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.     

Multiple pharmacological effects of olive oil phenols

Olive oil is a unique component of Mediterranean diet and is likely to be partially responsible for the health effects of this diet. Although the medicinal potential of olive oil has been largely attributed to the antioxidant effects of bio-phenols derived from olive oil, accumulating evidence strongly suggests that, to elucidate olive oil’s benefits to human health, we have to go beyond antioxidants. In this communication, through summarizing the reference-reported and database-recorded pharmacological information of olive oil phenols, we reveal that multiple pharmacological effects, other than antioxidant potential, are involved in olive oil phenols, which is of significance for understanding the health benefits of olive oil in the Mediterranean diet.     

Molecular mechanisms of the effects of olive oil and other dietary lipids on cancer

Cancer is one of the main causes of mortality worldwide. Geographical differences in incidence rates suggest a key effect of environmental factors, especially diet, in its aetiology. Epidemiologic and experimental studies have found a role of dietary lipids in cancer, particularly breast, colorectal, and prostate cancers. Their incidence in the Mediterranean countries, where the main source of fat is olive oil, is lower than in other areas of the world. Human studies about the effects of dietary lipids are little conclusive, probably due to methodological issues. On the other hand, experimental data have clearly demonstrated that the influence of dietary fats on cancer depends on the quantity and the type of lipids. Whereas a high intake of n-6 PUFA and saturated fat has tumor-enhancing effects, n-3 PUFA, conjugated linoleic acid and gamma-linolenic acid have inhibitory effects. Data regarding MUFA have not always been conclusive, but high olive oil diets seem to have protective effects. Such effects can be due to oleic acid, the main MUFA in olive oil, and to certain minor compounds such as squalene and phenolic compounds. This work aims to review the current knowledge about the relationship between dietary lipids and cancer, with a special emphasis on olive oil, and the molecular mechanisms underlying these effects: modifications on the carcinogenesis stages, hormonal status, cell membrane structure and function, signal transduction pathways, gene expression, and immune system.     

Oleuropein and hydroxytyrosol inhibit MCF‐7 breast cancer cell proliferation interfering with ERK1/2 activation

The growth of many breast tumors is stimulated by estradiol (E2), which activates a classic mechanism of regulation of gene expression and signal transduction pathways inducing cell proliferation. Polyphenols of natural origin with chemical similarity to estrogen have been shown to interfere with tumor cell proliferation. The aim of this study was to investigate whether hydroxytyrosol (HT) and oleuropein (OL), two polyphenols contained in extra‐virgin olive oil, can affect breast cancer cell proliferation interfering with E2‐induced molecular mechanisms. Both HT and OL inhibited proliferation of MCF‐7 breast cancer cells. Luciferase gene reporter experiments, using a construct containing estrogen responsive elements able to bind estrogen receptor alpha (ERα) and the study of the effects of HT or OL on ERα expression, demonstrated that HT and OL are not involved in ERα‐mediated regulation of gene expression. However, further experiments pointed out that both OL and HT determined a clear inhibition of E2‐dependent activation of extracellular regulated kinase1/2 belonging to the mitogen activating protein kinase family. Our study demonstrated that HT and OL can have a chemo‐preventive role in breast cancer cell proliferation through the inhibition of estrogen‐dependent rapid signals involved in uncontrolled tumor cell growth.     

Antitumor Perspectives of Oleuropein and Its Metabolite Hydroxytyrosol: Recent Updates

Olive fruit is a significant and promising source of potential bioactive compounds such as oleuropein and hydroxytyrosol. Oleuropein is the ester of elenolic acid and 3,4‐dihydroxyphenyl ethanol (HT). It is the main glycoside in olives, the degradation of which results in the formation of hydroxytyrosol in olive oil. Both plays a significant role in the reduction of coronary heart diseases and a certain type of cancers. Both olive oil phenols have an effective role counter to cell proliferation, cell growth, migration, invasion, and angiogenesis. They down regulate the expression of BCL‐2 and COX‐2 proteins, and reduced DNA damage. Hydroxytyrosol and oleuropein inhibited the multiple stages in colon carcinogenesis; initiation, promotion, and metastasis. They also provide protection against various human cancers including colorectal, skin, breast, thyroid, digestive, lung, brain, blood, and cervical. This review article discusses the anticancer perspectives and mechanisms of oleuropein and hydroxytyrosol in cell cultures and animal and human studies.     

Volatile aldehyde emissions from heated cooking oils

Low molecular weight aldehydes (LMWAs) formed during the heating of frying media (triglycerides) were adsorbed onto tenax and analyzed by GC‐MS after thermal desorption. Six alkanals (C₅ to C₁₀), seven 2‐alkenals (C₅ to C₁₁) and 3 alkadienals (C₇, C₉ and C₁₀) were found in the fumes of canola oil (control), extra virgin olive oil, and refined olive oil, heated at 180 and 240 °C. The emission rates of these aldehydes depended on the heating temperature. Frying in any type of olive oil, independently of its commercial category, will effectively decrease the emission of volatile aldehydes at temperatures below the smoking point. Thus, using the cheaper olive oil for deep‐frying purposes will not affect aldehyde emissions. This is important since olive oil is usually used for deep‐frying operations while extra virgin olive oil is used as salad dressing in Spain. The mixture of refined olive oil with some virgin olive oil is the most acceptable type of olive oil in non‐Mediterranean countries due to its milder flavor. However, if higher temperatures are needed the use of canola oil is more advisable due to its higher smoke point. Copyright © 2004 Society of Chemical Industry     

Comparison of the Frying Performance of Olive Oil and Palm Superolein

Abstract: Deep‐fat frying is an important method of food preparation in which foods are immersed in hot oil. Repeated use of frying oils is a common practice, and in the presence of atmospheric oxygen it produces various undesirable reactions in used oils. Stable frying oils usually require low linolenic acid (LnA < 3%), increased oleic acid (OA > 40%), and decreased linoleic acid (LA < 50%). The aim of this study was to establish the behavior of palm superolein (PSO) (OA 45%; LA 12.5%; LnA 0.2%) and olive oil (OO) during repeated, discontinuous deep frying of French fries. The behavior of the oils under controlled heating conditions was also studied by maintaining all of the process variables the same as those in deep frying, except that there was no food in the oil. The PSO selected to be tested in this study may represent an alternative to OO as a frying medium. Although PSO presented a faster increase in some oxidation indices, such as free fatty acid and total polar compounds, for other indicators, PSO showed better behavior than OO (less formation of C8:0 and lower peroxide value). Practical Application: The super palm olein selected for use in this study can be suggested as a suitable replacement for olive oil for frying and cooking purposes because it provides higher oxidative stability besides the beneficial effects of olive oil on human health. In fact, several studies have indicated that palm oil exhibits similar frying performance to high‐oleic oils, with the advantages of greater availability in the market and a lower price.     

Olive oil and longevity

Several lines of evidence point to olive oil and the olive oil-centered Mediterranean diet as conducive to longevity. The evidence stems from ecological, as well as analytic epidemiological studies assessing olive oil, monounsaturated lipids or the Mediterranean dietary pattern in relation to the incidence of, or mortality from, major common diseases, or overall mortality. Mechanistic considerations are addressed by biochemical studies, whereas randomized clinical trials provide further support to the evidence generated from observational investigations. The content of olive oil in several microcomponents with antioxidant potential, as well as its high content in monounsaturated lipids appear to be essential for the beneficial effect of this food.     

Vitamins, phytochemicals, diets, and their implementation in cancer chemoprevention

With progressive "Westernization" of the dietary pattern in Asian countries, such as Korea and Japan, unhealthy signs, such as increases in obesity and incidence rate of cancers, are starting to appear in recent statistics. These results support the hypothesis that a dietary pattern of low fats and high antioxidants based on plant foods will reduce the risk of cancer Recently, antioxidative vitamins and phenolic phytochemicals derived from our daily diet have received much attention because of their potential chemopreventive activities. Their chemopreventive mechanisms have been suggested mainly due to their protective effects against oxidative DNA damage. However. several studies have shown that dietary antioxidant supplements, such as vitamins and phenolic phytochemicals, are not beneficial; they may rather, cause DNA damage. These results suggest that a metabolomics approach might demonstrate that antioxidant rich whole diets play a more important role, rather than individual antioxidants in cancer prevention. On the other hand, the chemopreventive mechanisms of dietary vitamins and phenolic phytochemicals may be associated with the inhibition of other carcinogenic processes, particularly tumor promotion, rather than that of tumor initiation. In this article, possible cancer-preventive mechanisms of dietary vitamins and phenolic phytochemicals, are reviewed.     

Hydroxytyrosol inhibits the proliferation of human colon adenocarcinoma cells through inhibition of ERK1/2 and cyclin D1

Extra virgin olive oil is rich in phenolic compounds which are believed to exert beneficial effects against many pathological processes, including the development of colon cancer. We show that one of the major polyphenolic constituents of extra virgin olive oil, hydroxytyrosol (HT), exerts strong antiproliferative effects against human colon adenocarcinoma cells via its ability to induce a cell cycle block in G2/M. These antiproliferative effects were preceded by a strong inhibition of extracellular signal‐regulated kinase (ERK)1/2 phosphorylation and a downstream reduction of cyclin D1 expression, rather than by inhibition of p38 activity and cyclooxygenase‐2 (COX‐2) expression. These findings are of particular relevance due to the high colonic concentration of HT compared to the other olive oil polyphenols and may help explain the inverse link between colon cancer and olive oil consumption.     

Anticancer activities of cranberry phytochemicals: an update

Studies employing mainly in vitro tumor models show that extracts and compounds isolated from cranberry fruit (Vaccinium macrocarpon) inhibit the growth and proliferation of several types of tumor including breast, colon, prostate, and lung. Proanthocyanidin oligomers, flavonol and anthocyanin glycosides and triterpenoids are all likely contributors to the observed anticancer properties and may act in a complementary fashion to limit carcinogenesis. Possible chemopreventive mechanisms of action by cranberry phytochemicals include induction of apoptosis in tumor cells, reduced ornithine decarboxylase activity, decreased expression of matrix metalloproteinases associated with prostate tumor metastasis, and anti-inflammatory activities including inhibition of cyclooxygenases. A review of recent studies suggests a potential role for cranberry as a dietary chemopreventive and provides direction for future research.     

Olive oil and the haemostatic system

Interest in the Mediterranean diet (MD) has grown worldwide due to its link with greater longevity and lower cardiovascular disease rate, cancer and age cognitive decline. Despite the high complexity of its nutrients composition, olive oil emerges as its principal food, since it provides the higher percent of energy and a lot of bioactive compounds. In this review we will discuss the benefits of diets enriched in virgin olive oil, whose effects are probably due not only to its oleic acid content but also to its other potentially health-promoting components. Traditionally, the benefits of MD were linked to its effect on lipoprotein metabolism but today we realise that there exists a whole sheaf of other benefits, including the components of haemostasis: platelet function, thrombogenesis and fibrinolysis. A diet enriched in virgin olive oil can reduce the sensitivity of platelets to aggregation, decreasing von Willebrand and tromboxane B2 plasma levels. Moreover a particular interest has arisen about its capacity to decrease fasting Factor VII plasma levels and to avoid or modulate its postprandial activation. Also Tissue Factor expression in mononuclear cells could be reduced with the chronic intake of virgin olive oil and finally, studies performed in different experimental situation have shown that it could also increase fibrinolytic activity, reducing plasma concentration of Plasma Activator Inhibitor type-1.     

Anticancer activity of essential oils: a review

Natural essential oil constituents play an important role in cancer prevention and treatment. Essential oil constituents from aromatic herbs and dietary plants include monoterpenes, sesquiterpenes, oxygenated monoterpenes, oxygenated sesquiterpenes and phenolics among others. Various mechanisms such antioxidant, antimutagenic and antiproliferative, enhancement of immune function and surveillance, enzyme induction and enhancing detoxification, modulation of multidrug resistance and synergistic mechanism of volatile constituents are responsible for their chemopreventive properties. This review covers the most recent literature to summarize structural categories and molecular anticancer mechanisms of constituents from aromatic herbs and dietary plants. © 2013 Society of Chemical Industry     

Vasculoprotective potential of olive oil components

Epidemiological and clinical studies found that the traditional Mediterranean-style diet is associated with significantly lower mortality from coronary artery disease. Although it is difficult to isolate individual dietary factors, cumulative evidence suggests that olive oil, used as primary source of fat by Mediterranean populations, may play a key role in the observed cardiovascular benefit. Olive oil is a priceless source of vitamins and polyphenolic antioxidants, and has a balanced ratio of monounsaturated and polyunsaturated fatty acids. There are multiple mechanisms by which olive oil might impact the development of atherosclerosis. Olive oil decreases LDL-cholesterol and increases HDL-cholesterol, and also reduces oxidative stress due to polyphenols, which are able to scavenge free radicals and protect LDL from oxidation. In addition, olive oil components may interfere with the inflammatory response within atherosclerotic lesion, by inhibiting endothelial activation involved in monocyte recruitment during early atherogenesis and macrophage production of inflammatory cytokines and matrix degrading enzymes, thus improving vascular stability. Other vasculoprotective mechanisms by olive oil components derive from anti-thrombotic and anti-hypertensive actions. The available data support the need to preserve certain dietary traditions, such as olive oil consumption, to counteract the burden of cardiovascular disease.     

Digestion stability and evaluation of the metabolism and transport of olive oil phenols in the human small-intestinal epithelial Caco-2/TC7 cell line

The aims of this study were to investigate (i) the metabolism of olive oil phenolics by intestinal epithelial cells and (ii) their transport across epithelial cell monolayers. The various conjugates and derivatives produced by the intestinal epithelial cells were identified following separation by ultra-performance liquid chromatography (UPLC), using a combination of UV/visible spectra, mass spectrometry and specific enzyme treatments (β-glucuronidase and aryl-suphatase). Limited metabolism of olive oil phenolics was observed using Caco-2/Tc7 cells as a model of the human intestinal epithelium, and the methyslated conjugates were the major metabolites detected. The results of the transport rate data for phenols and their metabolites to the apical, cellular, and basolateral compartments after apical loading of the phenol at 100 μM showed a time-dependent efflux of various free and conjugated forms of phenols.     

Soy isoflavone genistein induces cell death in breast cancer cells through mobilization of endogenous copper ions and generation of reactive oxygen species

Scope: Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high isoflavone intake through soy consumption have lower rates of breast, prostate, and colon cancer. Isoflavone genistein in soybean is considered a potent chemopreventive agent against cancer. Although several mechanisms have been proposed, a clear anticancer action mechanism of genistein is still not known. Methods and results: Here, we show that the cytotoxic action of genistein against breast cancer cells involves mobilization of endogenous copper. Further, whereas the copper specific chelator neocuproine is able to inhibit the apoptotic potential of genistein, the molecules which specifically bind iron (desferroxamine mesylate) and zinc (histidine) are relatively ineffective in causing such inhibition. Also, genistein‐induced apoptosis in these cells is inhibited by scavengers of reactive oxygen species (ROS) implicating ROS as effector elements leading to cell death. Conclusions: As copper levels are known to be considerably elevated in almost all types of cancers, in this proof‐of‐concept study we show that genistein is able to target endogenous copper leading to prooxidant signaling and consequent cell death. We believe that such a mechanism explains the anticancer effect of genistein as also its preferential cytotoxicity towards cancer cells.