Journal of Nutrition Methodology and Mathematical Modeling

Food Consumed Away from Home Can Be a Part of a Healthy and Affordable Diet [Methodology and Mathematical Modeling]

You, W., Zhang, G., Davy, B. M., Carlson, A., Lin, B.-H. — Fri, 18 Sep 2009 10:01:30 PDT

The benefit calculation of the Supplemental Nutrition Assistance Program (SNAP), formerly the Food Stamp Program, is based primarily on results of the Thrifty Food Plan (TFP) developed by the USDA. By using a nonlinear mathematical programming approach, the TFP provides a dietary pattern recommendation that deviates the least from low-income consumers' consumption pattern, meets dietary guidelines, and is economical. The TFP stipulates that all foods should be purchased at stores and prepared at home [food at home (FAH)] and excludes an important part of current consumers' diet, food away from home (FAFH). Our purpose was to evaluate the feasibility and nutritional impact of adding a FAFH dimension into the TFP model framework. Measures of energy density, nutrients and food group composition, and the overall diet quality measured by the Healthy Eating Index 2005 were calculated and compared across the TFP, the TFP with FAFH, and low-income consumers' diet pattern. Our results indicated that considering moderate FAFH in the TFP yielded similar nutrient and food group composition as the original TFP while greatly increasing the practicality and adaptability of the recommended dietary pattern. These findings may be used by nutrition educators to develop healthful FAFH choices for individuals receiving SNAP benefits.

Mathematical Modeling of Serum 13C-Retinol in Captive Rhesus Monkeys Provides New Insights on Hypervitaminosis A [Methodology and Mathematical Modeling]

Escaron, A. L., Green, M. H., Howe, J. A., Tanumihardjo, S. A. — Fri, 18 Sep 2009 10:01:30 PDT

Hypervitaminosis A is increasingly a public health concern, and thus noninvasive quantitative methods merit exploration. In this study, we applied the ¹³C-retinol isotope dilution test to a nonhuman primate model with excessive liver stores. After baseline serum chemistries, rhesus macaques (Macaca mulatta; n = 16) were administered 3.5 µmol ¹³C₂-retinyl acetate. Blood was drawn at baseline, 5 h, and 2, 4, 7, 14, 21, and 28 d following the dose. Liver biopsies were collected 7 d before and 2 d after dosing (n = 4) and at 7, 14, and 28 d (n = 4/time) after dosing. Serum and liver were analyzed by HPLC and GC-combustion-isotope ratio MS for retinol and its enrichment, respectively. Model-based compartmental analysis was applied to serum data. Lactate dehydrogenase was elevated in 50% of the monkeys. Total body reserves (TBR) of vitamin A (VA) were calculated at 28 d. Predicted TBR (3.52 ± 2.01 mmol VA) represented measured liver stores (4.56 ± 1.38 mmol VA; P = 0.124). Predicted liver VA concentrations (13.3 ± 9.7 µmol/g) were similar to measured liver VA concentrations (16.4 ± 5.3 µmol/g). The kinetic models predict that 27–52% of extravascular VA is exchanging with serum in hypervitaminotic A monkeys. The test correctly diagnosed hypervitaminosis A in all monkeys, i.e. 100% sensitivity. Stable isotope techniques have important public health potential for the classification of VA status, including hypervitaminosis, because no other technique besides invasive liver biopsies, correctly identifies excessive liver VA stores.

Newborn Adiposity Measured by Plethysmography Is Not Predicted by Late Gestation Two-Dimensional Ultrasound Measures of Fetal Growth [Methodology and Mathematical Modeling]

Thu, 20 Aug 2009 10:02:31 PDT

Noninvasive measures of fetal and neonatal body composition may provide early identification of children at risk for obesity. Air displacement plethysmography provides a safe, precise measure of adiposity and has recently been validated in infants. Therefore, we explored relationships between term newborn percent body fat (%BF) measured by air displacement plethysmography to 2-dimensional ultrasound (2-D US) biometric measures of fetal growth and maternal and umbilical cord endocrine activity. A total of 47 mother/infant pairs were studied. Fetal biometrics by 2-D US and maternal blood samples were collected during late gestation (35 wk postmenstrual age); infants were measured within 72 h of birth. Fetal biometrics included biparietal diameter, femur length, head circumference, abdominal circumference (AC), and estimated fetal weight (EFW). Serum insulin, insulin-like growth factor (IGF) 1, IGF binding protein-3, and leptin concentrations were measured in umbilical cord and maternal serum. The mean %BF determined by plethysmography was 10.9 ± 4.8%. EFW and fetal AC had the largest correlations with newborn %BF (R² = 0.14 and 0.10, respectively; P < 0.05); however, stepwise linear regression modeling did not identify any fetal biometric parameters as a significant predictor of newborn %BF. Newborn mid-thigh circumference (MTC; cm) and ponderal index (PI; weight, kg/length, cm³) explained 21.8 and 14.4% of the variability in %BF, respectively, and gave the best stepwise linear regression model (%BF = 0.446 MTC + 0.347 PI –29.692; P < 0.001). We conclude that fetal growth biometrics determined by 2-D US do not provide a reliable assessment of %BF in term infants.