Comparison of an oleic acid enriched-diet vs NCEP-I diet on LDL susceptibility to oxidative modifications

The effects of olive oil consumption on blood lipids: a systematic review and dose-response meta-analysis of randomised controlled trials

We performed a systematic review and dose-response meta-analysis of randomised trials on the effects of olive oil consumption on blood lipids in adults. A systematic search was performed in PubMed, Scopus and Web of Science databases until May 2021. Randomised controlled trials (RCT) evaluating the effect of olive oil intake on serum total cholesterol (TC), TAG, LDL-cholesterol and HDL-cholesterol in adults were included. The mean difference (MD) and 95 % CI were calculated for each 10 g/d increment in olive oil intake using a random-effects model. A total of thirty-four RCT with 1730 participants were included. Each 10 g/d increase in olive oil consumption had minimal effects on blood lipids including TC (MD: 0·79 mg/dl; 95 % CI (-0·08, 1·66); I² = 57 %; n 31, GRADE = low certainty), LDL-cholesterol (MD: 0·04 mg/dl, 95 % CI (-1·01, 0·94); I² = 80 %; n 31, GRADE = very low certainty), HDL-cholesterol (MD: 0·22 mg/dl; 95 % CI (-0·01, 0·45); I² = 38 %; n 33, GRADE = low certainty) and TAG (MD: 0·39 mg/dl; 95 % CI (-0·33, 1·11); I² = 7 %; n 32, GRADE = low certainty). Levels of TC increased slightly with the increase in olive oil consumption up to 30 g/d (MD_{30 g/d}: 2·76 mg/dl, 95 % CI (0·01, 5·51)) and then appeared to plateau with a slight downward curve. A trivial non-linear dose-dependent increment was seen for HDL-cholesterol, with the greatest increment at 20 g/d (MD_{20 g/d}: 1·03 mg/dl, 95 % CI (-1·23, 3·29)). Based on existing evidence, olive oil consumption had trivial effects on levels of serum lipids in adults. More large-scale randomized trials are needed to present more reliable results.

Beneficial effects of dietary supplementation with olive oil, oleic acid, or hydroxytyrosol in metabolic syndrome: Systematic review and meta-analysis

BACKGROUND AND AIMS

Olive oil and components might have a beneficial effect on Metabolic Syndrome (MetS). The aim of this review and meta-analysis was to assess whether those effects are related to hydroxytyrosol or oleic acid contents, or the combination of them as olive oil, and how powerful is this effect.

METHODS

A systematic literature search was performed in MEDLINE via Pubmed, Web of Science (WOS) core collection, and Virtual Health Library (VHL) via LILACS and IBECS (Spain). MeSH terms used were "obesity", "body weight", "body mass index", "adipose tissue", "lipid metabolism", "LDL", "HDL", "VLDL", "insulin resistance", "glucose", "insulin", "hypertension", "arterial pressure", "olive oil", "oleic acid", and other (non-MeSH) terms: "total antioxidant capacity", "total antioxidant status", "hydroxytyrosol" (PROSPERO ID: CRD42021247614). Results of the included studies were meta-analyzed with the RevMan 5.3 program, assuming a random effects model.

RESULTS

76 articles (67 different trials) were identified. Hydroxytyrosol had no effect on MetS [combined standardized mean differences (SMD) = 0.01 (CI 95%: [-0.23, 0.25], I² = 83%; p = 0.920)]. Oleic acid had no significant beneficial effect on MetS [SMD = 0.03 (CI 95%: [-0.01, 0.07], I² = 0%); p = 0.150], but it improved lipid profile [SMD = 0.06 (CI 95%: [-0.00, 0.12], I² = 0%); p = 0. 050]. Olive oil had no effect on MetS [SMD = -0.01 (CI 95%: [-0.05, 0.03]), I² = 55%; p = 0.550)]. The supplementation with hydroxytyrosol, oleic acid or olive oil showed a beneficial effect on antioxidant capacity related to components of MetS [SMD = 0.31 (CI 95%: [-0.34, 0.95], I² = 81%)]; p = 0.35).

CONCLUSION

Most articles compared olive oil and oleic acid with other strategies specially designed for MetS management. Our findings suggest that olive oil or oleic acid consumption are as good as the other strategies to manage MetS.

Comparison of blood lipid-lowering effects of olive oil and other plant oils: A systematic review and meta-analysis of 27 randomized placebo-controlled clinical trials

Objective: We aim to report a systematic review and meta-analysis of randomized controlled trials (RCTs) on effects of olive oil consumption compared with other plant oils on blood lipids. Methods: PubMed, web of science, Scopus, ProQuest, and Embase were systematically searched until September 2017, with no age, language and design restrictions. Weighed mean difference (WMD) and 95% confidence interval (CI) were expressed as effect size. Sensitivity analyses and pre specified subgroup was conducted to evaluate potential heterogeneity. Meta-regression analyses were performed to investigate association between blood lipid-lowering effects of olive oil and duration of treatment. Results: Twenty-seven trials, comprising 1089 participants met the eligibility criteria. Results of this study showed that compared to other plant oils, high-density lipoprotein level increased significantly more for OO (1.37 mg/dl: 95% CI: 0.4, 2.36). Also OO consumption reduced total cholesterol (TC) (6.27 mg/dl, 95% CI: 2.8, 10.6), Low-density lipoprotein (LDL-c) (4.2 mg/dl, 95% CI: 1.4, 7.01), and triglyceride (TG) (4.31 mg/dl, 95% CI: 0.5, 8.12) significantly less than other plant oils. There were no significant effects on Apo lipoprotein A1 and Apo lipoprotein B. Conclusion: This meta-analysis suggested that OO consumption decreased serum TC, LDL-c, and TG less but increased HDL-c more than other plant oils.

Low-density lipoprotein oxidation biomarkers in human health and disease and effects of bioactive compounds

Based on the significance of oxidized low-density lipoprotein (LDL) in health and disease, this review focuses on human studies addressing oxidation of LDL, including three lines of biomarkers, (i) ex vivo LDL resistance to oxidation, a "challenge test" model, (ii) circulating oxidized LDL, indicating the "current in vivo status", and (iii) autoantibodies against oxidized LDL as fingerprints of an immune response to oxidized LDL, along with circulating oxysterols and 4-hydroxynonenal as biomarkers of lipid peroxidation. Lipid peroxidation and oxidized LDL are hallmarks in the development of various metabolic, cardiovascular and other diseases. Changes further occur across life stages from infancy to older age as well as in athletes and smokers. Given their responsiveness to targeted nutritional interventions, markers of LDL oxidation have been employed in a rapidly growing number of human studies for more than 2 decades. There is growing interest in foods, which, besides providing energy and nutrients, exert beneficial effects on human health, such as protection of DNA, proteins and lipids from oxidative damage. Any health claim, however, needs to be substantiated by supportive evidence derived from human studies, using reliable biomarkers to demonstrate such beneficial effects. A large body of evidence has accumulated, demonstrating protection of LDL from oxidation by bioactive food compounds, including vitamins, other micronutrients and secondary plant ingredients, which will facilitate the selection of oxidation biomarkers for future human intervention studies and health claim support.

Design of foods with bioactive lipids for improved health

Numerous studies have found an association between the consumption of certain bioactive lipids and improved human health, e.g., the prevention, delay, or treatment of chronic and acute diseases, such as cancer, cardiovascular disease (CVD), osteoporosis, and immune disorders. In this review, we discuss food-based sources and potential beneficial attributes of major dietary bioactive lipids: polyunsaturated fatty acids; carotenoids; phytosterols and phytostanols; and fat-soluble vitamins. We summarize the various challenges associated with incorporating these bioactive lipids into foods and beverages, such as poor water solubility, high melting point, and low chemical stability. Finally, we propose several techniques that have been used to solve the challenges and integrate dietary bioactive lipids into foods for improved health.

The effect of Mediterranean diet on metabolic syndrome and its components: a meta-analysis of 50 studies and 534,906 individuals

OBJECTIVES

The aim of this study was to meta-analyze epidemiological studies and clinical trials that have assessed the effect of a Mediterranean diet on metabolic syndrome (MS) as well as its components.

BACKGROUND

The Mediterranean diet has long been associated with low cardiovascular disease risk in adult population.

METHODS

The authors conducted a systematic review and random effects meta-analysis of epidemiological studies and randomized controlled trials, including English-language publications in PubMed, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials until April 30, 2010; 50 original research studies (35 clinical trials, 2 prospective and 13 cross-sectional), with 534,906 participants, were included in the analysis.

RESULTS

The combined effect of prospective studies and clinical trials showed that adherence to the Mediterranean diet was associated with reduced risk of MS (log hazard ratio: -0.69, 95% confidence interval [CI]: -1.24 to -1.16). Additionally, results from clinical studies (mean difference, 95% CI) revealed the protective role of the Mediterranean diet on components of MS, like waist circumference (-0.42 cm, 95% CI: -0.82 to -0.02), high-density lipoprotein cholesterol (1.17 mg/dl, 95% CI: 0.38 to 1.96), triglycerides (-6.14 mg/dl, 95% CI: -10.35 to -1.93), systolic (-2.35 mm Hg, 95% CI: -3.51 to -1.18) and diastolic blood pressure (-1.58 mm Hg, 95% CI: -2.02 to -1.13), and glucose (-3.89 mg/dl, 95% CI:-5.84 to -1.95), whereas results from epidemiological studies also confirmed those of clinical trials.

CONCLUSIONS

These results are of considerable public health importance, because this dietary pattern can be easily adopted by all population groups and various cultures and cost-effectively serve for primary and secondary prevention of the MS and its individual components.

Research in olive oil: challenges for the near future

Olive oil, a traditional food product with thousands of years of history, is continually evolving toward a more competitive global market. Being one of the most studied foods across different disciplines, olive oil still needs intensive research activity to face some vulnerabilities and challenges. This perspective describes some of them and shows a vision of research on olive oil for the near future, bringing together those aspects that are more relevant for better understanding and protection of this edible oil. To accomplish the most urgent challenges, some possible strategies are outlined, taking advantage of the latest analytical advances, considering six areas: (i) olive growing; (ii) processing, byproduct, and environmental issues; (iii) virgin olive oil sensory quality; (iv) purity, authentication, and traceability; (v) health and nutrition; (vi) consumers. The coming research, besides achieving those challenges, would increase the understanding of some aspects that are still the subject of debate and controversy among scientists focused on olive oil.

Olive oil and oxidative stress

Oxidative stress is defined as an imbalance between the oxidant and antioxidant systems of the body, in favor of the oxidants. Oxidative stress produced by free radicals has been linked to the development of several diseases such as cardiovascular, cancer, and neurodegenerative diseases Olive oil is the main source of fat of the Mediterranean diet which has been shown to be effective against oxidative stress associated diseases and also with ageing. Besides its richness in monounsaturated fatty acids, the oleic acid, olive oil contains minor components with antioxidant properties. In this review, we summarize the state of the art, and degree of evidence, of the body of knowledge concerning the protective role of the major and minor components of olive oil on oxidative stress.

Balance of unsaturated fatty acids is important to a cholesterol-lowering diet: comparison of mid-oleic sunflower oil and olive oil on cardiovascular disease risk factors

OBJECTIVE

To evaluate the effects of a trans fat-free monounsaturated fatty acid-rich vegetable oil (NuSun sunflower oil, National Sunflower Association, Bismark, ND) that is a good source of polyunsaturated fatty acids (PUFA) and low in saturated fatty acids on lipid and lipoprotein levels and oxidative stress.

DESIGN

A double-blinded, randomized, three period crossover, controlled feeding study.

SUBJECTS/SETTING

Thirty-one men (n=12) and women (n=19) with moderate hypercholesterolemia who were 25 to 64 years of age.

INTERVENTION

Experimental diets provided 30% fat (olive oil or NuSun sunflower oil contributed one half of the total fat), 8.3% vs 7.9% saturated fatty acid, 17.2% vs 14.2% monounsaturated fatty acid, and 4.3% vs. 7.7% PUFA (olive oil and NuSun sunflower oil, respectively), and 294 mg cholesterol. The control diet was an average American diet (34% fat, 11.2% saturated fatty acid, 14.9% monounsaturated fatty acid, 7.8% PUFA). Subjects consumed each diet for 4 weeks with a 2-week compliance break before crossing over to another diet.

MAIN OUTCOME MEASURES

Lipid and lipoprotein levels were measured, and measures of oxidative stress, including lag time, rate of oxidation, total dienes, and lipid hydroperoxides, were assessed.

STATISTICAL ANALYSIS

The mixed model procedure was used to test for main effects of diet, feeding period, and order of diets. Tukey-Kramer adjusted P values were used to determine diet effects.

RESULTS

The NuSun sunflower oil diet decreased both total and low-density lipoprotein cholesterol levels compared with the average American diet and the olive oil diet. There was no effect of the olive oil diet compared with the average American diet. Total cholesterol decreased 4.7% and low-density lipoprotein cholesterol decreased 5.8% on the NuSun sunflower oil diet vs the average American diet. There was no effect of the experimental diets on triglyceride levels, rate of oxidation, total dienes, lipid hydroperoxides, or alpha-tocopherol. Lag time was the longest following the olive oil diet and shortest following the NuSun sunflower oil diet.

CONCLUSIONS

The higher PUFA content appeared to account for the greater total and low-density lipoprotein cholesterol lowering and reduction in lag time of the NuSun sunflower oil diet. However, the fact that there were no differences in the resulting oxidation products suggests there were no adverse effects on low-density lipoprotein oxidation. Since PUFAs are important for cholesterol lowering, foods that replace saturated fatty acids should include a balance of unsaturated fatty acids.

Comparison of a high-carbohydrate and a high-monounsaturated fat, olive oil-rich diet on the susceptibility of LDL to oxidative modification in subjects with Type 2 diabetes mellitus

AIMS

To compare the effects of a high-carbohydrate (CHO) diet and a high-monounsaturated fatty acid (MUFA) diet on LDL oxidative resistance in free-living individuals with Type 2 diabetes mellitus.

METHODS

Twenty-two men and women out-patients with Type 2 diabetes, with mean age 61 years and in fair metabolic control (HbA1c<8.0%), were enrolled at a university hospital lipid clinic in a randomized, crossover feeding trial comparing two isocaloric diets for 6 weeks each: CHO (fat, 28% energy) and MUFA (fat, 40% energy) based on virgin olive oil. Outcome measurements were changes in LDL susceptibility to oxidation, body weight, glycaemic control, and lipoprotein profiles.

RESULTS

Planned and observed diets were well matched. Participants preferred the MUFA diet over the CHO diet. The lag time of conjugated diene formation during Cu2+-induced LDL oxidation was similar after the CHO and MUFA diets (36.4 +/- 12.2 min and 36.0 +/- 13.7 min, respectively). Body weight, glycaemic control, total triglycerides, and total, LDL- and HDL-cholesterol levels also were similar after the two diets. Compared with the CHO diet, the MUFA diet lowered VLDL-cholesterol by 35% (P=0.023) and VLDL triglyceride by 16% (P=0.016).

CONCLUSIONS

Natural food-based high-CHO and high-MUFA diets have similar effects on LDL oxidative resistance and metabolic control in subjects with Type 2 diabetes. A MUFA diet is a good alternative to high-CHO diets for nutrition therapy of diabetes because it also has a beneficial effect on the lipid profile and superior patient acceptance.

A reduction in dietary saturated fat decreases body fat content in overweight, hypercholesterolemic males

BACKGROUND AND AIM

The effect of the quality of dietary fat on body composition is unknown. Our objective was to determine whether body composition is modified by the isocaloric substitution of a diet rich in saturated fat by a diet high in monounsaturated fat (Mediterranean diet) or a carbohydrate-rich diet in overweight subjects with hypercholesterolemia.

METHODS AND RESULTS

The study involved 34 hypercholesterolemic males aged 18-63 years with a body mass index (BMI) of 28.2 (2.6), all of whom consumed a diet rich in saturated fat (SAT) for 28 days. They were then randomly divided into two groups of 17 subjects and underwent two dietary periods of 28 days each in a crossover design: a Mediterranean diet high in monounsaturated fat (MONO) and a carbohydrate-rich diet (CHO). The order of the diets was different for the two group. The CHO diet contained 57% CHO and 28% total fat (< 10% saturated fat, 12% monounsaturated fat and 6% polyunsaturated fat); the Mediterranean diet contained 47% CHO and 38% fat (< 10% saturated fat, 22% monounsaturated fat--75% of which was provided by olive oil- and 6% polyunsaturated fat). The variables measured at the end of each dietary intervention period were: 1) body composition by means of bioelectrical impedance; 2) plasma lipoproteins using enzymatic techniques; and 3) fatty acids in cholesterol esters by means of gas chromatography. BMI and the waist/hip ratio remained the same during the three dietary periods. A decrease in fat was observed when changing from a saturated fat diet (23.3 (6.3) kg) to a Mediterranean diet (20.8 (7.2) kg) (p < 0.05), or a carbohydrate-rich diet (20.6 (6.7) kg) (p < 0.05). Lean mass increased when changing from a SAT diet (58.4 (7.0) kg) to a CHO diet (60.2 (7.0) kg) (p < 0.05).

CONCLUSION

The isocaloric substitution of a saturated fat-rich diet by a Mediterranean or carbohydrate-rich diet decreases total body fat in hypercholesterolemic males.

Diet and physical activity: a healthful binomial

Individual health status is the result of a combination of different factors such as genetics, dowry, age, nutritional status, physical activity, as well as environmental factors, hygiene, salubrity, stress and tobacco consumption. The existence of bad food habits and other risk factors leads to an increase in the development of chronic diseases, obesity, diabetes, cardiovascular disease, osteoporosis and certain types of cancer. Such diseases occupy greater rates of morbidity and mortality in European countries. This situation seems to justify that in our country defective intervention on different risk factors or, perhaps, a worsening in the control of some of them is taking place where the diet and lifestyle seem clearly implied. It is clear that if we take as bases the angular determinants for cardiovascular health identified in the 'Victory Declaration on Cardiac Health', healthful food habits, free tobacco lifestyle, regular physical activity and positive psycho-social atmosphere, future perspectives in our country do not seem to be very favourable.

Dietary cis-monounsaturated fatty acids and metabolic control in type 2 diabetes

Whether low-fat, high-carbohydrate (CHO) diets or moderately high-fat, high-monounsaturated fatty acid (MUFA) diets are preferable for the treatment and prevention of diabetes has been a matter of debate. High-fat diets based on MUFA-rich oils or whole foods have been compared with high-CHO diets for effects on several cardiovascular risk outcomes in diabetic subjects. Early studies using metabolic diets with wide differences in total fat content (15-25% of energy) generally found a beneficial effect of MUFA diets on glycemic control and serum lipids. Recent studies using prescribed diets with a difference of </= 15% of energy in total fat between low-fat and high-MUFA diets show similar effects on glycemic profiles but still favor MUFA diets for effects on triacylglycerols and HDL cholesterol. It is unclear whether postprandial fat clearance is impaired by CHO diets and improved by MUFA diets, independent of effects on fasting triacylglycerol concentrations. Unless one diet contains abundant antioxidants, the 2 dietary approaches appear to have similar effects on LDL oxidation. Low-fat diets, however, are associated with atherogenic, dense LDL particles, while normal, buoyant LDL predominate with high-fat diets irrespective of fatty acid composition. Limited experimental evidence suggests that MUFA diets favorably influence blood pressure, coagulation, endothelial activation, inflammation, and thermogenic capacity. Energy-controlled high-MUFA diets do not promote weight gain and are more acceptable than low-fat diets for weight loss in obese subjects. Thus, there is good scientific support for MUFA diets as an alternative to low-fat diets for medical nutrition therapy in diabetes.

Dietary oils high in oleic acid but with different unsaponifiable fraction contents have different effects in fatty acid composition and peroxidation in rabbit LDL

OBJECTIVE

We investigated the influence of different edible oils high in oleic acid but with different unsaponifiable fractions on the fatty acid composition and lipid peroxidation in plasma and low-density lipoprotein (LDL) in rabbits.

METHODS

Thirty-two rabbits were randomly assigned to four groups of eight animals. For 8 wk each group was fed a semisynthetic isoenergetic diet that differed by lipid source (Picual virgin olive oil, Picual virgin olive oil that had been subjected to an exhaustive process of washing, Arbequina virgin olive oil, and sunflower oil high in oleic acid). We analyzed the fatty acid profile, thiobarbituric acid reactive substances, alpha-tocopherol, coenzyme Q, and retinol in plasma and the fatty acid profile, hydroperoxides, alpha-tocopherol, and coenzyme Q in LDL.

RESULTS

The two varieties of virgin olive oil behaved differently from the high-oleic sunflower oil, and the effect of the different ratios of oleic acid to linoleic acid in the lipid sources on fatty acid composition in plasma and LDL was significant. With regard to oxidative stress, LDL in the group that ingested the lipid sources with the greatest amount of phenolic compounds showed the highest level of antioxidants (alpha-tocopherol and coenzyme Q; P < 0.05) and the lowest susceptibility to lipid peroxidation (P < 0.05).

CONCLUSION

This study provides evidence in vivo of the considerable antioxidant capacity of the phenolic fraction of virgin olive oil in rabbit LDL and the important role that this unsaponifiable fraction can play in the overall antioxidant benefit attributed to these oils. However, these effects depend on the phenolic content of the oil.