut-offs to categorize population status. This has improved standardization, but inappropriate use of the crude proportion of UICs below the cut-off level of 100 µg/L to estimate the number of iodine-deficient children has led to an overestimation of the prevalence of iodine deficiency. In this review, a new approach is proposed in which UIC data are extrapolated to iodine intakes, adjusted for intraindividual variation, and then interpreted using the estimated average requirement cut-point model. This may allow national programs to define the prevalence of iodine deficiency in the population and to quantify the necessary increase in iodine intakes to ensure sufficiency. In addition, thyroglobulin can be measured on dried blood spots to provide an additional sensitive functional biomarker of iodine status.

Concordance with selected population recommendations for cancer prevention among third- and fourth-grade schoolchildren in Quetzaltenango, Guatemala

BACKGROUND

The World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) 1997 recommendations for cancer prevention were meant to apply to children as well as adults.

OBJECTIVE

To assess the concordance of behaviors and body composition of urban Guatemalan schoolchildren with the tenets of the WCRF/AICR 1997 recommendations.

METHODS

A survey was conducted involving determination of 24-hour consumption of foods and beverages by a pictorial registry and height and weight measurements in 355 third- and fourth-grade schoolchildren in the western highland city of Quetzaltenango, Guatemala. Based on a previous, exhaustive parsing of the population goal recommendations of the WCRF/AICR 1997 report, 25 subcomponents were identified. Eleven could be evaluated with the survey data collected. Adult population criteria could be applied in seven, whereas four components had unique criteria adapted to this juvenile survey setting.

RESULTS

The study sample was concordant on seven components-nutrient adequacy, total variety of foods consumed, plant-based diets, body mass index, vegetable and fruit intake, limitation of red meat consumption, and limitation of total fat consumption, and nonconcordant on four-variety of fruits and vegetables consumed, variety of starchy foods consumed, total intake of starchy foods, and limitation of sugar consumption.

CONCLUSIONS

Educational and public health actions need to be conceived and implemented to further improve the rate of concordance of these 11 components with the WCRF/AICR 1997 recommendations for cancer prevention.

Adherence to the Food Guide Pyramid recommendations among Japanese Americans, Native Hawaiians, and whites: results from the Multiethnic Cohort Study

The Food Guide Pyramid is designed to help Americans make healthful food choices. Whereas national data have been collected to examine adherence to the pyramid recommendations in whites, African-Americans, and Latinos, there are virtually no data available for Japanese Americans or Native Hawaiians. Here we present data on intakes of the Food Guide Pyramid food groups (as servings per day) as well as of the components of the pyramid tip (discretionary fat, added sugar, and alcohol) in these ethnic groups and examine adherence to each of the food group recommendations. Degree of adherence to the fruit group recommendation was similar among the ethnic groups and energy-intake categories, but adherence to the other recommendations was greatest for those consuming more than 2,800 kilocalories per day. However, subjects in this energy-intake group also consumed more than three times as much discretionary fat, added sugar, and alcohol.

Genetic research and nutritional individuality

Recent genetic research builds on a base established over the last century by physicians and nutritional scientists, who introduced the concept of biochemical individuality and documented its significance for understanding a wide variety of problems in human health. Current comparative genomic investigations on a variety of organisms (Haemophilus influenzae, Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, Homo sapiens) have established the existence of numerous orthologs (proteins in different organisms that show significant sequence similarities over 80% of their lengths), suggesting significant conservation of structure and probably some of function as well. At the same time, molecular comparisons among individuals within our own species show the existence of abundant molecular variants, many of which have been shown to have functional significance in nutritional and related metabolic contexts. The combination of biochemical individuality and known functional utilities of allelic variants should converge to create a situation in which nutritional optima can be specified as part of comprehensive lifestyle prescriptions tailored to the needs of each person.