Nutrition reviews最新文献

Context: Emerging research has suggested a potential link between high iron levels, indicated by serum ferritin levels, and the development of type 2 diabetes (T2D). However, the role of hepatic iron concentration (HIC) on T2D development and progression is not well understood.

Objectives: This study aims to systematically review the literature on HIC and/or the degree of hepatic iron overload (HIO) in individuals with prediabetes and/or diagnosed T2D, and to analyze associations between HIC and markers of glucose metabolism.

Data sources: The databases Medline, PubMed, Embase, CINAHL, and Web of Knowledge were searched for studies published in English from 1999 to March 2024. This review followed the Preferred Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist.

Data extraction: Data were extracted following the established eligibility criteria. Study characteristics and biomarkers related to prediabetes, T2D, and HIO were extracted. The risk of bias was analyzed using the Newcastle-Ottawa Scale. Data were stratified by the exposure and analyzed in subgroups according to the outcome. Data regarding the HIC values in controls, individuals with prediabetes, and individuals with T2D and the association estimates between HIC or HIO and markers of glycemic metabolism, prediabetes, or T2D were extracted.

Data analysis: A total of 12 studies were identified, and data from 4110 individuals were analyzed. HIO was not consistently observed in prediabetic/T2D populations; however, elevated HIC was frequently observed in prediabetic and T2D individuals, and was associated with the disruption of certain glycemic markers in some cases.

Conclusion: The extent of iron overload, as indicated by hepatic iron load, varied among the prediabetic and T2D populations studied. Further research is needed to understand the distribution and regulation of iron in T2D pathology.

Diet may influence the gut microbiota and subsequently affect the host's health. Recent developments in methods analyzing the composition and function of the gut microbiota allow a deeper understanding of diet-gut microbiota relationships. A state-of-the-art methodology, shotgun metagenomics sequencing, offers a higher taxonomic resolution of the gut microbiota at the bacterial species and strain levels, and more accurate information regarding the functional potential of gut microbiota. Here, the available evidence on the relationship between diet and gut microbiota was critically reviewed, focusing on results emerging from recent metagenomics sequencing studies applied in randomized controlled trials and observational studies. The PubMed and Embase databases were used to search publications between January 2011 and September 2023. Thus far, the number of studies is limited, and the study designs and methods utilized have been variable. Nevertheless, the cumulative evidence from interventions relates to dietary fiber as a modifier of bacterial species, such as Anaerostipes hadrus and Faecalibacterium prausnitzii. Furthermore, observational studies have detected associations between different dietary patterns and food groups with certain microbial species. Utilization of metagenomics sequencing is becoming more common and will undoubtedly provide further insights into diet-gut microbiota relationships at the species level as well as their functional pathways in the near future. For reproducible results and to draw reliable conclusions across various studies on diet-gut microbiota relationships, there is a need for harmonization of the study designs and standardized ways of reporting.

Context: During pregnancy, the underutilization of iron-folic acid supplements (IFAS) remains a considerable maternal and child health issue. Hence, health education intervention trials were conducted following the recommendation of the World Health Organization and epidemiological studies to enhance the utilization level of the supplements during pregnancy.

Objective: The objective of this meta-analysis was to evaluate the effectiveness of health education interventions in enhancing IFAS utilization during pregnancy.

Data sources: A thorough search was conducted across PubMed, EMBASE, Scopus, CINAHL, Web of Science, Medline, the Cochrane Library, and Google Scholar from August 28 until October 31, 2023.

Data extraction: This study incorporated randomized and quasi-experimental studies that examined the effectiveness of health education interventions in enhancing IFAS utilization during pregnancy.

Data analysis: Comprehensive Meta-Analysis, version 4, which includes the prediction interval, was used for the analysis.

Results: In this meta-analysis and systematic review, 21 articles comprising 6643 pregnant women from different countries were included. The random-effects model was applied to determine the pooled standardized differences in means (0.786; 95% CI: 0.551, 1.021). The prediction interval shows the range of true standardized differences in means (95% CI: -0.168, 1.740), which indicates the variations in the true effect size of health education interventions in enhancing IFAS utilization during pregnancy.

Conclusion: In addition to pooled effect size, another significant advantage of this meta-analysis is conducting the prediction interval to determine the range of the true effect size, which ranges from -0.168 to 1.740 across the groups of different pregnant women, indicating variability in the effectiveness of the interventions in enhancing IFAS utilization during pregnancy. This might occur because most of the primary studies in this meta-analysis were conducted at healthcare facilities and mostly focused on anemic pregnant women attending antenatal care, which did not control for sociocultural determinants. Therefore, future researchers should consider these limitations.

Time-restricted eating (TRE) is a form of intermittent fasting that involves reducing the time-period in which food is typically consumed daily. While TRE is known to induce health benefits, particularly for adults with obesity, there is currently debate about whether the time of day in which food is consumed also contributes to the health benefits of TRE. Early TRE (eTRE) and late TRE (lTRE) are subtypes of TRE that involve consuming food and caloric beverages either in the early or later part of the day. A growing body of literature indicates that eTRE may offer additional health benefits compared with lTRE. An important and unanswered question, however, is whether most adults can adhere to this type of eating pattern and whether adherence and retention differ between eTRE and lTRE. This narrative review compared adherence and retention in studies that implemented either eTRE or lTRE in adults for 8 weeks or longer. Five databases were searched, and 10 studies met our eligibility criteria. The key finding was that participants had high and comparable levels of adherence and retention in both eTRE and lTRE interventions. Specifically, the mean adherence rate was 81.4% for eTRE and 82.3% for lTRE, while the mean retention rate was 81% for eTRE and 85.8% for lTRE in eligible studies. Thus, the findings support the feasibility of both approaches. The lowest adherence and retention rates occurred in studies in which either eTRE or lTRE regimens were combined with other dietary interventions. Notably, the duration of the eating window did not seem to negatively affect adherence and retention rates for either eTRE or lTRE. More research is warranted to determine the influence of other factors, such as age and study location, on adherence to and retention of both eTRE and lTRE interventions.

The transition toward plant-based (PB) diets has gained attention as a plausible step toward achieving sustainable and healthy dietary goals. However, the complete elimination of all animal-sourced foods from the diet (ie, a vegan diet) may have nutritional ramifications that warrant close examination. Two such concerns are the adequacy and bioavailability of amino acids (AAs) from plant-sourced foods and the consequences for older vegan populations who have elevated AA requirements. This narrative review describes the challenges of achieving high protein quality from vegan diets. Data were synthesized from peer-reviewed research articles and reviews. Plant-sourced proteins provide poorer distribution of indispensable AAs (IAAs) and have poorer digestibility, partly due to their inherent structural components within the food matrix. The review addresses complexities of combinations of varied plant protein sources and why the inclusion of novel PB alternatives adds uncertainty to the achievement of adequate protein adequacy. Meal distribution patterns of protein and the ensuing physiological impacts deserve further research and are outlined in this review. Particular attention is given to describing the challenges of achieving sufficient protein and IAA intakes by aging populations who choose to follow a vegan diet. This review contributes to the emerging discussions of nutritional risks associated with vegan diets and adds perspective to the current dietary shifts toward PB diets.

Context: Chronic kidney disease (CKD) stands out as one of the most widespread diseases globally. Dietary interventions, such as adopting a low-protein diet (LPD), play a crucial role as a key approach in impeding the advancement of CKD.

Objective: The objective of this umbrella review was to provide understanding into the effects of an LPD on kidney function among individuals with CKD, along with evaluating the certainty of the available evidence.

Data sources: Searches for relevant studies were conducted without limitations through databases such as PubMed, Scopus, Web of Science, and Google Scholar, encompassing findings up to June 2023.

Data extraction: The effect sizes for each meta-analysis were recalibrated using a random-effects model. The certainty of the evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

Data analysis: Twenty-five meta-analyses including 47 randomized controlled trials were included in this study. Moderate certainty of the evidence suggests that LPDs may reduce glycated hemoglobin (HbA1c) and phosphorus levels, and the risk of progressing to end-stage renal disease in patients with CKD. Moreover, notable outcomes include increased glomerular filtration rate and decreased levels of serum albumin, blood urea nitrogen, and bicarbonate, although the certainty of evidence is low. In addition, LPDs can substantially decrease proteinuria, urine urea, and parathyroid hormone (PTH), although with very low certainty. The effects on serum creatinine, calcium, systolic blood pressure, and diastolic blood pressure are statistically nonsignificant, with the certainty of evidence ranging from low to moderate.

Conclusion: LPDs demonstrated beneficial effects on renal function in patients with CKD, which is supported by moderate to very low certainty evidence.

Systematic review registration: PROSPERO registration no. CRD42023473647.

Context: Clinical investigation has shown that the addition of saffron or crocin to standard antidiabetic medications improves a patient's metabolic profile, oxidative stress (OS), and inflammatory response. Despite a large number of studies examining the impact of saffron supplementation on OS, inflammation, and renal and liver function parameters, no systematic review or meta-analysis has been conducted to compile the outcomes in patients with type 2 diabetes mellitus (T2DM).

Objective: The current systematic review and meta-analysis was performed to investigate the effect of saffron or crocin intake on OS, inflammation, and renal and liver function parameters in patients with T2DM.

Data sources: Online databases including PubMed, Scopus, ISI Web of Science, and Cochrane Library were searched up to December 2023.

Data extraction: The mean differences and their respective SDs were extracted. Using a random-effects model, the pooled data were calculated as standardized mean difference (SMD) with 95% CI.

Data analysis: 17 eligible randomized controlled trials were included in this meta-analysis. The pooled findings showed that saffron supplementation remarkably decreased the levels of tumor necrosis factor-α (SMD: -0.37; 95% CI: -0.69 to -0.05; I2 = 40.77%, P = .15), interleukin-6 (IL-6) (SMD: -0.38; 95% CI: -0.65 to -0.10; I2 = 0%, P = .68), and malondialdehyde (MDA) (SMD: -0.36; 95% CI: -0.65 to -0.07; I2= 20.51%, P = .02) compared with the control. In addition, based on subgroup analyses, taking ≥100 mg of saffron daily in individuals with T2DM reduced the serum levels of IL-6 (SMD: -0.50; 95% CI: -0.90 to -0.10; I2 = 0%, P = .50) and MDA (SMD: -0.36; 95% CI: -0.68 to -0.03; I2 = 0, P = .97). Furthermore, the level of alanine transaminase was decreased (SMD: -0.43; 95% CI: -0.73 to -0.12; I2 = 0, P = .66) with a treatment period of <60 days of saffron or crocin supplementation.

Conclusion: Larger studies with more follow-up and higher doses of both saffron and crocin are needed in order to understand the efficacy and safety of these herbs for long-term use as routine therapies.

Systematic review registration: PROSPERO registration no. CRD42023458119.

Type 2 diabetes mellitus (T2DM) and progressive liver disease are 2 of the most significant global health concerns, and they have alarming and ever-increasing prevalence. A growing body of literature has demonstrated a potential multilateral link between gut microbiome dysbiosis and the development and progression of the above-mentioned conditions. Modulation of gut microbial composition from the norm is due to changes in diet allied with external factors such as age, genetics, and environmental changes. In this comprehensive review, we recapitulate the research to date investigating the links between gut microbiome dysbiosis and T2DM or liver disease, with special attention to the importance of diet. Additionally, we review the most commonly used tools and methodologies of investigating changes in the gut microbiome, highlighting the advantages and limitations of each strategy, before introducing a novel in vitro approach to the problem. Finally, the review offers recommendations for future research in this field that will allow better understanding of how the gut microbiota affects disease progression and of the prospects for intestinal microbiota-based therapeutic options.

Context: There are contradictory results regarding the relationship between dietary intakes of monounsaturated fatty acids (MUFAs) and risk of stroke.

Objective: The purpose of this study was to review the existing body of research on the relationship between MUFA consumption and stroke risk through a systematic review and meta-analysis.

Data source: PubMed, Scopus, and ISI Web of Science were all systematically searched up to January 2023.

Data extraction: A total of 11 prospective cohort studies that investigated MUFA consumption in relation to stroke risk were included.

Data analysis: Relative risk (RR) and 95% CIs for the highest vs lowest category of dietary MUFA intake were combined using a random-effects model. Linear and nonlinear dose-response relations were assessed through 1-stage weighted mixed-effects meta-analysis. These studies included 475 207 participants and 8438 cases. In highest vs lowest consumption analysis, MUFA intake was inversely associated with total stroke (RR: 0.80; 95% CI: 0.67, 0.96; I2 =65.2%, Q-test P = .001; n = 11) and hemorrhagic stroke (RR: 0.80; 95% CI: 0.68, 0.95; I2 = 0.0%, Q-test P = .77; n = 5) risk. Conversely, this association was not significant for ischemic stroke (RR: 0.86; 95% CI: 0.69, 1.07; I2 =62.3%, Q-test P = .01; n = 8). An inverse association was observed between each 10-g/d MUFA intake and hemorrhagic stroke (RR: 0.79; 95% CI: 0.65, 0.96) but not total and ischemic stroke. We did not find any evidence for a nonlinear association between MUFA intake and total stroke and its subtypes.

Conclusion: This meta-analysis shows that higher MUFA intake could lower the risk of total and hemorrhagic, but not ischemic, stroke. This could be important for public health.

Systematic review registration: PROSPERO registration no. CRD42023458555.

Context: Previous reviews have focused on the effects of probiotics on colitis, but there is a need to understand their impact on barrier integrity and tight junction protein improvement in colitis.

Objective: This study aimed to systematically examine the effects of probiotic use on barrier integrity in colitis disease. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Data sources: A systematic search in PubMed, Web of Science, Scopus, and Cochrane databases identified 2537 articles.

Data extraction: As a result of the search, 2537 articles were accessed. Study results were summarized descriptively through discussions by intervention conditions, study population, measurement methods, and key findings. The included studies were independently reviewed and all authors reached consensus on the quality and major findings from the included articles. Forty-six studies that met the inclusion criteria were analyzed within the scope of the systematic review.

Results: Although the study primarily utilized probiotics from the Lactobacillaceae family (notably, L casei, L reuteri, L rhamnosus, L plantarum, and L pentosus) and the Bifidobacteriaceae family (notably, B breve, B animalis, and B dentium), other probiotics also demonstrated positive effects on tight junction proteins. These effects are attributed to the production of bioactive and metabolic compounds, as well as short-chain fatty acids, which combat pathogens and reduce anti-inflammatory agents. However, it was observed that the effects of these probiotics on tight junction proteins varied depending on the strain and dose.

Conclusion: The beneficial effects of probiotics on remission in inflammatory bowel disease are well documented. Studies show that probiotics generally improve intestinal barrier function, but factors such as dose, duration, and bacterial species combinations need further clarification. Additionally, comprehensive studies are needed to understand how improved barrier function affects absorption in individuals.

Systematic review registration: PROSPERO registration no. CRD42023452774.