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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., (Copyright © 2018 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.)

A low vitamin D status could be a concern not only in children and the elderly in Europe, but also in adults. We do not know the effect of mild vitamin D deficiency on bone in this age group. The aim of this study was to detect the prevalence of low serum 25-hydroxyvitamin D [S-25(OH)D] and elevated serum intact parathyroid hormone (S-iPTH) concentrations in healthy young adults in the winter in northern Europe and to characterize the determinants of these variables. In addition, we studied the association between vitamin D status and forearm bone mineral density (BMD) in this population group. Three hundred and twenty-eight healthy adults (202 women and 126 men, 31-43 years) from southern Finland (60 degrees N) participated in this study conducted in February through March 1998. Fasting overnight blood samples were collected in the morning. Forearm BMD was measured by dual-energy X-ray absorptiometry (DXA). The mean daily vitamin D intake met the recommendations in the men (5.6 +/- 3.2 microg) and almost met it in the women (4.7 +/- 2.5 microg). The mean S-25(OH)D concentrations did not differ between genders (women, 47 +/- 34 nM; men, 45 +/- 35 nM; mean +/- SD), but the women had significantly higher mean S-iPTH levels than the men (women, 30 +/- 13 ng/liter; men, 24 +/- 12 ng/liter; p < 0.001). Low S-25(OH)D concentrations (<25 nM) were found in 26.2% of the women (53 women) and 28.6% of the men (36 men), respectively. Based on nonlinear regression analysis between S-25(OH)D and S-iPTH concentration, the S-iPTH concentration started to increase with S-25(OH)D concentrations lower than approximately 80 nM in the women and lower than approximately 40 nM in the men. Based on this relation between S-25(OH)D and S-iPTH concentrations, 86% of the women and 56% of the men had an insufficient vitamin D status. In linear regression analysis, the main positive determinants of S-25(OH)D were dietary vitamin D intake (p < 0.02), the use of supplements (p < 0.005), alcohol intake (p < 0.05), and age (p < 0.005). Smoking associated negatively with the S-25(OH)D concentration (p < 0.03). The main determinants of S-iPTH were S-25(OH)D (p < 0.01), dietary calcium intake (p < 0.02), and body mass index (BMI; p < 0.01). In addition, female gender was associated with higher S-iPTH concentration. The mean daily dietary calcium intake was 1,037 +/- 489 mg and 962 +/- 423 mg, in the men and women, respectively. Significantly lower forearm BMD was found in the men (p = 0.01) but not in the women (p = 0.14) with higher S-iPTH concentrations. Low vitamin D status was prevalent in these young adults in northern Europe in winter, although the vitamin D intake met the recommendation. This probably is not a local problem for northern Europe, because the natural sources of vitamin D are scarce and fortification is not very common in Europe, and with the exception of the southern part of Europe, sunshine is not very abundant in this part of the world. Thus, the results of this study indicate that more attention should be focused on vitamin D status and the sources of vitamin D in these countries.