Extra-virgin olive oil increases the resistance of LDL to oxidation more than refined olive oil in free-living men with peripheral vascular disease

Efficacy of Hydroxytyrosol-Rich Food Supplements on Reducing Lipid Oxidation in Humans

In the present study we report the efficacy of two food supplements derived from olives in reducing lipid oxidation. To this end, 12 healthy volunteers received a single dose (25 mL) of olive phenolics, mainly hydroxytyrosol (HT), provided as a liquid dietary supplement (30.6 or 61.5 mg HT), followed by an investigation of two reliable markers of oxidative stress. Blood and urine samples were collected at baseline and at 0.5, 1, 1.5, 2, 4, and 12 h post-intake. Plasma-oxidized low-density lipoprotein (oxLDL) cholesterol levels were measured with ELISA using a monoclonal antibody, while F2-isoprostanes (F2-IsoPs) were quantified in urine with UHPLC-DAD-MS/MS. Despite the great variability observed between individuals, a tendency to reduce lipoxidation reactions was observed in the blood in response to a single intake of the food supplements. In addition, the subgroup of individuals with the highest baseline oxLDL level showed a significant (p < 0.05) decrease in F2-IsoPs at 0.5 and 12 h post-intervention. These promising results suggest that HT supplementation could be a useful aid in preventing lipoxidation. Additionally, people with a redox imbalance could benefit even more from supplementing with bioavailable HT.

Effect of olive oil phenols on oxidative stress biomarkers: A systematic review and dose–response meta‐analysis of randomized clinical trials

The phenolic content of olive oil has a role in cardiovascular protection. Some clinical trial studies demonstrated that phenolic compounds of olive oil have antioxidant activity which can protect macronutrients from oxidative damages. The aim of this study was to summarize the results of clinical trials which assessed the effects of high- versus low-phenol olive oil on oxidative stress biomarkers levels. We searched Scopus, PubMed, Web of Science, Google Scholar, ProQuest, and Embase up to July 2021. Eight clinical trials which evaluated the effect of the phenolic content of olive oil on oxidized-LDL (ox-LDL), malondialdehyde (MDA), or ferric-reducing ability of plasma (FRAP) were included the meta analysis. A significant decrease was observed in ox-LDL level (WMD: -0.29 U/L; 95% CI: -0.51, -0.07) and MDA (WMD: -1.82 μmoL/L; 95% CI: -3.13, -0.50). However, after subgroup analysis for MDA, the result was not significant for not serious limitation (SMD: -0.05, 95% CI: -0.35 to 0.24), but significant for serious limitation (SMD: -3.64, 95% CI: -4.29 to -2.99). Also, no significant change was found in FRAP (WMD: 0.0 mmoL/L; 95% CI: -0.03, 0.04) level. Dose-response analysis indicated a significant linear relationship between the phenolic content of olive oil and ox-LDL. The present study showed some beneficial effects of high-phenol compared with low-phenol olive oil on ox-LDL and MDA levels. According to the meta-regression analysis along with the increasing phenolic content of olive oil, a reduction in oxidative stress biomarkers was observed.

Evidence Supporting the Involvement of the Minority Compounds of Extra Virgin Olive Oil, through Gut Microbiota Modulation, in Some of the Dietary Benefits Related to Metabolic Syndrome in Comparison to Butter

Extra virgin olive oil (EVOO) has proven to yield a better health outcome than other saturated fats widely used in the Western diet, including a distinct dysbiosis-preventive modulation of gut microbiota. Besides its high content in unsaturated fatty acids, EVOO also has an unsaponifiable polyphenol-enriched fraction that is lost when undergoing a depurative process that gives place to refined olive oil (ROO). Comparing the effects of both oils on the intestinal microbiota of mice can help us determine which benefits of EVOO are due to the unsaturated fatty acids, which remain the same in both, and which benefits are a consequence of its minority compounds, mainly polyphenols. In this work, we study these variations after only six weeks of diet, when physiological changes are not appreciated yet but intestinal microbial alterations can already be detected. Some of these bacterial deviations correlate in multiple regression models with ulterior physiological values, at twelve weeks of diet, including systolic blood pressure. Comparison between the EVOO and ROO diets reveals that some of these correlations can be explained by the type of fat that is present in the diet, while in other cases, such as the genus Desulfovibrio, can be better understood if the antimicrobial role of the virgin olive oil polyphenols is considered.

The Effect of Nutrition on Aging-A Systematic Review Focusing on Aging-Related Biomarkers

Despite the increasing life expectancy, an individual’s later years tends to be accompanied by a decrease in the quality of life. Though biological changes that occur through the natural process of aging cannot be controlled, the risk factors associated with lifestyle can. Thus, the main goal of this systematic review was to evaluate how nutrition can modulate aging. For this purpose, thirty-six studies were selected on (i) the efficiency of nutrition’s effect on aging, (ii) the evaluation of biomarkers that promote healthy aging, and (iii) how to increase longevity through nutrition, and their quality was assessed. The results showed that choosing low carbohydrate diets or diets rich in vegetables, fruits, nuts, cereals, fish, and unsaturated fats, containing antioxidants, potassium, and omega-3 decreased cardiovascular diseases and obesity risk, protected the brain from aging, reduced the risk of telomere shortening, and promoted an overall healthier life. With this study, the conclusion is that since the biological processes of aging cannot be controlled, changing one’s nutritional patterns is crucial to prevent the emergence and development of diseases, boost longevity, and, mostly, to enhance one’s quality of life and promote healthy aging.

Olive Leaf Powder Modulate Insulin Production and Circulating Adipokines in Streptozotocin Induced Diabetic Rats

Olives (Olea europaea) have natural phytochemical compounds that are of great importance for their potential beneficially health effects. This study aimed to evaluate the effects of olive leaf powder (OLP) on insulin production and circulating adipokines in streptozotocin-induced diabetic rats. Forty Wistar-albino male rats, weighing 200-225 g were divided into four groups (n = 10); group I: Normal healthy rats received balanced diet; group II: Diabetic control rats receiving balanced diet; group III: Diabetic rats receiving balanced diet + standard antidiabetic drugs (metformin, 600 mg/bw) and group four: Diabetic rats received diet supplemented with 2.0% OLP. The experiment was conducted for four weeks. Our results showed that the consumption of 2.0% OLP decreased serum glucose, triglycerides (TG), total cholesterol (TC), and low-density lipoprotein (LDL) levels, whereas serum high density lipoprotein (HDL) level was increased. OLP supplementation also inhibited the atherogenic index [AI; log (TG/HDL-C) and atherogenic coefficient (AC)] levels relative to those of the untreated diabetic group. Moreover, OLP increased serum adiponectin concentration, and decreased serum leptin concentration. Liver and kidney functions were also attenuated by OLP. This finding also implies that OLP can play an important role in the treatment and delay of diabetic complications.

Protection of natural antioxidants against low-density lipoprotein oxidation

This chapter reports essential information about the protective action of antioxidants against LDL oxidation. The activity of individual compounds (tocopherols, vitamin C, phenolic compounds) as well as extracts obtained from plant material (cereals, fruits, legumes, nuts, mushrooms, by-products of food industry) is reported. The structure-antioxidant activity relationship of phenolic compounds is discussed. This article summarizes the findings to date of both in vitro and in vivo studies using foods or phenolic extracts isolated from foodstuffs at inhibiting the incidence of LDL oxidation. This chapter summarizes also the reportings to date of in vivo studies using foods or beverages at inhibiting the incidence of LDL oxidation.

Is Extra Virgin Olive Oil an Ally for Women's and Men's Cardiovascular Health?

Noncommunicable diseases are long-lasting and slowly progressive and are the leading causes of death and disability. They include cardiovascular diseases (CVD) and diabetes mellitus (DM) that are rising worldwide, with CVD being the leading cause of death in developed countries. Thus, there is a need to find new preventive and therapeutic approaches. Polyphenols seem to have cardioprotective properties; among them, polyphenols and/or minor polar compounds of extra virgin olive oil (EVOO) are attracting special interest. In consideration of numerous sex differences present in CVD and DM, in this narrative review, we applied "gender glasses." Globally, it emerges that olive oil and its derivatives exert some anti-inflammatory and antioxidant effects, modulate glucose metabolism, and ameliorate endothelial dysfunction. However, as in prescription drugs, also in this case there is an important gender bias because the majority of the preclinical studies are performed on male animals, and the sex of donors of cells is not often known; thus a sex/gender bias characterizes preclinical research. There are numerous clinical studies that seem to suggest the benefits of EVOO and its derivatives in CVD; however, these studies have numerous limitations, presenting also a considerable heterogeneity across the interventions. Among limitations, one of the most relevant in the era of personalized medicine, is the non-attention versus women that are few and, also when they are enrolled, sex analysis is lacking. Therefore, in our opinion, it is time to perform more long, extensive and lessheterogeneous trials enrolling both women and men.

Impact of different types of olive oil on cardiovascular risk factors: A systematic review and network meta-analysis

BACKGROUND AND AIM

This network meta-analysis (NMA) compares the effects of different types of olive oil (OO) on cardiovascular risk factors.

METHODS AND RESULTS

Literature search was conducted on three electronic databases (Medline, Web of Science, and Cochrane Central).

INCLUSION CRITERIA

Randomized controlled trials (RCTs) (≥3 weeks duration of intervention) comparing at least two of the following types of OO: refined OO (ROO), mixed OO (MOO), low phenolic (extra) virgin OO (LP(E)VOO), and high phenolic (extra) virgin OO (HP(E)VOO). Random-effects NMA was performed for seven outcomes; and surface under the cumulative ranking curve (SUCRA) was estimated, using an analytical approach (P-score). Thirteen RCTs (16 reports) with 611 mainly healthy participants (mean age: 26-70 years) were identified. No differences for total cholesterol, HDL-cholesterol, triacylglycerols, and diastolic blood pressure were observed comparing ROO, MOO, LP(E)VOO and HP(E)VOO. HP(E)VOO slightly reduce LDL-cholesterol (LDL-C) compared to LP(E)VOO (mean difference [MD]: -0.14 mmol/L, 95%-CI: -0.28, -0.01). Both, HP(E)VOO and LP(E)VOO reduces SBP compared to ROO (range of MD: -2.99 to -2.87 mmHg), and HP(E)VOO may improve oxidized LDL-cholesterol (oxLDL-C) compared to ROO (standardized MD: -0.68, 95%-CI: -1.31, -0.04). In secondary analyses, EVOO may reduce oxLDL-C compared to ROO, and a dose-response relationship between higher intakes of phenolic compounds from OO and lower SBP and oxLDL-C values was detected. HP(E)VOO was ranked as best treatment for LDL-C (P-score: 0.83), oxLDL-C (0.88), and SBP (0.75).

CONCLUSIONS

HP(E)VOO may improve some cardiovascular risk factors, however, public health implications are limited by overall low or moderate certainty of evidence.

Network Meta-Analysis of Metabolic Effects of Olive-Oil in Humans Shows the Importance of Olive Oil Consumption With Moderate Polyphenol Levels as Part of the Mediterranean Diet

The beneficial role of olive oil consumption is nowadays widely recognized. However, it is not clear whether its health effects are due to the presence of monounsaturated lipids and/or to the antioxidant fraction of microconstituents present in olive oil. The aim of the present study was to analyze the exact role of olive oil in the modification of metabolic factors (glucose and circulating lipids) and explore the role of its antioxidant polyphenols. In the present work, we have performed a network meta-analysis of 30 human intervention studies, considering direct and indirect interactions and impact of each constituent. Interestingly, we show that the impact of olive oil on glucose, triglycerides, and LDL-cholesterol is mediated through an adherence to the Mediterranean diet, with the only notable effect of olive oil polyphenols being the increase of HDL-cholesterol, and the amelioration of the antioxidant and inflammatory status of the subjects. Additionally, we report for the first time that lower antioxidant polyphenol levels may be sufficient for the beneficial effects of olive oil, while we show that the lipid fraction of olive oil may be responsible for some of its beneficial actions. In all parameters examined the beneficial effect of olive oil was more pronounced in subjects with an established metabolic syndrome or other chronic conditions/diseases. In conclusion, all these findings provide new knowledge that could lead to re-establishment of the role of olive oil in human nutrition.

Olive Oil Effects on Colorectal Cancer

Colorectal cancer is the fourth cause of cancer-related death worldwide. A Mediterranean diet showed protective action against colorectal cancer due to the intake of different substances. Olive oil is a fundamental component of the Mediterranean diet. Olive oil is rich in high-value health compounds (such as monounsaturated free fatty acids, squalene, phytosterols, and phenols). Phenolic compounds exert favourable effects on free radicals, inflammation, gut microbiota, and carcinogenesis. The interaction between gut microbiota and olive oil consumption could modulate colonic microbial composition or activity, with a possible role in cancer prevention. Gut microbiota is able to degrade some substances found in olive oil, producing active metabolites with chemopreventive action. Further clinical research is needed to clarify the beneficial effects of olive oil and its components. A better knowledge of the compounds found in olive oil could lead to the development of nutritional supplements or chemotherapeutic agents with a potential in the prevention and treatment of colorectal cancer.

Cardiovascular Benefits of Phenol-Enriched Virgin Olive Oils: New Insights from the Virgin Olive Oil and HDL Functionality (VOHF) Study

SCOPE

The main findings of the "Virgin Olive Oil and HDL Functionality" (VOHF) study and other related studies on the effect of phenol-enriched virgin olive oil (VOO) supplementation on cardiovascular disease are integrated in the present work.

METHODS AND RESULTS

VOHF assessed whether VOOs, enriched with their own phenolic compounds (FVOO) or with those from thyme (FVOOT), improve quantity and functionality of HDL. In this randomized, double-blind, crossover, and controlled trial, 33 hypercholesterolemic subjects received a control VOO (80 mg kg-1 ), FVOO (500 mg kg-1 ), and FVOOT (500 mg kg-1 ; 1:1) for 3 weeks. Both functional VOOs promoted cardioprotective changes, modulating HDL proteome, increasing fat-soluble antioxidants, improving HDL subclasses distribution, reducing the lipoprotein insulin resistance index, increasing endogenous antioxidant enzymes, protecting DNA from oxidation, ameliorating endothelial function, and increasing fecal microbial metabolic activity. Additional cardioprotective benefits were observed according to phenol source and content in the phenol-enriched VOOs. These insights support the beneficial effects of OO and PC from different sources.

CONCLUSION

Novel therapeutic strategies should increase HDL-cholesterol levels and enhance HDL functionality. The tailoring of phenol-enriched VOOs is an interesting and useful strategy for enhancing the functional quality of HDL, and thus, it can be used as a complementary tool for the management of hypercholesterolemic individuals.

The Potential Protective Effects of Phenolic Compounds against Low-density Lipoprotein Oxidation

BACKGROUND

The exact mechanism(s) of atherosclerosis in humans remains elusive, but one theory hypothesizes that this deleterious process results from the oxidative modification of low-density lipoprotein (LDL). Research suggests that foods rich in dietary phenolic compounds with antioxidant activity can mitigate the extent of LDL oxidation in vivo. With regard to the different classes of flavonoids, there appears to be a structurefunction relationship between the various moieties/constituents attached to the flavonoids' three ring system and their impact at retarding LDL oxidation.

METHODS

This article summarizes the findings to date of both in vitro and in vivo studies using foods or phenolic extracts isolated from foodstuffs at inhibiting the incidence of LDL oxidation. Three bases: SCOPUS, Web Science, and PubMed were used for search.

RESULTS

An often used method for the determination of antioxidant properties of natural phenolic compounds is the LDL oxidation assay. LDLs are isolated from human plasma and their oxidation is induced by Cu2+ ions or 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The sample is incubated with a phenolic extract or individual/isolated phenolic compounds. LDL oxidation is then monitored by various chemical methods (e.g., measurement of the generation of conjugated dienes and trienes). This technique confirmed the antioxidant properties of several extracts as obtained from plant material (e.g., grapes, berries, orange, grapefruit, coffee, tea, chocolate, olives, nuts) as well as the individual phenolic compounds (e.g., luteolinidin, apigenidin, caffeic acid, chlorogenic acid, catechin, quercetin, rutin). Several studies in vivo confirmed protective effects of phenolic compounds against LDL oxidation. They covered the healthy subjects with hyperlipidaemia, overweight, obesity, metabolic syndrome, heavy smokers, patients receiving haemodialysis, patients with peripheral vascular disease, and subjects at high cardiovascular risk. The studies comprise individuals of all ages, and the number of participants in the different experiments varied widely.

CONCLUSION

Properly designed double-blind, placebo-controlled randomised clinical trials offer stronger evidence as to the impact of dietary phenolics consumption at retarding LDL oxidation. More such clinical trials are needed to strengthen the hypothesis that foods rich in dietary phenolic compounds with antioxidant activity can mitigate the extent of LDL oxidation in vivo.

The relationship between lipid phytochemicals, obesity and its related chronic diseases

This review focuses on phytochemicals in oils, and summarizes the mechanisms of the anti-obesity effects of these compounds in in vitro studies, animal models, and human trials.

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.

Flavonols reduce aortic atherosclerosis lesion area in apolipoprotein E deficient mice: A systematic review and meta-analysis

Diets rich in flavonoids have been reported to have beneficial effects in the primary prevention of cardiovascular events. There are limited data, however, on the cardiovascular benefits of purified flavonoids. The aim of this systematic review and meta-analysis was to examine the reported effects of isolated flavonoids on aortic atherosclerosis in a mouse model. Medline, Pubmed, Science direct and Web of Science were searched to identify studies which examined the effect of isolated flavonoids on aortic atherosclerosis in apolipoprotein E deficient mice. A meta-analysis was performed to determine the overall effect of the flavonoids, and sub-analyses were performed to compare the effects of the flavonols and flavan-3-ols. Eleven studies, which examined a total of 208 mice receiving a flavonoid and 126 control mice, were included. Overall the flavonoids significantly reduced aortic atherosclerosis (SMD 1.10, 95% CI 0.69, 1.51). Of the 18 flavonoid interventions examined 12 were flavonols and 3 were flavan-3-ols. Sub-analyses suggested that the flavonols (SMD 1.31, 95% CI 0.66, 1.91) but not the flavan-3-ols (SMD 0.33, 95% CI -0.19, 0.85) significantly decreased atherosclerosis area. Of the eleven studies, only one examined histological markers of atherosclerosis plaque stability. Most studies did not report blinding of outcome assessors or reproducibility of the primary outcome, and did not justify the sample size used and flavonoid dose administered. Based on the included studies, the flavonols appear to be the most effective flavonoids for reducing aortic atherosclerotic lesion area in apolipoprotein E deficient mice.

Olive Polyphenols and the Metabolic Syndrome

Here, the effects of consuming polyphenol-rich olive products, including olive leaves, their crude extract, and extra virgin olive oil, on aspects of the metabolic syndrome are reviewed. We have sought to summarize the available scientific evidence from dietary intervention trials demonstrating a role for these phytochemicals in ameliorating aberrant glucose metabolism, high blood pressure and elevated blood lipids, and we discuss the potential mechanisms underpinning these observations. Searches for relevant literature published in English were conducted via PubMed and Science Direct. Based on published dietary intervention studies, there is convincing evidence to show that olive polyphenols, independently of olive lipids, reduce risk factors for metabolic syndrome, in particular by improving blood sugar and blood pressure control, and in reducing low density lipoprotein oxidation. There is more limited evidence to suggest that the consumption of olive polyphenols or related products can reduce body weight and visceral fat or impede weight gain, and similarly there are some limited data suggesting improved lipid profiles. There is some mechanistic data to support observations made in human volunteers, but further work is needed in this area. The consumption of olive polyphenols within the context of a healthy pattern of food intake may, in part, explain the reduced risk of metabolic disease associated with adherence to the Mediterranean diet.

Impact of phenolic-rich olive leaf extract on blood pressure, plasma lipids and inflammatory markers: a randomised controlled trial

PURPOSE

Dietary polyphenols have been demonstrated to favourably modify a number of cardiovascular risk markers such as blood pressure (BP), endothelial function and plasma lipids. We conducted a randomised, double-blind, controlled, crossover trial to investigate the effects of a phenolic-rich olive leaf extract (OLE) on BP and a number of associated vascular and metabolic measures.

METHODS

A total of 60 pre-hypertensive [systolic blood pressure (SBP): 121-140 mmHg; diastolic blood pressure (DBP): 81-90 mmHg] males [mean age 45 (±SD 12.7 years, BMI 26.7 (±3.21) kg/m2] consumed either OLE (136 mg oleuropein; 6 mg hydroxytyrosol) or a polyphenol-free control daily for 6 weeks before switching to the alternate arm after a 4-week washout.

RESULTS

Daytime [-3.95 (±SD 11.48) mmHg, p = 0.027] and 24-h SBP [-3.33 (±SD 10.81) mmHg, p = 0.045] and daytime and 24-h DBP [-3.00 (±SD 8.54) mmHg, p = 0.025; -2.42 (±SD 7.61) mmHg, p = 0.039] were all significantly lower following OLE intake, relative to the control. Reductions in plasma total cholesterol [-0.32 (±SD 0.70) mmol/L, p = 0.002], LDL cholesterol [-0.19 (±SD 0.56) mmol/L, p = 0.017] and triglycerides [-0.18 (±SD 0.48), p = 0.008] were also induced by OLE compared to control, whilst a reduction in interleukin-8 [-0.63 (±SD 1.13) pg/ml; p = 0.026] was also detected. Other markers of inflammation, vascular function and glucose metabolism were not affected.

CONCLUSION

Our data support previous research, suggesting that OLE intake engenders hypotensive and lipid-lowering effects in vivo.

The antimicrobial and antioxidant activity of Muscari neglectum flower ethanol extract

Introduction: Muscari neglectum has been used as food in some countries.

Objective: The antimicrobial and antioxidant activities of M. neglectum were the subject of the study.

Methods: In this study, the total phenolic, flavonoid, monomeric anthocyanin contents, antioxidant and antimicrobial activity of M. neglectum flowers ethanol extract were determined by different methods against some food poisoning microorganisms.

Results: Total phenolic, flavonoids and anthocyanin contents of the extract were 18.2, 0.94 and 0.11%, respectively. The IC50 for M. neglectum was higher than that of BHT. M. neglectum extract showed no inhibition zone (IZ) against Staphylococcus aureus and had small IZ against Candida albicans and Aspergillus niger. Shigella flexneri and Escherichia coli had the higher IZ than the others. The lower MIC and MLC values were for C. albicans, followed by Sh. flexneri and E. coli. S. aureus had the higher MIC and MLC values than the others.

Conclusion: Therefore, the M. neglectum flower extract can be used as a natural preservative and coloring agent in foods as replacement of synthetic ones.

Extra-virgin olive oil attenuates amyloid-β and tau pathologies in the brains of TgSwDI mice

Extra-virgin olive oil (EVOO) is one of the main elements of Mediterranean diet. Several studies have suggested that EVOO has several health promoting effects that could protect from and decrease the risk of Alzheimer's disease (AD). In this study, we investigated the effect of consumption of EVOO-enriched diet on amyloid- and tau-related pathological alterations that are associated with the progression of AD and cerebral amyloid angiopathy (CAA) in TgSwDI mice. Feeding mice with EVOO-enriched diet for 6months, beginning at an age before amyloid-β (Aβ) accumulation starts, has significantly reduced total Aβ and tau brain levels with a significant improvement in mouse cognitive behavior. This reduction in brain Aβ was explained by the enhanced Aβ clearance pathways and reduced brain production of Aβ via modulation of amyloid-β precursor protein processing. On the other hand, although feeding mice with EVOO-enriched diet for 3months, beginning at an age after Aβ accumulation starts, showed improved clearance across the blood-brain barrier and significant reduction in Aβ levels, it did not affect tau levels or improve cognitive functions of TgSwDI mouse. Collectively, results of this study suggest that the long-term consumption of EVOO-containing diet starting at early age provides a protective effect against AD and its related disorder CAA.

Effects of high phenolic olive oil on cardiovascular risk factors: A systematic review and meta-analysis

BACKGROUND

Cardiovascular diseases are the world's leading cause of death. Prevention by nutrition is an easy and effective approach especially by advising foods with nutraceutic properties like high phenolic olive oil (HPOO).

AIM

The aim of this review was to systematically access and meta-analyse the effects of HPOO on risk factors of the cardiovascular system and thusly to evaluate its use as a nutraceutical in prevention.

DATA SYNTHESIS

Medline/PubMed, EMBase, the Cochrane Library, CAMbase and CAM-QUEST were searched through July 2013. Randomized controlled trials (RCTs) comparing high vs. low (resp. non) phenolic olive oils in either healthy participants or patients with cardiovascular diseases were included. For study appraisal the Cochrane Collaboration's risk of bias tool was used. Main outcomes were blood pressure, serum lipoproteins and oxidation markers. Standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated and analysed by the generic inverse variance methods using a random effects model. Eight cross over RCTs comparing ingestion (21-90 d) of high vs. low (resp. non) phenolic olive oils with a total of 355 subjects were included.

RESULTS

There were medium effects for lowering systolic blood pressure (n = 69; SMD -0.52; CI -0.77/-0.27; p < 0.01) and small effects for lowering oxLDL (n = 300; SMD -0.25; CI [-0.50/0.00]; p = 0.05). No effects were found for diastolic blood pressure (n = 69; SMD -0.20; CI -1.01/0.62; p = 0.64); malondialdehyde (n = 71; SMD -0.02; CI [-0.20/0.15]; p = 0.79), total cholesterol (n = 400; SMD -0.05; CI [-0.16/0.05]; p = 0.33); HDL (n = 400; SMD -0.03; CI [-0.14/0.08]; p = 0.62); LDL (n = 400; SMD -0.03; CI [-0.15/0.09]; p = 0.61); and triglycerides (n = 360; SMD 0.02; CI [-0.22/0.25]; p = 0.90).

LIMITATIONS

The small number of studies/participants limits this review.

CONCLUSIONS

HPOO provides small beneficial effects on systolic blood pressure and serum oxidative status (oxLDL). HPOO should be considered as a nutraceutical in cardiovascular prevention.

Olive oil in the prevention and treatment of osteoporosis after artificial menopause

Purpose

The goal of this study was to investigate the anti-osteoporosis effect of extra virgin olive oil (EVOO) in vivo, and explore its antioxidant, anti-inflammatory properties in Sprague Dawley rats and its anticancer properties in patients.

Materials and methods

A total of 120 healthy female Sprague Dawley rats aged 6 months were divided into four groups: 1) sham-operated control (Sham group, n=30); 2) ovariectomized (OVX group, n=30); 3) ovariectomized rats supplemented with EVOO (OVX + Olive, n=30); 4) ovariectomized rats supplemented with estrogen (OVX + E₂, n=30). EVOO and estrogen were administered by oral gavage at a dose of 1 mL/100 g weight on a daily basis for 12 consecutive weeks. Twelve weeks later blood samples were obtained to detect the levels of calcium, alkaline phosphatase, phosphorus, interleukin-6 (IL-6), malonyldialdehyde (MDA), and nitrate content. Dual energy X-ray absorptiometer measured bone mineral density (BMD) of ovariectomized Sprague Dawley rats that had been fed olive oil for 3 months. Blood samples from patients, who regularly consumed olive oil over a 1 year period were also used to measure carbohydrate antigen 125, carcino-embryonic antigen, α-fetoprotein, and carbohydrate antigen 19-9 levels. BMD of lumbar spine and left femur was also evaluated by dual energy X-ray absorptiometry.

Results

Animal experiments showed that EVOO significantly increased BMD and decreased phosphatase, alkaline phosphatase, IL-6, MDA, and nitrate levels. However, it had no significant effect on the Ca²⁺ level. In clinical follow-up, EVOO also improved patient BMD levels on L3, L4, and left femoral neck, and reduced carbohydrate antigen 125, α-fetoprotein, and carcino-embryonic antigen levels. But it had no significant effect on the carbohydrate antigen 19-9 level.

Conclusion

EVOO illustrated significant anti-osteoporosis, antioxidant, anti-inflammatory, and anticancer properties in vivo. However, further studies are required to determine the active component(s) responsible for these effects.

The long-term ingestion of a diet high in extra virgin olive oil produces obesity and insulin resistance but protects endothelial function in rats: a preliminary study

BACKGROUND

It has been hypothesized that fatty acids derived from a diet high in saturated fat may negatively affect endothelial function more significantly than a diet high in unsaturated fat; nevertheless, the effects of the long-term ingestion of monounsaturated fatty acids on endothelial function have been poorly studied.

METHODS

To examine the chronic effects of monounsaturated (e.g., extra virgin olive oil (EVOO)) or saturated (e.g., margarine (M)) fatty acid-rich diets on the development of insulin resistance and endothelial dysfunction in rats, three groups of rats were fed control, high-EVOO or high-M diets for 20 weeks. Body weight, energy consumption, insulin resistance, lipid peroxidation and in vitro vascular reactivity with and without metformin were assessed during the study period.

RESULTS

Both high-fat diets produced obesity and insulin resistance. EVOO-fed rats showed smaller increases in total cholesterol and arterial lipid peroxidation when compared with M-fed rats. Vascular reactivity to phenylephrine and sodium nitroprusside was not modified, but the vasodilating effect of carbachol was especially reduced in the M-fed rats compared with the EVOO-fed or control groups. Metformin addition to the incubation media decreased the vascular response to phenylephrine; decrease that was lower in rats fed with both high fat diets, and increased the carbachol and nitroprusside effects, but the metformin-enhanced response to carbachol was lower in the M group.

CONCLUSIONS

Our results suggest that feeding rats with high quantities of EVOO, despite producing obesity and insulin resistance, produces low levels of circulating cholesterol and arterial lipoperoxidation compared to M fed rats and shows a preserved endothelial response to carbachol, effect that is significantly enhanced by metformin only in rats fed with control and EVOO diets.

Health effects of olive oil polyphenols: recent advances and possibilities for the use of health claims

The Mediterranean diet and consumption of olive oil have been connected in several studies with longevity and a reduced risk of morbidity and mortality. Lifestyle, such as regular physical activity, a healthy diet, and the existing social cohesion in Southern European countries have been recognised as candidate protective factors that may explain the Mediterranean Paradox. Along with some other characteristics of the Mediterranean diet, the use of olive oil as the main source of fat is common in Southern European countries. The benefits of consuming olive oil have been known since antiquity and were traditionally attributed to its high content in oleic acid. However, it is now well established that these effects must also be attributed to the phenolic fraction of olive oil with its anti-oxidant, anti-inflammatory and anti-microbial activities. The mechanisms of these activities are varied and probably interconnected. For some activities of olive oil phenolic compounds, the evidence is already strong enough to enable the legal use of health claims on foods. This review discusses the health effects of olive oil phenols along with the possibilities of communicating these effects on food labels.

Oxidation of low-density lipoprotein by iron at lysosomal pH: implications for atherosclerosis

Low-density lipoprotein (LDL) has recently been shown to be oxidized by iron within the lysosomes of macrophages, and this is a novel potential mechanism for LDL oxidation in atherosclerosis. Our aim was to characterize the chemical and physical changes induced in LDL by iron at lysosomal pH and to investigate the effects of iron chelators and α-tocopherol on this process. LDL was oxidized by iron at pH 4.5 and 37 °C and its oxidation monitored by spectrophotometry and high-performance liquid chromatography. LDL was oxidized effectively by FeSO(4) (5-50 μM) and became highly aggregated at pH 4.5, but not at pH 7.4. The level of cholesteryl esters decreased, and after a pronounced lag, the level of 7-ketocholesterol increased greatly. The total level of hydroperoxides (measured by the triiodide assay) increased up to 24 h and then decreased only slowly. The lipid composition after 12 h at pH 4.5 and 37 °C was similar to that of LDL oxidized by copper at pH 7.4 and 4 °C, i.e., rich in hydroperoxides but low in oxysterols. Previously oxidized LDL aggregated rapidly and spontaneously at pH 4.5, but not at pH 7.4. Ferrous iron was much more effective than ferric iron at oxidizing LDL when added after the oxidation was already underway. The iron chelators diethylenetriaminepentaacetic acid and, to a lesser extent, desferrioxamine inhibited LDL oxidation when added during its initial stages but were unable to prevent aggregation of LDL after it had been partially oxidized. Surprisingly, desferrioxamine increased the rate of LDL modification when added late in the oxidation process. α-Tocopherol enrichment of LDL initially increased the rate of oxidation of LDL but decreased it later. The presence of oxidized and highly aggregated lipid within lysosomes has the potential to perturb the function of these organelles and to promote atherosclerosis.

Mediterranean diet supplemented with coenzyme Q10 induces postprandial changes in p53 in response to oxidative DNA damage in elderly subjects

Coenzyme Q10 (CoQ) is a powerful antioxidant that reduces oxidative stress. We explored whether the quality of dietary fat alters postprandial oxidative DNA damage and whether supplementation with CoQ improves antioxidant capacity by modifying the activation/stabilization of p53 in elderly subjects. In this crossover study, 20 subjects were randomly assigned to receive three isocaloric diets during 4 weeks each: (1) Mediterranean diet (Med diet), (2) Mediterranean diet supplemented with CoQ (Med+CoQ diet), and (3) saturated fatty acid-rich diet (SFA diet). Levels of mRNAs were determined for p53, p21, p53R2, and mdm2. Protein levels of p53, phosphorylated p53 (Ser20), and monoubiquitinated p53 were also measured, both in cytoplasm and nucleus. The extent of DNA damage was measured as plasma 8-OHdG. SFA diet displayed higher postprandial 8-OHdG concentrations, p53 mRNA and monoubiquitinated p53, and lower postprandial Mdm2 mRNA levels compared with Med and Med+CoQ diets (p < 0.05). Moreover, Med+CoQ diet induced a postprandial decrease of cytoplasmatic p53, nuclear p-p53 (Ser20), and nuclear and cytoplasmatic monoubiquitinated p53 protein (p < 0.05). In conclusion, Med+CoQ diet improves oxidative DNA damage in elderly subjects and reduces processes of cellular oxidation. Our results suggest a starting point for the prevention of oxidative processes associated with aging.

Nutritional and biological properties of extra virgin olive oil

The nutritional benefits generally recognized for the consumption of extra virgin olive oil (EVOO) are based on a large number of dietary trials of several international populations and intervention studies. Unfortunately, many authors in this field used questionable analytical methods and commercial kits that were not validated scientifically to evaluate the complex bioactive constituents of EVOO and lipid oxidation and decomposition products. Many questionable antiradical methods were commonly used to evaluate natural polyphenolic antioxidants, including an indirect method to determine low-density lipoprotein (LDL) cholesterol. Extensive differences were observed in experimental design, diet control, populations of different ages and problems of compliance intervention, and questionable biomarkers of oxidative stress. Analyses in many nutritional studies were limited by the use of one-dimensional methods to evaluate multifunctional complex bioactive compounds and plasma lipid profiles by the common applications of commercial kits. Although EVOO contains polyphenolic compounds that exhibit significant in vitro antioxidant activity, much more research is needed to understand the absorption and in vivo activity. Many claims of in vivo human beneficial effects by the consumption of EVOO may be overstated. No distinctions were apparently made between in vivo studies based on general health effects in large populations of human subjects and smaller scale well-controlled feeding trials using either pure or mixtures of known phenolic constituents of EVOO. More reliable protocols and testing methods are needed to better validate the complex nutritional properties of EVOO.

Dietary monounsaturated fatty acids appear not to provide cardioprotection

Dietary interventions have been consistently proposed as a part of a comprehensive strategy to lower the incidence and severity of coronary heart disease (CHD), in the process providing long-term cardioprotection. Replacement of dietary saturated fatty acids (SFA) with higher intakes of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) has been reported to be inversely associated with risk of CHD. The observed lower incidence of CHD among populations consuming a Mediterranean-type diet, mainly enriched in MUFA from olive oil, has long supported the belief that MUFA are an optimal substitution for SFA. However, both epidemiologic and interventional studies suggest that although substituting MUFA-rich foods for SFA-rich foods in the diet can potentially lower total plasma cholesterol concentrations, this substitution does not lower the extent of coronary artery atherosclerosis. In addition, although recent evidence suggests that the source of MUFA (animal fat vs vegetable oils) may differentially influence the correlation between MUFA intake and CHD mortality, animal studies suggest that neither source is cardioprotective.

Hydroxytyrosol: from laboratory investigations to future clinical trials

Mediterranean countries have lower rates of mortality from cardiovascular disease and cancer than Northern European or other Western countries. This has been attributed, at least in part, to the so-called Mediterranean diet, which is composed of specific local foods, including olive oil. Traditionally, many beneficial properties associated with this oil have been ascribed to its high oleic acid content. Today, it is clear that many of the beneficial effects of ingesting virgin olive oil are due to its minor compounds. This review summarizes the existing knowledge concerning the chemistry, pharmacokinetics, and toxicology of hydroxytyrosol, a minor compound of virgin olive oil, as well as this compound's importance for health. The main findings in terms of its beneficial effects in cardiovascular disease and cancer, including its properties against inflammation and platelet aggregation, are emphasized. New evidence and strategies regarding the use of hydroxytyrosol as a natural drug for the prevention and treatment of diseases with high incidences in Western countries are also presented.

Biological activities of phenolic compounds present in virgin olive oil

The Mediterranean diet is associated with a lower incidence of atherosclerosis, cardiovascular disease, neurodegenerative diseases and certain types of cancer. The apparent health benefits have been partially ascribed to the dietary consumption of virgin olive oil by Mediterranean populations. Much research has focused on the biologically active phenolic compounds naturally present in virgin olive oils to aid in explaining reduced mortality and morbidity experienced by people consuming a traditional Mediterranean diet. Studies (human, animal, in vivo and in vitro) have demonstrated that olive oil phenolic compounds have positive effects on certain physiological parameters, such as plasma lipoproteins, oxidative damage, inflammatory markers, platelet and cellular function, antimicrobial activity and bone health. This paper summarizes current knowledge on the bioavailability and biological activities of olive oil phenolic compounds.

A 2-D-HPLC-CE platform coupled to ESI-TOF-MS to characterize the phenolic fraction in olive oil

A 2-D-HPLC/CE method was developed to separate and characterize more in depth the phenolic fraction of olive oil samples. The method involves the use of semi-preparative HPLC (C18 column 250x10 mm, 5 microm) as a first dimension of separation to isolate phenolic fractions from commercial extra-virgin olive oils and CE coupled to TOF-MS (CE-TOF-MS) as a second dimension, to analyze the composition of the isolated fractions. Using this method, a large number of compounds were tentatively identified, some of them by first time, based on the information concerning high mass accuracy and the isotopic pattern provided by TOF-MS analyzer together with the chemical knowledge and the behavior of the compounds in HPLC and CE. From these results it can be concluded that 2-D-HPLC-CE-MS provides enough resolving power to separate hundreds of compounds from highly complex samples, such as olive oil. Furthermore, in this paper, the isolated phenolic fractions have been used for two specific applications: quantification of some components of extra-virgin olive oil samples in terms of pure fractions, and in vitro studies of its anti-carcinogenic capacity.

Olive oil-supplemented diet alleviates acute heat stress-induced mitochondrial ROS production in chicken skeletal muscle

We have previously shown that avian uncoupling protein (avUCP) is downregulated on exposure to acute heat stress, stimulating mitochondrial reactive oxygen species (ROS) production and oxidative damage. In this study, we investigated whether upregulation of avUCP could attenuate oxidative damage caused by acute heat stress. Broiler chickens ( Gallus gallus) were fed either a control diet or an olive oil-supplemented diet (6.7%), which has been shown to increase the expression of UCP3 in mammals, for 8 days and then exposed either to heat stress (34°C, 12 h) or kept at a thermoneutral temperature (25°C). Skeletal muscle mitochondrial ROS (measured as H2O2) production, avUCP expression, oxidative damage, mitochondrial membrane potential, and oxygen consumption were studied. We confirmed that heat stress increased mitochondrial ROS production and malondialdehyde levels and decreased the amount of avUCP. As expected, feeding birds an olive oil-supplemented diet increased the expression of avUCP in skeletal muscle mitochondria and decreased ROS production and oxidative damage. Studies on mitochondrial function showed that heat stress increased membrane potential in state 4, which was reversed by feeding birds an olive oil-supplemented diet, although no differences in basal proton leak were observed between control and heat-stressed groups. These results show that under heat stress, mitochondrial ROS production and olive oil-induced reduction of ROS production may occur due to changes in respiratory chain activity as well as avUCP expression in skeletal muscle mitochondria.

Chemistry and health of olive oil phenolics

The Mediterranean diet is associated with a lower incidence of atherosclerosis, cardiovascular disease, and certain types of cancer. The apparent health benefits have been partially attributed to the dietary consumption of virgin olive oil by Mediterranean populations. Most recent interest has focused on the biologically active phenolic compounds naturally present in virgin olive oils. Studies (human, animal, in vivo and in vitro) have shown that olive oil phenolics have positive effects on certain physiological parameters, such as plasma lipoproteins, oxidative damage, inflammatory markers, platelet and cellular function, and antimicrobial activity. Presumably, regular dietary consumption of virgin olive oil containing phenolic compounds manifests in health benefits associated with a Mediterranean diet. This paper summarizes current knowledge on the physiological effects of olive oil phenolics. Moreover, a number of factors have the ability to affect phenolic concentrations in virgin olive oil, so it is of great importance to understand these factors in order to preserve the essential health promoting benefits of olive oil phenolic compounds.