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Under the classical long-span asymptotic framework, we develop a class of generalized laplace (GL) inference methods for the change-point dates in a linear time series regression model with multiple structural changes analyzed in, e.g., Bai and Perron (1998, Econometrica 66, 47–78). The GL estimator is defined by an integration rather than optimization-based method and relies on the LS criterion function. It is interpreted as a classical (non-Bayesian) estimator, and the inference methods proposed retain a frequentist interpretation. This approach provides a better approximation about the uncertainty in the data of the change-points relative to existing methods. On the theoretical side, depending on some input (smoothing) parameter, the class of GL estimators exhibits a dual limiting distribution, namely the classical shrinkage asymptotic distribution or a Bayes-type asymptotic distribution. We propose an inference method based on highest density regions using the latter distribution. We show that it has attractive theoretical properties not shared by the other popular alternatives, i.e., it is bet-proof. Simulations confirm that these theoretical properties translate to good finite-sample performance.
There is growing interest in understanding how diet can modulate the gut microbiota (GM), including its possible association with disease states. The aim of the present study is to compare in a group of subjects in primary prevention for cardiovascular disease (CVD) the effects of Mediterranean (MD) and Vegetarian (VD) dietary patterns on the GM composition and on the short-chain fatty acids (SCFA) production.
Materials and Methods
Twenty-three clinically healthy subjects (16 F; mean age: 58.6 ± 9.8 years) were randomly assigned to isocaloric MD or VD diets lasting 3-months each and then crossed. Anthropometric measurements, body composition, blood and fecal samples were obtained from each participant at the beginning and at the end of each intervention phase. Next Generation Sequencing (NGS) of 16S rRNA were performed to analyze the GM, while the SCFA were evaluated through the Gas Chromatography-Mass Spectrometry system.
Dietary interventions didn't produce significant diversity in the GM composition at higher ranks (family and above), neither between nor within MD and VD, but they did it at genus level. MD significantly changed the abundance of three genera (Enterohabdus, Lachnoclostridium and Parabacteroides), while VD significantly affected the abundance of four genera (Anaerostipes, Streptococcus, Clostridium sensu stricto and Odoribacter). Comparison of the mean variation of each SCFA between MD and VD showed an opposite and statistically significant trend for propionic acid (+ 10% vs -28%, respectively, p = 0.034). In addition, variations of SCFA resulted to be negatively correlated with changes of some inflammatory cytokines such as VEGF, MCP-1, IL-17, IP-10 and IL-12, only after MD. Finally, correlation analyses showed several associations between changes of genera, clinical and biochemical parameters, after both the dietary interventions.
Our study indicates that a short-term dietary intervention with MD or VD does not induce major change in the GM, suggesting that a diet should last for longer periods to scratch the resilience of GM. In addition, the negative association between SCFA and a number of inflammatory cytokines reported only after MD, seems to support the anti-inflammatory properties of the MD. Furthermore, several associations between certain bacterial groups, clinical and biochemical parameters, let us hypothesized that the cardiovascular protection associated with the two diets could be due – at least in part – to a modulation of the GM.
The aim of the present study was to examine the effect of a replacement diet with organic, semi-whole-grain products derived from Triticum turgidum subsp. turanicum (ancient) wheat on irritable bowel syndrome (IBS) symptoms and inflammatory/biochemical parameters. A double-blinded randomised cross-over trial was performed using twenty participants (thirteen females and seven males, aged 18–59 years) classified as having moderate IBS. Participants received products (bread, pasta, biscuits and crackers) made either from ancient or modern wheat for 6 weeks in a random order. Symptoms due to IBS were evaluated using two questionnaires, which were compiled both at baseline and on a weekly basis during the intervention period. Blood analyses were carried out at the beginning and end of each respective intervention period. During the intervention period with ancient wheat products, patients experienced a significant decrease in the severity of IBS symptoms, such as abdominal pain (P< 0·0001), bloating (P= 0·004), satisfaction with stool consistency (P< 0·001) and tiredness (P< 0·0001). No significant difference was observed after the intervention period with modern wheat products. Similarly, patients reported significant amelioration in the severity of gastrointestinal symptoms only after the ancient wheat intervention period, as measured by the intensity of pain (P= 0·001), the frequency of pain (P< 0·0001), bloating (P< 0·0001), abdominal distension (P< 0·001) and the quality of life (P< 0·0001). Interestingly, the inflammatory profile showed a significant reduction in the circulating levels of pro-inflammatory cytokines, including IL-6, IL-17, interferon-γ, monocyte chemotactic protein-1 and vascular endothelial growth factor after the intervention period with ancient wheat products, but not after the control period. In conclusion, significant improvements in both IBS symptoms and the inflammatory profile were reported after the ingestion of ancient wheat products.
To update previous meta-analyses of cohort studies that investigated the association between the Mediterranean diet and health status and to utilize data coming from all of the cohort studies for proposing a literature-based adherence score to the Mediterranean diet.
We conducted a comprehensive literature search through all electronic databases up to June 2013.
Cohort prospective studies investigating adherence to the Mediterranean diet and health outcomes. Cut-off values of food groups used to compute the adherence score were obtained.
The updated search was performed in an overall population of 4 172 412 subjects, with eighteen recent studies that were not present in the previous meta-analyses.
A 2-point increase in adherence score to the Mediterranean diet was reported to determine an 8 % reduction of overall mortality (relative risk = 0·92; 95 % CI 0·91, 0·93), a 10 % reduced risk of CVD (relative risk = 0·90; 95 % CI 0·87, 0·92) and a 4 % reduction of neoplastic disease (relative risk = 0·96; 95 % CI 0·95, 0·97). We utilized data coming from all cohort studies available in the literature for proposing a literature-based adherence score. Such a score ranges from 0 (minimal adherence) to 18 (maximal adherence) points and includes three different categories of consumption for each food group composing the Mediterranean diet.
The Mediterranean diet was found to be a healthy dietary pattern in terms of morbidity and mortality. By using data from the cohort studies we proposed a literature-based adherence score that can represent an easy tool for the estimation of adherence to the Mediterranean diet also at the individual level.
Trans fatty acids are unsaturated fatty acids produced by the partial hydrogenation of polyunsaturated oils. Over the last few years, an increasing interest on these fatty acids has been shown because of their role in the pathogenesis of cardiovascular diseases. To date, major scientific associations strongly recommend consuming a low intake of trans fatty acids for the prevention of cardiovascular diseases, but data on the consumption of these fatty acids in the general population are still lacking. We conducted this observational study on a population of Italian teenagers in order to evaluate the consumption of trans fatty acids in the diet. We studied 81 Italian teenagers, 45 males and 36 females, with a median age of 16 years. To assess their consumption of trans fatty acids, we used the “High School Survey”, a questionnaire prepared by the Harvard Medical School. Total calories of the studied population were 2359.2 ± 591.5 kcal/day with a mean intake of trans fatty acids of 3.24 ± 1.48 g/day, corresponding to 1.23% of the total energy. A relevant proportion of subjects, namely 51 (62.9%), exceeded the limit contribution of 1% of energy from trans fatty acids. Their intake of total calories and trans fatty acids significantly increased according to their increasing age (p = 0.0003 for trend). Our data, therefore, obtained in a limited population of Italian adolescents, showed that a consistent proportion of adolescents does not follow the nutritional recommendations for intake of trans fatty acids, likely increasing their risk of cardiovascular diseases.
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