Adopting a Mediterranean-style eating pattern with low, but not moderate, unprocessed, lean red meat intake reduces fasting serum trimethylamine N-oxide (TMAO) in adults who are overweight or obese

A Mediterranean-style eating pattern (MED-EP) may include moderate red meat intake. However, it is unknown if the pro-atherogenic metabolite trimethylamine N-oxide (TMAO) is affected by the amount of red meat consumed with a MED-EP. The results presented are from a secondary, retrospective objective of an investigator-blinded, randomized, crossover, controlled feeding trial (two 5-wk interventions separated by a 4-wk washout) to determine if a MED-EP with 200g unprocessed lean red meat/wk (MED-CONTROL) reduces circulating TMAO concentrations compared to a MED-EP with 500g unprocessed lean red meat/wk (MED-RED). Participants were 27 women and 12 men (n=39 total) who were either overweight or obese (BMI: 30.5 ± 0.3 kg/m2 mean ± SEM). Serum samples were obtained following an overnight fast both before (pre) and after (post) each intervention. Fasting serum TMAO, choline, carnitine, and betaine concentrations were measured using a targeted Liquid chromatography-mass spectrometry. Data were analyzed to assess if (a) TMAO and related metabolites differed by intervention, and (b) if changes in TMAO were associated with changes in Framingham 10-year risk score. Serum TMAO was lower post-intervention following MED-CONTROL compared to MED-RED intervention (post-MED-CONTROL 3.1 ± 0.2 µM vs. post-MED-RED 5.0 ± 0.5 µM, p<0.001), and decreased following MED-CONTROL (pre- vs post-MED-CONTROL, p = 0.025). Exploratory analysis using mixed model analysis of covariance identified a positive association between changes in TMAO and changes in HOMA-IR (p = 0.036). These results suggest that lower amounts of red meat intake leads to lower TMAO concentrations in the context of a MED-EP.

Red Meat Intake and Risk of Rheumatoid Arthritis: A Categorical and Dose-Response Meta-Analysis

Objective: Findings from previous observational studies on the association between red meat intake and risk of rheumatoid arthritis (RA) are inconsistent. Therefore, we aimed to evaluate the impact of red meat intake on the incidence of RA by meta-analysis.Methods: PubMed and Web of Science were searched for eligible observational studies regarding the association between red meat intake and the risk of RA until June 30, 2021. Risk estimates with corresponding 95% confidence interval (95% CI) were pooled. Subgroup analysis and meta-regression analysis were performed to explore the potential sources of heterogeneity. Sensitivity analysis and publication bias test were also carried out.Results: A total of eleven studies were selected, involving 4 cohort studies with 5 203 identified cases from 349 776 individuals and 7 case-control studies with 3 762 cases and 6 856 controls. The pooled risk estimate of RA risk was 0.94 (95% CI: 0.77 to 1.15) for ever versus non/occasional red meat intake, while high dose of red meat intake increased the risk of RA (OR: 1.26, 95% CI: 1.07 to 1.50) in the categorical meta-analysis. Dose-response meta-analysis suggested a non-linear dose-response relationship between red meat intake and RA (P=0.028). Red meat intake was found to be a risk factor of RA when the dose ranged from 96 to 166 g/day.Conclusion: High dose of red meat intake could increase the risk of RA. Mechanistic studies are warranted to clarify the aetiologic pathways through which high dose of red meat intake may promote RA.

Minimal Associations between Short-Term Dietary Intake and Salivary Microbiome Composition

Background: Increasing evidence points to the esophageal microbiome as an important co-factor in esophageal neoplasia. Esophageal microbiome composition is strongly influenced by the oral microbiome. Salivary microbiome assessment has emerged as a potential non-invasive tool to identify patients at risk for esophageal cancer, but key host and environmental factors that may affect the salivary microbiome have not been well-defined. This study aimed to evaluate the impact of short-term dietary intake on salivary microbiome composition. Methods: Saliva samples were collected from 69 subjects prior to upper endoscopy who completed the Automated Self-Administered 24-Hour (ASA24) Dietary Assessment. Salivary microbiome composition was determined using 16S rRNA amplicon sequencing. Results: There was no significant correlation between alpha diversity and primary measures of short-term dietary intake (total daily calories, fat, fiber, fruit/vegetables, red meat intake, and fasting time). There was no evidence of clustering on beta diversity analyses. Very few taxonomic alterations were found for short-term dietary intake; an increased relative abundance of Neisseria oralis and Lautropia sp. was associated with high fruit and vegetable intake, and an increased relative abundance of a taxon in the family Gemellaceae was associated with increased red meat intake. Conclusions: Short-term dietary intake was associated with only minimal salivary microbiome alterations and does not appear to have a major impact on the potential use of the salivary microbiome as a biomarker for esophageal neoplasia.

Red and White Meat Intake in Relation to Mental Disorders in Iranian Adults

Background: The association between meat consumption and mental disorders is less investigated in Iranian population. We examined the association between meat consumption and prevalence of symptoms of depression, anxiety, and psychological distress in Iranian adults.Methods: This cross-sectional study included 3,362 participants aged 18–55 years old. A dish-based 106-item semiquantitative food frequency questionnaire (FFQ) was used to assess usual dietary intake of study population. Hospital Anxiety and Depression Scale (HADS) and General Health Questionnaire (GHQ), all validated in Iranian population, were applied to collect data on symptoms of anxiety, depression, and psychological distress, respectively.Results: The prevalence of symptoms of depression, anxiety, and psychological distress in the study population was 28.6, 13.6, and 22.6%, respectively. After considering potential confounders, individuals in the top quartile of red meat intake had 43% increased risk of depression symptoms [odds ratio (OR) = 1.43; 95% CI: 1.09–1.89] compared to those in the first quartile. No significant relation was observed between red meat intake and anxiety or psychological distress symptoms. White meat consumption was not associated with mental disorders. Stratified analysis by sex showed that male participants in the highest quartile of red meat intake had 92% greater risk of depression symptoms (95% CI: 1.17–3.15) than those individuals in the lowest category. Red and white meat intake was not associated with mental disorders in women. In overweight or obese individuals, despite lack of any association between red meat intake and mental disorders, high intake of white meat was associated with a lower odds of psychological distress symptoms (OR = 0.64; 95% CI: 0.42–0.99) and a lower risk of depression symptoms (OR = 0.68; 95% CI: 0.45–1.00). In normal-weight participants, those in the highest quartile of red meat intake had greater odds for depression symptoms than those in the lowest quartile (OR = 1.66; 95% CI: 1.14–2.42).Conclusions: We found that red meat consumption was associated with increased risk of depression symptoms, especially in men, and normal-weight participants. In overweight or obese participants, white meat intake was inversely associated with psychological distress symptoms.

High Red Meat Intake Exacerbates Dextran Sulfate-Induced Colitis by Altering Gut Microbiota in Mice

Inflammatory bowel disease (IBD) is a serious hazard to public health, but the precise etiology of the disease is unclear. High intake of red meat diet is closely related to the occurrence of IBD. In this study, we investigated whether the high intake of red meat can increase the sensitivity of colitis and the underlying mechanism. Mice were fed with different levels of red meat for 8 weeks and then the colonic contents were analyzed by 16S rRNA sequencing. Then 3% dextran sulfate sodium was used to induce colitis in mice. We observed the severity of colitis and inflammatory cytokines. We found that high-dose red meat caused intestinal microbiota disorder, reduced the relative abundance of Lachnospiraceae_NK4A136_group, Faecalibaculum, Blautia and Dubosiella, and increased the relative abundance of Bacteroides and Alistipes. This in turn leads to an increase in colitis and inflammatory cytokine secretion. Moreover, we found that high red meat intake impaired the colon barrier integrity and decreased the expression of ZO-1, claudin, and occludin. We also found high red meat intake induced the production of more inflammatory cytokines such as IL-1β, TNF-α, IL-17, and IL-6 and inflammatory inducible enzymes such as COX-2 and iNOS in dextran sulfate sodium-induced colitis. These results suggest that we should optimize the diet and reduce the intake of red meat to prevent the occurrence of IBD.

The price penalty for red meat substitutes in popular dishes and the diversity in substitution

Life cycle assessments (LCA) often highlight the environmental and health benefits for consumers if western diets substitute red meat. However, the specific trade-off consumer face when asked to substitute a red meat dish is scarcely researched, often neglecting the bouquet of substitution options and/or the price component involved. Four substitution strategies are evaluated within an individually adapted choice based conjoint: the substitution by (1) the same red meat dishes with a halved meat portion size, (2) novel plant-based products that mimic the functionality and taste, (3) authentic plant-based components that just mimic the functionality, and (4) vegetarian dishes that just neglect the meat component if still familiar to consumers. The analysis is executed for three popular red meat dishes to account for consistency across meal scenarios, namely Meatballs, Spaghetti Bolognese and Sausage Buns. The analysis is sensitive to red meat consumption habits to better understand the preferences of consumers that can actually substitute a red meat intake.

Variation in Red Meat Categories Meaningfully Influences Red Meat Intake Estimates of the U.S. Population Aged 2 + Years

Objectives Limitations in dietary assessment methodology lead to broad and inconsistent red meat intake categories. For example, red meat is often combined with processed meat, which includes processed poultry. Our objective was to quantitatively assess how these limitations influence red meat intake estimates of the U.S. population. Methods Three distinct red meat categories were identified from a series of systematic literature reviews. By systematically disaggregating and reaggregating meat variables (lean meat oz-eq) from the USDA's Food Pattern Equivalents Database, the following categories were created: 1) ‘unprocessed red meat’, 2) ‘total red meat’ [unprocessed red meat + processed red meat], and 3) ‘mixed red and processed meat’ [unprocessed red meat + total processed meat which includes processed poultry]. The 2015–16 and 2017–18 cycles of NHANES (n = 15,039) were combined to estimate and compare mean intakes across these three categories as well as the proportion of the population that exceeded age- and sex-specific red meat allotments in the Dietary Guidelines for Americans recommended eating patterns for those aged 2 + years. The two-part correlated model of the NCI Usual Intake method in SAS was used. Estimates were adjusted for age, sex, race, and ethnicity and pairwise comparisons were made across categories; P &lt; 0.05. Results Mean intake estimates (lean meat oz-eq/day) differed by red meat category (pairwise comparisons P &lt; 0.00,001): 1.5 ± 0.04 for unprocessed red meat, 2.2 ± 0.05 for total red meat, 2.4 ± 0.05 for mixed red and processed meat. The % of the population exceeding their respective age-sex red meat allotment in the DGA eating patterns also differed by category (pairwise comparisons P &lt; 0.00,001): 18.3 ± 1.9% for unprocessed red meat, 45.1 ± 1.8% for total red meat, 55.2 ± 1.8% for mixed red and processed meat. Conclusions Our results emphasize the importance of accurate and transparent red meat categories in nutrition epidemiology when estimating population intakes. Future research should examine how differences in these intake categories can influence associations between red meat intake and chronic disease. Funding Sources Not applicable.

Red Meat Intake and Glycemic and Insulinemic Risk Factors for Type 2 Diabetes: A Systematic Review and Meta-Analysis

Objectives Results from observational studies have suggested an association of red meat intake with increased risk of type 2 diabetes (T2D). However, results from randomized controlled trials (RCTs) have not shown clear evidence to support a mechanistic link between red meat intake and T2D risk factors. The objective of this systematic review and meta-analysis was to evaluate the impact of red meat intake on markers of glucose tolerance, including fasting glucose and insulin, postprandial glucose and insulin, insulin sensitivity and glycated hemoglobin (HbA1c). Methods A systematic review and meta-analysis was conducted on RCTs evaluating the effect of red meat intake, compared to lower or no red meat intake, on markers of glucose tolerance in adults. A search of PubMed yielded 17 relevant RCTs. Pooled estimates were expressed as standardized mean differences (SMD) between the red meat intervention and the control intervention with less or no red meat. Results Compared to diets with little or no red meat intake, there was no significant impact of red meat intake on insulin sensitivity (SMD: −0.12; 95% CI: −0.43, 0.19), insulin resistance (SMD: 0.23; 95% CI: −0.22, 0.68), fasting glucose (SMD: 0.12; 95% CI: −0.06, 0.30), fasting insulin (SMD: 0.16; 95% CI: −0.10, 0.42) or HbA1c (SMD: 0.00; 95% CI: −0.42, 0.43). Red meat intake modestly, but significantly, reduced postprandial glucose (SMD: −0.46; 95% CI: −0.77, −0.16; P &lt; 0.003) compared to diets with little or no red meat intake in a small number of studies (n = 3). However, there was no effect on postprandial insulin (SMD: −0.74; 95% CI: −1.64, 0.16). Conclusions The results of this meta-analysis suggest red meat intake does not impact several glycemic and insulinemic risk factors for T2D. Thus, it is unclear whether there is a causal relationship with red meat intake and T2D risk or if other confounding lifestyle factors may be driving the observed association. Further investigations are needed, particularly on other markers of glucose tolerance, such as pancreatic beta-cell function, to better understand whether a causal relationship exists between red meat intake and risk of T2D. PROSPERO Registration: CRD42020176059 Funding Sources This research was funded by Beef Checkoff.

A Prospective Analysis of Red and Processed Meat Intake in Relation to Colorectal Cancer Incidence in the Black Women's Health Study

Objectives African Americans have the highest incidence of colorectal cancer (CRC) of any racial/ethnic group in the US. High intake of red and processed meats has been shown to increase CRC risk in populations of European ancestry, but evidence in African American populations is limited. The association between saturated and monounsaturated fatty acid intakes, the primary types of fat in red and processed meat, and CRC is inconclusive. Thus, we prospectively assessed the intake of red and processed meats and dietary saturated and monounsaturated fatty acids in relation to CRC risk, utilizing the Black Women's Health Study (BWHS, 1995–2018). Methods Dietary data were derived from validated food frequency questionnaires completed in 1995 and 2001 by 52,695 BWHS participants. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression adjusted for energy, fiber, and discretionary fat. Results Over a median follow-up of 22 years, 564 women developed incident CRC. Total red meat intake was associated with a 25% increased risk of CRC per 100 g/day (HR = 1.25; 95% CI: 0.94–1.66), which was primarily due to intake of unprocessed red meat (HR = 1.33, 95% CI: 1.05–1.70). Processed meat and total saturated and monounsaturated fatty acid intakes were not associated with an increased risk of CRC. Conclusions Unprocessed red meat intake was associated with an increased risk of CRC in this cohort of African American women. The strong evidence, now including African American women, that red meat plays a role in the etiology of CRC suggests opportunities for prevention. Funding Sources This research was funded by National Institutes of Health grants U01 CA164974 and R01 CA058420, the Karin Grunebaum Cancer Research Foundation, and the Boston University Peter Paul Career Development Professorship.

Interplay between diet and gut microbiome, and circulating concentrations of trimethylamine N-oxide: findings from a longitudinal cohort of US men

ObjectivesGut-produced trimethylamine N-oxide (TMAO) is postulated as a possible link between red meat intake and poor cardiometabolic health. We investigated whether gut microbiome could modify associations of dietary precursors with TMAO concentrations and cardiometabolic risk markers among free-living individuals.DesignWe collected up to two pairs of faecal samples (n=925) and two blood samples (n=473), 6 months apart, from 307 healthy men in the Men’s Lifestyle Validation Study. Diet was assessed repeatedly using food-frequency questionnaires and diet records. We profiled faecal metagenome and metatranscriptome using shotgun sequencing and identified microbial taxonomic and functional features.ResultsTMAO concentrations were associated with the overall microbial compositions (permutational analysis of variance (PERMANOVA) test p=0.001). Multivariable taxa-wide association analysis identified 10 bacterial species whose abundance was significantly associated with plasma TMAO concentrations (false discovery rate <0.05). Higher habitual intake of red meat and choline was significantly associated with higher TMAO concentrations among participants who were microbial TMAO-producers (p<0.05), as characterised based on four abundant TMAO-predicting species, but not among other participants (for red meat, P-interaction=0.003; for choline, P-interaction=0.03). Among abundant TMAO-predicting species, Alistipes shahii significantly strengthened the positive association between red meat intake and HbA1c levels (P-interaction=0.01). Secondary analyses revealed that some functional features, including choline trimethylamine-lyase activating enzymes, were associated with TMAO concentrations.ConclusionWe identified microbial taxa that were associated with TMAO concentrations and modified the associations of red meat intake with TMAO concentrations and cardiometabolic risk markers. Our data underscore the interplay between diet and gut microbiome in producing potentially bioactive metabolites that may modulate cardiometabolic health.