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Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease.
Abdelhamid, AS, Brown, TJ, Brainard, JS, Biswas, P, Thorpe, GC, Moore, HJ, Deane, KH, AlAbdulghafoor, FK, Summerbell, CD, Worthington, HV, et al
The Cochrane database of systematic reviews. 2018;7:CD003177
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Dietary intake or supplementation with omega-3 fats from fish and some plant foods such as flaxseed, are commonly believed to reduce the risk of cardiovascular disease. This systematic review of 79 trials, including 112,000 individuals, aimed to assess the impacts of greater omega-3 intake versus lower or no omega-3 intake for heart and circulatory disease. The results of this systematic review showed that increasing EPA and DHA (omega-3 oils from fish) had little or no effect on all cause death or cardiovascular events and probably little or no effect on cardiovascular deaths (evidence mainly from supplement trials). EPA and DHA were found to reduce blood fat levels (triglycerides) and raise HDL (good cholesterol). Eating more ALA (omega-3 fats from walnuts for example) probably makes little or no difference to all-cause or cardiovascular death but probably slightly reduce cardiovascular events.
Abstract
BACKGROUND Researchers have suggested that omega-3 polyunsaturated fatty acids from oily fish (long-chain omega-3 (LCn3), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)), as well as from plants (alpha-linolenic acid (ALA)) benefit cardiovascular health. Guidelines recommend increasing omega-3-rich foods, and sometimes supplementation, but recent trials have not confirmed this. OBJECTIVES To assess effects of increased intake of fish- and plant-based omega-3 for all-cause mortality, cardiovascular (CVD) events, adiposity and lipids. SEARCH METHODS We searched CENTRAL, MEDLINE and Embase to April 2017, plus ClinicalTrials.gov and World Health Organization International Clinical Trials Registry to September 2016, with no language restrictions. We handsearched systematic review references and bibliographies and contacted authors. SELECTION CRITERIA We included randomised controlled trials (RCTs) that lasted at least 12 months and compared supplementation and/or advice to increase LCn3 or ALA intake versus usual or lower intake. DATA COLLECTION AND ANALYSIS Two review authors independently assessed studies for inclusion, extracted data and assessed validity. We performed separate random-effects meta-analysis for ALA and LCn3 interventions, and assessed dose-response relationships through meta-regression. MAIN RESULTS We included 79 RCTs (112,059 participants) in this review update and found that 25 were at low summary risk of bias. Trials were of 12 to 72 months' duration and included adults at varying cardiovascular risk, mainly in high-income countries. Most studies assessed LCn3 supplementation with capsules, but some used LCn3- or ALA-rich or enriched foods or dietary advice compared to placebo or usual diet.Meta-analysis and sensitivity analyses suggested little or no effect of increasing LCn3 on all-cause mortality (RR 0.98, 95% CI 0.90 to 1.03, 92,653 participants; 8189 deaths in 39 trials, high-quality evidence), cardiovascular mortality (RR 0.95, 95% CI 0.87 to 1.03, 67,772 participants; 4544 CVD deaths in 25 RCTs), cardiovascular events (RR 0.99, 95% CI 0.94 to 1.04, 90,378 participants; 14,737 people experienced events in 38 trials, high-quality evidence), coronary heart disease (CHD) mortality (RR 0.93, 95% CI 0.79 to 1.09, 73,491 participants; 1596 CHD deaths in 21 RCTs), stroke (RR 1.06, 95% CI 0.96 to 1.16, 89,358 participants; 1822 strokes in 28 trials) or arrhythmia (RR 0.97, 95% CI 0.90 to 1.05, 53,796 participants; 3788 people experienced arrhythmia in 28 RCTs). There was a suggestion that LCn3 reduced CHD events (RR 0.93, 95% CI 0.88 to 0.97, 84,301 participants; 5469 people experienced CHD events in 28 RCTs); however, this was not maintained in sensitivity analyses - LCn3 probably makes little or no difference to CHD event risk. All evidence was of moderate GRADE quality, except as noted.Increasing ALA intake probably makes little or no difference to all-cause mortality (RR 1.01, 95% CI 0.84 to 1.20, 19,327 participants; 459 deaths, 5 RCTs),cardiovascular mortality (RR 0.96, 95% CI 0.74 to 1.25, 18,619 participants; 219 cardiovascular deaths, 4 RCTs), and it may make little or no difference to CHD events (RR 1.00, 95% CI 0.80 to 1.22, 19,061 participants, 397 CHD events, 4 RCTs, low-quality evidence). However, increased ALA may slightly reduce risk of cardiovascular events (from 4.8% to 4.7%, RR 0.95, 95% CI 0.83 to 1.07, 19,327 participants; 884 CVD events, 5 RCTs, low-quality evidence), and probably reduces risk of CHD mortality (1.1% to 1.0%, RR 0.95, 95% CI 0.72 to 1.26, 18,353 participants; 193 CHD deaths, 3 RCTs), and arrhythmia (3.3% to 2.6%, RR 0.79, 95% CI 0.57 to 1.10, 4,837 participants; 141 events, 1 RCT). Effects on stroke are unclear.Sensitivity analysis retaining only trials at low summary risk of bias moved effect sizes towards the null (RR 1.0) for all LCn3 primary outcomes except arrhythmias, but for most ALA outcomes, effect sizes moved to suggest protection. LCn3 funnel plots suggested that adding in missing studies/results would move effect sizes towards null for most primary outcomes. There were no dose or duration effects in subgrouping or meta-regression.There was no evidence that increasing LCn3 or ALA altered serious adverse events, adiposity or lipids, although LCn3 slightly reduced triglycerides and increased HDL. ALA probably reduces HDL (high- or moderate-quality evidence). AUTHORS' CONCLUSIONS This is the most extensive systematic assessment of effects of omega-3 fats on cardiovascular health to date. Moderate- and high-quality evidence suggests that increasing EPA and DHA has little or no effect on mortality or cardiovascular health (evidence mainly from supplement trials). Previous suggestions of benefits from EPA and DHA supplements appear to spring from trials with higher risk of bias. Low-quality evidence suggests ALA may slightly reduce CVD event risk, CHD mortality and arrhythmia.
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Resistance Training Prevents Muscle Loss Induced by Caloric Restriction in Obese Elderly Individuals: A Systematic Review and Meta-Analysis.
Sardeli, AV, Komatsu, TR, Mori, MA, Gáspari, AF, Chacon-Mikahil, MPT
Nutrients. 2018;10(4)
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Caloric restriction (55% carbohydrate, 15% protein, 30% fat) is associated with increased lifespans and the attenuation of the harmful effects of aging. Furthermore, it has been shown that resistance training increases lean body mass, promotes strength, and attenuates muscle loss and function in elderly people. The aim of the study is to determine the level of lean body mass that can be preserved when resistance training is associated with caloric restriction interventions in elderly obese humans. The study is a meta-analysis, based on data from randomised-controlled trials. The participants were older adults or elderly people with a mean age > 57 year. Results indicate that caloric restriction associated with resistance training prevents 93% lean body mass loss induced by caloric restriction. Authors conclude that caloric restriction with resistance training almost stopped caloric restriction induced lean body mass loss completely.
Abstract
It remains unclear as to what extent resistance training (RT) can attenuate muscle loss during caloric restriction (CR) interventions in humans. The objective here is to address if RT could attenuate muscle loss induced by CR in obese elderly individuals, through summarized effects of previous studies. Databases MEDLINE, Embase and Web of Science were used to perform a systematic search between July and August 2017. Were included in the review randomized clinical trials (RCT) comparing the effects of CR with (CRRT) or without RT on lean body mass (LBM), fat body mass (FBM), and total body mass (BM), measured by dual-energy X-ray absorptiometry, on obese elderly individuals. The six RCTs included in the review applied RT three times per week, for 12 to 24 weeks, and most CR interventions followed diets of 55% carbohydrate, 15% protein, and 30% fat. RT reduced 93.5% of CR-induced LBM loss (0.819 kg [0.364 to 1.273]), with similar reduction in FBM and BM, compared with CR. Furthermore, to address muscle quality, the change in strength/LBM ratio tended to be different (p = 0.07) following CRRT (20.9 ± 23.1%) and CR interventions (−7.5 ± 9.9%). Our conclusion is that CRRT is able to prevent almost 100% of CR-induced muscle loss, while resulting in FBM and BM reductions that do not significantly differ from CR.
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Effectiveness and safety of carbohydrate counting in the management of adult patients with type 1 diabetes mellitus: a systematic review and meta-analysis.
Vaz, EC, Porfírio, GJM, Nunes, HRC, Nunes-Nogueira, VDS
Archives of endocrinology and metabolism. 2018;62(3):337-345
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Glycaemic control of patients with diabetes mellitus is important because it impacts the development of diabetic complications. Carbohydrate counting is a meal planning tool that allows for great variation and flexibility in food choices among individuals with diabetes mellitus. The aim of the study was to evaluate the effectiveness and safety of carbohydrate counting in the treatment of adult patients with type 1 diabetes mellitus using a systematic literature review. The study included randomised controlled trials with at least 3 months of follow-up, and evaluation of outcomes in which patients were randomly divided into two groups. The meta-analysis showed that the final haemoglobin A1c (HbA1c) - a test that shows the average blood glucose levels for the last two to three months - was significantly lower in the carbohydrate counting group than in the control group. Authors conclude that the meta-analysis showed evidence favouring the use of carbohydrate counting in the management of adult patients with type 1 diabetes mellitus. However, this benefit was limited to the final HbA1c.
Abstract
OBJECTIVE This study aimed to evaluate the effectiveness and safety of carbohydrate counting (CHOC) in the treatment of adult patients with type 1 diabetes mellitus (DM1). MATERIALS AND METHODS We performed a systematic review of randomized studies that compared CHOC with general dietary advice in adult patients with DM1. The primary outcomes were changes in glycated hemoglobin (HbA1c), quality of life, and episodes of severe hypoglycemia. We searched the following electronic databases: Embase, PubMed, Lilacs, and the Cochrane Central Register of Controlled Trials. The quality of evidence was analyzed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE). RESULTS A total of 3,190 articles were identified, and two reviewers independently screened the titles and abstracts. From the 15 potentially eligible studies, five were included, and 10 were excluded because of the lack of randomization or different control/intervention groups. Meta-analysis showed that the final HbA1c was significantly lower in the CHOC group than in the control group (mean difference, random, 95% CI: -0.49 (-0.85, -0.13), p = 0.006). The meta-analysis of severe hypoglycemia and quality of life did not show any significant differences between the groups. According to the GRADE, the quality of evidence for severe hypoglycemia, quality of life, and change in HbA1c was low, very low, and moderate, respectively. CONCLUSION The meta-analysis showed evidence favoring the use of CHOC in the management of DM1. However, this benefit was limited to final HbA1c, which was significantly lower in the CHOC than in the control group.
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Low-carbohydrate diets for type 1 diabetes mellitus: A systematic review.
Turton, JL, Raab, R, Rooney, KB
PloS one. 2018;13(3):e0194987
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Type 1 diabetes is an autoimmune condition that affects the ability to produce insulin, the hormone that regulates blood sugar levels. Patients with Type 1 diabetes manage their condition with daily insulin injections or patches, and the standard dietary advice is to continue to eat a normal diet, and adjust the insulin dose to keep blood sugar under control. This systematic review of 9 studies of varying types, aimed to examine the effects of low-carbohydrate diets on type 1 diabetes management. 8 of the studies reported a change in HbA1c (the blood marker used to assess long-term blood sugar management); 3 of these reported statistically significant reductions. 2 studies reported statistically significant reductions in daily insulin use whilst following a low-carbohydrate diet. The study authors were unable to conclude an overall effect due to the differences in design and methods used in the 9 studies included. They call for more primary research to be conducted.
Abstract
Type 1 diabetes is an autoimmune condition characterised by pancreatic beta cell destruction and absolute insulin deficiency. The strongest predictor of diabetes complications is glycaemic control and achieving HbA1c ≤ 7.0% is the primary management target. However, standard treatment appears to be lacking and adjunctive strategies require consideration. A systematic review was conducted to examine the effect of low-carbohydrate diets on type 1 diabetes management. Four databases were searched from inception until 28 March 2017: MEDLINE; CINAHL; Cochrane Library; and EMBASE. All primary studies containing a methods section (excluding cross-sectional) were included. Reports had to quantitatively measure the effect(s) of a dietary intervention or observed intake over at least two weeks where carbohydrate is below 45% total energy in adults and/or children with type 1 diabetes. The primary outcome was HbA1c and secondary outcomes were severe hypoglycaemia, total daily insulin, BMI, quality of life and mean daily glucose. Seventy-nine full-text articles were assessed for eligibility and nine were included (two randomised controlled trials, four pre-post interventions, two case-series, one case-report). Eight studies reported a mean change in HbA1c with a low-carbohydrate diet. Of these, four reported a non-significant change (P ≥ 0.05) and three reported statistically significant reductions (P < 0.05). Two studies reported severe hypoglycaemia, five reported total insulin, three reported BMI, and one reported blood glucose. Due to the significant heterogeneity of included studies, an overall effect could not be determined. This review presents all available evidence on low-carbohydrate diets for type 1 diabetes and suggests an urgent need for more primary studies.
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Bariatric Surgery and Precision Nutrition.
Nicoletti, CF, Cortes-Oliveira, C, Pinhel, MAS, Nonino, CB
Nutrients. 2017;9(9)
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Bariatric surgery, including gastric bypass, is the most effective strategy to treat obesity and the associated health complications. The major goal is long-term excess body weight reduction, but weight gain after time does occur in a proportion of patients. There is a wide range of responses to bariatric surgery; the different surgical techniques and genetic background of the individual patient account for this. The interactions between nutrients and genes are complex and have not been fully elucidated. This paper summarises the main literature findings relating nutritional genomics and bariatric surgery. It also describes the importance of nutritional genomics concepts in personalized bariatric management. Points discussed are: The genetic variations associated with obesity and telemore length (a marker for cellular ageing). How bariatric surgery affects epigenetics and the expression of various genes involved in different metabolic pathways. The role of bariatric surgery on gut microbiota. The authors believe that nutritional genomics will soon enable the delivery of precise nutrition recommendations to patients undergoing bariatric surgery, to provide high-risk individuals with personalized treatment and to prevent complications.
Abstract
This review provides a literature overview of new findings relating nutritional genomics and bariatric surgery. It also describes the importance of nutritional genomics concepts in personalized bariatric management. It includes a discussion of the potential role bariatric surgery plays in altering the three pillars of nutritional genomics: nutrigenetics, nutrigenomics, and epigenetics. We present studies that show the effect of each patient's genetic and epigenetic variables on the response to surgical weight loss treatment. We include investigations that demonstrate the association of single nucleotide polymorphisms with obesity phenotypes and their influence on weight loss after bariatric surgery. We also present reports on how significant weight loss induced by bariatric surgery impacts telomere length, and we discuss studies on the existence of an epigenetic signature associated with surgery outcomes and specific gene methylation profile, which may help to predict weight loss after a surgical procedure. Finally, we show articles which evidence that bariatric surgery may affect expression of numerous genes involved in different metabolic pathways and consequently induce functional and taxonomic changes in gut microbial communities. The role nutritional genomics plays in responses to weight loss after bariatric surgery is evident. Better understanding of the molecular pathways involved in this process is necessary for successful weight management and maintenance.
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Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.
Martineau, AR, Jolliffe, DA, Hooper, RL, Greenberg, L, Aloia, JF, Bergman, P, Dubnov-Raz, G, Esposito, S, Ganmaa, D, Ginde, AA, et al
BMJ (Clinical research ed.). 2017;356:i6583
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Acute respiratory tract infections are responsible for more than 2.5 million deaths worldwide. Previous studies report consistent associations between low vitamin D levels and an increased risk of acute respiratory tract infection. Vitamin D may protect against respiratory pathogens of viral and bacterial origin, due to antimicrobial and other mechanisms. This paper is a systematic review and meta-analysis of 25 randomised double-blind placebo controlled trials of vitamin D supplementation for the prevention of acute respiratory tract infection. The trials were conducted in 14 countries in 4 continents and included a total of 11,321 participants of both sexes, aged 0-95 years. The follow-up durations ranged from seven weeks to 1.5 years. All studies administered vitamin D3 orally, using either daily or weekly doses or bolus doses 1-3 months apart, or combined daily and bolus doses. Individual participant data were obtained from 96.6% of participants. The majority of studies that were included in the analyses were considered to be of a high quality, with a low risk of bias. The analyses showed that vitamin D supplementation reduced the risk of acute respiratory tract infections among all participants. The strongest positive effects were seen in those with baseline vitamin D levels less than 25 nmol/l, when compared to those with levels higher than 25 nmol/l, although benefits were also seen in the latter. Furthermore, daily or weekly vitamin D supplementation, without additional bolus doses were shown to protect against acute respiratory tract infections, while regimens with large bolus doses did not. The authors concluded that people who are very deficient in vitamin D are most likely to benefit from daily or weekly vitamin D supplementation, without additional bolus doses, in the prevention of acute respiratory tract infections. They call for the introduction of public health measures, such as food fortification, to improve vitamin D status, particularly in settings where vitamin D deficiency is common.
Abstract
Objectives To assess the overall effect of vitamin D supplementation on risk of acute respiratory tract infection, and to identify factors modifying this effect.Design Systematic review and meta-analysis of individual participant data (IPD) from randomised controlled trials.Data sources Medline, Embase, the Cochrane Central Register of Controlled Trials, Web of Science, ClinicalTrials.gov, and the International Standard Randomised Controlled Trials Number registry from inception to December 2015.Eligibility criteria for study selection Randomised, double blind, placebo controlled trials of supplementation with vitamin D3 or vitamin D2 of any duration were eligible for inclusion if they had been approved by a research ethics committee and if data on incidence of acute respiratory tract infection were collected prospectively and prespecified as an efficacy outcome.Results 25 eligible randomised controlled trials (total 11 321 participants, aged 0 to 95 years) were identified. IPD were obtained for 10 933 (96.6%) participants. Vitamin D supplementation reduced the risk of acute respiratory tract infection among all participants (adjusted odds ratio 0.88, 95% confidence interval 0.81 to 0.96; P for heterogeneity <0.001). In subgroup analysis, protective effects were seen in those receiving daily or weekly vitamin D without additional bolus doses (adjusted odds ratio 0.81, 0.72 to 0.91) but not in those receiving one or more bolus doses (adjusted odds ratio 0.97, 0.86 to 1.10; P for interaction=0.05). Among those receiving daily or weekly vitamin D, protective effects were stronger in those with baseline 25-hydroxyvitamin D levels <25 nmol/L (adjusted odds ratio 0.30, 0.17 to 0.53) than in those with baseline 25-hydroxyvitamin D levels ≥25 nmol/L (adjusted odds ratio 0.75, 0.60 to 0.95; P for interaction=0.006). Vitamin D did not influence the proportion of participants experiencing at least one serious adverse event (adjusted odds ratio 0.98, 0.80 to 1.20, P=0.83). The body of evidence contributing to these analyses was assessed as being of high quality.Conclusions Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall. Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.Systematic review registration PROSPERO CRD42014013953.
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Diet Behavior Change Techniques in Type 2 Diabetes: A Systematic Review and Meta-analysis.
Cradock, KA, ÓLaighin, G, Finucane, FM, McKay, R, Quinlan, LR, Martin Ginis, KA, Gainforth, HL
Diabetes care. 2017;40(12):1800-1810
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Dietary behaviour is intrinsically linked to type 2 diabetes. Dietary factors have been linked to the highest proportion of deaths in type 2 diabetes, stroke, and heart disease. Identifying effective ways to help suffers successfully change to more effective dietary behaviours may help condition management and reduce disease progression. The objective of the systemic review and meta-analysis was to identify dietary behaviour change techniques, intervention features, and specific diets associated with changes in blood glucose levels (HbA1c) and body weight in type 2 diabetes. It included 54 studies, all of whose participants have type 2 diabetes. High-protein diets and meal replacement programs produced the greatest reductions in blood glucose (measured by HbA1c). Behavioural change techniques including 'problem solving,' 'feedback on behaviour,' 'adding objects to the environment' and 'social comparison' as well as interventions that were build on behavioural change theory were associated with clinically significant reductions in blood glucose as measured by HbA1c (a reduction of ≥0.3% (3.3 mmol/mol). However, the findings show that changing or controlling (e.g. providing all food) dietary environmental factors may be more effective than strategies to change dietary behaviour to reduce blood glucose levels in adults with type 2 diabetes. The authors conclude that changing the dietary environment may be more important than focusing on dietary behaviour in type 2 diabetes treatment.
Abstract
OBJECTIVE Dietary behavior is closely connected to type 2 diabetes. The purpose of this meta-analysis was to identify behavior change techniques (BCTs) and specific components of dietary interventions for patients with type 2 diabetes associated with changes in HbA1c and body weight. RESEARCH DESIGN AND METHODS The Cochrane Library, CINAHL, Embase, PubMed, PsycINFO, and Scopus databases were searched. Reports of randomized controlled trials published during 1975-2017 that focused on changing dietary behavior were selected, and methodological rigor, use of BCTs, and fidelity and intervention features were evaluated. RESULTS In total, 54 studies were included, with 42 different BCTs applied and an average of 7 BCTs used per study. Four BCTs-"problem solving," "feedback on behavior," "adding objects to the environment," and "social comparison"-and the intervention feature "use of theory" were associated with >0.3% (3.3 mmol/mol) reduction in HbA1c. Meta-analysis revealed that studies that aimed to control or change the environment showed a greater reduction in HbA1c of 0.5% (5.5 mmol/mol) (95% CI -0.65, -0.34), compared with 0.32% (3.5 mmol/mol) (95% CI -0.40, -0.23) for studies that aimed to change behavior. Limitations of our study were the heterogeneity of dietary interventions and poor quality of reporting of BCTs. CONCLUSIONS This study provides evidence that changing the dietary environment may have more of an effect on HbA1c in adults with type 2 diabetes than changing dietary behavior. Diet interventions achieved clinically significant reductions in HbA1c, although initial reductions in body weight diminished over time. If appropriate BCTs and theory are applied, dietary interventions may result in better glucose control.
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Could gestational diabetes mellitus be managed through dietary bioactive compounds? Current knowledge and future perspectives.
Santangelo, C, Zicari, A, Mandosi, E, Scazzocchio, B, Mari, E, Morano, S, Masella, R
The British journal of nutrition. 2016;115(7):1129-44
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Gestational diabetes mellitus (GDM) is the most common metabolic disorder during pregnancy. Women with GDM are at a high risk of developing type 2 diabetes (T2D) later in life. Moreover, uncontrolled GDM is linked with a detrimental intra-uterine environment, which leads to foetal complications and an increased risk for the child of developing obesity and metabolic disorders. The aim of the review is to examine the current knowledge and issues about the impact of dietary polyphenols on the mechanisms and/or factors regulating glucose homeostasis, inflammation and adipose tissue function in metabolic alterations linked with GDM. Moreover, this study also reviews the role of Omega-3 fatty acids in pregnancy. The study is a descriptive review based on several studies. Literature data is mainly derived from in vitro and animal models. In vitro and animal studies show that almost all subclasses of flavonoids, stilbene RSV and some olive oil phenolic compounds, interact and modulate several molecular pathways regulating insulin. Obesity worsens GDM with increased risk of developing metabolic disorders in both mother and offspring later in life. The adoption of healthy lifestyle, with adherence to a healthy dietary pattern, has positive effects on the prevention and management of diabetes.
Abstract
Gestational diabetes mellitus (GDM) is a serious problem growing worldwide that needs to be addressed with urgency in consideration of the resulting severe complications for both mother and fetus. Growing evidence indicates that a healthy diet rich in fruit, vegetables, nuts, extra-virgin olive oil and fish has beneficial effects in both the prevention and management of several human diseases and metabolic disorders. In this review, we discuss the latest data concerning the effects of dietary bioactive compounds such as polyphenols and PUFA on the molecular mechanisms regulating glucose homoeostasis. Several studies, mostly based on in vitro and animal models, indicate that dietary polyphenols, mainly flavonoids, positively modulate the insulin signalling pathway by attenuating hyperglycaemia and insulin resistance, reducing inflammatory adipokines, and modifying microRNA (miRNA) profiles. Very few data about the influence of dietary exposure on GDM outcomes are available, although this approach deserves careful consideration. Further investigation, which includes exploring the 'omics' world, is needed to better understand the complex interaction between dietary compounds and GDM.
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The microbiome: A key regulator of stress and neuroinflammation.
Rea, K, Dinan, TG, Cryan, JF
Neurobiology of stress. 2016;4:23-33
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This study discusses the concept of intestinal microbiota as the key regulator involved in energy regulation, gut barrier function, protection from pathogens, and immune system function amongst others. The gut microbiota is the complex community of microorganisms that lives in the digestive tracts of humans. The main aim of this study is to summarise the role of gastrointestinal microbiota in fundamental physiological and pathophysiological processes and thereafter to understand and treat a range of stress and immune-related disorders. This review outlines the numerous complex relationships between gastrointestinal microbiota, stress and immune responses at the three critical stages of life The authors concluded that the evidence from this study suggests that resilience to stress and immune-related disorders and dysfunction of stress and immune systems may be dependent on the diversity and complexity of gastrointestinal microbiota. However, gut microbiota mediated relationship to stress and neuro-inflammation is still unconfirmed as previous studies mostly, have largely been, preclinical and further studies are warranted.
Abstract
There is a growing emphasis on the relationship between the complexity and diversity of the microorganisms that inhabit our gut (human gastrointestinal microbiota) and health/disease, including brain health and disorders of the central nervous system. The microbiota-gut-brain axis is a dynamic matrix of tissues and organs including the brain, glands, gut, immune cells and gastrointestinal microbiota that communicate in a complex multidirectional manner to maintain homeostasis. Changes in this environment can lead to a broad spectrum of physiological and behavioural effects including hypothalamic-pituitary-adrenal (HPA) axis activation, and altered activity of neurotransmitter systems and immune function. While an appropriate, co-ordinated physiological response, such as an immune or stress response are necessary for survival, a dysfunctional response can be detrimental to the host contributing to the development of a number of CNS disorders. In this review, the involvement of the gastrointestinal microbiota in stress-mediated and immune-mediated modulation of neuroendocrine, immune and neurotransmitter systems and the consequential behaviour is considered. We also focus on the mechanisms by which commensal gut microbiota can regulate neuroinflammation and further aim to exploit our understanding of their role in stress-related disorders as a consequence of neuroinflammatory processes.
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Effect of Flavonoids on Upper Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis.
Somerville, VS, Braakhuis, AJ, Hopkins, WG
Advances in nutrition (Bethesda, Md.). 2016;7(3):488-97
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Upper respiratory tract infections (URTIs) are common and include sinusitis, tonsillitis, pharyngitis, otitis media, laryngitis, and the “common cold”. More than 90% of URTIs are cause by viruses. Flavonoids are found in many plant foods and have a range of physiologic effects in humans, including antiviral, anti-inflammatory, cytotoxic, antimicrobial, and antioxidant. The purpose of this systematic review and meta-analysis of 14 randomised controlled trials was to investigate the efficacy of flavonoids on URTIs and immune function. The authors found that flavonoids decrease URTI incidence by 33% compared with controls with no increase in adverse effects. There was also a non-significant decrease in URTI severity and duration with the flavonoid intervention. The meta-analysis demonstrated that differences between flavonoids and control for all immune biomarkers were clinically irrelevant. The authors therefore suggest that flavonoids do not attenuate URTI incidence by altering immune function but by an antiviral mechanism. They call for further research to establish the optimal dose and type of flavonoids.
Abstract
Previous research on animals indicates flavonoid compounds have immunomodulatory properties; however, human research remains inconclusive. The aim of this systematic review was to assess the efficacy of dietary flavonoids on upper respiratory tract infections (URTIs) and immune function in healthy adults. A created search strategy was run against Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE and EMBASE classic, CINAHL, and AMED. The returned studies were initially screened, and 2 reviewers independently assessed the remaining studies for eligibility against prespecified criteria. Fourteen studies, of 387 initially identified, were included in this review, and the primary outcome measure was the effect of flavonoids on URTI incidence, duration, and severity. Of the included studies, flavonoid supplementation ranged from 0.2 to 1.2 g/d. Overall, flavonoid supplementation decreased URTI incidence by 33% (95% CI: 31%, 36%) compared with control, with no apparent adverse effects. Sick-day count was decreased by 40% with flavonoid supplementation, although unclear. Differences in bio-immune markers (e.g., interleukin-6, tumor necrosis factor-α, interferon-γ, neutrophils) were trivial between the intervention and control groups during the intervention and after exercise when a postintervention exercise bout was included. These findings suggest that flavonoids are a viable supplement to decrease URTI incidence in an otherwise healthy population.