Using Capillary Whole Blood to Quantitatively Measure Ferritin: A Validation Trial of a Point-of-Care System

Iron deficiency is a public health problem with devastating health, developmental and behavioral effects which often exacerbated due to affordability and access to screening and diagnosis. Using IronScan™ a portable, point-of-care diagnostic system capable of quantitatively measuring ferritin in blood, we validated IronScan™ ferritin measurements using whole blood and serum with a lab-based, regulator-approved analytical device for measuring ferritin in venous serum. Capillary (finger stick) and venous whole blood samples were obtained from 44 male and female volunteers. Venous serum (vSer) ferritin concentrations were measured on Immulite 2000 Xpi (gold standard). Capillary whole blood (cWB), venous whole blood (vWB), and vSer ferritin levels were measured by IronScan™. cWB ferritin concentrations from IronScan™ were significantly correlated (R2 = 0.86) with vSer measured with the FDA-approved Immulite system. The results from the multiple regression analysis indicate that 10% of the variability was due to the method of blood collection (venous vs. capillary) and 6% was due to the form of blood analysis (whole blood vs. serum). The sensitivity of diagnosing iron deficiency using the WHO cutoff of <30 ng/mL is 90%, with a specificity of 96%. In conclusion, IronScan™ is a rapid viable option for measuring ferritin as a point-of-care system.

A Randomized Trial of Quadruple-Fortified Salt for Anemia and Birth Defects Prevention in Southern India: Protocol Design and Methods

Background

Women of reproductive age are at an increased risk of anemia and micronutrient deficiencies. Evidence supports the role of periconceptional nutrition in the development of neural tube defects (NTDs) and other pregnancy complications. Vitamin B12 deficiency is a risk factor for NTDs and may modify folate biomarkers that predict NTD risk at the population level. There is an interest in mandatory fortification with vitamin B12 and folic acid for anemia and birth defect prevention. However, there are limited population-representative data needed to inform policy and guidelines.

Objectives

This randomized trial will be conducted to evaluate the efficacy of quadruple-fortified salt (QFS; iron, iodine, folic acid, vitamin B12) in 1,000 households in Southern India.

Methods

Women 18 to 49 y who are not pregnant or lactating and reside within the catchment area of our community-based research site in Southern India will be screened and invited to participate in the trial. After informed consent, women and their households will be randomized to receive one of the following 4 interventions: 1) double-fortified salt (DFS; iron, iodine), 2) DFS + folic acid (iron, iodine, folic acid), 3) DFS + vitamin B12 (iron, iodine, vitamin B12), or 4) DFS + folic acid and vitamin B12 (QFS; iron, iodine, folic acid, vitamin B12) for 12 mo. Structured interviews will be conducted by trained nurse enumerators to collect sociodemographic, anthropometric, dietary, health, and reproductive history data. Biological samples will be collected at baseline, midpoint, and endpoint. Whole blood will be analyzed for hemoglobin using Coulter Counter. Total vitamin B12 will be measured by chemiluminescence; red blood cell folate and serum folate will be evaluated using the World Health Organization-recommended microbiologic assay.

Conclusions

The results of this randomized trial will help to evaluate the efficacy of QFS to prevent anemia and micronutrient deficiencies. Clinical trial registration numbers: NCT03853304 and Clinical Trial Registry of India REF/2019/03/024479.

Registration number

NCT03853304 and REF/2019/03/024479.

Modeling relationships between iron status, behavior, and brain electrophysiology: evidence from a randomized study involving a biofortified grain in Indian adolescents

Background

Iron deficiency (ID) and iron deficiency anemia (IDA) are highly-prevalent nutrient deficiencies and have been shown to have a range of negative effects on cognition and brain function. Human intervention studies including measures at three levels—blood, brain, and behavior—are rare and our objective was to model the relationships among measures at these three levels in school-going Indian adolescents.

Methods

Male and female adolescents in rural India were screened for ID/IDA. Subjects consumed 2 meals/day for 6 months; half were randomly assigned to consume meals made from a standard grain (pearl millet) and half consumed meals made from an iron biofortified pearl millet (BPM). Prior to and then at the conclusion of the feeding trial, they completed a set of cognitive tests with concurrent electroencephalography (EEG).

Results

Overall, serum ferritin (sFt) levels improved over the course of the study. Ten of 21 possible measures of cognition showed improvements from baseline (BL) to endline (EL) that were larger for those consuming BPM than for those consuming the comparison pearl millet (CPM). Critically, the best model for the relationship between change in iron status and change in cognition had change in brain measures as a mediating factor, with both change in serum ferritin as a primary predictor and change in hemoglobin as a moderator.

Conclusions

A dietary intervention involving a biofortified staple grain was shown to be efficacious in improving blood iron biomarkers, behavioral measures of cognition, and EEG measures of brain function. Modeling the relationships among these variables strongly suggests multiple mechanisms by which blood iron level affects brain function and cognition.

Trial registration

Registered at ClinicalTrials.gov, NCT02152150, 02 June 2014.

Supplementary Information

The online version contains supplementary material available at (10.1186/s12889-022-13612-z).

A randomized trial of iron- and zinc-biofortified pearl millet-based complementary feeding in children aged 12 to 18 months living in urban slums

BACKGROUND & AIMS

Biofortification of staple crops with higher levels of micronutrients via traditional breeding methods is a sustainable strategy and can possibly complement fortification and other interventions to target micronutrient deficiencies in low resource settings, particularly among vulnerable populations such as children. We aimed to determine if iron- and zinc-biofortified pearl millet (FeZnPM, Dhanashakti, ICTP-8203Fe)-based complementary feeding improves nutritional status, including iron biomarkers and growth, in children living in urban slums of Mumbai.

METHODS

We conducted a randomized controlled trial of FeZnPM among 223 children aged 12-18 months who were not severely anemic at baseline (hemoglobin ≥9.0 g/dL). Children were randomized to receive either FeZnPM or conventional non-biofortified pearl millet (CPM) daily for 9 months. Iron status (hemoglobin, serum ferritin), plasma zinc, and anthropometric indicators (length, weight, mid-upper arm circumference, triceps and subscapular skinfolds) were evaluated at enrollment and throughout the trial. World Health Organization (WHO) anthropometric z-scores were calculated using WHO growth standards. Primary outcomes were hemoglobin and serum ferritin concentrations, and growth, defined as WHO z-scores. An intent to treat approach was used for analyses. We used the Hodges-Lehmann-Sen test to assess the change in primary outcomes between baseline and the last visit and report corresponding 95% confidence intervals.

RESULTS

At baseline, 67.7% of children were anemic (hemoglobin <11.0 g/dL) and 59.6% were iron deficient (serum ferritin <12.0 μg/L). FeZnPM did not significantly increase iron biomarkers or improve growth, compared to CPM. In subgroup analyses, FeZnPM improved hemoglobin concentrations in male children, and in children with iron deficiency or iron depletion (serum ferritin <25.0 μg/L) at baseline, relative to CPM.

CONCLUSIONS

Daily consumption of FeZnPM-based complementary foods did not significantly impact iron and zinc status or growth in children living in Mumbai's urban slums. However, the intervention significantly improved hemoglobin concentrations among male children and among individuals who were iron-deficient or iron-depleted at baseline.

TRIAL REGISTRATION

This trial is registered with Clinicaltrials.gov (ID: NCT02233764), and Clinical Trials Registry of India (ID: REF/2014/10/007731).

Limited Shared Variance among Measures of Cognitive Performance Used in Nutrition Research: The Need to Prioritize Construct Validity and Biological Mechanisms in Choice of Measures

BACKGROUND

The literature on correlates of nutrition has seen an increase in studies focused on functional consequences at the levels of neural, perceptual, and cognitive functioning. A range of measurement methodologies have been used in these studies, and investigators and funding agencies have raised the questions of how and if these various methodologies are at all comparable.

OBJECTIVE

The aim was to determine the extent to which 3 different sets of cognitive measures provide comparable information across 2 subsamples that shared culture and language but differed in terms of socioeconomic status (SES) and academic preparation.

METHODS

A total of 216 participants were recruited at 2 US universities. Each participant completed 3 sets of cognitive measures: 1 custom-designed set based on well-understood laboratory measures of cognition [cognitive task battery (COGTASKS)] and 2 normed batteries [Cambridge Neuropsychological Test Automated Battery (CANTAB), Weschler Adult Intelligence Scale, fourth edition (WAIS-IV)] designed for assessing general cognitive function.

RESULTS

The 3 sets differed with respect to the extent to which SES and educational preparation affected the results, with COGTASKS showing no differences due to testing location and WAIS-IV showing substantial differences. There were, at best, weak correlations among tasks sharing the same name or claiming to measure the same construct.

CONCLUSIONS

Comparability of measures of cognition cannot be assumed, even if measures have the same name or claim to assess the same construct. In selecting and evaluating different measures, construct validity and underlying biological mechanisms need to be at least as important as population norms and the ability to connect with existing literatures.

Iron status is associated with worker productivity, independent of physical effort in Indian tea estate workers

Iron deficiency is the most common nutrient deficiency in the world, affecting roughly 40% of women in nonindustrialized countries. Iron is the essential element in hemoglobin, the major carrier of blood oxygen and oxidative metabolism that supports physical and cognitive performance. The relationship between iron and physical work capacity suggests that iron deficient individuals could experience reduced work output. Participants were 138 experienced tea pluckers aged 18–55 years from the Panighatta Tea Estate in Darjeeling District of northern West Bengal, India. Hemoglobin, serum ferritin, and soluble transferrin receptor were measured from venous blood. Energy expenditure was estimated from accelerometry and heart rate, and plucking productivity was measured as amount of tea plucked during the morning work session when temperature and rainfall conditions are optimal. At a given level of energy expenditure, iron deficient, anemic, and iron deficient anemic women plucked less tea during a 3-h period. The results warrant further research as to whether interventions providing supplemental iron might improve worker productivity and work efficiency. Further study should examine evidence of economic incentives for policies and programs targeting nutritional deficiencies.

Novelty Anemia predicts up to 2.02 kg (9.1%) less tea plucked per 3 h, or 4.0% lower wage per 3 h, compared with nonanemic women, controlling for physical effort. An increase of 1.0 g/L in hemoglobin concentration predicts 0.71 kg (3.3%) more tea plucked over 3 h. An increase of 1.0 g/L in hemoglobin concentration predicts a 1.6% wage increase.

The Effects of Improved Nutrition in Early Childhood on Adolescent and Early Adulthood Body Size, Composition, Maturity, and Function: Results From the First INCAP Follow-Up Study

The first follow-up study of the original Institute of Nutrition of Central America and Panama Longitudinal Study was conducted in 1988 to 1989 when participants were between the ages of 11 and 27 years. The longer term effects of the original supplementation in early life of either high protein and energy, Atole, or no protein and low energy, Fresco, were seen in anthropometry, skeletal maturation, physical work capacity, and intellectual development, with maximum benefit seen in those participants who had maximum exposure to the supplementation during prenatal and early postnatal years. No effects were observed in bone mineralization and menarche. The long-term positive effects are consistent with the promotion of improved nutrition during the first 1000 days and established the foundation for further follow-up studies as the participants move into adulthood and further develop their human capital.

Increased Iron Status during a Feeding Trial of Iron-Biofortified Beans Increases Physical Work Efficiency in Rwandan Women

BACKGROUND

Iron-biofortified staple foods can improve iron status and resolve iron deficiency. However, whether improved iron status from iron biofortification can improve physical performance remains unclear.

OBJECTIVE

This study aimed to examine whether changes in iron status from an iron-biofortified bean intervention affect work efficiency.

METHODS

A total of 125 iron-depleted (ferritin <20 μg/L) female Rwandan university students (18-26 y) were selected from a larger sample randomly assigned to consume iron-biofortified beans (Fe-Bean; 86.1 mg Fe/kg) or conventional beans (control: 50.6 mg Fe/kg) twice daily for 18 wk (average of 314 g beans consumed/d). Blood biomarkers of iron status (primary outcome) and physical work efficiency (secondary outcome) were measured before and after the intervention. Work performed was assessed during 5-min steady-state periods at 0-, 25-, and 40-W workloads using a mechanically braked cycle ergometer. Work efficiency was calculated at 25 W and 40 W as the work accomplished divided by the energy expended at that workload above that expended at 0 W. General linear models were used to evaluate the relation between changes in iron status biomarkers and work efficiency.

RESULTS

The Fe-Bean intervention had significant positive effects on hemoglobin, serum ferritin, and body iron stores but did not affect work efficiency. However, 18-wk change in hemoglobin was positively related to work efficiency at 40 W in the full sample (n = 119; estimate: 0.24 g/L; 95% CI: 0.01, 0.48 g/L; P = 0.044) and among women who were anemic (hemoglobin <120 g/L) at baseline (n = 43; estimate: 0.64 g/L; 95% CI: 0.05, 1.23 g/L; P = 0.036). Among women who were nonanemic at baseline, change in serum ferritin was positively related to change in work efficiency at 40 W (n = 60; estimate: 0.50 μg/L; 95% CI: 0.06, 0.95 μg/L; P = 0.027).

CONCLUSIONS

Increasing iron status during an iron-biofortified bean feeding trial improves work efficiency in iron-depleted, sedentary women. This trial was registered at clinicaltrials.gov as NCT01594359.

A Randomized Crossover Study to Evaluate Recipe Acceptability in Breastfeeding Mothers and Young Children in India Targeted for a Multiple Biofortified Food Crop Intervention

Background

A multiple biofortified food crop trial targeting iron, zinc, and vitamin A deficiencies among young children and their breastfeeding mothers is planned in India.

Objective

To determine the acceptability of recipes prepared with control and biofortified pearl millet, wheat, lentils, and sweet potato.

Methods

Children (6-24 months) and their mothers were enrolled as pairs (n = 52). Weight and height/length were determined. Mothers and children were separately, individually randomized in a crossover design to control or biofortified recipes. Children’s 3-day intake was measured per recipe and crop variety. For mothers, a 9-point hedonic scale evaluated color, odor, taste, and overall acceptability.

Results

Children’s mean (SD) length-/height-for-age Z-score was −1.2 (1.7), with 27% < −2 (stunted). Mean weight-for-length Z-score was −0.6 (1.2) with 9.6% < −2 (wasted). Mother’s body mass index showed 17% <18.5 and 38% >25. There was no difference in the children’s intake of biofortified versus control varieties of any recipe (P ≥ .22); overall median daily intake was 75 g (Q1: 61, Q3: 100). Mother’s hedonic scores for color, odor, taste, or overall acceptability did not demonstrate any notable differences (P ≥ .23 for overall acceptability); combined median overall acceptability score was 8.5 (Q1: 8.0, Q3: 9.0).

Conclusions

Recipes were consumed readily, were rated as highly acceptable, and did not show any differences between biofortified and control varieties.

Changes in Iron Status Are Related to Changes in Brain Activity and Behavior in Rwandan Female University Students: Results from a Randomized Controlled Efficacy Trial Involving Iron-Biofortified Beans

BACKGROUND

Evidence suggests that iron deficiency (ID) affects cognitive performance, as measured in behavior. Although such effects must be mediated by changes in the brain, very few studies have included measures of brain activity to assess this relation.

OBJECTIVE

We tested the hypothesis that provision of iron-biofortified beans would result in improvements in measures of iron status, brain dynamics, and behavior.

METHODS

A double-blind, randomized, intervention study was conducted in 55 women aged 18-27 y with low iron status (serum ferritin <20 µg/L). Women were randomly assigned to consume iron-biofortified (86.1 ppm iron) or comparison beans (50.1 ppm iron) daily for 18 wk. Iron status was assessed by hemoglobin, ferritin, transferrin receptor, and body iron; cognitive performance with 5 computerized tasks; and brain dynamics by concurrent electroencephalography (EEG). All measures were taken at baseline and endline.

RESULTS

The groups did not differ on any measures at baseline. Intention-to-treat analyses revealed significant (all P < 0.05) improvements in hemoglobin (partial effect size attributable to the independent variable, η2 = 0.16), ferritin (η2 = 0.17), and body iron (η2 = 0.10), speed of responding in attentional and mnemonic tasks (η2 = 0.04-0.29), sensitivity and efficiency of memory retrieval (η2 = 0.12-0.55), and measures of EEG amplitude and spectral power (η2 = 0.08 to 0.49). Mediation models provided evidence in support of the hypothesis that changes in iron status produce changes in behavior by way of changes in brain activity.

CONCLUSIONS

Behavioral performance and brain activity, as measured by EEG, are sensitive to iron status, and the consumption of iron-biofortified beans for 18 wk resulted in improvements in measures of both, relative to what was obtained with a comparison bean, in a sample of female university students. Furthermore, the results support the conclusion that changes in brain activity resulting from consumption of biofortified beans mediate the relations between changes in iron biomarkers and changes in cognition. Clinical trial registry: ClinicalTrials.gov Reg No. NCT01594359.

Increasing Iron Status through Dietary Supplementation in Iron-Depleted, Sedentary Women Increases Endurance Performance at Both Near-Maximal and Submaximal Exercise Intensities

BACKGROUND

Iron deficiency persists as the most common micronutrient deficiency globally, despite having known detrimental effects on physical performance. Although iron supplementation and aerobic exercise have been examined individually and are known to improve physical performance, the impact of simultaneous iron supplementation and aerobic training remains unclear.

OBJECTIVE

The aim of this study was to examine the individual and combined effects of iron supplementation and aerobic training on improving maximal and submaximal physical performance in iron-depleted, nonanemic (IDNA) women. We hypothesized that women receiving iron would improve their endurance performance but not their estimated maximal oxygen consumption (eVO2max).

METHODS

Seventy-three sedentary, previously untrained IDNA (serum ferritin <25 µg/L and hemoglobin >110 g/L) women aged 18-26 y with a body mass index (kg/m2) of 17-25 participated in a double-blind, 8-wk, randomized controlled trial with a 2 × 2 factorial design including iron supplementation (42 mg elemental Fe/d) or placebo and aerobic exercise training (5 d/wk for 25 min at 75-85% of age-predicted maximum heart rate) or no training. Linear models were used to examine relations between training, supplement, and changes in the primary outcomes of observed maximal oxygen consumption (VO2peak) and eVO2max and ventilatory threshold (absolute oxygen consumption and percentage of maximum). Re-evaluation of a published meta-analysis was used to compare effects of iron supplementation on maximal oxygen consumption (VO2max) and VO2peak.

RESULTS

There were significant training-by-supplement interactions for VO2peak, volume of oxygen consumption at the ventilatory threshold, and the percentage of eVO2max where the threshold occurred, with the iron-untrained group performing better than the placebo-untrained group. There was no beneficial effect of iron supplementation for VO2max (mean difference: 0.53; 95% CI: -0.75, 1.81; P = 0.42), but a significant benefit was observed for VO2peak (mean difference: 1.87; 95% CI: 0.15, 3.60; P = 0.03).

CONCLUSIONS

Iron supplementation increases endurance performance at submaximal and maximal (VO2peak) exercise intensities in IDNA women. However, increasing iron status does not increase eVO2max. This trial was registered at clinicaltrials.gov as NCT03002090.

Nutrition Status and the Risk of Mortality in Children 6–36 Months Old in Tanzania

Anthropometric measurements were taken on 2,452 children between 6 and 36 months of age at baseline and at two-month intervals thereafter in rural Tanzania. The children were followed for one year. All deaths occurring in this group were recorded using a village registration system introduced as part of a village nutrition status monitoring system. The relationship between the anthropometric indicators (weight for age, height for age, and weight for height, as well as weight increment) and subsequent mortality was assessed. The results indicate that over the one-year period, nutrition status was a significant predictor of mortality, with the probability of survival lower in children of low nutrition status. Low weight for age (<60% of the standard) was associated with a nine-fold increase in risk compared to weight for age above 80%; low weight for height (<80%) earned an almost fourfold increase in risk compared to weight for height>90%; and low height for age had a twofold increase in risk compared to the normal categories. An overall linear relationship was found between nutrition status and mortality, suggesting a gradual increase in mortality as nutrition status deteriorates. Incremental weight appears to be a good short-term predicator of mortality.

Cognitive Performance in Indian School-Going Adolescents Is Positively Affected by Consumption of Iron-Biofortified Pearl Millet: A 6-Month Randomized Controlled Efficacy Trial

BACKGROUND

Iron deficiency remains the most prevalent micronutrient deficiency globally, but few studies have examined how iron status relates to cognition in adolescents. Iron biofortification of staple food crops is being scaled up, yet it is unknown whether consuming biofortified crops can benefit cognition.

Objective

Our objective was to determine the efficacy of iron-biofortified pearl millet in improving attention and memory in Indian school-going adolescents.

Methods

A double-blind, randomized, intervention study was conducted in 140 Indian boys and girls, aged 12-16 y, who were assigned to consume iron-biofortified [Fe = 86 parts per million (ppm)] or conventional (Fe = 21-52 ppm) pearl millet. Hemoglobin, ferritin, and transferrin receptor (TfR) were measured and body iron (BI) was calculated at baseline and after 4 and 6 mo. Five measures of cognitive function were obtained at baseline and 6 mo: simple reaction time (SRT), Go/No-Go (GNG) task, Attentional Network Task (ANT), Composite Face Effect (CFE) task, and Cued Recognition Task (CRT). Intention-to-treat analysis was used.

Results

Daily iron intake from pearl millet was higher in those consuming biofortified compared with conventional pearl millet (19.6 compared with 4.8 mg/d). Effects on ferritin, TfR, and BI at 4 mo, and on TfR at 6 mo (all P < 0.05), indicated efficacy of biofortified pearl millet over conventional pearl millet in improving iron status. Compared with conventional pearl millet, the consumption of biofortified pearl millet resulted in greater improvement in attention (SRT, GNG, and ANT) and memory (CFE and CRT). Reaction time decreased twice as much from 0 to 6 mo in those consuming biofortified compared with conventional pearl millet on attention tasks (SRT: -123 compared with -63 ms; GNG: -67 compared with -30 ms; ANT double cue: -74 compared with -32 ms; all P < 0.01).

Conclusion

Consuming iron-biofortified pearl millet improves iron status and some measures of cognitive performance in Indian adolescents. This trial was registered at http://www.clinicaltrials.gov as NCT02152150.

Consumption of a Double-Fortified Salt Affects Perceptual, Attentional, and Mnemonic Functioning in Women in a Randomized Controlled Trial in India

Background: Iron deficiency and iron deficiency anemia have been shown to have negative effects on aspects of perception, attention, and memory.Objective: The purpose of this investigation was to assess the extent to which increases in dietary iron consumption are related to improvements in behavioral measures of perceptual, attentional, and mnemonic function.Methods: Women were selected from a randomized, double-blind, controlled food-fortification trial involving ad libitum consumption of either a double-fortified salt (DFS) containing 47 mg potassium iodate/kg and 3.3 mg microencapsulated ferrous fumarate/g (1.1 mg elemental Fe/g) or a control iodized salt. Participants' blood iron status (primary outcomes) and cognitive functioning (secondary outcomes) were assessed at baseline and after 10 mo at endline. The study was performed on a tea plantation in the Darjeeling district of India. Participants (n = 126; 66% iron deficient and 49% anemic at baseline) were otherwise healthy women of reproductive age, 18-55 y.Results: Significant improvements were documented for iron status and for perceptual, attentional, and mnemonic function in the DFS group (percentage of variance accounted for: 16.5%) compared with the control group. In addition, the amount of change in perceptual and cognitive performance was significantly (P < 0.05) related to the amount of change in blood iron markers (mean percentage of variance accounted for: 16.0%) and baseline concentrations of blood iron markers (mean percentage of variance accounted for: 25.0%). Overall, there was evidence that the strongest effects of change in iron status were obtained for perceptual and low-level attentional function.Conclusion: DFS produced measurable and significant improvements in the perceptual, attentional, and mnemonic performance of Indian female tea pickers of reproductive age. This trial was registered at clinicaltrials.gov as NCT01032005.

Efficacy of iron supplementation may be misinterpreted using conventional measures of iron status in iron-depleted, nonanemic women undergoing aerobic exercise training

Background: Despite its known detrimental effects, iron deficiency remains the most common micronutrient deficiency in the world. Many interventions that aim to improve iron status involve physically active populations. Intense aerobic exercise training negatively affects iron status; however, the impact of regular moderate aerobic exercise on the effectiveness of iron supplementation remains unclear.Objective: This study aimed to determine whether aerobic training modifies the assessment of the effectiveness of iron supplementation in improving conventional iron status measures.Design: Seventy-two iron-depleted, nonanemic Chinese women [serum ferritin (sFer) <25 μg/L and hemoglobin >110 g/L] were included in an 8-wk, partially blinded, randomized controlled trial with a 2 × 2 factorial design including iron supplements (42 mg elemental Fe/d) or placebo and aerobic training (five 25-min sessions/wk at 75-85% of maximum heart rate) or no training. Linear mixed models were used to evaluate the relation between supplement type, training, and changes in iron status over time, measured by sFer, hemoglobin, soluble transferrin receptor (sTfR), and estimated total body iron.Results: After treatment, both the iron-supplemented trained and untrained groups showed significantly improved sFer, sTfR, and body iron values compared with either of the placebo groups. Similarly, trained participants had significantly higher aerobic fitness measures than untrained participants. Training modified the sFer response to supplementation (training by supplement interaction, P = 0.07), with the iron-supplemented trained group having significantly lower sFer than the iron-supplemented untrained group at week 8 (mean ± SD: 31.8 ± 13.5 and 47.6 ± 15.7 μg/L, respectively; P = 0.042), whereas there was no significant difference between the placebo trained and untrained groups (21.3 ± 12.2 and 20.3 ± 7.0 μg/L, respectively; P = 1.00).Conclusions: Regular aerobic training reduces the apparent effectiveness of iron supplementation in improving sFer and calls into question whether conventional measures of iron status accurately reflect iron metabolism in physically active, nonanemic women. This trial was registered at clinicaltrials.gov as NCT03002090.

Effect of iron and zinc-biofortified pearl millet consumption on growth and immune competence in children aged 12-18 months in India: study protocol for a randomised controlled trial

INTRODUCTION

Biofortified crops represent a sustainable agricultural solution for the widespread micronutrient malnutrition in India and other resource-limited settings. This study aims to investigate the effect of the consumption of foods prepared with iron- and zinc-biofortified pearl millet (FeZn-PM) by children on biomarkers of iron and zinc status, growth, and immune function.

METHODS AND ANALYSIS

We will conduct a randomised controlled feeding trial in identified slums of Mumbai, India among 200 children aged between 12 and 18 months. Children will be randomised to receive foods prepared with the biofortified PM (FeZn-PM, ICTP8203-Fe) or non-biofortified PM. Anthropometric and morbidity data will be gathered every month for 9 months. Biological samples will be collected at baseline, midline and endline to assess iron and zinc status, including haemoglobin, serum ferritin, serum transferrin receptor, serum zinc, C-reactive protein and alpha-1 acid glycoprotein. Biological samples will be archived for future analyses. The midline measurement will be a random serial sample between baseline and endline. Immune function will be assessed at each time point by the measurement of T cell counts and vaccine responses in a subset, respectively.

ETHICS AND DISSEMINATION

This study has obtained clearance from the Health Ministry Screening Committee of the Indian Council of Medical Research. Ethical clearance has been obtained from Cornell University's Institutional Review Board, the Inter System Biomedica Ethics Committee and St John's Research Institute's Institutional Ethics Review Board. The results of this study will be disseminated at several research conferences and as published articles in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

Clinical trial registration number NCT02233764. CTRI registration number REF/2014/10/007731.

Consumption of Iron-Biofortified Beans Positively Affects Cognitive Performance in 18- to 27-Year-Old Rwandan Female College Students in an 18-Week Randomized Controlled Efficacy Trial

Background: Evidence shows that iron deficiency in adulthood may affect cognitive performance, possibly by disrupting neurotransmitter regulation or brain energy metabolism. Women of reproductive age (WRA) are among those who are most vulnerable to iron deficiency; however, they have been largely ignored in the literature relating iron status to cognition.Objective: Our aim was to determine the efficacy of iron-biofortified beans in improving cognition in WRA compared with control beans.Methods: A double-blind, randomized intervention study was conducted in 150 women aged 18-27 y with low iron status (ferritin <20 μg/L). Women were randomly assigned to consume iron-biofortified beans (86.1 ppm iron) or control beans (50.1 ppm iron) daily for 18 wk. Iron status was assessed based on hemoglobin, ferritin, transferrin receptor, and body iron values and on cognitive performance on 5 computerized tasks at baseline and endline.Results: Groups did not differ on any variables at baseline. Per protocol analyses revealed that consumption of the biofortified beans resulted in a 17% larger improvement in the speed of spatial selective attention; a nearly 7-fold larger improvement in the speed, a 68% greater improvement in the efficiency, and a >2-fold greater improvement in the specificity of memory retrieval; and a >2-fold larger improvement in the speed and a >3-fold larger improvement in the efficiency of memory search-all of which are relative to consumption of the control beans (P < 0.01 for all comparisons).Conclusions: Cognitive performance is sensitive to iron status, and consumption of iron-biofortified beans for 18 wk improved cognitive performance, especially the efficiency of search and the speed of retrieval on memory tasks, in young adult women. This trial was registered at clinicaltrials.gov as NCT01594359.

Effect of iron deficiency on simultaneous measures of behavior, brain activity, and energy expenditure in the performance of a cognitive task

OBJECTIVES

Iron deficiency (ID) - the highly prevalent nutritional deficiency - has been shown to have deleterious effects on measures of cognitive performance and brain activity. Many of these results are suggestive of the impact of ID on neurotransmitter regulation and myelination. A third critical potential effect of ID on brain function is at the level of brain energy expenditure; however, to date there has not been any method for indirectly estimating the impact of ID on energy expenditure in humans in the context of cognitive work.

METHODS

We report here a study comparing ID and iron sufficient (IS) college students in which simultaneous behavioral, encephelographic (EEG), and metabolic data were collected in a task designed as a cognitive analog to standard physical exertion tasks.

RESULTS

We show that increases in cognitive demands produced decrements in behavioral measures of performance, and increases in EEG and metabolic measures of work. Critically, we found that the magnitudes of those changes were directly related to iron levels.

DISCUSSION

We find support for the idea that brain activity mediates the relationship between cognitive demands and energy expenditure, with ferritin and hemoglobin moderating those relationships in distinct ways. Finally, we show that levels of energy expenditure can be indirectly estimated by measures of EEG spectral power.

Iron-biofortified staple food crops for improving iron status: a review of the current evidence

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Iron deficiency and anemia are major threats to public health worldwide.

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Biofortification is a promising and sustainable strategy to target iron deficiency.

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Three randomized efficacy trials of iron-biofortification have been conducted to date.

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Iron-biofortification improved iron status, with the greatest effects in iron deficient individuals.

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Future trials are needed to assess the effects on functional outcomes and in other high-risk populations.

Iron deficiency is the most common micronutrient deficiency globally and represents a major threat to public health. Biofortification, the process of enhancing micronutrient content and bioavailability in staple crops, represents an exciting sustainable food-based strategy to combat and prevent iron deficiency, particularly in resource-limited settings. In this review, we examine the evidence to date of the efficacy of iron-biofortified staple food crops on improving iron status in at-risk populations, including rice, pearl millet, and beans. Three randomized efficacy trials of iron biofortified interventions were included in this analysis, conducted in the Philippines, India, and Rwanda. Iron status (hemoglobin, serum ferritin, soluble transferrin receptor (sTfR), C-reactive protein, alpha-1 acid glycoprotein) was measured at enrollment, midline, and endline in each trial. The primary outcomes evaluated included hemoglobin, serum ferritin, sTfR, and total body iron. A meta-analysis using random effects models was conducted to examine the effects of interventions on hematological outcomes, with the DerSimonian and Laird method. In meta-analyses of data from the three trials, iron-biofortified interventions significantly increased serum ferritin concentrations and total body iron. Evidence to date from randomized trials suggest that iron-biofortified crops are an efficacious intervention to improve iron status. In particular, findings from all three trials also indicate that the effects of biofortified staple crops were highest among individuals who were iron deficient at baseline, suggesting the greatest potential to benefit. Assessment of functional outcomes and consideration of other high-risk populations such as young children, are warranted to elucidate the impact of iron-biofortified interventions on human health.

Ultrasound measurement of fetal size in rural Guatemala

OBJECTIVES

To describe the fetal growth pattern of a population from rural Guatemala and determine when during gestation growth faltering becomes evident.

METHODS

Ultrasound examinations were conducted for 319 women. Femur length (FL), biparietal diameter (BPD), abdominal (AC) and head circumference (HC) were compared with reference values.

RESULTS

FL and AC were similar to reference values throughout gestation. BPD and HC were below the 50th percentile by 30 weeks' gestation and below the 10th percentile later in gestation. We expected all four dimensions to show marked growth restriction during gestation. Measurement differences may explain the results but would call into question the value of cross-study comparisons. Infants born small for gestational age were small in all measures as early as 15 weeks.

CONCLUSIONS

Fetal growth faltering begins in early gestation among infants who were born small. The lack of deviation from reference data for FL and AC requires further clarification.

A Human Feeding Trial of Iron-enhanced Rice

A key unknown in the strategy of breeding for micronutrient-dense staple food crops is the bioavailability of the additional trace minerals in nutritionally improved lines. This paper describes a feeding trial to be undertaken in the Philippines during 2001 using human subjects that will examine the effect on iron status of long-term consumption of IR68-144, a high-yielding, aromatic, iron-dense rice that is currently undergoing agronomic testing at the International Rice Research Institute (IRRI). The subjects will be religious sisters-in-training who live year-round in convents in Greater Manila.

This population was selected because they represent a sex and age segment of the population at high risk for iron deficiency. The iron status of the sample of 27 sisters indicates that 74% were anaemic (haemoglobin <120 g/L) and 48% iron deficient (serum ferritin <12 μg/L). These subjects consume large quantities of rice (400 g/day), and all their meals are prepared in common kitchens where different varieties of rice can be easily introduced to the menu. A pilot study found that the introduction of IR68-144 rice was highly tolerated by the kitchen staff who prepared the rice and the sisters who consumed it. There were no perceived differences in taste, texture, colour, or other properties compared with the commercial variety normally consumed.

The high prevalence of iron deficiency, the considerable amount of rice consumed, the high level of cooperation of the subjects, and the structured routine of the convent make this an ideal research setting to investigate the effect of improving iron intakes through a staple food.

Consuming Iron Biofortified Beans Increases Iron Status in Rwandan Women after 128 Days in a Randomized Controlled Feeding Trial

BACKGROUND

Food-based strategies to reduce nutritional iron deficiency have not been universally successful. Biofortification has the potential to become a sustainable, inexpensive, and effective solution.

OBJECTIVE

This randomized controlled trial was conducted to determine the efficacy of iron-biofortified beans (Fe-Beans) to improve iron status in Rwandan women.

METHODS

A total of 195 women (aged 18-27 y) with serum ferritin <20 μg/L were randomly assigned to receive either Fe-Beans, with 86 mg Fe/kg, or standard unfortified beans (Control-Beans), with 50 mg Fe/kg, 2 times/d for 128 d in Huye, Rwanda. Iron status was assessed by hemoglobin, serum ferritin, soluble transferrin receptor (sTfR), and body iron (BI); inflammation was assessed by serum C-reactive protein (CRP) and serum α1-acid glycoprotein (AGP). Anthropometric measurements were performed at baseline and at end line. Random weekly serial sampling was used to collect blood during the middle 8 wk of the feeding trial. Mixed-effects regression analysis with repeated measurements was used to evaluate the effect of Fe-Beans compared with Control-Beans on iron biomarkers throughout the course of the study.

RESULTS

At baseline, 86% of subjects were iron-deficient (serum ferritin <15 μg/L) and 37% were anemic (hemoglobin <120 g/L). Both groups consumed an average of 336 g wet beans/d. The Fe-Beans group consumed 14.5 ± 1.6 mg Fe/d from biofortified beans, whereas the Control-Beans group consumed 8.6 ± 0.8 mg Fe/d from standard beans (P < 0.05). Repeated-measures analyses showed significant time-by-treatment interactions for hemoglobin, log serum ferritin, and BI (P < 0.05). The Fe-Beans group had significantly greater increases in hemoglobin (3.8 g/L), log serum ferritin (0.1 log μg/L), and BI (0.5 mg/kg) than did controls after 128 d. For every 1 g Fe consumed from beans over the 128 study days, there was a significant 4.2-g/L increase in hemoglobin (P < 0.05).

CONCLUSION

The consumption of iron-biofortified beans significantly improved iron status in Rwandan women. This trial was registered at clinicaltrials.gov as NCT01594359.

A Randomized Trial of Iron-Biofortified Pearl Millet in School Children in India

BACKGROUND

Iron deficiency is the most widespread nutritional deficiency in the world.

OBJECTIVE

The objective of this randomized efficacy trial was to determine the effects of iron-biofortified pearl millet (Fe-PM) on iron status compared with control pearl millet (Control-PM).

METHODS

A randomized trial of biofortified pearl millet (Pennisetum glaucum), bred to enhance iron content, was conducted in 246 children (12-16 y) for 6 mo in Maharashtra, India. Iron status [hemoglobin, serum ferritin (SF), soluble transferrin receptor (sTfR), and total body iron (TBI)], inflammation (C-reactive protein and α-1 acid glycoprotein), and anthropometric indices were evaluated at enrollment and after 4 and 6 mo. Hodges-Lehmann-Sen 95% CIs were used to examine the effect of the Fe-PM on iron status compared with commercially available Control-PM. Linear and binomial regression models were used to evaluate the effects of Fe-PM on iron status and incidence of anemia and iron deficiency, compared with Control-PM.

RESULTS

At baseline, 41% of children were iron deficient (SF <15 μg/L) and 28% were anemic (hemoglobin <12.0 g/dL). Fe-PM significantly increased SF concentrations and TBI after 4 mo compared with Control-PM. Among children who were iron deficient at baseline, those who received Fe-PM were 1.64 times more likely to become iron replete by 6 mo than were those receiving Control-PM (RR: 1.64, 95% CI: 1.07, 2.49, P = 0.02). The effects of Fe-PM on iron status were greater among children who were iron deficient at baseline than among children who were not iron deficient at baseline.

CONCLUSIONS

Fe-PM significantly improved iron status in children by 4 mo compared with Control-PM. This study demonstrated that feeding Fe-PM is an efficacious approach to improve iron status in school-age children and it should be further evaluated for effectiveness in a broader population context. This trial was registered at clinicaltrials.gov as NCT02152150.

Are biofortified staple food crops improving vitamin A and iron status in women and children? New evidence from efficacy trials

Biofortification is the breeding of crops to increase their nutritional value, including increased contents of micronutrients or their precursors. Biofortification aims to increase nutrient levels in crops during plant growth rather than during processing of the crops into foods. Emerging research from 8 human trials conducted in the past decade with staple food crops that have been biofortified by traditional plant breeding methods were presented in this symposium. Specifically, data from 6 efficacy and 2 effectiveness trials were discussed to assess the effects of regular consumption of these enhanced staple crops on improving population vitamin A and iron status and reducing the burden of micronutrient deficiencies in targeted populations living in South Asia, Sub-Saharan Africa, and Latin America. Biofortified food crops appear to have a positive impact on nutritional and functional health outcomes, as the results from the trials suggest. Additional implementation research will be needed to ensure maximization of the beneficial impact of this intervention and a smooth scaling up to make biofortification a sustainable intervention in public health. The challenge for the global health community remains how to take this efficacious intervention and implement at large scale in the real world.

Double-fortified salt is efficacious in improving indicators of iron deficiency in female Indian tea pickers

Poor iron status affects 50% of Indian women and compromises work productivity, cognitive performance, and reproduction. Among the many strategies to reduce iron deficiency is the commercial fortification of iodized table salt with iron to produce a double-fortified salt (DFS). The objective of this study was to test the efficacy of DFS in reducing iron deficiency in rural women of reproductive age from northern West Bengal, India. The participants were 212 women between 18 and 55 y of age who worked as full-time tea pickers on a large tea estate. Participants in the randomized, controlled, double-blind study were assigned to use either DFS or a control iodized salt for 7.5 to 9 mo. The DFS was fortified with 3.3-mg ferrous fumarate (1.1-mg elemental iron) per kg of iodized salt, whereas the control salt contained only iodine (47 mg/kg potassium iodate), and both salt varieties were distributed gratis to the families of participants at 0.5 kg/mo for each 2 household members. At baseline, 53% of participants were anemic (hemoglobin <120 g/L), 25% were iron deficient (serum ferritin <12 μg/L), and 23% were iron-deficient anemic. Also, 22% had a transferrin receptor concentration >8.6 mg/L and 22% had negative (<0.0 mg/kg) body iron stores. After 9 mo the participants receiving DFS showed significant improvements compared with controls in hemoglobin (+2.4 g/L), ferritin (+0.13 log10 μg/L), soluble transferrin receptor (-0.59 mg/L), and body iron (+1.43 mg/kg), with change in status analyzed by general linear models controlling for baseline values. This study demonstrated that DFS is an efficacious approach to improving iron status and should be further evaluated for effectiveness in the general population. This trial was registered at clinicaltrials.gov as NCT01032005.

Changes in family income status and the development of overweight and obesity from 2 to 15 years: a longitudinal study

Background

An emerging body of research suggests the trajectory of a family’s income affects children’s health and development more profoundly than the often-measured income at a single time point. The purpose of this study was to examine the associations between changes in family income status, early-life risk factors, and body mass index (BMI) z-score trajectory from age 2 to 15 years.

Methods

This longitudinal study employed a birth cohort (n = 595) located in a rural region of New York State. Data were collected through an audit of medical records and mailed questionnaires. Family low-income and BMI z-score trajectories were identified using latent-class modeling techniques that group children based on similar trends across time. We examined five early-life risk factors in relation to income and BMI z-score trajectories: maternal overweight/obesity, maternal gestational weight gain, maternal smoking during pregnancy, breastfeeding duration, and early-life weight gain trajectory. We used multinomial logistic regression models to estimate the odds of being in a BMI z-score trajectory group based on income trajectory and early-life risk factors.

Results

Children who remain low-income throughout childhood were more likely to maintain overweight (AOR = 2.55, 95% CI = 1.03, 5.42) and children who moved into low-income during childhood were more likely to be obese (AOR = 2.36, 95% CI = 1.12, 5.93) compared to children who were never low-income. Maternal overweight/obesity was significantly associated with a child become obese (AOR = 8.31, 95% CI = 3.80, 18.20), become overweight (AOR = 2.37, 95% CI = 1.34, 4.22), and stay overweight (AOR = 1.79, 95% CI = 1.02, 3.14). Excessive gestational weight gain was associated with increased likelihood of a child becoming overweight trajectory (AOR = 2.01, 95% CI = 1.01, 4.00).

Conclusions

Our findings further supports the growing evidence that there are several preventable early-life risk factors that could be targeted for intervention. This study provides new evidence that remaining in low-income and moving into low-income increases risk for adolescent overweight and obesity.

Quantification of training load and intensity in female collegiate rowers: validation of a daily assessment tool

Session rating of perceived exertion (RPE) has been used to quantify a variety of training activities but has not been tested in rowers, who engage in intermittent patterns of activity. The objective of this study was to evaluate the ability of the subjective session RPE method to quantify on- and off-water rowing training load (TL) compared with a heart rate (HR) summation method. Seven female collegiate rowers (19.7 ± 0.8 years) were monitored during 2 workout simulations differing in intensity level in the laboratory and several training sessions outside of the laboratory. Training load was calculated using an HR summation method, and RPE was measured after the completion of each simulation or training activity (session RPE). During the workout simulations, despite poor correlation between the HR summation and session RPE methods (r = -0.21, p = 0.52), the session RPE method was significantly correlated with peak WR (r = 0.59, p = 0.05) and posttest blood lactate concentration (r = 0.73, p = 0.007). During training sessions outside of the laboratory, the HR summation (280.7 ± 108.3) and session RPE (6,432.5 ± 4,002.0) methods were highly correlated (r = 0.88, p < 0.001). Regression analyses revealed that after controlling for time, training intensity rating was a significant predictor of TL (p < 0.001). We conclude that the session RPE method is a valid metric of TL in female rowers. The method's convenience renders it a feasible option for researchers and coaches to quantify and monitor TL in rowers.

Validity of ActiGraph 2-regression model, Matthews cut-points, and NHANES cut-points for assessing free-living physical activity

BACKGROUND

The purpose of this study was to compare the 2006 and 2010 Crouter algorithms for the ActiGraph accelerometer and the NHANES and Matthews cut-points, to indirect calorimetry during a 6-hr free-living measurement period.

METHODS

Twenty-nine participants (mean ± SD; age, 38 ± 11.7 yrs; BMI, 25.0 ± 4.6 kg·m-2) were monitored for 6 hours while at work or during their leisure time. Physical activity (PA) data were collected using an ActiGraph GT1M and energy expenditure (METs) was measured using a Cosmed K4b2. ActiGraph prediction equations were compared with the Cosmed for METs and time spent in sedentary behaviors, light PA (LPA), moderate PA (MPA), and vigorous PA (VPA).

RESULTS

The 2010 Crouter algorithm overestimated time spent in LPA, MPA, and VPA by 9.0%-44.5% and underestimated sedentary time by 20.8%. The NHANES cut-points overestimated sedentary time and LPA by 8.3%-9.9% and underestimated MPA and VPA by 50.4%-56.7%. The Matthews cut-points overestimated sedentary time (9.9%) and MPA (33.4%) and underestimated LPA (25.7%) and VPA (50.1%). The 2006 Crouter algorithm was within 1.8% of measured sedentary time; however, mean errors ranged from 34.4%-163.1% for LPA, MPA, and VPA.

CONCLUSION

Of the ActiGraph prediction methods examined, none of them was clearly superior for estimating free-living PA compared with indirect calorimetry.

Secular changes in the height of Polish schoolboys from 1955 to 1988

Secular changes in height have been observed in many regions of Poland using cross-sectional data; however, data from four nationally representative surveys conducted from 1955 to 1988 have only been partially analyzed. Dramatic social and economic transitions during this 33 year period provide a unique opportunity to understand changes in growth within this historic context. We analyzed the changes in height of boys, aged 7-18 years, from surveys conducted in 1955, 1966, 1978 and 1988. Data for height were converted to Z-scores using the LMS method and the 2000 National Center for Health Statistics reference. In each consecutive survey year, boys at all ages were significantly taller than the same aged boys from the previous survey year, with mean height increases of a 2.35 cm, 3.43 cm and 1.47 cm between 1955 and 1966, 1966 and 1978 and 1978 and 1988, respectively. There were significant declines with age in height Z-scores from 7 to 14 years of age, followed by improvements relative to the reference between 14 and 18 years of age. The decline in Z-scores may be partially explained by an effect of delayed maturation. However, historic context also supports that some birth cohorts likely experienced a more adverse environment during early childhood than did other birth cohorts.

Relationship between physical activity, physical performance, and iron status in adult women

Iron deficiency affects approximately 16% of US females 18-45 years old. Iron is a key component of heme-containing proteins, which are essential for oxygen transport throughout the body. With low iron levels, performance and intense physical activity may be compromised. Thus, the purpose of this study was to examine the relationship between iron status, physical performance, and physical activity in 18- to 45-year-old females. Participants (N = 109) were screened for iron status using a venous blood sample, had their height and mass measured, and self-reported their physical activity level. The screening was used to match iron-depleted nonanemic females (hemoglobin, Hgb > 120 g·L(-1); serum ferritin, sFer < 20 µg·L(-1)) to females with normal iron levels. After participant matching, they had their body composition measured, performed three cycle ergometer tests (maximal, endurance, and efficiency), and wore an ActiGraph GT1M accelerometer for five consecutive days, except when sleeping or during water activities. The final sample consisted of 25 iron-depleted participants and 24 with normal iron levels. Key findings were as follows: (i) after controlling for fat-free mass and vigorous physical activity, iron-depleted females had a significantly lower [Formula: see text]O(2) at ventilatory threshold compared with those with normal iron levels (P < 0.05); and (ii) after controlling for age, iron-depleted females spent significantly more time in sedentary behaviors and significantly less time in light physical activity than those with normal iron levels (P < 0.05). The increased sedentary time in iron-depleted females may contribute to excess mass gain over time; however, further investigation is needed to confirm these results.

Validity of estimating minute-by-minute energy expenditure of continuous walking bouts by accelerometry

BACKGROUND

Objective measurement of physical activity remains an important challenge. For wearable monitors such as accelerometer-based physical activity monitors, more accurate methods are needed to convert activity counts into energy expenditure (EE).

PURPOSE

The purpose of this study was to examine the accuracy of the refined Crouter 2-Regression Model (C2RM) for estimating EE during the transition from rest to walking and walking to rest. A secondary purpose was to determine the extent of overestimation in minute-by-minute EE between the refined C2RM and the 2006 C2RM.

METHODS

Thirty volunteers (age, 28 ± 7.7 yrs) performed 15 minutes of seated rest, 8 minutes of over-ground walking, and 8 minutes of seated rest. An ActiGraph GT1M accelerometer and Cosmed K4b2 portable metabolic system were worn during all activities. Participants were randomly assigned to start the walking bout at 0, 20, or 40 s into the minute (according to the ActiGraph clock). Acceleration data were analyzed by two methods: 2006 Crouter model and a new refined model.

RESULTS

The 2006 Crouter 2-Regression model over-predicted measured kcal kg-1 hr-1 during the first and last transitional minutes of the 20-s and 40-s walking conditions (P < 0.001). It also over-predicted the average EE for a walking bout (4.0 ± 0.5 kcal kg-1 hr-1), compared to both the measured kcal kg-1 hr-1 (3.6 ± 0.7 kcal kg-1 hr-1) and the refined Crouter model (3.5 ± 0.5 kcal kg-1 hr-1) (P < 0.05).

CONCLUSION

The 2006 Crouter 2-regression model over-predicts EE at the beginning and end of walking bouts, due to high variability in accelerometer counts during the transitional minutes. The new refined model eliminates this problem and results in a more accurate prediction of EE during walking.