Eucaloric diets enriched in palm olein, cocoa butter, and soybean oil did not differentially affect liver fat concentration in healthy participants: a 16-week randomized controlled trial

Circulating fatty acids and risk of severe non-alcoholic fatty liver disease in the UK biobank: a prospective cohort of 116 223 individuals

Fatty acid (FA) metabolism plays an important role in the development of nonalcoholic fatty liver disease (NAFLD). However, data on the relationship between circulating FAs and NAFLD risk are limited. This study aims to assess the associations between specific circulating FAs and severe NAFLD risk among the general population. Overall 116 223 participants without NAFLD and other liver diseases from the UK Biobank were enrolled between 2006 and 2010 and were followed up until the end of 2021. Plasma concentrations of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) were analyzed using an NMR-based biomarker profiling platform. Hazard ratios (HRs) and 95% confidence intervals (CIs) of NAFLD risk were estimated using Cox proportional-hazard models adjusted for other potential confounders. During a mean follow-up of 12.3 years, we documented 1394 cases of severe NAFLD. After multivariate adjustment, plasma SFAs and MUFAs were associated with a higher risk of severe NAFLD, whereas plasma n-3 PUFAs, n-6 PUFAs, and linoleic acid (LA) were associated with a lower risk. As compared with the lowest quartile, HRs (95% CIs) of severe NAFLD risk in the highest quartiles were 1.85 (1.45-2.36) for SFAs, 1.74 (1.23-2.44) for MUFAs, 0.79 (0.65-0.97) for n-3 PUFAs, 0.68 (0.48-0.96) for n-6 PUFAs, and 0.73 (0.54-0.99) for LA. The significant relationships were mainly mediated by serum TG for SFAs, HDL-C for MUFAs and n-6 PUFAs, and C-reactive protein for n-3 PUFAs. Plasma SFAs were associated with a more pronounced increase in the risk of severe NAFLD among participants with fewer SFA-associated alleles (P interaction = 0.032). Dietary recommendations for reducing plasma SFAs and MUFAs while increasing n-3 and n-6 PUFAs may be protective for severe NAFLD, which could be mediated by lipid metabolism and inflammation.

Associations between dietary fatty acid and plasma fatty acid composition in non-alcoholic fatty liver disease: secondary analysis from a randomised trial with a hypoenergetic low-carbohydrate high-fat and intermittent fasting diet

Dietary fatty acids (FA) affect metabolic risk factors. The aim of this study was to explore if changes in dietary fat intake during energy restriction were associated with plasma FA composition. The study also investigated if these changes were associated with changes in liver fat, liver stiffness and plasma lipids among persons with non-alcoholic fatty liver disease. Dietary and plasma FA were investigated in patients with non-alcoholic fatty liver disease (n 48) previously enrolled in a 12-week-long open-label randomised controlled trial comparing two energy-restricted diets: a low-carbohydrate high-fat diet and intermittent fasting diet (5:2), to a control group. Self-reported 3 d food diaries were used for FA intake, and plasma FA composition was analysed using GC. Liver fat content and stiffness were measured by MRI and transient elastography. Changes in intake of total FA (r 0·41; P = 0·005), SFA (r 0·38; P = 0·011) and MUFA (r 0·42; P = 0·004) were associated with changes in liver stiffness. Changes in plasma SFA (r 0·32; P = 0·032) and C16 : 1n-7 (r 0·33; P = 0·028) were positively associated with changes in liver fat, while total n-6 PUFA (r -0·33; P = 0·028) and C20 : 4n-6 (r -0·42; P = 0·005) were inversely associated. Changes in dietary SFA, MUFA, cholesterol and C20:4 were positively associated with plasma total cholesterol and LDL-cholesterol. Modifying the composition of dietary fats during dietary interventions causes changes in the plasma FA profile in patients with non-alcoholic fatty liver disease. These changes are associated with changes in liver fat, stiffness, plasma cholesterol and TAG. Replacing SFA with PUFA may improve metabolic parameters in non-alcoholic fatty liver disease patients during weight loss treatment.

Effects of saturated fatty acid consumption on lipoprotein (a): a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

An inverse relationship between saturated fatty acid (SFA) intake and Lp(a) concentration has been observed; however, there has been no quantification of this effect.

OBJECTIVES

The objective was to determine whether SFA consumption alters Lp(a) concentrations among adults without atherosclerotic cardiovascular disease (ASCVD).

METHODS

A systematic review and meta-analysis of randomized controlled trials contrasting a lower SFA diet(s) with a higher SFA diet(s) among adults without ASCVD was conducted. PubMed, Cochrane Central Register of Clinical Trials, clinicaltrials.gov, and Web of Science databases and registers were searched through October 2023. The standardized mean difference (SMD) in Lp(a) between diets lower and higher in SFA [percentage of energy (%E)] was determined using random-effects meta-analysis. Analyses were also conducted to examine the effect of replacing SFA with carbohydrates (CHO), monounsaturated (MUFAs), polyunsaturated (PUFAs), or trans fatty acids (TFAs).

RESULTS

In total, 6255 publications were identified in the systematic search. Twenty-six publications reporting 27 randomized controlled trials, including 1325 participants and 49 diet comparisons, were included. The mean difference in SFA between lower and higher SFA diets was 7.6%E (3.7%-17.8%E). After lower SFA diets, Lp(a) concentration was higher (SMD: 0.14; 95% confidence interval [CI]: 0.03, 0.24) than after higher SFA diets. Subgroup analyses showed higher Lp(a) following diets where SFA was replaced by CHO (trials = 8; n = 539; SMD: 0.21; 95% CI: 0.02, 0.40) or TFAs (trials = 8; n = 300; SMD: 0.32; 95% CI: 0.17, 0.48). No differences in Lp(a) were observed when MUFA (trials = 16; n = 641; SMD: 0.04; 95% CI: -0.08, 0.16) or PUFA (trials = 8; n = 415; SMD: 0.09; 95% CI: -0.04, 0.22) replaced SFA.

CONCLUSIONS

Lower SFA diets modestly increase Lp(a) compared to higher SFA diets among individuals without ASCVD. This effect appeared to be driven by replacement of SFA with CHO or TFA. Research investigating the atherogenicity of diet-induced Lp(a) changes is needed to inform dietary management of lipid/lipoprotein disorders. This trial was registered with PROSPERO as CRD42020154169.

HDL-Cholesterol Subfraction Dimensional Distribution Is Associated with Cardiovascular Disease Risk and Is Predicted by Visceral Adiposity and Dietary Lipid Intake in Women

HDL-cholesterol quality, including cholesterol distribution in HDL subfractions, is emerging as a key discriminant in dictating the effects of these lipoproteins on cardiovascular health. This study aims at elucidating the relationship between cholesterol distribution in HDL subfractions and CVD risk factors as well as diet quality and energy density in a population of pre- and postmenopausal women. Seventy-two women aged 52 ± 6 years were characterized metabolically and anthropometrically. Serum HDL-C subfractions were quantified using the Lipoprint HDL System. Cholesterol distribution in large HDL subfractions was lower in overweight individuals and study participants with moderate to high estimated CVD risk, hypertension, or insulin resistance. Cholesterol distribution in large, as opposed to small, HDL subfractions correlated negatively with insulin resistance, circulating triglycerides, and visceral adipose tissue (VAT). VAT was an independent positive and negative predictor of cholesterol distribution in large and small HDL subfractions, respectively. Furthermore, an increase in energy intake could predict a decrease in cholesterol levels in large HDL subfractions while lipid intake positively predicted cholesterol levels in small HDL subfractions. Cholesterol distribution in HDL subfractions may represent an additional player in shaping CVD risk and a novel potential mediator of the effect of diet on cardiovascular health.

Effect of lard plus soybean oil on blood pressure and other cardiometabolic risk factors in healthy subjects: a randomized controlled-feeding trial

Lard has been consumed by humans for thousands of years, but its consumption has declined substantially in the last few decades, because of negative publicity about the consumption of animal-derived saturated fats. Emerging evidence highlights that lard plus soybean oil (blend oil) could be more beneficial for body weight and liver function than the individual use of the two oils. This study aimed to evaluate the effects of blend oil on cardiometabolic risk factors in healthy subjects. This was a parallel, three-arm, randomized controlled-feeding trial. 334 healthy subjects (mean age: 33.1 years, 60% women) were randomized into three isoenergetic diet groups with three different edible oils (30 g day^-1) (soybean oil, lard, and blend oil [50% lard and 50% soybean oil]) for 12 weeks. 245 (73.4%) participants completed the study. After the 12-week intervention, reductions in both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were greater in the blend oil group than in the other two groups (P = 0.023 and 0.008 for the interaction between the diet group and time, respectively). Reductions of SBP and DBP in the blend oil group were more significant than those in the soybean oil group with P = 0.008 and P = 0.026 and the lard group with P < 0.001 and P < 0.001. Changes in SBP/DBP at 12 weeks were -6.0 (95% CI: -8.6 to -3.4)/0.8 (95% CI: -1.7 to 3.2) mmHg in the blend oil group, -3.3 (95% CI: -5.7 to -0.9)/1.5 (95% CI: -1.0 to 4.0) mmHg in the soybean oil group and -1.2 (95% CI: -3.7 to 1.4)/3.3 (95% CI: 0.9 to 5.8) mmHg in the lard group. Subgroup analyses showed that blend oil significantly decreased SBP and DBP compared with the other two groups in participants with BP ≥ 130/80 mmHg and body mass index ≥25. There were no significant differences in the changes in body weight, waist circumference, serum lipids, or glucose between groups. In conclusion, our findings suggest that blend oil (lard plus soybean oil) reduces BP compared with soybean oil and lard in healthy subjects.

Effect of Lard or Plus Soybean Oil on Markers of Liver Function in Healthy Subjects: A Randomized Controlled-Feeding Trial

Humans have consumed lard for thousands of years, but in recent decades, it has become much less popular because it is regarded as saturated fat. Animal studies showed that lard plus soybean oil (blend oil) was more advantageous for liver health than using either oil alone. This study aims to assess the effects of blend oil on liver function markers in healthy subjects. The 345 healthy subjects were randomized into 3 isoenergetic diet groups with different edible oils (30 g/day) (soybean oil, lard, and blend oil (50% lard and 50% soybean oil)) for 12 weeks. The reductions in both aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were greater in the blend oil group than in the two other groups (p = 0.001 and <0.001 for the interaction between diet group and time, respectively). The reductions in AST and ALT in the blend oil group were more significant compared with those in the soybean oil group (p < 0.001) or lard group (p < 0.001). There were no significant differences in the other liver function markers between the groups. Thus, blend oil was beneficial for liver function markers such as AST and ALT compared with soybean oil and lard alone, which might help prevent non-alcoholic fatty liver disease in the healthy population.

A Review of Low-Density Lipoprotein-Lowering Diets in the Age of Anti-Sense Technology

This narrative review discusses an important issue, the primary role of diet in reducing low-density lipoprotein cholesterol (LDLc) concentrations in polygenic hypercholesterolemia. Two effective drugs, statins, and ezetimibe, that lower LDLc > 20% are relatively inexpensive and potential competitors to strict dieting. Biochemical and genomic studies have shown that proprotein convertase subtilisin kexin type 9 (PCSK9) plays an important role in low-density lipoprotein (LDL) and lipid metabolism. Clinical trials have demonstrated that inhibitory monoclonal antibodies of PCSK9 dose-dependently lower LDLc up to 60%, with evidence of both regression and stabilization of coronary atherosclerosis and a reduction in cardiovascular risk. Recent approaches using RNA interference to achieve PCSK9 inhibition are currently undergoing clinical evaluation. The latter presents an attractive option of twice-yearly injections. They are, however, currently expensive and unsuitable for moderate hypercholesterolemia, which is largely due to inappropriate patterns of eating. The best dietary approach, the substitution of saturated fatty acids by polyunsaturated fatty acids at 5% energy, yields > 10% lowering of LDLc. Foods such as nuts and brans, especially within a prudent, plant-based diet low in saturates complemented by supplements such as phytosterols, have the potential to reduce LDLc further. A combination of such foods has been shown to lower LDLc by 20%. A nutritional approach requires backing from industry to develop and market LDLc-lowering products before pharmacology replaces the diet option. Energetic support from health professionals is vital.

Associations of serum n-3 and n-6 polyunsaturated fatty acids with prevalence and incidence of nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver diseases worldwide, and lifestyle and diet are significant factors in its development. Recent studies have suggested that dietary fat quality is associated with the development of NAFLD.

OBJECTIVES

Our purpose was to investigate the cross-sectional and longitudinal associations of serum n-3 (ω-3) and n-6 (ω-6) PUFAs with NAFLD among middle-aged and older men and women from eastern Finland. We also investigated the associations of estimated Δ5-desaturase and Δ6-desaturase activities, enzymes involved in PUFA metabolism, with NAFLD.

METHODS

After exclusions, the cross-sectional analyses included 1533 men examined in 1984-1989 and 674 men and 870 women examined in 1998-2001 in the Kuopio Ischaemic Heart Disease Risk Factor Study. The longitudinal analyses included 520 men examined in 1991-1993 and 301 men and 466 women examined in 2005-2008. Fatty liver index (FLI) was used as a surrogate for NAFLD. Hepatic steatosis was defined as FLI >60. ANCOVA and logistic regression were used for analyses.

RESULTS

In the longitudinal analyses, participants with higher serum concentrations of total n-6 PUFA and linoleic acid, the major n-6 PUFA, had markedly lower FLI and lower odds for hepatic steatosis (e.g., odds ratios for incident hepatic steatosis in the highest compared with lowest quartiles were ≤0.41), whereas serum γ-linolenic acid concentration was associated with a higher FLI and higher odds for hepatic steatosis. The associations with the other PUFAs were generally weaker and nonsignificant. In the cross-sectional analyses, also the long-chain n-3 PUFAs had inverse associations. In most analyses, high estimated Δ5-desaturase activity was associated with lower risk and high estimated Δ6-desaturase activity with higher risk for NAFLD.

CONCLUSIONS

In middle-aged and older Finnish adults, higher serum concentrations of total n-6 PUFAs and linoleic acid were associated with lower odds for future NAFLD.

Linoleic Acid-Rich Oil Alters Circulating Cardiolipin Species and Fatty Acid Composition in Adults: A Randomized Controlled Trial

SCOPE

Higher circulating linoleic acid (LA) and muscle-derived tetralinoleoyl-cardiolipin (LA4 CL) are each associated with decreased cardiometabolic disease risk. Mitochondrial dysfunction occurs with low LA4 CL. Whether LA-rich oil fortification can increase LA4 CL in humans is unknown. The aims of this study are to determine whether dietary fortification with LA-rich oil for 2 weeks increases: 1) LA in plasma, erythrocytes, and peripheral blood mononuclear cells (PBMC); and 2) LA4 CL in PBMC in adults.

METHODS AND RESULTS

In this randomized controlled trial, adults are instructed to consume one cookie per day delivering 10 g grapeseed (LA-cookie, N = 42) or high oleate (OA) safflower (OA-cookie, N = 42) oil. In the LA-cookie group, LA increases in plasma, erythrocyte, and PBMC by 6%, 7%, and 10% respectively. PBMC and erythrocyte OA increase by 7% and 4% in the OA-cookie group but is unchanged in the plasma. PBMC LA4 CL increases (5%) while LA3 OA1 CL decreases (7%) in the LA-cookie group but are unaltered in the OA-cookie group.

CONCLUSIONS

LA-rich oil fortification increases while OA-oil has no effect on LA4 CL in adults. Because LA-rich oil fortification reduces cardiometabolic disease risk and increases LA4 CL, determining whether mitochondrial dysfunction is repaired through dietary fortification is warranted.

The Effect of MUFA-Rich Food on Lipid Profile: A Meta-Analysis of Randomized and Controlled-Feeding Trials

Since the effects of mono-unsaturated fatty acids (MUFA) on lipid profile are still controversial, a meta-analysis of randomized controlled trials was conducted in the present study to assess the effect of MUFA-rich food on lipid profiles. The study was designed, conducted, and reported according to the guidelines of the 2020 preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement. A systematic and comprehensive search was performed in several databases from inception up to 30 January 2022. The results showed that the intake of edible oil-derived MUFA (EDM) could increase the blood HDL-C level (mean difference = 0.08; 95%CI: -0.01, 0.17, p = 0.03), but did not affect the level of TC, TG, or LDL-C. Moreover, the consumption of other food-derived MUFA (ODM) significantly decreased TG concentration (mean difference = -0.35; 95%CI: -0.61, -0.09, p = 0.01)), but did not affect the level of TC, LDL-C, or HDL-C. Findings from this study suggest that MUFA-rich food might be beneficial to modulate the blood lipid profile.

Impact of Replacement of Individual Dietary SFAs on Circulating Lipids and Other Biomarkers of Cardiometabolic Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Humans

Little is known of the impact of individual SFAs and their isoenergetic substitution with other SFAs or unsaturated fatty acids (UFAs) on the prevention of cardiometabolic disease (CMD). This systematic literature review assessed the impact of such dietary substitutions on a range of fasting CMD risk markers, including lipid profile, markers of glycemic control and inflammation, and metabolic hormone concentrations. Eligible randomized controlled trials (RCTs) investigated the effect of isoenergetic replacements of individual dietary SFAs for ≥14 d on ≥1 CMD risk markers in humans. Searches of the PubMed, Embase, Scopus, and Cochrane CENTRAL databases on 14 February, 2021 identified 44 RCTs conducted in participants with a mean ± SD age of 39.9 ± 15.2 y. Studies' risk of bias was assessed using the Cochrane Risk of Bias tool 2.0 for RCTs. Random-effect meta-analyses assessed the effect of ≥3 similar dietary substitutions on the same CMD risk marker. Other dietary interventions were described in qualitative syntheses. We observed reductions in LDL-cholesterol concentrations after the replacement of palmitic acid (16:0) with UFAs (-0.36 mmol/L; 95% CI: -0.50, -0.21 mmol/L; I2 = 96.0%, n = 18 RCTs) or oleic acid (18:1n-9) (-0.16 mmol/L; 95% CI: -0.28, -0.03 mmol/L; I2 = 89.6%, n = 9 RCTs), with a similar impact on total cholesterol and apoB concentrations. No effects on other CMD risk markers, including HDL-cholesterol, triacylglycerol, glucose, insulin, or C-reactive protein concentrations, were evident. Similarly, we found no evidence of a benefit from replacing dietary stearic acid (18:0) with UFAs on CMD risk markers (n = 4 RCTs). In conclusion, the impact of replacing dietary palmitic acid with UFAs on lipid biomarkers is aligned with current public health recommendations. However, owing to the high heterogeneity and limited studies, relations between all individual SFAs and biomarkers of cardiometabolic health need further confirmation from RCTs. This systematic review was registered at www.crd.york.ac.uk/prospero/ as CRD42020084241.