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Ultra-Processed Food Consumption and Mental Health: A Systematic Review and Meta-Analysis of Observational Studies.
Lane, MM, Gamage, E, Travica, N, Dissanayaka, T, Ashtree, DN, Gauci, S, Lotfaliany, M, O'Neil, A, Jacka, FN, Marx, W
Nutrients. 2022;14(13)
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Poor dietary quality is well established as a potentially modifiable risk factor for mental disorders. The NOVA food classification system was recently developed to enable the categorisation of food items based on distinctive levels of processing. The aim of this study was to synthesise and provide quantitative analyses of the most up-to-date evidence assessing associations between consumption of ultra-processed food, as defined by the NOVA food classification system, and mental disorders. This study is systematic review and meta-analysis of 17 studies with a total of 385,541 participants. The studies were 15 cross-sectional and 2 prospectively designed studies. Results show that ultra-processed food consumption is bidirectionally associated with adverse mental health. In fact, greater intake of ultra-processed food was associated with increased odds of depressive and anxiety symptoms, both when these outcomes were assessed together as well as separately. Authors conclude that further prospective and experimental studies are required to better determine directionality and causality and ensure that global preventative and treatment strategies are efficacious and appropriate.
Abstract
Since previous meta-analyses, which were limited only to depression and by a small number of studies available for inclusion at the time of publication, several additional studies have been published assessing the link between ultra-processed food consumption and depression as well as other mental disorders. We aimed to build on previously conducted reviews to synthesise and meta-analyse the contemporary evidence base and clarify the associations between the consumption of ultra-processed food and mental disorders. A total of 17 observational studies were included (n = 385,541); 15 cross-sectional and 2 prospective. Greater ultra-processed food consumption was cross-sectionally associated with increased odds of depressive and anxiety symptoms, both when these outcomes were assessed together (common mental disorder symptoms odds ratio: 1.53, 95%CI 1.43 to 1.63) as well as separately (depressive symptoms odds ratio: 1.44, 95%CI 1.14 to 1.82; and, anxiety symptoms odds ratio: 1.48, 95%CI 1.37 to 1.59). Furthermore, a meta-analysis of prospective studies demonstrated that greater ultra-processed food intake was associated with increased risk of subsequent depression (hazard ratio: 1.22, 95%CI 1.16 to 1.28). While we found evidence for associations between ultra-processed food consumption and adverse mental health, further rigorously designed prospective and experimental studies are needed to better understand causal pathways.
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The Clinical, Microbiological, and Immunological Effects of Probiotic Supplementation on Prevention and Treatment of Periodontal Diseases: A Systematic Review and Meta-Analysis.
Gheisary, Z, Mahmood, R, Harri Shivanantham, A, Liu, J, Lieffers, JRL, Papagerakis, P, Papagerakis, S
Nutrients. 2022;14(5)
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Periodontal disease is preventable and reversible in its early stages; however, it can progress to chronic, irreversible states with significant destruction of the tooth-supporting tissues. The cause of periodontal disease is multifactorial with modifiable risk factors, including smoking, unhealthy diet (e.g., a western diet with high sugars and saturated fats), poor oral hygiene, hormonal changes, stress, various medications, and poorly managed comorbidities (e.g., type 2 diabetes), while non-modifiable risk factors include age, sex, and genetics. The aim of this study was to assess the effects on the clinical, microbiological, and immunological outcomes related to periodontal disease prevention and management. This study is systematic review and meta-analysis of randomized clinical trials involving adults with periodontal diseases or healthy volunteers receiving probiotic supplementation (control groups did not receive probiotic supplementation). Results show that probiotic supplementation improved the clinical parameters, reduced the subgingival bacterial counts of specific periodontopathogens, and reduced the gingival crevicular fluid levels of some proinflammatory mediators in periodontal disease patients. Authors conclude that further research is required to better assess the therapeutic and preventive value of probiotic supplementation in patients with gingivitis (early disease), as well as in healthy (without periodontal disease) individuals.
Abstract
(1) Background: Periodontal diseases are a global health concern. They are multi-stage, progressive inflammatory diseases triggered by the inflammation of the gums in response to periodontopathogens and may lead to the destruction of tooth-supporting structures, tooth loss, and systemic health problems. This systematic review and meta-analysis evaluated the effects of probiotic supplementation on the prevention and treatment of periodontal disease based on the assessment of clinical, microbiological, and immunological outcomes. (2) Methods: This study was registered under PROSPERO (CRD42021249120). Six databases were searched: PubMed, MEDLINE, EMBASE, CINAHL, Web of Science, and Dentistry and Oral Science Source. The meta-analysis assessed the effects of probiotic supplementation on the prevention and treatment of periodontal diseases and reported them using Hedge's g standardized mean difference (SMD). (3) Results: Of the 1883 articles initially identified, 64 randomized clinical trials were included in this study. The results of this meta-analysis indicated statistically significant improvements after probiotic supplementation in the majority of the clinical outcomes in periodontal disease patients, including the plaque index (SMD = 0.557, 95% CI: 0.228, 0.885), gingival index, SMD = 0.920, 95% CI: 0.426, 1.414), probing pocket depth (SMD = 0.578, 95% CI: 0.365, 0.790), clinical attachment level (SMD = 0.413, 95% CI: 0.262, 0.563), bleeding on probing (SMD = 0.841, 95% CI: 0.479, 1.20), gingival crevicular fluid volume (SMD = 0.568, 95% CI: 0.235, 0.902), reduction in the subgingival periodontopathogen count of P. gingivalis (SMD = 0.402, 95% CI: 0.120, 0.685), F. nucleatum (SMD = 0.392, 95% CI: 0.127, 0.658), and T. forsythia (SMD = 0.341, 95% CI: 0.050, 0.633), and immunological markers MMP-8 (SMD = 0.819, 95% CI: 0.417, 1.221) and IL-6 (SMD = 0.361, 95% CI: 0.079, 0.644). (4) Conclusions: The results of this study suggest that probiotic supplementation improves clinical parameters, and reduces the periodontopathogen load and pro-inflammatory markers in periodontal disease patients. However, we were unable to assess the preventive role of probiotic supplementation due to the paucity of studies. Further clinical studies are needed to determine the efficacy of probiotic supplementation in the prevention of periodontal diseases.
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The Role of Diet Quality in Mediating the Association between Ultra-Processed Food Intake, Obesity and Health-Related Outcomes: A Review of Prospective Cohort Studies.
Dicken, SJ, Batterham, RL
Nutrients. 2021;14(1)
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Diet has long been a cornerstone of weight management, with dietary policies being a core feature of government and health organisation strategies to reduce obesity worldwide. Indeed, poor diets are a leading cause of preventable obesity-related death and non-communicable diseases, including cancer, cardiovascular disease and type 2 diabetes. The aim of this study was to provide novel insights into the relative impact of nutrient content and dietary patterns vs. ultra-processing on obesity and adverse health-related outcomes. This study is a review of prospective cohort studies. Findings show that adjustment for fat, sugar and sodium intake, or adjustment for adherence to a range of healthy or unhealthy dietary patterns has a minimal impact on the adverse associations between UPF intake and a diverse range of health-related outcomes. Authors conclude that their findings raise important questions regarding current policy and future research needs, suggesting that the nature and extent of processing is an important dietary dimension.
Abstract
Prospective cohort studies show that higher intakes of ultra-processed food (UPF) increase the risk of obesity and obesity-related outcomes, including cardiovascular disease, cancer and type 2 diabetes. Whether ultra-processing itself is detrimental, or whether UPFs just have a lower nutritional quality, is debated. Higher UPF intakes are inversely associated with fruit, vegetables, legumes and seafood consumption. Therefore, the association between UPFs and poor health could simply be from excess nutrient intake or from a less healthful dietary pattern. If so, adjustment for dietary quality or pattern should explain or greatly reduce the size of the significant associations between UPFs and health-related outcomes. Here, we provide an overview of the literature and by using a novel approach, review the relative impact of adjusting for diet quality/patterns on the reported associations between UPF intake and health-related outcomes in prospective cohort studies. We find that the majority of the associations between UPFs, obesity and health-related outcomes remain significant and unchanged in magnitude after adjustment for diet quality or pattern. Our findings suggest that the adverse consequences of UPFs are independent of dietary quality or pattern, questioning the utility of reformulation to mitigate against the obesity pandemic and wider negative health outcomes of UPFs.
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Vegetarian and Vegan Diet in Fibromyalgia: A Systematic Review.
Nadal-Nicolás, Y, Miralles-Amorós, L, Martínez-Olcina, M, Sánchez-Ortega, M, Mora, J, Martínez-Rodríguez, A
International journal of environmental research and public health. 2021;18(9)
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Fibromyalgia (FM) is a chronic non-degenerative disease of unknown etiology without effective medical treatment that mostly affects women. The aim of this study was to evaluate the efficacy of mainly plant-based diets in patients with FM compared to omnivorous diets. A secondary aim was to examine the main effects of these diets on patients’ symptoms and the improvement in their quality of life. This study is a systemic review of six studies (n = 4 clinical trials and n = 2 observational cohort studies). The selected studies included 157 FM patients in both the intervention and control groups, and more than 117 were women. Results indicate that a mainly plant-based diet improves biochemical parameters and body inflammation; body weight, sleep quality, quality of life, pain at rest as well as other symptoms of FM and their impact on health. Authors conclude that even though their findings are promising further well-designed clinical trials are needed to consolidate these dietary recommendations in FM patient.
Abstract
Fibromyalgia (FM) is a chronic non-degenerative disease characterized by the presence of multiple symptoms such as chronic pain, which negatively influence the quality of life of sufferers, most of whom are women. Currently, there is no effective treatment to limit the impact of these symptoms. The aim of this research is to review the scientific evidence on the effect of following a vegetarian or vegan diet on fibromyalgia patients. A systematic review included the original articles that answered the research question. These articles were in 2021 in the PubMed, Web of Science and Scopus databases. The research used the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. No time restriction was applied, and grey literature was not included. The evaluation of the methodological quality of the articles was carried out using the following different scales: STROBE (strengthening the reporting of observational studies in epidemiology), PEDro (Physiotherapy Evidence Database), and MMAT (Mixed Methods Appraisal Tool) scales. A total of 88 studies were analyzed, of which 6 investigations were included in this systematic review (n = 4 clinical trials and n = 2 cohort studies). These investigations show significant improvements in biochemical parameters, quality of life, quality of sleep, pain at rest and general health status when following mainly plant-based dietary patterns. In conclusion, these findings are promising but interpretation of the findings is limited due to the methodological quality of the studies. Well-designed clinical trials are needed to consolidate these dietary recommendations in FM patients.
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The impact of nutrition on COVID-19 susceptibility and long-term consequences.
Butler, MJ, Barrientos, RM
Brain, behavior, and immunity. 2020;87:53-54
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The impacts of Covid-19 are being felt across the world, affecting health, healthcare and economies. Statistics from across the world are showing that the elderly, those with underlying medical conditions and under-represented minority groups are particularly vulnerable to severe complications and have a higher risk of dying of Covid-19. This opinion piece presents arguments for the importance of focusing on diet to support health resilience in general and the immune system in particular, to minimise the impact of this and future viruses. Research is presented on excessive intake of saturated fat leading to chronic activation of the innate immune system (first line, rapid defence against infection), resulting in inflammation, and associated heightened susceptibility to complications of viral infection. The standard western diet (high saturated fat, refined carbohydrates and sugars, low levels of fibre, unsaturated fat and antioxidants) has also been shown to affect the adaptive immune system (second line, delayed defence against infection), depressing its action against infection. The piece also discusses possible long-term, future impacts of those recovered from Covid-19 infection, particularly in relation to neurodegenerative diseases such as Alzheimer’s. The authors call for fresh, healthy wholefoods to be readily available and affordable to everyone in society.
Abstract
While all groups are affected by the COVID-19 pandemic, the elderly, underrepresented minorities, and those with underlying medical conditions are at the greatest risk. The high rate of consumption of diets high in saturated fats, sugars, and refined carbohydrates (collectively called Western diet, WD) worldwide, contribute to the prevalence of obesity and type 2 diabetes, and could place these populations at an increased risk for severe COVID-19 pathology and mortality. WD consumption activates the innate immune system and impairs adaptive immunity, leading to chronic inflammation and impaired host defense against viruses. Furthermore, peripheral inflammation caused by COVID-19 may have long-term consequences in those that recover, leading to chronic medical conditions such as dementia and neurodegenerative disease, likely through neuroinflammatory mechanisms that can be compounded by an unhealthy diet. Thus, now more than ever, wider access to healthy foods should be a top priority and individuals should be mindful of healthy eating habits to reduce susceptibility to and long-term complications from COVID-19.
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Optimum nutritional strategies for cardiovascular disease prevention and rehabilitation (BACPR).
Butler, T, Kerley, CP, Altieri, N, Alvarez, J, Green, J, Hinchliffe, J, Stanford, D, Paterson, K
Heart (British Cardiac Society). 2020;106(10):724-731
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There are multiple modifiable risk factors for cardiovascular disease (CVD), many of which are modifiable via changes in diet and physical activity. The aim of this study was to review the area of cardiovascular nutrition and provide recommendations for practitioners to help patients make healthy eating decisions. This review highlighted the complexities of nutrition. Thus, improving diet quality post-myocardial infarction is associated with a reduction in risk for all-cause mortality, with evidence to suggest it is the whole diet, rather than individual components, that drives this association. One of the dietary patterns mostly associated with cardiovascular health is the ‘Mediterranean’ diet. Various studies suggest that it is linked with lower all-cause mortality in both primary and secondary prevention of CVD. Additionally, the DASH diet is also associated with decreased incidence of stroke, CVD, coronary heart disease, diabetes, in addition to improvements in cardiovascular. Improvement in patients’ cardiovascular outcomes can result from providing patients with food-based advice. However, it is important that the health practitioners dispensing this information have an understanding of nutritional science and an appreciation for the patients’ comorbidities. Authors conclude that nutritional advice needs to be patient-focused, flexible, and should be adapted to each individual with CVD and their other comorbidities.
Abstract
Nutrition has a central role in both primary and secondary prevention of cardiovascular disease yet only relatively recently has food been regarded as a treatment, rather than as an adjunct to established medical and pharmacotherapy. As a field of research, nutrition science is constantly evolving making it difficult for patients and practitioners to ascertain best practice. This is compounded further by the inherent difficulties in performing double-blind randomised controlled trials. This paper covers dietary patterns that are associated with improved cardiovascular outcomes, including the Mediterranean Diet but also low-carbohydrate diets and the potential issues encountered with their implementation. We suggest there must be a refocus away from macronutrients and consideration of whole foods when advising individuals. This approach is fundamental to practice, as clinical guidelines have focused on macronutrients without necessarily considering their source, and ultimately people consume foods containing multiple nutrients. The inclusion of food-based recommendations aids the practitioner to help the patient make genuine and meaningful changes in their diet. We advocate that the cardioprotective diet constructed around the traditional Mediterranean eating pattern (based around vegetables and fruits, nuts, legumes, and unrefined cereals, with modest amounts of fish and shellfish, and fermented dairy products) is still important. However, there are other approaches that can be tried, including low-carbohydrate diets. We encourage practitioners to adopt a flexible dietary approach, being mindful of patient preferences and other comorbidities that may necessitate deviations away from established advice, and advocate for more dietitians in this field to guide the multi-professional team.
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Nutrients, Genetic Factors, and Their Interaction in Non-Alcoholic Fatty Liver Disease and Cardiovascular Disease.
Lombardi, R, Iuculano, F, Pallini, G, Fargion, S, Fracanzani, AL
International journal of molecular sciences. 2020;21(22)
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Non-alcoholic fatty liver disease (NAFLD) and heart disease are influenced by diet and genetics. NAFLD cannot be managed with drugs and so lifestyle modification is the main recommendation, which is also advised in heart disease. The aim of this large review of 176 papers was to discuss the role of nutrients and genetics in NAFLD and heart disease. Amongst the main nutrients, excess fructose (a simple sugar) and high saturated and trans-fats were all shown to contribute to the development of both diseases. The influence of protein on NAFLD is controversial. Animal studies suggest that protein can be of benefit, but studies on humans have failed to support this. This is similar for heart disease where large scale trials in humans are not definitive. The role of fibre in NAFLD and heart disease appears to be beneficial. Several micronutrients were also reviewed including vitamins D, K, curcumin, plant chemicals and caffeine. The complex interplay involving genetics was also discussed and although fairly new science, evidence is mounting in support of genetic considerations when making dietary recommendations. It was concluded that diet and genetics influence the development of NAFLD, and heart disease and dietary recommendations need to reflect this. This study could be used by health care professionals to understand the interaction between diet and genetics and the importance of making personalised nutrition recommendations to individuals with NAFLD or heart disease.
Abstract
Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries and expose patients to increased risk of hepatic and cardiovascular (CV) morbidity and mortality. Both environmental factors and genetic predisposition contribute to the risk. An inappropriate diet, rich in refined carbohydrates, especially fructose, and saturated fats, and poor in fibers, polyunsaturated fats, and vitamins is one of the main key factors, as well as the polymorphism of patatin-like phospholipase domain containing 3 (PNPLA3 gene) for NAFLD and the apolipoproteins and the peroxisome proliferator-activated receptor (PPAR) family for the cardiovascular damage. Beyond genetic influence, also epigenetics modifications are responsible for various clinical manifestations of both hepatic and CV disease. Interestingly, data are accumulating on the interplay between diet and genetic and epigenetic modifications, modulating pathogenetic pathways in NAFLD and CV disease. We report the main evidence from literature on the influence of both macro and micronutrients in NAFLD and CV damage and the role of genetics either alone or combined with diet in increasing the risk of developing both diseases. Understanding the interaction between metabolic alterations, genetics and diet are essential to treat the diseases and tailoring nutritional therapy to control NAFLD and CV risk.
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Consumption of ultra-processed foods and health outcomes: a systematic review of epidemiological studies.
Chen, X, Zhang, Z, Yang, H, Qiu, P, Wang, H, Wang, F, Zhao, Q, Fang, J, Nie, J
Nutrition journal. 2020;19(1):86
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Unhealthy diets are recognized as a major determinant of the occurrence of non-communicable diseases (NCDs). The aim of this study was to summarize the evidence for the association between ultra-processed food (UPFs) consumption and health outcomes. This study is a systemic review of 20 published epidemiological studies (12 cohort and 8 cross-sectional studies), with a total of 334,114 participants and 10 diseases. Results indicate a positive association between UPFs consumption and risk of all-cause mortality, overall cardiovascular diseases, coronary heart diseases, cerebrovascular diseases, hypertension, metabolic syndrome, overweight and obesity, depression, irritable bowel syndrome, overall cancer, postmenopausal breast cancer, gestational obesity, adolescent asthma and wheezing, and frailty. However, on the contrary, there was not an obvious association with cardiovascular disease mortality, prostate and colorectal cancer, gestational diabetes mellitus and gestational overweight. Authors conclude that their findings encouraged a decrease in UPFs consumption and an increase in the proportion of unprocessed or minimally processed foods, such as fruits and vegetables.
Abstract
BACKGROUND Consumption of ultra-processed foods (UPFs) plays a potential role in the development of obesity and other diet-related noncommunicable diseases (NCDs), but no studies have systematically focused on this. This study aimed to summarize the evidence for the association between UPFs consumption and health outcomes. METHODS A comprehensive search was conducted in PubMed, Embase, and Web of Science to identify all relevant studies. Epidemiological studies were included, and identified studies were evaluated for risk of bias.A narrative review of the synthesized findings was provided to assess the association between UPFs consumption and health outcomes. RESULTS 20 studies (12 cohort and 8 cross-sectional studies) were included in the analysis, with a total of 334,114 participants and 10 health outcomes. In a narrative review, high UPFs consumption was obviously associated with an increased risk of all-cause mortality, overall cardiovascular diseases, coronary heart diseases, cerebrovascular diseases, hypertension, metabolic syndrome, overweight and obesity, depression, irritable bowel syndrome, overall cancer, postmenopausal breast cancer, gestational obesity, adolescent asthma and wheezing, and frailty. It showed no significant association with cardiovascular disease mortality, prostate and colorectal cancers, gestational diabetes mellitus and gestational overweight. CONCLUSIONS This study indicated a positive association between UPFs consumption and risk of several health outcomes. Large-scale prospective designed studies are needed to confirm our findings.
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Sociodemographic and lifestyle-related risk factors for identifying vulnerable groups for type 2 diabetes: a narrative review with emphasis on data from Europe.
Kyrou, I, Tsigos, C, Mavrogianni, C, Cardon, G, Van Stappen, V, Latomme, J, Kivelä, J, Wikström, K, Tsochev, K, Nanasi, A, et al
BMC endocrine disorders. 2020;20(Suppl 1):134
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Type 2 diabetes mellitus (T2DM) results from progressive loss of insulin secretion, which is typically combined with various degrees of insulin resistance. The aim of this study is to provide a comprehensive overview of key sociodemographic and lifestyle-related risk factors for identifying vulnerable groups for T2DM with emphasis on data from Europe. This study is a narrative review which includes 101 publications. Literature shows that prevention of T2DM should be a collaborative effort which mobilizes multiple partners/ stakeholders at a national and international (e.g. European) level. In addition, a holistic approach is becoming increasingly essential in order to put into effect multidimensional public health programs and integrated interventions for effective T2DM prevention which will take into account both traditional and socioeconomic/socioecological factors. Authors conclude that a multidimensional approach for the prevention of T2DM may have a broader impact against the current diabesity epidemic within and across countries in Europe.
Abstract
BACKGROUND Type 2 diabetes mellitus (T2DM) comprises the vast majority of all diabetes cases in adults, with alarmingly increasing prevalence over the past few decades worldwide. A particularly heavy healthcare burden of diabetes is noted in Europe, where 8.8% of the population aged 20-79 years is estimated to have diabetes according to the International Diabetes Federation. Multiple risk factors are implicated in the pathogenesis of T2DM with complex underlying interplay and intricate gene-environment interactions. Thus, intense research has been focused on studying the role of T2DM risk factors and on identifying vulnerable groups for T2DM in the general population which can then be targeted for prevention interventions. METHODS For this narrative review, we conducted a comprehensive search of the existing literature on T2DM risk factors, focusing on studies in adult cohorts from European countries which were published in English after January 2000. RESULTS Multiple lifestyle-related and sociodemographic factors were identified as related to high T2DM risk, including age, ethnicity, family history, low socioeconomic status, obesity, metabolic syndrome and each of its components, as well as certain unhealthy lifestyle behaviors. As Europe has an increasingly aging population, multiple migrant and ethnic minority groups and significant socioeconomic diversity both within and across different countries, this review focuses not only on modifiable T2DM risk factors, but also on the impact of pertinent demographic and socioeconomic factors. CONCLUSION In addition to other T2DM risk factors, low socioeconomic status can significantly increase the risk for prediabetes and T2DM, but is often overlooked. In multinational and multicultural regions such as Europe, a holistic approach, which will take into account both traditional and socioeconomic/socioecological factors, is becoming increasingly crucial in order to implement multidimensional public health programs and integrated community-based interventions for effective T2DM prevention.
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Influence of diet on the gut microbiome and implications for human health.
Singh, RK, Chang, HW, Yan, D, Lee, KM, Ucmak, D, Wong, K, Abrouk, M, Farahnik, B, Nakamura, M, Zhu, TH, et al
Journal of translational medicine. 2017;15(1):73
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Gut microbiome plays an important role in modulating the risk of many chronic diseases through its impact on host immunity and metabolic health. Diet, in turn, can alter the composition of the microbiota. This paper reviewed current understanding of the effects of common dietary components and three select diets on gut microbiota composition and host health. Dietary components included plant and animal protein, saturated and unsaturated fats, digestible and non-digestible carbohydrates, probiotics and polyphenols. The diets included Western diet, gluten-free diet and Mediterranean diet. Based on the reviewed papers, the authors concluded that diet can modify the intestinal microbiome, which in turn has a profound impact on overall health. The impact can be beneficial or detrimental, depending on the abundance and identity of microbial populations and the nature of their interactions with the host. The authors also state that further research using large, long-term clinical trials to evaluate a greater variety of food components would be helpful in making specific dietary recommendations to patients.
Abstract
Recent studies have suggested that the intestinal microbiome plays an important role in modulating risk of several chronic diseases, including inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. At the same time, it is now understood that diet plays a significant role in shaping the microbiome, with experiments showing that dietary alterations can induce large, temporary microbial shifts within 24 h. Given this association, there may be significant therapeutic utility in altering microbial composition through diet. This review systematically evaluates current data regarding the effects of several common dietary components on intestinal microbiota. We show that consumption of particular types of food produces predictable shifts in existing host bacterial genera. Furthermore, the identity of these bacteria affects host immune and metabolic parameters, with broad implications for human health. Familiarity with these associations will be of tremendous use to the practitioner as well as the patient.