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Background According to the CONSORT statement, significance testing of baseline differences in randomized controlled trials should not be performed. In fact, this practice has been discouraged by numerous authors throughout the last forty years. During that time span, reporting of baseline differences has substantially decreased in the leading general medical journals. Our own experience in the field of nutrition behavior research however, is that coauthors, reviewers and even editors are still very persistent in their demand for these tests. The aim of this paper is therefore to negate this demand by providing clear evidence as to why testing for baseline differences between intervention groups statistically is superfluous and why such results should not be published. Discussion Testing for baseline differences is often propagated because of the belief that it shows whether randomization was successful and it identifies real or important differences between treatment arms that should be accounted for in the statistical analyses. Especially the latter argument is flawed, because it ignores the fact that the prognostic strength of a variable is also important when the interest is in adjustment for confounding. In addition, including prognostic variables as covariates can increase the precision of the effect estimate. This means that choosing covariates based on significance tests for baseline differences might lead to omissions of important covariates and, less importantly, to inclusion of irrelevant covariates in the analysis. We used data from four supermarket trials on the effects of pricing strategies on fruit and vegetables purchases, to show that results from fully adjusted analyses sometimes do appreciably differ from results from analyses adjusted for significant baseline differences only. We propose to adjust for known or anticipated important prognostic variables. These could or should be pre-specified in trial protocols. Subsequently, authors should report results from the fully adjusted as well as crude analyses, especially for dichotomous and time to event data. Summary Based on our arguments, which were illustrated by our findings, we propose that journals in and outside the field of nutrition behavior actively adopt the CONSORT 2010 statement on this topic by not publishing significance tests for baseline differences anymore. [ABSTRACT FROM AUTHOR]

Objective: Our objective was to assess the distribution of energy, macro- and micronutrient intakes by meal (breakfast, lunch, dinner and combined snacks) in a cross-sectional sample of schoolchildren. Design: Cross-sectional dietary survey in schoolchildren. Setting: Twelve private and public schools in the urban setting of Quetzaltenango, Guatemala. Subjects: A total of 449 schoolchildren (from higher and lower socio-economic strata) were enrolled in the study. Methods: Each child completed a single, pictorial 24 h prospective diary and a face-to-face interview to check completeness and estimate portion sizes. Estimated daily intakes were examined by mealtime as: (i) absolute intakes; (ii) relative nutrient distribution; and (iii) critical micronutrient density (i.e. nutrient density in relation to the WHO Recommended Nutrient Intakes/median age-specific Guatemalan energy requirements). Results: The daily distribution of energy intake was 24% at breakfast, 30% at lunch, 23% at dinner and 23% among snacks. Lunch was also the leading meal for macronutrients, providing 35% of proteins, 27% of fat and 30% of carbohydrate. The distribution of selected micronutrients did not follow the pattern of energy, insofar as lunch provided relatively more vitamin C and Zn, whereas breakfast led in terms of vitamins A and D, thiamin, riboflavin, folate, Ca and Fe. Conclusions: Meal-specific distribution of energy, macro- and micronutrients provides a unique and little used perspective for evaluation of children's habitual intake, and may provide guidance to strategies to improve dietary balance in an era of coexisting energy overnutrition and micronutrient inadequacy. [ABSTRACT FROM AUTHOR]

Although the nutrition community's focus has been on quantifying the intake of nutrients, and more recently on selection of foods and beverages, inquiry into their distribution among meals has lagged behind. Our objective was to assess the distribution of energy, macro-and micronutrients among the 4 meal-types (breakfast {B}, lunch {L}, dinner {D}, and combined snacks {S}) in a convenience sample of 449 third and fourth grade schoolchildren from private and public elementary schools from the city of Quetzaltenango, Guatemala. We administered a single pictorial 24-h prospective diary, checked for completeness and estimated portion sizes. The distribution of energy intake was 24% (B), 30% (L), 23% (D), and 23% (S), respectively. Although L led in terms of energy (30% of daily intake) and macronutrients (35% of PRO, 27% of fat and 30% of CHO), it was not the most micronutrient-dense meal. L was the leading source of vitamin C and zinc, whereas B was the major source of vitamins A, D, B1, and B2, and folate, calcium and iron. Where overnutrition and micronutrient deficiencies coexist, analysis of nutrient density in meals may improve strategies to achieve adequate balance. [ABSTRACT FROM AUTHOR]

Traditional models of chemostat systems looking at interactions between predator, prey and nutrients have used only a single currency, such as energy or nitrogen. In reality, growth of autotrophs and heterotrophs may be limited by various elements, e.g. carbon, nitrogen, phosphorous or iron. In this study we develop a dynamic energy budget model chemostat which has both carbon and nitrogen as currencies, and examine how the dual availability of these elements affects the growth of phytoplankton, trophic transfer to zooplankton, and the resulting stability of the chemostat ecosystem. Both species have two reserve pools to obtain a larger metabolic flexibility with respect to changing external environments. Mineral nitrogen and carbon form the base of the food chain, and they are supplied at a constant rate. In addition, the biota in the chemostat recycle nutrients by means of respiration and excretion, and organic detritus is recycled at a fixed rate. We use numerical bifurcation analysis to assess the model's dynamic behavior. In the model, phytoplankton is nitrogen limited, and nitrogen enrichment can lead to oscillations and multiple stable states. Moreover, we found that recycling has a destabilizing effect on the food chain due to the increased repletion of mineral nutrients. We found that both carbon and nitrogen enrichment stimulate zooplankton growth. Therefore, we conclude that the concept of single-element limitation may not be applicable in an ecosystem context.