Effect of Mediterranean diet on liver enzymes: a systematic review and meta-analysis of randomised controlled trials

Mediterranean diet for the management of metabolic dysfunction-associated steatotic liver disease in non-Mediterranean, Western countries: What's known and what's needed?

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common liver disease worldwide, affecting 30% of the population in Western countries. MASLD is considered the hepatic manifestation of the metabolic syndrome, pathophysiologically underpinned by insulin resistance and frequently co-exists with hypertension, central obesity and dyslipidaemia. Currently, safe and effective pharmacotherapies for MASLD are limited, making weight loss with lifestyle changes the mainstay therapy. A Mediterranean diet (MedDiet) has emerged as an effective dietary pattern for preventing and managing MASLD, but most studies have been conducted in Mediterranean countries, necessitating further investigation into its benefits in Western populations. Additionally, the effect of holistic multimodal lifestyle interventions, including physical activity combined with the MedDiet, is not well established. Finally, MASLD's widespread prevalence and rapid growth require improved accessibility to interventions. Digital health delivery platforms, designed for remote access, could be a promising approach to providing timely support to individuals with MASLD. This narrative review summarises the current evidence related to the effects of the MedDiet in Western, multicultural populations with MASLD. This includes a detailed description of the composition, prescription and adherence to dietary interventions in terms of how they have been designed and applied. The evidence related to the role of physical activity or exercise interventions prescribed in combination with the MedDiet for MASLD will also be reviewed. Finally, recommendations for the design and delivery of dietary and physical activity or exercise interventions to inform the design of future randomised controlled trials to facilitate the optimal management of MASLD are outlined.

Efficacy of the Mediterranean Diet Containing Different Macronutrients on Non-Alcoholic Fatty Liver Disease

This study aimed to investigate the effects of the typical Mediterranean diet (TMD), low-carbohydrate Mediterranean diet (LCMD), and low-fat Mediterranean diet (LFMD) on biochemical findings, fatty liver index (FLI), anthropometric measurements, and body composition in individuals with obesity with non-alcoholic fatty liver disease (NAFLD) and insulin resistance. This study included 63 participants with obesity with insulin resistance diagnosed with NAFLD by ultrasonography to investigate the effects of an 8-week energy-restricted TMD, LCMD, and LFMD on biochemical findings, FLI, fibrosis-4 index (FIB-4), anthropometric measurements, and body composition. Patients were randomized into three groups and were interviewed face-to-face every week. According to the food consumption records (baseline end), the difference in the amount of sucrose and total fat consumed in the TMD group; the difference in energy intake from sucrose, monounsaturated fatty acids, and oleic acid in the LCMD group; and the difference in energy intake from fiber, sucrose, monounsaturated and polyunsaturated fatty acids, and cholesterol in the LFMD group showed significant correlations with liver enzymes and FLI (p < 0.05). In conclusion, although it has a different macronutrient composition, the Mediterranean diet may positively affect biochemical parameters and FLI in individuals with NAFLD, albeit in different ways.

NAFLD in the 21st Century: Current Knowledge Regarding Its Pathogenesis, Diagnosis and Therapeutics

Non-alcoholic fatty liver disease (NAFLD) is a major public health issue worldwide. It is the most common liver disease in Western countries, andits global prevalence is estimated to be up to 35%. However, its diagnosis may be elusive, because liver biopsy is relatively rarely performed and usually only in advanced stages of the disease. Therefore, several non-invasive scores may be applied to more easily diagnose and monitor NAFLD. In this review, we discuss the various biomarkers and imaging scores that could be useful in diagnosing and managing NAFLD. Despite the fact that general measures, such as abstinence from alcohol and modulation of other cardiovascular disease risk factors, should be applied, the mainstay of prevention and management is weight loss. Bariatric surgery may be suggested as a means to confront NAFLD. In addition, pharmacological treatment with GLP-1 analogues or the GIP agonist tirzepatide may be advisable. In this review, we focus on the utility of GLP-1 analogues and GIP agonists in lowering body weight, their pharmaceutical potential, and their safety profile, as already evidenced inanimal and human studies. We also elaborate on other options, such as the use of vitamin E, probiotics, especially next-generation probiotics, and prebiotics in this context. Finally, we explore future perspectives regarding the administration of GLP-1 analogues, GIP agonists, and probiotics/prebiotics as a means to prevent and combat NAFLD. The newest drugs pegozafermin and resmetiron, which seem to be very promising, arealso discussed.

The Effects of Olive Oil Consumption on Biochemical Parameters and Body Mass Index of People with Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disorder, is closely associated with insulin resistance, obesity, and metabolic syndromes. A body of research has proposed that olive oil, a basic component of the Mediterranean diet with antioxidant and anti-inflammatory properties, may alleviate metabolic disturbances and retard the progression of NAFLD. We conducted a systematic review and meta-analysis to assess the effectiveness of olive oil intake in people with NAFLD. We systematically searched the major electronic databases (PubMed/MEDLINE, Scopus, Cochrane Central Register of Controlled Trials), as well as grey literature sources, to identify randomized controlled trials (RCTs) investigating the effects of olive oil consumption on biochemical and anthropometric parameters of individuals with NAFLD. The quality of the studies was evaluated using the risk-of-bias tool 2.0 (RoB 2). The mean difference (MD) and the 95% confidence interval (CI) were calculated using fixed-effects and random-effects models. Seven RCTs involving 515 subjects were included in the analysis. In the random-effects model, no statistically significant differences were identified with respect to alanine transaminase (MD = -1.83 IU/L, 95% CI: -5.85, 2.19 IU/L, p = 0.37, I2 = 69%) and aspartate transaminase (MD = -1.65 IU/L, 95% CI: -4.48, 1.17 IU/L, p = 0.25, I2 = 72%) levels or waist circumference values (MD = -0.23 cm, 95% CI: -1.23, 0.76 cm, p = 0.65, I2 = 0%). However, a significant effect on body mass index was observed (MD = -0.57 kg/m2, 95% CI: -1.08, -0.06 kg/m2, p = 0.03, I2 = 51%) for subjects who received olive oil compared to those who received an alternative diet or placebo. The findings of the present meta-analysis suggest a modestly positive impact of olive oil intake on body weight in people with NAFLD.

Natural products and dietary interventions on liver enzymes: an umbrella review and evidence map

Background

The association between natural products and dietary interventions on liver enzymes is unclear; therefore, this study aimed to examine their effects on liver enzymes in adults.

Methods

PubMed, Embase, and Cochrane Library of Systematic Reviews databases were searched from inception until March 2023. The Assessment of Multiple Systematic Reviews-2 (AMSTAR-2) and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) systems were used to assess the methodological and evidence quality, and the therapeutic effects were summarized in a narrative form.

Results

A total of 40 meta-analyses on natural products (n = 25), dietary supplements (n = 10), and dietary patterns (n = 5) were evaluated, and results were presented in a narrative form. The overall methodological quality of the included studies was relatively poor. The results indicated that positive effects were observed for nigella sativa, garlic, artichoke, curcumin, silymarin, vitamin E, vitamin D, L-carnitine, propolis, and polyunsaturated fatty acids on certain liver enzymes. The dietary patterns, including high-protein, Mediterranean, and calorie-restriction diets and evening snacks, may reduce liver enzymes; however, other supplements and herbs did not reduce liver enzyme levels or have minimal effects. The evidence quality was generally weak given the risk of bias, heterogeneity, and imprecision.

Conclusion

This umbrella review suggests that natural products and dietary interventions have beneficial therapeutic effects on liver enzymes levels. Further clinical trials are necessary to establish the effectiveness of supplements that reduce liver enzymes.

Dietary approaches to stop hypertension (DASH) diet improves hepatic fibrosis, steatosis and liver enzymes in patients with non-alcoholic fatty liver disease: a randomized controlled trial

PURPOSE

Recent evidence suggests that adherence to dietary approaches to stop hypertension (DASH) diet can be effective in managing non-alcoholic fatty liver disease (NAFLD). We investigated the effect of DASH diet on hepatic fibrosis, steatosis and liver enzymes in patients with NAFLD.

METHODS

This 12-week randomized controlled trial was conducted among seventy patients with NAFLD who were randomly assigned into two groups including intervention group (DASH diet containing 50-55% carbohydrate, 15-20% protein, and 30% total fat) and the control group (a healthy diet containing 50-55% carbohydrate, 15-20% protein, and 30% total fat). Both diets were calorie-restricted (500-700 kcal lower than the energy requirement). The primary outcomes included hepatic fibrosis, hepatic steatosis, alanine transaminase (ALT), aspartate transaminase (AST) and gamma-glutamyl transpeptidase (GGT).

RESULTS

At the baseline, there was no significant difference between two groups in the level of hepatic fibrosis (P = 0.63), hepatic steatosis (P = 0.53), ALT (P = 0.93), AST (P = 0.18) and GGT (P = 0.76). A significant reduction was found in the intervention group compared to the control group in hepatic fibrosis (23 grades reduction vs. 7 grades reduction; P = 0.008) and hepatic steatosis (31 grades reduction vs. 9 grades reduction; P = 0.03) after intervention. In addition, a significant change was observed in the intervention group compared to control group in ALT ( - 8.50 ± 8.98 vs.  - 2.09 ± 7.29; P = 0.002), and AST ( - 5.79 ± 6.83 vs.  - 0.51 ± 6.62; P = 0.002).

CONCLUSIONS

Adherence to DASH diet may be effective in management of NAFLD.

TRIAL REGISTRATION

The trial was registered on 06 February 2022 at Iranian Registry of Clinical Trials (IRCT20170117032026N3) with URL: https://www.irct.ir/trial/60887 .

The effects of powdered drinks enriched with curcumin and probiotics on lipid profile and atherogenic indices in patients with metabolic syndrome: A randomized, double-blinded, placebo-controlled clinical trial

Cardiovascular disease is prevalent globally and is the most common complication of metabolic syndrome (MetS). Previous studies have suggested that curcumin and probiotics may improve the lipid profile, so we aimed to investigate the effects of the edible powder enriched with these substances on lipid profile level and atherogenic indices such as Atherogenic Coefficient (AC), Castelli Risk Index-I (CRI-I), Castelli Risk Index-II (CRI-II), and Atherogenic Index of Plasma (AIP). In the present parallel randomized double-blinded placebo-controlled clinical trial, 124 people with MetS with overweight or obesity were randomly allocated to 4 groups and were followed up for 8 weeks. The participants received a low-calorie diet and a daily sachet of enriched powder drink. The sachets contained either 109 CFU of probiotics or 1 g of curcumin, or probiotic + curcumin (pro + cur), or placebo, respectively. The fasting lipid profile and atherogenic indices were measured at the beginning and end of the study. One hundred and fourteen participants completed the study. At the end of the study, the within- and between-group comparisons showed no significant differences in lipid profile and atherogenic indices (p > .05). Based on the results of the current study, taking an oral powder containing 1 g curcumin and 109 CFU probiotics for 8 weeks had no effect on the lipid profile level and atherogenic indices; however, more studies are recommended.

Scientific evidence supporting the newly developed one-health labeling tool "Med-Index": an umbrella systematic review on health benefits of mediterranean diet principles and adherence in a planeterranean perspective

BACKGROUND

Med-Index is a one-health front-of-pack (FOP) label, based on Mediterranean diet (MedDiet) principles, developed to summarize information about the nutritional properties and related-health benefits of any food as well as its sustainable production processes, and the associated food company's social responsibility parameters in a new "Planeterranean" perspective. Thus, Med-Index can be adopted in and by any European region and authority as well as worldwide; this is achieved by consumption and cooking of locally available and sourced foods that respect MedDiet principles, both in terms of healthy nutrition and sustainable production. The huge body of scientific evidence about the health benefits of the MedDiet model and principles requires a comprehensive framework to encompass the scientific reliability and robustness of this tool. A systematic review was carried out to examine the association between human health and adherence to MedDiet patterns upon which the "Med-Index" tool was subsequently developed.

METHODS

MEDLINE and PubMed databases were searched for eligible publications from 1990 to April 2023. Systematic literature reviews, with or without meta-analysis, of clinical trials and observational studies were screened by two independent investigators for eligibility, data extraction, and quality assessment. English language and the time interval 1990-2023 were applied. A registry code CRD42023464807 was generated on PROSPERO and approved for this search protocol. The corrected covered area (CCA), calculated to quantify the degree of overlap between reviews, gave a slight overlap (CCA = 4%).

RESULTS

A total of 84 systematic reviews out of 6681 screened records were selected. Eligible reviews included studies with predominantly observational designs (61/84, 72.6%%), of which 26/61 referenced studies of mixed observational and RCT designs, while 23/84 (27.4%) were RCT-only systematic reviews. Seventy-nine different entries were identified for health outcomes, clustered into 10 macro-categories, each reporting a statistically significant association with exposure to the MedDiet. Adherence to MedDiet was found to strongly benefit age-related chronic diseases (21.5%), neurological disorders (19%), and obesity-related metabolic features (12.65), followed by CVDs (11.4%), cancer (10.1%), diabetes (7.5%), liver health (6.3%), inflammation (5%), mortality (5%), and renal health (1.2%). The quality of the studies was moderate to high.

CONCLUSION

In the context of a "Planeterranean" framework and perspective that can be adopted in any European region and worldwide, MedDiet represents a healthy and sustainable lifestyle model, able to prevent several diseases and reduce premature mortality. In addition, the availability of a FOP, such as Med-Index, might foster more conscious food choices among consumers, paying attention both to human and planetary health.

Effect of Cornus mas L. fruit extract on blood pressure, anthropometric and body composition indices in patients with non-alcoholic fatty liver disease: A double-blind randomized controlled trial

BACKGROUND & AIMS

Obesity is linked to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Patients with NAFLD are at increased risk for hypertension. Some investigations have hypothesized that Cornus mas L. fruit can improve obesity and hypertension. We investigated the effect of C. mas L. fruit extract on blood pressure, anthropometric and body composition indices in patients with NAFLD.

METHODS

This 12-week double-blind randomized controlled trial was conducted on fifty patients with NAFLD. Patients received 20 cc/d C. mas L. fruit extract or placebo. We measured diastolic blood pressure (DBP), systolic blood pressure (SBP), weight, waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), body fat mass (BFM), body fat percent (BFP) and fat free mass (FFM) before and after intervention.

RESULTS

Treatment group compared to control group showed a significant reduction in DBP (-8.62 ± 11.86 mmHg vs. 0.53 ± 8.53 mmHg; P_crude = 0.003; P_adjucted = 0.03) and SBP (-8.63 ± 14.37 mmHg vs. 0.0 ± 12.67 mmHg; P_crude = 0.02; P_adjucted = 0.02). We found no difference between groups in weight, WC, HC, WHR, BFM, BFP and FFM (P > 0.05). After adjusting for confounding factors, a significant reduction was observed in treatment group compared to control group in BFM (-0.2 ± 3.9 kg vs. 0.7 ± 2.4 kg; P = 0.01) and BFP (-0.2 ± 4.9% vs. 0.8 ± 2.8%; P = 0.02).

CONCLUSIONS

C. mas L. fruit extract statistically reduced blood pressure and body fat. However, it had no effect on other anthropometric and body composition indices. Studies with larger sample sizes and higher dosages of extract are needed.

TRIAL REGISTRATION

Registered on 30/9/2018 at Iranian Registry of Clinical Trials IRCT20180419039359N1 (https://www.irct.ir/trial/30707).

The Development of Nonalcoholic Fatty Liver Disease and Metabolic Syndromes in Diet-Induced Rodent Models

Dietary macronutrients are essential for metabolic regulation and insulin function. The present study examined the effects of different high-fat diets (HFDs) and high-carbohydrate diets (HCDs) on the development of non-alcoholic fatty liver disease and metabolic syndrome indices in healthy adult male Wistar albino rats. Forty-two rats were distributed into six groups (n = 7), which were fed the following for 22 weeks: (1) a control diet; (2) a high-carbohydrate, low-fat diet (HCD-LFD); (3) high-saturated-fat, low-carbohydrate diet (HSF-LCD); (4) a high-monounsaturated-fat diet (HMUSF); (5) a high medium-chain fat diet (HMCF); and a (6) a high-carbohydrate, high-fiber diet (HCHF). In comparison to the control, the body weight increased in all the groups. The HSF-LCD group showed the highest levels of cholesterol, triglyceride, low-density lipoprotein, hepatic enzyme, insulin resistance, and Homeostatic Model Assessment for Insulin Resistance. A liver histology analysis of the HSF-LCD group showed macrovesicular hepatic steatosis associated with large hepatic vacuolation. Additionally, it showed marked periportal fibrosis, especially around the blood vessels and blood capillaries. The lowest levels of fasting glycemia, insulin, and HOMA-IR were observed in the HCHF group. In conclusion, these findings show that dietary saturated fat and cholesterol are principal components in the development and progression of non-alcoholic fatty liver disease in rats, while fiber showed the greatest improvement in glycemic control.

Dietary antioxidants and liver enzymes in Rafsanjan, a Region in Southeast Iran

Oxidative stress has been considered the main contributor to liver injury. Dietary antioxidants would be expected to improve liver function. The hepatoprotective effects of antioxidants are controversial. In the present study, the associations of some dietary antioxidants and the levels of serum liver enzymes were examined. This cross-sectional study was conducted using the Rafsanjan Cohort Study (RCS) data as a population-based prospective cohort which is a part of the Prospective Epidemiological Research Studies in IrAN (PERSIAN). A total of 9942 participants aged 35-70 years old were included in this study. Among this population, 4631 (46.59%) were male, and 5311 (53.42%) were female. Dietary intakes were collected by a validated food frequency questionnaire (FFQ) with 128 items. Aspartate transaminase (AST), Alanine transaminase (ALT), γ-glutamyl transferase (GGT), and Alkaline phosphatase (ALP) were measured by a biotecnica analyzer. Dichotomous logistics regression models were used to investigate the association between the elevated liver enzymes and intake of dietary antioxidants using crude and adjusted models. In the adjusted model, in subjects with higher consumption of Se, Vit A, Vit E, β-carotene, α-carotene, and β-cryptoxanthin, the odds ratios of elevated ALP were decreased compared to the reference group (ORs 0.79 (0.64-0.96), 0.80 (0.66-0.98), 0.73 (0.60-0.89), 0.79 (0.64-0.96), 0.78 (0.64-0.95), 0.80 (0.66-0.98), and 0.79 (0.64-0.98), respectively). Subjects with higher consumption of Se, Vit A, Vit E, and provitamin A carotenoids (β-carotene, α-carotene, β-cryptoxanthin) showed decreased odds of elevated ALP. These findings support the hypothesis that Se, Vit A, Vit E, and provitamin A carotenoids may be associated with improvements in ALP and act as suppressors against the development of liver injury.

Does the Mediterranean Diet Have Any Effect on Lipid Profile, Central Obesity and Liver Enzymes in Non-Alcoholic Fatty Liver Disease (NAFLD) Subjects? A Systematic Review and Meta-Analysis of Randomized Control Trials

The effectiveness of the Mediterranean diet (MD) in non-alcoholic fatty liver disease (NAFLD) subjects has been evaluated in several randomized controlled trials (RCTs). This systematic review and meta-analysis aimed to evaluate the overall effects of MD intervention in a cohort of NAFLD patients targeting specific markers such as central obesity, lipid profile, liver enzymes and fibrosis, and intrahepatic fat (IHF). Google Scholar, PubMed, and Scopus were explored to collect relevant studies from the last 10 years. RCTs with NAFLD subjects were included in this systematic review with a mean intervention duration from 6 weeks to 1 year, and different intervention strategies, mainly including energy restriction MD (normal or low glycaemic index), low-fat MD with increased monounsaturated and polyunsaturated fatty acids, and increased exercise expenditure. The outcomes measured in this meta-analysis were gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), total cholesterol (TC), waist circumference (WC), and liver fibrosis. Ten randomized controlled trials, which involved a total of 737 adults with NAFLD, were included. According to the results, the MD seems to decrease the liver stiffness (kPa) by -0.42 (CI95% -0.92, 0.09) (p = 0.10) and significantly reduce the TC by -0.46 mg/dl (CI95% -0.55, -0.38) (p = 0.001), while no significant findings were documented for liver enzymes and WC among patients with NAFLD. In conclusion, the MD might reduce indirect and direct outcomes linked with NAFLD severity, such as TC, liver fibrosis, and WC, although it is important to consider the variations across trials. Further RCTs are necessary to corroborate the findings obtained and provide further evidence on the role of the MD in the modulation of other disorders related to NAFLD.

TM6SF2-rs58542926 Genetic Variant Modifies the Protective Effect of a "Prudent" Dietary Pattern on Serum Triglyceride Levels

The epidemic prevalence of non-alcoholic fatty liver disease (NAFLD), despite extensive research in the field, underlines the importance of focusing on personalized therapeutic approaches. However, nutrigenetic effects on NAFLD are poorly investigated. To this end, we aimed to explore potential gene-dietary pattern interactions in a NAFLD case-control study. The disease was diagnosed with liver ultrasound and blood collection was performed after an overnight fast. Adherence to four a posteriori, data-driven, dietary patterns was used to investigate interactions with PNPLA3-rs738409, TM6SF2-rs58542926, MBOAT7-rs641738, and GCKR-rs738409 in disease and related traits. IBM SPSS Statistics/v21.0 and Plink/v1.07 were used for statistical analyses. The sample consisted of 351 Caucasian individuals. PNPLA3-rs738409 was positively associated with disease odds (OR = 1.575, p = 0.012) and GCKR-rs738409 with lnC-reactive protein (CRP) (beta = 0.098, p = 0.003) and Fatty Liver Index (FLI) levels (beta = 5.011, p = 0.007). The protective effect of a "Prudent" dietary pattern on serum triglyceride (TG) levels in this sample was significantly modified by TM6SF2-rs58542926 (pinteraction = 0.007). TM6SF2-rs58542926 carriers may not benefit from a diet rich in unsaturated fatty acids and carbohydrates in regard to TG levels, a commonly elevated feature in NAFLD patients.

NAFLD Nutritional Management: Results from a Multidisciplinary Approach

Introduction

Lifestyle changes are the mainstay treatment of nonalcoholic fatty liver disease (NAFLD). We aimed to assess the magnitude of weight loss in a group of NAFLD patients followed on a combined lifestyle intervention by a multidisciplinary team.

Methods

Patients were assessed before and after a 12-month dietary intervention (Mediterranean diet aiming at weight loss). Patients who received a structured dietary plan along with general lifestyle recommendations were designated as the multidisciplinary treatment (MdT) group. Patients who declined follow-up still received general lifestyle recommendations and were designated as the conventional treatment group, being used as a control group.

Results

From the 77 patients with documented NAFLD, 31.2% of patients were overweight and 55.8% obese; 66 patients constituted the MdT group and 11 the conventional treatment group. After 3 months, 89% of patients lost weight; at 6 months, 75.4% maintained the weight lost. At 12 months, 65% of patients still decreased their weight, with 92.2% of patients in the MdT group still maintaining a lower weight than baseline versus just 50% in the conventional group (p = 0.008). Only patients in the MdT group presented a weight loss higher than 10% (9.6%; n = 6). At 12 months patients in the MdT group presented an average reduction of 4.2 kg versus a reduction of just 0.6 kg in the conventional treatment group (p = 0.016). The MdT group, but not the conventional group, presented significant differences in liver enzymes at 12 months compared to baseline.

Conclusion

Adherence to a multidisciplinary approach, compared to management solely by a hepatologist, in NAFLD patients, is effective with greater weight loss after a 12-month follow-up and a lower rate of weight gain recurrence.