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.

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.

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.

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.

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.

Interpopulation variation in height among children 7 to 18 years of age.

The objective of this review is to examine the degree of variation that exists in the achieved height of preadolescent and adolescent children across populations experiencing favorable conditions that support linear growth. Fifty-three population groups were identified that reported mean heights for economically privileged populations from all major continents. Graphic representation of the heights for these populations indicates that the mean height of preadolescent children differs by 3 to 5 cm, whereas population means begin to diverge from the National Center for Health Statistics/World Health Organization (NCHS/WHO) reference at puberty, with most non-European populations falling to approximately 5 cm below the reference and northern European populations exceeding the reference by a similar amount. We conclude that the evidence for limited interpopulation variation in the height of preadolescents supports consideration of a single growth reference for children up to puberty, but the uncertainty of the causes of the divergence in achieved height during puberty requires further research in order to establish an appropriate adolescent growth reference.