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Advances in Nutrition (Bethesda, Md.) May 2015Inflammation is believed to play a central role in many of the chronic diseases that characterize modern society. In the past decade, our understanding of how dietary... (Review)
Review
Inflammation is believed to play a central role in many of the chronic diseases that characterize modern society. In the past decade, our understanding of how dietary fats affect our immune system and subsequently our inflammatory status has grown considerably. There are compelling data showing that high-fat meals promote endotoxin [e.g., lipopolysaccharide (LPS)] translocation into the bloodstream, stimulating innate immune cells and leading to a transient postprandial inflammatory response. The nature of this effect is influenced by the amount and type of fat consumed. The role of various dietary constituents, including fats, on gut microflora and subsequent health outcomes in the host is another exciting and novel area of inquiry. The impact of specific fatty acids on inflammation may be central to how dietary fats affect health. Three key fatty acid-inflammation interactions are briefly described. First, the evidence suggests that saturated fatty acids induce inflammation in part by mimicking the actions of LPS. Second, the often-repeated claim that dietary linoleic acid promotes inflammation was not supported in a recent systematic review of the evidence. Third, an explanation is offered for why omega-3 (n-3) polyunsaturated fatty acids are so much less anti-inflammatory in humans than in mice. The article closes with a cautionary tale from the genomic literature that illustrates why extrapolating the results from inflammation studies in mice to humans is problematic.
Topics: Animals; Diet; Dietary Fats; Disease Models, Animal; Endotoxins; Fatty Acids; Humans; Inflammation
PubMed: 25979502
DOI: 10.3945/an.114.006940 -
Nutrients Aug 2019Weight regain after a successful weight loss intervention is very common. Most studies show that, on average, the weight loss attained during a weight loss intervention... (Meta-Analysis)
Meta-Analysis
Weight regain after a successful weight loss intervention is very common. Most studies show that, on average, the weight loss attained during a weight loss intervention period is not or is not fully maintained during follow-up. We review what is currently known about dietary strategies for weight loss maintenance, focusing on nutrient composition by means of a systematic review and meta-analysis of studies and discuss other potential strategies that have not been studied so far. Twenty-one studies with 2875 participants who were overweight or obese are included in this systematic review and meta-analysis. Studies investigate increased protein intake (12 studies), lower dietary glycemic index (four studies), green tea (three studies), conjugated linoleic acid (three studies), higher fibre intake (three studies), and other miscellaneous interventions (six studies). The meta-analysis shows a significant beneficial effect of higher protein intake on the prevention of weight regain (SMD (standardized mean difference) -0.17 (95% CI -0.29, -0.05), = 2.80, = 0.005), without evidence for heterogeneity among the included studies. No significant effect of the other strategies is detected. Diets that combine higher protein intake with different other potentially beneficial strategies, such as anti-inflammatory or anti-insulinemic diets, may have more robust effects, but these have not been tested in randomized clinical trials yet.
Topics: Adolescent; Adult; Aged; Diet, Healthy; Dietary Fiber; Dietary Proteins; Dietary Supplements; Energy Intake; Female; Glycemic Index; Humans; Linoleic Acids, Conjugated; Male; Middle Aged; Nutritive Value; Obesity; Recurrence; Treatment Outcome; Weight Gain; Weight Loss; Young Adult
PubMed: 31443231
DOI: 10.3390/nu11081916 -
BMJ (Clinical Research Ed.) Apr 2016To examine the traditional diet-heart hypothesis through recovery and analysis of previously unpublished data from the Minnesota Coronary Experiment (MCE) and to put... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
To examine the traditional diet-heart hypothesis through recovery and analysis of previously unpublished data from the Minnesota Coronary Experiment (MCE) and to put findings in the context of existing diet-heart randomized controlled trials through a systematic review and meta-analysis.
DESIGN
The MCE (1968-73) is a double blind randomized controlled trial designed to test whether replacement of saturated fat with vegetable oil rich in linoleic acid reduces coronary heart disease and death by lowering serum cholesterol. Recovered MCE unpublished documents and raw data were analyzed according to hypotheses prespecified by original investigators. Further, a systematic review and meta-analyses of randomized controlled trials that lowered serum cholesterol by providing vegetable oil rich in linoleic acid in place of saturated fat without confounding by concomitant interventions was conducted.
SETTING
One nursing home and six state mental hospitals in Minnesota, United States.
PARTICIPANTS
Unpublished documents with completed analyses for the randomized cohort of 9423 women and men aged 20-97; longitudinal data on serum cholesterol for the 2355 participants exposed to the study diets for a year or more; 149 completed autopsy files.
INTERVENTIONS
Serum cholesterol lowering diet that replaced saturated fat with linoleic acid (from corn oil and corn oil polyunsaturated margarine). Control diet was high in saturated fat from animal fats, common margarines, and shortenings.
MAIN OUTCOME MEASURES
Death from all causes; association between changes in serum cholesterol and death; and coronary atherosclerosis and myocardial infarcts detected at autopsy.
RESULTS
The intervention group had significant reduction in serum cholesterol compared with controls (mean change from baseline -13.8%v-1.0%; P<0.001). Kaplan Meier graphs showed no mortality benefit for the intervention group in the full randomized cohort or for any prespecified subgroup. There was a 22% higher risk of death for each 30 mg/dL (0.78 mmol/L) reduction in serum cholesterol in covariate adjusted Cox regression models (hazard ratio 1.22, 95% confidence interval 1.14 to 1.32; P<0.001). There was no evidence of benefit in the intervention group for coronary atherosclerosis or myocardial infarcts. Systematic review identified five randomized controlled trials for inclusion (n=10,808). In meta-analyses, these cholesterol lowering interventions showed no evidence of benefit on mortality from coronary heart disease (1.13, 0.83 to 1.54) or all cause mortality (1.07, 0.90 to 1.27).
CONCLUSIONS
Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid.
Topics: Adult; Aged; Aged, 80 and over; Cause of Death; Cholesterol; Coronary Artery Disease; Coronary Disease; Diet, Fat-Restricted; Dietary Fats; Double-Blind Method; Female; History, 20th Century; Humans; Kaplan-Meier Estimate; Linoleic Acid; Male; Middle Aged; Minnesota; Myocardial Infarction; Plant Oils; Randomized Controlled Trials as Topic; Risk Factors; Young Adult
PubMed: 27071971
DOI: 10.1136/bmj.i1246 -
Circulation Oct 2014Previous studies on intake of linoleic acid (LA), the predominant n-6 fatty acid, and coronary heart disease (CHD) risk have generated inconsistent results. We performed... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Previous studies on intake of linoleic acid (LA), the predominant n-6 fatty acid, and coronary heart disease (CHD) risk have generated inconsistent results. We performed a systematic review and meta-analysis of prospective cohort studies to summarize the evidence regarding the relation of dietary LA intake and CHD risk.
METHODS AND RESULTS
We searched MEDLINE and EMBASE databases through June 2013 for prospective cohort studies that reported the association between dietary LA and CHD events. In addition, we used unpublished data from cohort studies in a previous pooling project. We pooled the multivariate-adjusted relative risk (RR) to compare the highest with the lowest categories of LA intake using fixed-effect meta-analysis. We identified 13 published and unpublished cohort studies with a total of 310 602 individuals and 12 479 total CHD events, including 5882 CHD deaths. When the highest category was compared with the lowest category, dietary LA was associated with a 15% lower risk of CHD events (pooled RR, 0.85; 95% confidence intervals, 0.78-0.92; I(2)=35.5%) and a 21% lower risk of CHD deaths (pooled RR, 0.79; 95% confidence intervals, 0.71-0.89; I(2)=0.0%). A 5% of energy increment in LA intake replacing energy from saturated fat intake was associated with a 9% lower risk of CHD events (RR, 0.91; 95% confidence intervals, 0.87-0.96) and a 13% lower risk of CHD deaths (RR, 0.87; 95% confidence intervals, 0.82-0.94).
CONCLUSIONS
In prospective observational studies, dietary LA intake is inversely associated with CHD risk in a dose-response manner. These data provide support for current recommendations to replace saturated fat with polyunsaturated fat for primary prevention of CHD.
Topics: Coronary Disease; Dietary Fats; Humans; Linoleic Acid; Observational Studies as Topic; Prospective Studies; Risk Factors
PubMed: 25161045
DOI: 10.1161/CIRCULATIONAHA.114.010236 -
Nutrients Feb 2023Increasingly, studies have discovered that different fatty acids (Fas) are linked to colorectal cancer (CRC) risk. (Meta-Analysis)
Meta-Analysis
BACKGROUND
Increasingly, studies have discovered that different fatty acids (Fas) are linked to colorectal cancer (CRC) risk.
METHODS
We systematically searched Embase and Medline databases to identify eligible studies that examined the associations of different types of Fas with CRC risk. The effect estimates and their 95% confidence intervals (Cis) were pooled using a random-effects model. Subgroup and sensitivity analyses were performed to examine the robustness of the study findings.
RESULTS
This study evaluated the associations of 28 dietary and 18 blood Fas with CRC risk by summarizing the most updated evidence from 54 observational and four Mendelian Randomization (MR) studies. The present findings suggested that high dietary intake of eicosapentaenoic acid (EPA), docosahexanoic acid (DHA), and docosapentaenoic acid (DPA) are related to low risk of CRC, while the -6/-3 PUFA ratio and trans-FA are related to high risk of CRC. The summary of all cohort studies found that a high intake of SFA and DHA was a protective factor for CRC, and a high intake of the -6/-3 PUFA ratio was a risk factor for CRC. In the subgroup analysis of cancer subsites, we found that the dietary intake of linoleic acid (LA) and trans-FA are risk factors, while DPA is a protective factor for colon cancer. High dietary DHA intake was associated with a lower risk of rectal cancer, while the dietary -6/-3 PUFA ratio was associated with a higher risk of rectal cancer. Meta-analysis of blood FA levels showed a significant reverse association between blood pentadecanoic acid and CRC risk, whilst other blood Fas showed no significant association with CRC risk. All included MR studies showed that high plasma arachidonic acid (AA) is associated with increased CRC risk.
CONCLUSIONS
Current evidence on the dietary intake and blood levels of Fas in relation to CRC risk is less consistent. Future studies are needed to investigate how the metabolism of Fas contributes to CRC development.
Topics: Humans; Fatty Acids; Fatty Acids, Omega-3; Eating; Risk Factors; Colorectal Neoplasms; Rectal Neoplasms; Observational Studies as Topic
PubMed: 36771436
DOI: 10.3390/nu15030730 -
Nutrition Journal Oct 2023The present systematic review and meta-analysis sought to evaluate the effects of conjugated linoleic acid (CLA) supplementation on glycemic control, adipokines,... (Meta-Analysis)
Meta-Analysis Review
The effects of conjugated linoleic acid supplementation on glycemic control, adipokines, cytokines, malondialdehyde and liver function enzymes in patients at risk of cardiovascular disease: a GRADE-assessed systematic review and dose-response meta-analysis.
BACKGROUND
The present systematic review and meta-analysis sought to evaluate the effects of conjugated linoleic acid (CLA) supplementation on glycemic control, adipokines, cytokines, malondialdehyde (MDA) and liver function enzymes in patients at risk of cardiovascular disease.
METHODS
Relevant studies were obtained by searching the PubMed, SCOPUS and Web of Science databases (from inception to January 2023). Weighted mean differences (WMD) and 95% confidence intervals (CIs) were pooled using a random-effects model. Heterogeneity, sensitivity analysis, and publication bias were reported using standard methods.
RESULTS
A pooled analysis of 13 randomized controlled trials (RCTs) revealed that CLA supplementation led to a significant increment in fasting blood glucose (FBG) (WMD: 4.49 mg/dL; 95%CI: 2.39 to 6.59; P < 0.001), and aspartate aminotransferase (AST) (WMD: 2.54 IU/L; 95%CI: 0.06 to 5.01; P = 0.044). Moreover, CLA supplementation decreased leptin (WMD: -1.69 ng/ml; 95% CI: -1.80 to -1.58; P < 0.001), and interleukin 6 (IL-6) (WMD: -0.44 pg/ml; 95%CI: -0.86 to -0.02; P = 0.037). However, there was no effect on hemoglobin A1c (HbA1c), homeostatic model assessment for insulin resistance (HOMA-IR), C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), and alanine aminotransferase (ALT) adiponectin compared to the control group.
CONCLUSION
Our findings showed the overall favorable effect of CLA supplementation on the adipokines and cytokines including serum IL-6, and leptin, while increasing FBG and AST. It should be noted that the mentioned metabolic effects of CLA consumption were small and may not reach clinical importance.
PROSPERO REGISTERATION COD
CRD42023426374.
Topics: Humans; Dietary Supplements; Leptin; Cytokines; Linoleic Acids, Conjugated; Interleukin-6; Adipokines; Cardiovascular Diseases; Glycemic Control; Malondialdehyde; Liver; Blood Glucose
PubMed: 37794481
DOI: 10.1186/s12937-023-00876-3 -
Frontiers in Immunology 2023Many studies have investigated the effect of conjugated linoleic acid (CLA) supplementation on inflammatory cytokines and adipokines. However, the results of these... (Meta-Analysis)
Meta-Analysis
The effects of conjugated linoleic acid supplementation on inflammatory cytokines and adipokines in adults: A GRADE-assessed systematic review and dose-response meta-analysis.
BACKGROUND AND AIMS
Many studies have investigated the effect of conjugated linoleic acid (CLA) supplementation on inflammatory cytokines and adipokines. However, the results of these studies are not consistent. Therefore, this systematic review and meta-analysis were designed to comprehensively evaluate the effect of CLA supplementation on inflammatory cytokines and adipokines.
METHODS
Randomized controlled trials (RCTs) examining the effects of CLA supplementation on C-reactive protein (CRP), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), adiponectin, and leptin, published up to March 2022, were identified through PubMed, SCOPUS, and ISI Web of Science databases. A random-effects model was used to calculate weighted mean differences (WMDs) with 95% confidence intervals (CI) for 42 studies that included 1,109 participants.
RESULTS
Findings from 42 studies with 58 arms indicated that CLA supplementation significantly decreased IL-6 and TNF-α levels and also slightly increased CRP levels. However, adiponectin and leptin levels did not change after CLA supplementation. A subgroup analysis found that CLA supplementation reduced adiponectin and leptin in women.
CONCLUSION
Our results demonstrated that CLA supplementation increased CRP levels and decreased TNF-α and IL-6 levels. Therefore, it seems that CLA can have both proinflammatory and anti-inflammatory roles.
SYSTEMATIC REVIEW REGISTRATION
https://www.crd.york.ac.uk/prospero/, identifier (CRD42022331110).
Topics: Female; Humans; Adult; Cytokines; Adipokines; Leptin; Interleukin-6; Linoleic Acids, Conjugated; Tumor Necrosis Factor-alpha; Adiponectin; Dietary Supplements
PubMed: 36911696
DOI: 10.3389/fimmu.2023.1092077 -
The American Journal of Clinical... Jul 2020Current evidence on associations between intakes of linoleic acid (LA), the predominant n-6 (ω-6) fatty acid, and mortality is inconsistent and has not been summarized... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Current evidence on associations between intakes of linoleic acid (LA), the predominant n-6 (ω-6) fatty acid, and mortality is inconsistent and has not been summarized by a systematic review and meta-analysis.
OBJECTIVE
The aim was to perform a systematic review and meta-analysis of prospective cohort studies to examine associations between LA intake and mortality.
METHODS
We conducted a comprehensive search of MEDLINE and EMBASE databases through 31 July 2019 for prospective cohort studies reporting associations of LA (assessed by dietary surveys and/or LA concentrations in adipose tissue or blood compartments) with mortality from all causes, cardiovascular disease (CVD), and cancer. Multivariable-adjusted RRs were pooled using random-effects meta-analysis.
RESULTS
Thirty-eight studies reporting 44 prospective cohorts were identified; these included 811,069 participants with dietary intake assessment (170,076 all-cause, 50,786 CVD, and 59,684 cancer deaths) and 65,411 participants with biomarker measurements (9758 all-cause, 6492 CVD, and 1719 cancer deaths). Pooled RRs comparing extreme categories of dietary LA intake (high vs low) were 0.87 (95% CI: 0.81, 0.94; I2 = 67.9%) for total mortality, 0.87 (95% CI: 0.82, 0.92; I2 = 3.7%) for CVD mortality, and 0.89 (95% CI: 0.85, 0.93; I2 = 0%) for cancer mortality. Pooled RRs for each SD increment in LA concentrations in adipose tissue/blood compartments were 0.91 (95% CI: 0.87, 0.95; I2 = 64.1%) for total mortality, 0.89 (95% CI: 0.85, 0.94; I2 = 28.9%) for CVD mortality, and 0.91 (95% CI: 0.84, 0.98; I2 = 26.3%) for cancer mortality. Meta-regressions suggested baseline age and dietary assessment methods as potential sources of heterogeneity for the association between LA and total mortality.
CONCLUSIONS
In prospective cohort studies, higher LA intake, assessed by dietary surveys or biomarkers, was associated with a modestly lower risk of mortality from all causes, CVD, and cancer. These data support the potential long-term benefits of PUFA intake in lowering the risk of CVD and premature death.
Topics: Adult; Aged; Aged, 80 and over; Cardiovascular Diseases; Fatty Acids, Omega-6; Female; Humans; Linoleic Acid; Male; Middle Aged; Neoplasms; Prospective Studies; Randomized Controlled Trials as Topic; Young Adult
PubMed: 32020162
DOI: 10.1093/ajcn/nqz349 -
International Journal of Molecular... Sep 2023The objective of this meta-analysis was to examine the impact of a low-ratio linoleic acid/α-linolenic acid (LA/ALA) diet on the glycemic profile of adults. A... (Meta-Analysis)
Meta-Analysis Review
The objective of this meta-analysis was to examine the impact of a low-ratio linoleic acid/α-linolenic acid (LA/ALA) diet on the glycemic profile of adults. A comprehensive search was performed across four databases (Web of Science, Scopus, Embase, and PubMed) to evaluate the influence of the low-ratio LA/ALA. Relevant references were screened up until February 2023. Intervention effects were analyzed by calculating change values as weighted mean differences (WMD) and 95% confidence intervals (CI) using fixed-effects models. Additionally, subgroup analysis and meta-regression were employed to investigate potential sources of heterogeneity. Twenty-one randomized controlled trials (RCTs) were included, and the low-ratio LA/ALA diet had no significant effect on fasting blood sugar (FBS, WMD: 0.00 mmol/L, 95% CI: -0.06, 0.06, = 0.989, I = 0.0%), insulin levels (WMD: 0.20 μIU/mL, 95% CI: -0.23, 0.63, = 0.360, I = 3.2%), homeostatic model assessment insulin resistance (HOMA-IR, WMD: 0.09, 95% CI: -0.06, 0.23, = 0.243, I = 0.0%), and hemoglobin A1c (HbA1c, WMD: -0.01%, 95% CI: -0.07, 0.06, = 0.836, I = 0.0%). Based on subgroup analyses, it was observed that the impact of a low-ratio LA/ALA diet on elevated plasma insulin (WMD: 1.31 μIU/mL, 95% CI: 0.08, 2.54, = 0.037, I = 32.0%) and HOMA-IR (WMD: 0.47, 95% CI: 0.10, 0.84, = 0.012, I = 0.0%) levels exhibited greater prominence in North America compared to Asian and European countries. Publication bias was not detected for FBS, insulin, HOMA-IR, and HbA1c levels according to the Begg and Egger tests. Furthermore, the conducted sensitivity analyses indicated stability, as the effects of the low-ratio LA/ALA diet on various glycemic and related metrics remained unchanged even after removing individual studies. Overall, based on the available studies, it can be concluded that the low-ratio LA/ALA diet has limited impact on blood glucose-related biomarker levels.
Topics: Adult; Humans; Glycated Hemoglobin; Linoleic Acid; alpha-Linolenic Acid; Glucose; Insulin
PubMed: 37762686
DOI: 10.3390/ijms241814383 -
The British Journal of Nutrition Mar 2016Demand for organic milk is partially driven by consumer perceptions that it is more nutritious. However, there is still considerable uncertainty over whether the use of... (Meta-Analysis)
Meta-Analysis Review
Higher PUFA and n-3 PUFA, conjugated linoleic acid, α-tocopherol and iron, but lower iodine and selenium concentrations in organic milk: a systematic literature review and meta- and redundancy analyses.
Demand for organic milk is partially driven by consumer perceptions that it is more nutritious. However, there is still considerable uncertainty over whether the use of organic production standards affects milk quality. Here we report results of meta-analyses based on 170 published studies comparing the nutrient content of organic and conventional bovine milk. There were no significant differences in total SFA and MUFA concentrations between organic and conventional milk. However, concentrations of total PUFA and n-3 PUFA were significantly higher in organic milk, by an estimated 7 (95 % CI -1, 15) % and 56 (95 % CI 38, 74) %, respectively. Concentrations of α-linolenic acid (ALA), very long-chain n-3 fatty acids (EPA+DPA+DHA) and conjugated linoleic acid were also significantly higher in organic milk, by an 69 (95 % CI 53, 84) %, 57 (95 % CI 27, 87) % and 41 (95 % CI 14, 68) %, respectively. As there were no significant differences in total n-6 PUFA and linoleic acid (LA) concentrations, the n-6:n-3 and LA:ALA ratios were lower in organic milk, by an estimated 71 (95 % CI -122, -20) % and 93 (95 % CI -116, -70) %. It is concluded that organic bovine milk has a more desirable fatty acid composition than conventional milk. Meta-analyses also showed that organic milk has significantly higher α-tocopherol and Fe, but lower I and Se concentrations. Redundancy analysis of data from a large cross-European milk quality survey indicates that the higher grazing/conserved forage intakes in organic systems were the main reason for milk composition differences.
Topics: Animals; Cattle; Dairying; Dietary Fats, Unsaturated; Evidence-Based Practice; Fatty Acids, Omega-3; Food, Organic; Humans; Iodine; Iron, Dietary; Linoleic Acids, Conjugated; Livestock; Milk; Nutritive Value; Selenium; alpha-Tocopherol
PubMed: 26878105
DOI: 10.1017/S0007114516000349