Identifying sources of measurement error in assessing dietary intakes - Results of a multi-country ring-trial.

BACKGROUND AND AIMS: Epidemiological investigations include dietary intakes as primary exposures or potential confounders. To reduce bias, data collection protocols include the administration of questionnaires together with measurements of biomarkers. Some error, however, remains and needs to be considered in the analysis and interpretation of results. The European Food Safety Authority supported a ring-trial to compare the precision and reproducibility of dietary assessment methods applied in Europe. METHODS AND RESULTS: Software applications used to collect 24-hour recalls and food records in six countries (Estonia, Italy, Latvia, Portugal, Spain, and Sweden) were assessed. The intake of 256 foods was identically reported to each method. Experienced interviewers participated and were instructed to repeat national protocols closely. The error in recording quantities, compared with reference values, was variable but in about 60% of recorded quantities was in the range of ±20%. Errors were however unsystematic and independent of the food type or quantification method used - although food pictures performed better. The reproducibility of some tools was limited. The methods generally captured additional ingredients (usually flavoring agents), but not sweetening agents or fortification and failed to record packaging information in about 60% of the cases. CONCLUSION: In a design that eliminated respondent bias, this study indicates that softwares, supporting databases and interviewers generally introduce random error in dietary assessments. The inclusion of large sample sizes and food pictures to quantify portions, together with enhanced attention on interviewers' training, standardisation of procedures and regular tool upgrades are essential in assuring a study's quality and comparability.

Leptin administration in physiological or pharmacological doses does not alter circulating irisin levels in humans.

Leptin is an adipokine causing browning of adipose tissue, and it thus increases energy expenditure. The same is true for irisin. We studied whether exogenously administered metreleptin affects serum irisin concentrations in humans, which would suggest a direct interplay between leptin and irisin. We performed two studies: a dose-escalating 1-day-long study and a randomized placebo-controlled study. Study 1: 15 healthy, normal-weight and/or obese male and female individuals participated in three 1-day-long trials of metreleptin administration in the fed state. Metreleptin was administered once at physiological and pharmacological (0.01, 0.1 and 0.3 mg per kg body weight) doses. Study 2: 18 apparently healthy hypoleptinemic young women with hypoleptinemia and secondary amenorrhea took part in this study. Subjects received either metreleptin in replacement doses (0.08 and/or 0.12 mg kg(-1)) or placebo for 16 weeks. Blood samples were analyzed for leptin and irisin. We found no effect of metreleptin administration on irisin levels of subjects studied at either the fasting or the fed state either in the short or the long term. We provide evidence that leptin is not altering circulating irisin levels in humans.

Effect of different amounts of coffee on dietary intake and appetite of normal-weight and overweight/obese individuals.

OBJECTIVE: To investigate the effects of different coffee amounts on dietary intake and appetite feelings in normal-weight and overweight/obese individuals. DESIGN AND METHODS: Thirty-three volunteers (16 normal-weight, 17 overweight/obese) participated in three trials: they consumed a standard breakfast along with 200 ml of either coffee with 3 or 6 mg caffeine/kg body weight (Coffee 3 and Coffee 6, respectively), or water. At fasting and at standard time points for the 3 h following breakfast/drink consumption participants recorded their appetite feelings on visual analogue scales. At 180 min, participants consumed an ad libitum meal and the next day they recalled their food intake during the experimental day. RESULTS: A significant intervention effect was found for the energy intake of the ad libitum meal (P = 0.05) and of the whole day (P = 0.02) only in overweight/obese individuals. Specifically, Coffee 6 resulted in a reduced energy intake during the ad libitum meal compared to Coffee 3 (P = 0.03) and in the total day compared to both water (P = 0.04) and Coffee 3 (P = 0.008). No effect was observed for the appetite feelings. CONCLUSIONS: A moderate coffee amount can effectively reduce energy intake in the following meal and in the total day compared to lower or no coffee intake in overweight/obese participants.