Little is known about the impact of habitual fluid intake on physiology. Specifically, biomarkers of hydration status and body water regulation have not been adequately explored in adults who consume different fluid volumes in everyday conditions, without prolonged exercise or environmental exposure. The purpose of the present study was to compare adults with habitually different fluid intakes with respect to biomarkers implicated in the assessment of hydration status, the regulation of total body water and the risk of kidney pathologies. In the present cross-sectional study, seventy-one adults (thirty-two men, thirty-nine women, age 25–40 years) were classified according to daily fluid intake: thirty-nine low drinkers (LD; ≤ 1·2 litres/d) and thirty-two high drinkers (HD; 2–4 litres/d). During four consecutive days, urinary parameters (first morning urine (FMU) on day 1 and subsequent 24 h urine (24hU) collections), blood parameters, and food and beverage intake were assessed. ANOVA and non-parametric comparisons revealed significant differences between the LD and HD groups in 24hU volume (1·0 (se 0·1) v. 2·4 (se 0·1) litres), specific gravity (median 1·023 v. 1·010), osmolality (767 (se 27) v. 371 (se 33) mOsm/kg) and colour (3·1 (se 0·2) v. 1·8 (se 0·2)). Similarly, in the FMU, the LD group produced a smaller amount of more concentrated urine. Plasma cortisol, creatinine and arginine vasopressin concentrations were significantly higher among the LD. Plasma osmolality was similar between the groups, suggesting physiological adaptations to preserve plasma osmolality despite low fluid intake. The long-term impact of adaptations to preserve plasma osmolality must be examined, particularly in the context of renal health.

BACKGROUND/OBJECTIVES:In sedentary adults, hydration is mostly influenced by total fluid intake and not by sweat losses; moreover, low daily fluid intake is associated with adverse health outcomes. This study aimed to model the relation between total fluid intake and urinary hydration biomarkers. SUBJECTS/METHODS: During 4 consecutive weekdays, 82 adults (age, 31.6±4.3 years; body mass index, 23.2±2.7 kg/m 2 ; 52% female) recorded food and fluid consumed, collected one first morning urine (FMU) void and three 24-h (24hU) samples. The strength of linear association between urinary hydration biomarkers and fluid intake volume was evaluated using simple linear regression and Pearson's correlation. Multivariate partial least squares (PLS) modeled the association between fluid intake and 24hU hydration biomarkers. RESULTS: Strong associations (|r|X0.6; Po0.001) were found between total fluid intake volume and 24hU osmolality, color, specific gravity (USG), volume and solute concentrations. Many 24hU biomarkers were collinear (osmolality versus color: r ¼ 0.49-0.76; USG versus color: r ¼ 0.46-0.78; osmolality versus USG: 0.86-0.97; Po0.001). Measures in FMU were not strongly correlated to intake. Multivariate PLS and simple linear regression using urine volume explained 450% of the variance in fluid intake volume (r 2 ¼ 0.59 and 0.52, respectively); however the error in both models was high and the limits of agreement very large. CONCLUSIONS: Hydration biomarkers in 24hU are strongly correlated with daily total fluid intake volume in sedentary adults in free-living conditions; however, the margin of error in the present models limits the applicability of estimating fluid intake from urinary biomarkers.

Culture independent techniques, such as shotgun metagenomics and 16S rRNA amplicon sequencing have dramatically changed the way we can examine microbial communities. Recently, changes in microbial community structure and dynamics have been associated with a growing list of human diseases. The identification and comparison of bacteria driving those changes requires the development of sound statistical tools, especially if microbial biomarkers are to be used in a clinical setting. We present , a novel multivariate data analysis framework for metagenomic biomarker discovery. accounts for the compositional nature of 16S data and enables detection of subtle differences when high inter-subject variability is present due to microbial sampling performed repeatedly on the same subjects, but in multiple habitats. Through data dimension reduction the multivariate methods provide insightful graphical visualisations to characterise each type of environment in a detailed manner. We applied to 16S microbiome studies focusing on multiple body sites in healthy individuals, compared our results with existing statistical tools and illustrated added value of using multivariate methodologies to fully characterise and compare microbial communities.

The present study was conducted on aromatised fat-free stirred yoghurts and dealt with the influence of some thickeners andsweeteners on aroma compounds release and rheology.Thickeners (starch, pectin, locust bean gum and guar) and sweeteners (fructose, fructo-oligosaccahrides, aspartame andacesulfame) were added and mixed together in fruit preparations, which were then introduced in yoghurt. Different concentrationsof thickeners and sweeteners were used in the fruit preparations and were obtained with an experimental design. The headspacecomposition was assessed by solid-phase microextraction during shear conditions in a closed vessel. Rheological properties ofyoghurts were determined to obtain the flow behaviour index n and the consistency index K with the Ostwald law.The presence of pectin in yoghurts, tended to reduce the concentration of aroma compounds in the headspace of the samples. Weobserved also a significant decrease of aroma compounds in the headspace of yoghurt in the presence of starch. In the case of locustbean gum, a significant increase of flavour release was observed. Sweeteners and guar appeared to have no effect. We concluded thatrheological parameters did not explain the difference on aroma release and it seemed that during shear conditions, the compositionof fruit preparations showed a major role on aroma release. The influence of aroma compounds characteristics on the flavour releasewas observed, but experiments must be performed to highlight this observation

The lactulose challenge test seems to be a promising tool to assess visceral sensitivity in IBS, and to subgroup IBS patients based on their symptom pattern.