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Nutrients Dec 2020The rise in obesity has emphasised a focus on lifestyle and dietary habits. We aimed to address the debate between low-carbohydrate and low-fat diets and compare their... (Meta-Analysis)
Meta-Analysis
BACKGROUND
The rise in obesity has emphasised a focus on lifestyle and dietary habits. We aimed to address the debate between low-carbohydrate and low-fat diets and compare their effects on body weight, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total cholesterol, and triglycerides in an adult population.
METHOD
Medline and Web of Science were searched for randomised controlled trials (RCTs) comparing low-fat and low-carbohydrate diets up to September 2019. Three independent reviewers extracted data. Risk of bias was assessed using the Cochrane tool. The meta-analysis was stratified by follow-up time using the random-effects models.
RESULTS
This meta-analysis of 38 studies assessed a total of 6499 adults. At 6-12 months, pooled analyses of mean differences of low-carbohydrate vs. low-fat diets favoured the low-carbohydrate diet for average weight change (mean difference -1.30 kg; 95% CI -2.02 to -0.57), HDL (0.05 mmol/L; 95% CI 0.03 to 0.08), and triglycerides (TG) (-0.10 mmol/L; -0.16 to -0.04), and favoured the low-fat diet for LDL (0.07 mmol/L; 95% CI 0.02 to 0.12) and total cholesterol (0.10 mmol/L; 95% CI 0.02 to 0.18). Conclusion and Relevance: This meta-analysis suggests that low-carbohydrate diets are effective at improving weight loss, HDL and TG lipid profiles. However, this must be balanced with potential consequences of raised LDL and total cholesterol in the long-term.
Topics: Adult; Cholesterol, HDL; Cholesterol, LDL; Diet, Carbohydrate-Restricted; Diet, Fat-Restricted; Humans; Lipids; Triglycerides; Weight Loss
PubMed: 33317019
DOI: 10.3390/nu12123774 -
Human Reproduction Update Nov 2022Lifestyle (dietary and/or physical activity [PA]) modification is recommended as first-line therapy to manage polycystic ovary syndrome (PCOS). Current recommendations... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Lifestyle (dietary and/or physical activity [PA]) modification is recommended as first-line therapy to manage polycystic ovary syndrome (PCOS). Current recommendations are based on healthy lifestyle practices for the general public since evidence for unique lifestyle approaches in PCOS is limited and low quality.
OBJECTIVE AND RATIONALE
We aimed to synthesize evidence on dietary and PA behaviors between women with PCOS and those without PCOS. Primary outcomes were overall diet quality, total energy intake and total PA, and secondary outcomes included macronutrients, micronutrients, food groups, foods, glycemic indices, sedentary time and sitting levels. We conducted this work to identify any unique lifestyle behaviors in women with PCOS that could underlie the propensity of weight gain and obesity in PCOS and be targeted for precision nutrition and PA interventions. These findings could be used to inform future practice recommendations and research that more effectively address complications (weight gain, obesity, diabetes, infertility, cardiovascular disease and mental health) in this high-risk population.
SEARCH METHODS
Databases of MEDLINE, Web of Science, Scopus and CINAHL were searched until 15 February 2022 to identify observational studies documenting dietary and PA behaviors between women with PCOS and without PCOS (Controls). Studies on children, adolescents (<18 years), pregnant or menopausal-aged women (>50 years) were excluded. Data were pooled by random-effects models and expressed as (standardized) mean differences (MD) and 95% CIs. The risk of bias was assessed by the Newcastle-Ottawa scale (NOS).
OUTCOMES
Fifty-four studies (N = 39 471 participants; [n = 8736 PCOS; 30 735 Controls]) were eligible (96%; [52/54] NOS scores ≥ 7). Women with PCOS had higher cholesterol (MD: 12.78, 95% CI: 1.48 to 24.08 mg/day; P = 0.03; I2 = 19%), lower magnesium (MD: -21.46, 95% CI: -41.03 to -1.91 mg/day; P = 0.03; I2 = 76%), and a tendency for lower zinc (MD: -1.08, 95% CI: -2.19 to -0.03 mg/day; P = 0.05; I2 = 96%) intake, despite lower alcohol consumption (MD: -0.95, 95% CI: -1.67 to 0.22 g/day; P = 0.02; I2 = 0%) versus Controls. Also, women with PCOS had lower total PA (standardized mean difference: -0.38, 95% CI: -0.72 to 0.03; P = 0.03; I2 = 98%). Conversely, energy, macronutrients (carbohydrate, fat, protein, fiber), micronutrients (folic acid, iron, calcium, sodium), glycemic index and glycemic load were similar (all: P ≥ 0.06). Most eligible studies reported lower total adherence to healthy eating patterns or poorer consumption of major food groups (grains, fruits, vegetables, proteins, seeds, nuts, dairy) in women with PCOS, as described narratively since variable study methodology did not permit meta-analyses.
WIDER IMPLICATIONS
Collective evidence supports that women with PCOS have a lower overall diet quality, poorer dietary intakes (higher cholesterol, lower magnesium and zinc) and lower total PA, despite lower alcohol consumption versus those without PCOS. Considerable heterogeneity among studies reinforces the need for research to address any relative contributions of other factors (e.g. genetic, metabolic or sociodemographic) to the observed differences. These clarifications may contribute to future evidence-based guideline recommendations on monitoring and managing PCOS in the era of precision lifestyle medicine.
Topics: Adolescent; Child; Female; Humans; Aged; Polycystic Ovary Syndrome; Magnesium; Diet; Obesity; Exercise; Weight Gain; Micronutrients; Zinc; Cholesterol
PubMed: 35639552
DOI: 10.1093/humupd/dmac023 -
Dietary Cholesterol and Cardiovascular Risk: A Science Advisory From the American Heart Association.Circulation Jan 2020The elimination of specific dietary cholesterol target recommendations in recent guidelines has raised questions about its role with respect to cardiovascular disease.... (Meta-Analysis)
Meta-Analysis
The elimination of specific dietary cholesterol target recommendations in recent guidelines has raised questions about its role with respect to cardiovascular disease. This advisory was developed after a review of human studies on the relationship of dietary cholesterol with blood lipids, lipoproteins, and cardiovascular disease risk to address questions about the relevance of dietary cholesterol guidance for heart health. Evidence from observational studies conducted in several countries generally does not indicate a significant association with cardiovascular disease risk. Although meta-analyses of intervention studies differ in their findings, most associate intakes of cholesterol that exceed current average levels with elevated total or low-density lipoprotein cholesterol concentrations. Dietary guidance should focus on healthy dietary patterns (eg, Mediterranean-style and DASH [Dietary Approaches to Stop Hypertension]-style diets) that are inherently relatively low in cholesterol with typical levels similar to the current US intake. These patterns emphasize fruits, vegetables, whole grains, low-fat or fat-free dairy products, lean protein sources, nuts, seeds, and liquid vegetable oils. A recommendation that gives a specific dietary cholesterol target within the context of food-based advice is challenging for clinicians and consumers to implement; hence, guidance focused on dietary patterns is more likely to improve diet quality and to promote cardiovascular health.
Topics: Cardiovascular Diseases; Cholesterol, Dietary; Diet, Western; Humans; Nutrition Policy; Recommended Dietary Allowances
PubMed: 31838890
DOI: 10.1161/CIR.0000000000000743 -
Nutrition and Health Jun 2023A recent meta-analysis found low-carbohydrate, high-protein diets (> 3.4 g/kg of bodyweight/day) (g/kg/day) decreased men's total testosterone (∼5.23 nmol/L)... (Meta-Analysis)
Meta-Analysis
A recent meta-analysis found low-carbohydrate, high-protein diets (> 3.4 g/kg of bodyweight/day) (g/kg/day) decreased men's total testosterone (∼5.23 nmol/L) [Whittaker and Harris (2022) Low-carbohydrate diets and men's cortisol and testosterone: systematic review and meta-analysis. . DOI: 10.1177/02601060221083079]. This finding has generated substantial discussion, however, it has often lacked clarity and context, with the term 'high-protein' being used unqualified. Firstly, diets < 3.4 g/kg/day are not associated with a consistent decrease in testosterone. Secondly, the average protein intake is ∼1.3 g/kg/day, conventional 'high-protein' diets are ∼1.8-3 g/kg/day and the vast majority of athletes are < 3.4 g/kg/day; meaning very few individuals will ever surpass 3.4 g/kg/day. To avoid such confusion in the future, the following definitions are proposed: very high (> 3.4 g/kg/day), high (1.9-3.4 g/kg/day), moderate (1.25-1.9 g/kg/day) and low (<1.25 g/kg/day). Using these, very high-protein diets (> 3.4 g/kg/day) appear to decrease testosterone, however high- and moderate-protein diets (1.25-3.4 g/kg/day) do not.
Topics: Male; Humans; Testosterone; Body Weight; Diet, Carbohydrate-Restricted; Nutritional Status; Diet, High-Protein
PubMed: 36266956
DOI: 10.1177/02601060221132922 -
Nutrition & Diabetes Nov 2020At present, the beneficial effect of the ketogenic diet (KD) on weight loss in obese patients is generally recognized. However, a systematic research on the role of KD... (Meta-Analysis)
Meta-Analysis
BACKGROUND
At present, the beneficial effect of the ketogenic diet (KD) on weight loss in obese patients is generally recognized. However, a systematic research on the role of KD in the improvement of glycemic and lipid metabolism of patients with diabetes is still found scarce.
METHODS
This meta-study employed the meta-analysis model of random effects or of fixed effects to analyze the average difference before and after KD and the corresponding 95% CI, thereby evaluating the effect of KD on T2DM.
RESULTS
After KD intervention, in terms of glycemic control, the level of fasting blood glucose decreased by 1.29 mmol/L (95% CI: -1.78 to -0.79) on average, and glycated hemoglobin A1c by 1.07 (95% CI: -1.37 to -0.78). As for lipid metabolism, triglyceride was decreased by 0.72 (95% CI: -1.01 to -0.43) on average, total cholesterol by 0.33 (95% CI: -0.66 to -0.01), and low-density lipoprotein by 0.05 (95% CI: -0.25 to -0.15); yet, high-density lipoprotein increased by 0.14 (95% CI: 0.03-0.25). In addition, patients' weight decreased by 8.66 (95% CI: -11.40 to -5.92), waist circumference by 9.17 (95% CI: -10.67 to -7.66), and BMI by 3.13 (95% CI: -3.31 to -2.95).
CONCLUSION
KD not only has a therapeutic effect on glycemic and lipid control among patients with T2DM but also significantly contributes to their weight loss.
Topics: Adult; Aged; Blood Glucose; Body Mass Index; Cholesterol; Diabetes Mellitus, Type 2; Diet, Ketogenic; Female; Glycated Hemoglobin; Glycemic Control; Humans; Insulin Resistance; Lipid Metabolism; Lipids; Male; Middle Aged; Triglycerides; Waist Circumference; Weight Loss
PubMed: 33257645
DOI: 10.1038/s41387-020-00142-z -
Circulation May 2022Despite substantial research highlighting the importance of exogenous dietary cholesterol intake and endogenous serum cholesterol level in human health, a thorough... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Despite substantial research highlighting the importance of exogenous dietary cholesterol intake and endogenous serum cholesterol level in human health, a thorough evaluation of the associations is lacking. Our study objective was to examine overall and cause-specific mortality in relation to dietary and serum cholesterol, as well as egg consumption, and conduct an updated meta-regression analysis of cohort studies.
METHODS
We conducted a prospective analysis of 27 078 men in the ATBC Study (Alpha-Tocopherol, Beta-Carotene Cancer Prevention). Multivariable-controlled cause-specific Cox proportional hazards regression models were used to calculate hazard ratios and 31-year absolute mortality risk differences. A systematic review and meta-analysis of cohort studies was also performed (PROSPERO [URL: https://www.crd.york.ac.uk/prospero/; Unique identifier: CRD42021272756]).
RESULTS
Based on 482 316 person-years of follow-up, we identified 22 035 deaths, including 9110 deaths from cardiovascular disease (CVD). Greater dietary cholesterol and egg consumption were associated with increased risk of overall and CVD-related mortality. Hazard ratios for each additional 300 mg cholesterol intake per day were 1.10 and 1.13 for overall and CVD-related mortality, respectively; for each additional 50-g egg consumed daily, hazard ratios were 1.06 and 1.09, respectively, for overall and CVD-related mortality (all values<0.0001). After multivariable adjustment, higher serum total cholesterol concentrations were associated with increased risk of CVD-related mortality (hazard ratios per 1 SD increment, 1.14; <0.0001). The observed associations were generally similar across cohort subgroups. The updated meta-analysis of cohort studies on the basis of 49 risk estimates, 3 601 401 participants, and 255 479 events showed consumption of 1 additional 50-g egg daily was associated with significantly increased CVD risk (pooled relative risk, 1.04 [95% CI, 1.00-1.08]; I=80.1%). In the subgroup analysis of geographic regions (=0.02), an increase of 50-g egg consumed daily was associated with a higher risk of CVD in US cohorts (pooled relative risk, 1.08 [95% CI, 1.02-1.14]) and appeared related to a higher CVD risk in European cohorts with borderline significance (pooled relative risk, 1.05), but was not associated with CVD risk in Asian cohorts.
CONCLUSIONS
In this prospective cohort study and updated meta-analysis, greater dietary cholesterol and egg consumption were associated with increased risk of overall and CVD-related mortality. Our findings support restricted consumption of dietary cholesterol as a means to improve long-term health and longevity.
Topics: Cardiovascular Diseases; Cause of Death; Cholesterol, Dietary; Eggs; Humans; Male; Prospective Studies; Risk Factors
PubMed: 35360933
DOI: 10.1161/CIRCULATIONAHA.121.057642 -
Nutrients Jul 2023Psoriasis is a chronic immune-dysregulated inflammatory disease and hypovitaminosis D is considered a risk factor. We conducted an online database search to review and... (Meta-Analysis)
Meta-Analysis Review
Psoriasis is a chronic immune-dysregulated inflammatory disease and hypovitaminosis D is considered a risk factor. We conducted an online database search to review and meta-analyze the relationship between vitamin D, other bone metabolism parameters, and psoriasis. The efficacy of oral vitamin D supplementation in improving Psoriasis Area and Severity Index (PASI) was also evaluated. Non-original articles, case reports, and animal studies were excluded. Bias risk was assessed according to the Cochrane Collaboration's tool and the Newcastle-Ottawa scale in randomized controlled trials (RCTs) and case-control studies, respectively. Unstandardized mean differences were used for data synthesis. Twenty-three studies reported serum 25 hydroxyvitamin D (25(OH)D) levels in 1876 psoriasis patients and 7532 controls. Psoriasis patients had significantly lower 25(OH)D levels than controls (21.0 ± 8.3 vs. 27.3 ± 9.8, < 0.00001). Conversely, 450 psoriasis patients had lower levels of parathormone than 417 controls (38.7 ± 12.8 vs. 43.7 ± 16.5, = 0.015). Four RCTs examined the effect of oral vitamin D supplementation on psoriasis for 173 patients and 160 patients were treated with placebo. No significant differences were found in PASI after 3, 6, and 12 months of supplementation. It is shown that 25(OH)D serum levels are significantly lower in psoriasis, but, although the granularity of RCT methodology may have influenced the pooled analysis, vitamin D supplementation did not seem to improve clinical manifestations.
Topics: Humans; Vitamin D; Vitamins; Psoriasis; Vitamin D Deficiency; Calcifediol; Dietary Supplements
PubMed: 37571324
DOI: 10.3390/nu15153387 -
European Journal of Heart Failure Sep 2021To appraise meta-analytically determined effect of dietary interventions and nutritional supplements on heart failure (HF)-related outcomes, and create an evidence map...
AIMS
To appraise meta-analytically determined effect of dietary interventions and nutritional supplements on heart failure (HF)-related outcomes, and create an evidence map to visualize the findings and certainty of evidence.
METHODS AND RESULTS
Online databases were systematically searched for meta-analyses of randomized controlled trials (RCTs) evaluating the effect of dietary interventions and nutritional supplements on HF outcomes and incidence. These were then updated if new RCTs were available. Estimates were pooled using a random-effects model and reported as risk ratios (RRs) or mean differences with 95% confidence intervals. We identified 14 relevant meta-analyses, to which 21 new RCTs were added. The total evidence base reviewed included 122 RCTs (n = 176 097 participants) assessing 14 interventions. We found that coenzyme Q10 was associated with lower all-cause mortality [RR 0.69 (0.50-0.96); I = 0%; low certainty of evidence] in HF patients. Incident HF risk was reduced with Mediterranean diet [RR 0.45 (0.26-0.79); I = 0%; low certainty of evidence]. Vitamin E supplementation was associated with a small but significant increase in the risk of HF hospitalization [RR 1.21 (1.04-1.40); I2 = 0%; moderate certainty of evidence]. There was moderate certainty of evidence that thiamine, vitamin D, iron, and L-carnitine supplementation had a beneficial effect on left ventricular ejection fraction.
CONCLUSION
Coenzyme Q10 may reduce all-cause mortality in HF patients, while a Mediterranean diet may reduce the risk of incident HF; however, the low certainty of evidence warrants the need for further RCTs to confirm a definite clinical role. RCT data were lacking for several common interventions including intermittent fasting, caffeine, DASH diet, and ketogenic diet. More research is needed to fill the knowledge gap.
Topics: Dietary Supplements; Heart Failure; Humans; Meta-Analysis as Topic; Randomized Controlled Trials as Topic; Vitamin D; Vitamins
PubMed: 34173307
DOI: 10.1002/ejhf.2278 -
The Cochrane Database of Systematic... May 2020Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally, it is unclear whether the energy from... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally, it is unclear whether the energy from saturated fats eliminated from the diet are more helpfully replaced by polyunsaturated fats, monounsaturated fats, carbohydrate or protein.
OBJECTIVES
To assess the effect of reducing saturated fat intake and replacing it with carbohydrate (CHO), polyunsaturated (PUFA), monounsaturated fat (MUFA) and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.
SEARCH METHODS
We updated our searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and Embase (Ovid) on 15 October 2019, and searched Clinicaltrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) on 17 October 2019.
SELECTION CRITERIA
Included trials fulfilled the following criteria: 1) randomised; 2) intention to reduce saturated fat intake OR intention to alter dietary fats and achieving a reduction in saturated fat; 3) compared with higher saturated fat intake or usual diet; 4) not multifactorial; 5) in adult humans with or without cardiovascular disease (but not acutely ill, pregnant or breastfeeding); 6) intervention duration at least 24 months; 7) mortality or cardiovascular morbidity data available.
DATA COLLECTION AND ANALYSIS
Two review authors independently assessed inclusion, extracted study data and assessed risk of bias. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity analyses, funnel plots and GRADE assessment.
MAIN RESULTS
We included 15 randomised controlled trials (RCTs) (16 comparisons, ~59,000 participants), that used a variety of interventions from providing all food to advice on reducing saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of combined cardiovascular events by 21% (risk ratio (RR) 0.79; 95% confidence interval (CI) 0.66 to 0.93, 11 trials, 53,300 participants of whom 8% had a cardiovascular event, I² = 65%, GRADE moderate-quality evidence). Meta-regression suggested that greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials. The number needed to treat for an additional beneficial outcome (NNTB) was 56 in primary prevention trials, so 56 people need to reduce their saturated fat intake for ~four years for one person to avoid experiencing a CVD event. In secondary prevention trials, the NNTB was 32. Subgrouping did not suggest significant differences between replacement of saturated fat calories with polyunsaturated fat or carbohydrate, and data on replacement with monounsaturated fat and protein was very limited. We found little or no effect of reducing saturated fat on all-cause mortality (RR 0.96; 95% CI 0.90 to 1.03; 11 trials, 55,858 participants) or cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 10 trials, 53,421 participants), both with GRADE moderate-quality evidence. There was little or no effect of reducing saturated fats on non-fatal myocardial infarction (RR 0.97, 95% CI 0.87 to 1.07) or CHD mortality (RR 0.97, 95% CI 0.82 to 1.16, both low-quality evidence), but effects on total (fatal or non-fatal) myocardial infarction, stroke and CHD events (fatal or non-fatal) were all unclear as the evidence was of very low quality. There was little or no effect on cancer mortality, cancer diagnoses, diabetes diagnosis, HDL cholesterol, serum triglycerides or blood pressure, and small reductions in weight, serum total cholesterol, LDL cholesterol and BMI. There was no evidence of harmful effects of reducing saturated fat intakes.
AUTHORS' CONCLUSIONS
The findings of this updated review suggest that reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events. Replacing the energy from saturated fat with polyunsaturated fat or carbohydrate appear to be useful strategies, while effects of replacement with monounsaturated fat are unclear. The reduction in combined cardiovascular events resulting from reducing saturated fat did not alter by study duration, sex or baseline level of cardiovascular risk, but greater reduction in saturated fat caused greater reductions in cardiovascular events.
Topics: Adult; Cardiovascular Diseases; Cause of Death; Cholesterol; Dietary Carbohydrates; Dietary Fats; Dietary Fats, Unsaturated; Dietary Proteins; Energy Intake; Fatty Acids; Female; Humans; Male; Myocardial Infarction; Randomized Controlled Trials as Topic; Stroke
PubMed: 32428300
DOI: 10.1002/14651858.CD011737.pub2 -
Reproductive Biology and Endocrinology... Dec 2022There is a growing body of human, animal and in vitro studies on vitamin D (vit D) substitution in endometriosis. The aim of this systematic review is to critically... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
There is a growing body of human, animal and in vitro studies on vitamin D (vit D) substitution in endometriosis. The aim of this systematic review is to critically appraise and qualitatively synthesize the results of the available studies that examine the supplementation of vit D for endometriosis treatment.
METHODS
A systematic search of the literature was conducted in four electronic databases (Medline, Cochrane, Scopus, Embase) and grey literature for original research articles on humans, animals and in vitro models published in any language.
RESULTS
Four human studies, four animal studies and four in vitro studies were included. Quantitative synthesis of human studies showed no significant effect of vit D intake for dysmenorrhea (2 studies, 44 vit D vs 44 placebo, mean -0.71, 95% CI -1.94, 0.51) and non-cyclic pelvic pain (2 studies, 42 vit D vs 38 placebo, mean 0.34, 95% CI -0.02, 0.71). Regarding reproductive outcomes in women with endometriosis after in vitro fertilization, the only available study showed no differences between women taking vit D and women taking placebo. Three of the four included animal studies showed regression of endometriotic implants when treated with vit D. The in vitro studies demonstrated that vit D decreases invasion and proliferation of endometriotic lesions without affecting apoptosis.
CONCLUSIONS
Although in vitro and animal studies suggest regression of the endometriotic implants and decrease of invasion and proliferation after vit D supplementation, this was not reflected in the results of the meta-analysis, which showed no benefit of vit D supplementation in patients with endometriosis and dysmenorrhea or non-cyclic pelvic pain as well as on the outcome of IVF treatment. However, given the heterogeneity and the diversity of the available studies, more research is required to shed light on the role of vit D supplementation in women with endometriosis.
Topics: Animals; Humans; Female; Endometriosis; Dysmenorrhea; Vitamin D; Vitamins; Pelvic Pain; Dietary Supplements
PubMed: 36578019
DOI: 10.1186/s12958-022-01051-9