Alicia L. Carriquiry

A Semiparametric Transformation Approach to Estimating Usual Daily Intake Distributions

Abstract The distribution of usual intakes of dietary components is important to individuals formulating food policy and to persons designing nutrition education programs. The usual intake of a dietary component for a person is the long-run average of daily intakes of that component for that person. Because it is impossible to directly observe usual intake for an individual, it is necessary to develop an estimator of the distribution of usual intakes based on a sample of individuals with a small number of daily observations on a subsample of the individuals. Daily intake data for individuals are nonnegative and often very skewed. Also, there is large day-to-day variation relative to the individual-to-individual variation, and the within-individual variance is correlated with the individual means. We suggest a methodology for estimating usual intake distributions that allows for varying degrees of departure from normality and recognizes the measurement error associated with one-day dietary intakes. The est...

Simple Food Group Diversity Indicators Predict Micronutrient Adequacy of Women’s Diets in 5 Diverse, Resource-Poor Settings

Women of reproductive age living in resource-poor settings are at high risk of inadequate micronutrient intakes when diets lack diversity and are dominated by staple foods. Yet comparative information on diet quality is scarce and quantitative data on nutrient intakes is expensive and difficult to gather. We assessed the potential of simple indicators of dietary diversity, such as could be generated from large household surveys, to serve as proxy indicators of micronutrient adequacy for population-level assessment. We used 5 existing data sets (from Burkina Faso, Mali, Mozambique, Bangladesh, and the Philippines) with repeat 24-h recalls to construct 8 candidate food group diversity indicators (FGI) and to calculate the mean probability of adequacy (MPA) for 11 micronutrients. FGI varied in food group disaggregation and in minimum consumption required for a food group to count. There were large gaps between intakes and requirements across a range of micronutrients in each site. All 8 FGI were correlated with MPA in all sites; regression analysis confirmed that associations remained when controlling for energy intake. Assessment of dichotomous indicators through receiver-operating characteristic analysis showed moderate predictive strength for the best choice indicators, which varied by site. Simple FGI hold promise as proxy indicators of micronutrient adequacy.

Sodium and potassium intakes among US adults: NHANES 2003–2008

BACKGROUND The American Heart Association (AHA), Institute of Medicine (IOM), and US Departments of Health and Human Services and Agriculture (USDA) Dietary Guidelines for Americans all recommend that Americans limit sodium intake and choose foods that contain potassium to decrease the risk of hypertension and other adverse health outcomes. OBJECTIVE We estimated the distributions of usual daily sodium and potassium intakes by sociodemographic and health characteristics relative to current recommendations. DESIGN We used 24-h dietary recalls and other data from 12,581 adults aged ≥20 y who participated in NHANES in 2003-2008. Estimates of sodium and potassium intakes were adjusted for within-individual day-to-day variation by using measurement error models. SEs and 95% CIs were assessed by using jackknife replicate weights. RESULTS Overall, 99.4% (95% CI: 99.3%, 99.5%) of US adults consumed more sodium daily than recommended by the AHA (<1500 mg), and 90.7% (89.6%, 91.8%) consumed more than the IOM Tolerable Upper Intake Level (2300 mg). In US adults who are recommended by the Dietary Guidelines to further reduce sodium intake to 1500 mg/d (ie, African Americans aged ≥51 y or persons with hypertension, diabetes, or chronic kidney disease), 98.8% (98.4%, 99.2%) overall consumed >1500 mg/d, and 60.4% consumed >3000 mg/d-more than double the recommendation. Overall, <2% of US adults and ~5% of US men consumed ≥4700 mg K/d (ie, met recommendations for potassium). CONCLUSION Regardless of recommendations or sociodemographic or health characteristics, the vast majority of US adults consume too much sodium and too little potassium.

Close correspondence between the motions from principal component analysis of multiple HIV-1 protease structures and elastic network modes.

The large number of available HIV-1 protease structures provides a remarkable sampling of conformations of the different conformational states, which can be viewed as direct structural information about the dynamics of the HIV-1 protease. After structure matching, we apply principal component analysis (PCA) to obtain the important apparent motions for both bound and unbound structures. There are significant similarities between the first few key motions and the first few low-frequency normal modes calculated from a static representative structure with an elastic network model (ENM), strongly suggesting that the variations among the observed structures and the corresponding conformational changes are facilitated by the low-frequency, global motions intrinsic to the structure. Similarities are also found when the approach is applied to an NMR ensemble, as well as to molecular dynamics (MD) trajectories. Thus, a sufficiently large number of experimental structures can directly provide important information about protein dynamics, but ENM can also provide similar sampling of conformations.

A large-scale intervention to introduce orange sweet potato in rural Mozambique increases vitamin A intakes among children and women.

β-Carotene-rich orange sweet potato (OSP) has been shown to improve vitamin A status of infants and young children in controlled efficacy trials and in a small-scale effectiveness study with intensive exposure to project inputs. However, the potential of this important food crop to reduce the risk of vitamin A deficiency in deficient populations will depend on the ability to distribute OSP vines and promote its household production and consumption on a large scale. In rural Mozambique, we conducted a randomised, controlled effectiveness study of a large-scale intervention to promote household-level OSP production and consumption using integrated agricultural, demand creation/behaviour change and marketing components. The following two intervention models were compared: a low-intensity (1 year) and a high-intensity (nearly 3 years) training model. The primary nutrition outcomes were OSP and vitamin A intakes by children 6-35 months and 3-5·5 years of age, and women. The intervention resulted in significant net increases in OSP intakes (model 1: 46, 48 and 97 g/d) and vitamin A intakes (model 1: 263, 254 and 492 μg retinol activity equivalents/d) among the younger children, older children and women, respectively. OSP accounted for 47-60 % of all sweet potato consumed and, among reference children, provided 80 % of total vitamin A intakes. A similar magnitude of impact was observed for both models, suggesting that group-level trainings in nutrition and agriculture could be limited to the first project year without compromising impact. Introduction of OSP to rural, sweet potato-producing communities in Mozambique is an effective way to improve vitamin A intakes.

Folic acid source, usual intake, and folate and vitamin B-12 status in US adults: National Health and Nutrition Examination Survey (NHANES) 2003–2006

BACKGROUND US adults have access to multiple sources of folic acid. The contribution of these sources to usual intakes above the tolerable upper intake level (UL) (1000 microg/d) and to folate and vitamin B-12 status is unknown. OBJECTIVE The objective was to estimate usual folic acid intake above the UL and adjusted serum and red blood cell folate, vitamin B-12, methylmalonic acid, and homocysteine concentrations among US adults by 3 major folic acid intake sources-enriched cereal-grain products (ECGP), ready-to-eat cereals (RTE), and supplements (SUP)-categorized into 4 mutually exclusive consumption groups. DESIGN We used data from the National Health and Nutrition Examination Survey (NHANES) 2003-2006 (n = 8258). RESULTS Overall, 2.7% (95% CI: 1.9%, 3.5%) of adults consumed more than the UL of folic acid. The proportions of those who consumed folic acid from ECGP only, ECGP+RTE, ECGP+SUP, and ECGP+RTE+SUP were 42%, 18%, 25%, and 15%, respectively. Of 60% of adults who did not consume supplements containing folic acid (ECGP only and ECGP+RTE), 0% had intakes that exceeded the UL. Of 34% and 6% of adults who consumed supplements with an average of < or = 400 and >400 microg folic acid/d, <1% and 47.8% (95% CI: 39.6%, 56.0%), respectively, had intakes that exceeded the UL. Consumption of RTE and/or supplements with folic acid was associated with higher folate and vitamin B-12 and lower homocysteine concentrations, and consumption of supplements with vitamin B-12 was associated with lower methylmalonic acid concentrations (P < 0.001). CONCLUSION At current fortification levels, US adults who do not consume supplements or who consume an average of < or =400 microg folic acid/d from supplements are unlikely to exceed the UL in intake for folic acid.

Gene Expression Patterns During Somatic Embryo Development and Germination in Maize Hi II Callus Cultures

Gene expression patterns were profiled during somatic embryogenesis in a regeneration-proficient maize hybrid line, Hi II, in an effort to identify genes that might be used as developmental markers or targets to optimize regeneration steps for recovering maize plants from tissue culture. Gene expression profiles were generated from embryogenic calli induced to undergo embryo maturation and germination. Over 1,000 genes in the 12,060 element arrays showed significant time variation during somatic embryo development. A substantial number of genes were downregulated during embryo maturation, largely histone and ribosomal protein genes, which may result from a slowdown in cell proliferation and growth during embryo maturation. The expression of these genes dramatically recovered at germination. Other genes up-regulated during embryo maturation included genes encoding hydrolytic enzymes (nucleases, glucosidases and proteases) and a few storage genes (an α-zein and caleosin), which are good candidates for developmental marker genes. Germination is accompanied by the up-regulation of a number of stress response and membrane transporter genes, and, as expected, greening is associated with the up-regulation of many genes encoding photosynthetic and chloroplast components. Thus, some, but not all genes typically associated with zygotic embryogenesis are significantly up or down-regulated during somatic embryogenesis in Hi II maize line regeneration. Although many genes varied in expression throughout somatic embryo development in this study, no statistically significant gene expression changes were detected between total embryogenic callus and callus enriched for transition stage somatic embryos.

Validity of predictive equations for 24-h urinary sodium excretion in adults aged 18–39 y

BACKGROUND Collecting a 24-h urine sample is recommended for monitoring the mean population sodium intake, but implementation can be difficult. OBJECTIVE The objective was to assess the validity of published equations by using spot urinary sodium concentrations to predict 24-h sodium excretion. DESIGN This was a cross-sectional study, conducted from June to August 2011 in metropolitan Washington, DC, of 407 adults aged 18-39 y, 48% black, who collected each urine void in a separate container for 24 h. Four timed voids (morning, afternoon, evening, and overnight) were selected from each 24-h collection. Published equations were used to predict 24-h sodium excretion with spot urine by specimen timing and race-sex subgroups. We examined mean differences with measured 24-h sodium excretion (bias) and individual differences with the use of Bland-Altman plots. RESULTS Across equations and specimens, mean bias in predicting 24-h sodium excretion for all participants ranged from -267 to 1300 mg (Kawasaki equation). Bias was least with International Cooperative Study on Salt, Other Factors, and Blood Pressure (INTERSALT) equations with morning (-165 mg; 95% CI: -295, 36 mg), afternoon (-90 mg; -208, 28 mg), and evening (-120 mg; -230, -11 mg) specimens. With overnight specimens, mean bias was least when the Tanaka (-23 mg; 95% CI: -141, 95 mg) or Mage (-145 mg; -314, 25 mg) equations were used but was statistically significant when using the Tanaka equations among females (216 to 243 mg) and the Mage equations among races other than black (-554 to -372 mg). Significant over- and underprediction occurred across individual sodium excretion concentrations. CONCLUSIONS Using a single spot urine, INTERSALT equations may provide the least biased information about population mean sodium intakes among young US adults. None of the equations evaluated provided unbiased estimates of individual 24-h sodium excretion.

Association between usual sodium and potassium intake and blood pressure and hypertension among U.S. adults: NHANES 2005-2010.

Objectives Studies indicate high sodium and low potassium intake can increase blood pressure suggesting the ratio of sodium-to-potassium may be informative. Yet, limited studies examine the association of the sodium-to-potassium ratio with blood pressure and hypertension. Methods We analyzed data on 10,563 participants aged ≥20 years in the 2005–2010 National Health and Nutrition Examination Survey who were neither taking anti-hypertensive medication nor on a low sodium diet. We used measurement error models to estimate usual intakes, multivariable linear regression to assess their associations with blood pressure, and logistic regression to assess their associations with hypertension. Results The average usual intakes of sodium, potassium and sodium-to-potassium ratio were 3,569 mg/d, 2,745 mg/d, and 1.41, respectively. All three measures were significantly associated with systolic blood pressure, with an increase of 1.04 mmHg (95% CI, 0.27–1.82) and a decrease of 1.24 mmHg (95% CI, 0.31–2.70) per 1,000 mg/d increase in sodium or potassium intake, respectively, and an increase of 1.05 mmHg (95% CI, 0.12–1.98) per 0.5 unit increase in sodium-to-potassium ratio. The adjusted odds ratios for hypertension were 1.40 (95% CI, 1.07–1.83), 0.72 (95% CI, 0.53–0.97) and 1.30 (95% CI, 1.05–1.61), respectively, comparing the highest and lowest quartiles of usual intake of sodium, potassium or sodium-to-potassium ratio. Conclusions Our results provide population-based evidence that concurrent higher sodium and lower potassium consumption are associated with hypertension.

Three-Phase Model Harmonizes Estimates of the Maximal Suppression of Parathyroid Hormone by 25-Hydroxyvitamin D in Persons 65 Years of Age and Older

The concentration or threshold of 25-hydroxyvitamin D [25(OH)D] needed to maximally suppress intact serum parathyroid hormone (iPTH) has been suggested as a measure of optimal vitamin D status. Depending upon the definition of maximal suppression of iPTH and the 2-phase regression approach used, 2 distinct clusters for a single 25(OH)D threshold have been reported: 16-20 ng/mL (40-50 nmol/L) and 30-32 ng/mL (75-80 nmol/L). To rationalize the apparently disparate published results, we compared thresholds from several regression models including a 3-phase one to estimate simultaneously 2 thresholds before and after adjusting for possible confounding for age, BMI, glomerular filtration rate, dietary calcium, and season (April-September vs. October-March) within a single data set, i.e. data from the Tufts University Sites Testing Osteoporosis Prevention/Intervention Treatment study, consisting of 181 men and 206 women (total n = 387) ages 65-87 y. Plasma 25(OH)D and serum iPTH concentrations were (mean +/- SD) 22.1 +/- 7.44 ng/mL (55.25 +/- 18.6 nmol/L) and 36.6 +/- 16.03 pg/mL (3.88 +/- 1.7 pmol/L), respectively. The 3-phase model identified 2 thresholds of 12 ng/mL (30 nmol/L) and 28 ng/mL (70 nmol/L); similar results were found from the 2-phase models evaluated, i.e. 13-20 and 27-30 ng/mL (32.5-50 and 67.5-75 nmol/L) and with previous results. Adjusting for confounding did not change the results substantially. Accordingly, the 3-phase model appears to be superior to the 2-phase approach, because it simultaneously estimates the 2 threshold clusters found from the 2-phase approaches along with estimating confidence limits. If replicated, it may be of both clinical and public health importance.