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Major update listing the latest published clinical trials on the health benefits of polyphenols in olive and olive leaf extracts
Full citations to recent studies added
Line 36: Line 36:
Cardiovascular protection:
Cardiovascular protection:
OLE appears to lower cardiovascular disease risk via multiple mechanisms: anti-atherosclerotic, hypotensive, antioxidant, anti-inflammatory, hypocholesterolaemic and hypolipidaemic.
OLE appears to lower cardiovascular disease risk via multiple mechanisms: anti-atherosclerotic, hypotensive, antioxidant, anti-inflammatory, hypocholesterolaemic and hypolipidaemic.

⚫
Blood pressure: There is extensive evidence from well-conducted dietary intervention studies that consumption of polyphenol-rich extra virgin olive oil compared with refined olive oil or other low polyphenol vegetable oils, is associated with improvements in blood pressure in hypertensive and pre-hypertensive volunteers.<ref>{{cite journal|pmid=26251666}}</ref><ref>{{cite journal|pmid=15939067}}</ref><ref>{{cite journal|pmid=10737284}}</ref>. These studies suggest that the hypotensive effects of the extra virgin olive oil may principally be due to the polyphenolic compounds in the olive oil rather than its fat composition. These beneficial polyphenols are concentrated in the leaves of the olive trees: 100g of fresh olive leaves contains around 60 times more of these beneficial compounds than 100 ml of extra virgin olive oil.<ref>{{cite journal|pmid=26951205}}</ref>
Blood pressure:
⚫
There is extensive evidence from well-conducted dietary intervention studies that consumption of polyphenol-rich extra virgin olive oil compared with refined olive oil or other low polyphenol vegetable oils, is associated with improvements in blood pressure in hypertensive and pre-hypertensive volunteers.<ref>{{cite journal|pmid=26251666}}</ref><ref>{{cite journal|pmid=15939067}}</ref><ref>{{cite journal|pmid=10737284}}</ref>. These studies suggest that the hypotensive effects of the extra virgin olive oil may principally be due to the polyphenolic compounds in the olive oil rather than its fat composition. These beneficial polyphenols are concentrated in the leaves of the olive trees: 100g of fresh olive leaves contains around 60 times more of these beneficial compounds than 100 ml of extra virgin olive oil.<ref>{{cite journal|pmid=26951205}}</ref>
Several randomized double-blind, controlled, studies with OLE supplements provide strong support for hypotensive and other beneficial cardiovascular effects of polyphenols. One such study randomised 40 borderline hypertensive subjects to consume either 500 mg or 1000 mg of OLE daily (equivalent to 104 or 208 mg oleuropein respectively) for 8 weeks. It found a dose-dependent reduction in systolic blood pressure (mean of 6 and 13 mmHg for lower and higher doses) [7].<ref>{{cite journal|pmid=18729245}}</ref>.
Several randomized double-blind, controlled, studies with OLE supplements provide strong support for hypotensive and other beneficial cardiovascular effects of polyphenols. One such study randomised 40 borderline hypertensive subjects to consume either 500 mg or 1000 mg of OLE daily (equivalent to 104 or 208 mg oleuropein respectively) for 8 weeks. It found a dose-dependent reduction in systolic blood pressure (mean of 6 and 13 mmHg for lower and higher doses) [7].<ref>{{cite journal|pmid=18729245}}</ref>.
In an 8 week, randomized, double-blind, active drug-controlled clinical trial, stage-1 hypertensive patients (n = 46) received either 1000 mg OLE (199 mg oleuropein) or the hypotensive drug captopril. Significant reductions compared with baseline in systolic and diastolic BP were seen with OLE supplementation at a magnitude similar to the captopril control group <ref>{{cite journal|pmid=21036583}}</ref>.
In an 8 week, randomized, double-blind, active drug-controlled clinical trial, stage-1 hypertensive patients (n = 46) received either 1000 mg OLE (199 mg oleuropein) or the hypotensive drug captopril. Significant reductions compared with baseline in systolic and diastolic BP were seen with OLE supplementation at a magnitude similar to the captopril control group <ref>{{cite journal|pmid=21036583}}</ref>.
Line 44: Line 46:


Cholesterol and blood lipids
Cholesterol and blood lipids
The evidence for the anti-hyperlipidaemic effects of olive phenolics is not as strong as it is for its anti-hypertensive effects. Nevertheless, several randomized placebo controlled controlled clinical studies with OLE have reported beneficial responses in plasma lipids including total cholesterol, LDL-cholesterol and triglycerides. Perrinjaquet-Moccetti et al.[7], Sasulit et al. [8], Lockyer et al.[9] and Fonollá J et al [10] reported significant reductions in total cholesterol, LDL-cholesterol and triglyceride levels in human volunteers, although such improvements in lipid profiles after OLE supplementation were not observed by De Bock et al but this study used a lower total daily dose of OLE [2].
The evidence for the anti-hyperlipidaemic effects of olive phenolics is not as strong as it is for its anti-hypertensive effects. Nevertheless, several randomized placebo controlled controlled clinical studies with OLE have reported beneficial responses in plasma lipids including total cholesterol, LDL-cholesterol and triglycerides. Perrinjaquet-Moccetti et al.[7]<ref>{{cite journal|pmid=18729245}}</ref>, Sasulit et al.<ref>{{cite journal|pmid=21036583}}</ref>, Lockyer et al.<ref>{{cite journal|pmid=26951205}}</ref> and Fonollá J et al <ref>{{cite journal|doi=10.1016/S1567-5688(10)70859-X}}</ref> reported significant reductions in total cholesterol, LDL-cholesterol and triglyceride levels in human volunteers, although such improvements in lipid profiles after OLE supplementation were not observed by De Bock et al but this study used a lower total daily dose of OLE <ref>{{cite journal|pmid=23516412}}</ref>.
There are consistent data on the beneficial effects of extra virgin olive oil on markers of lipid peroxidation, including oxidized-LDL[5]. It seems likely that the protection against oxidative stress is mediated by olive phenolics. Evidence from human studies however is very limited. In a small (n=13) , acute, randomized, crossover, double-blind study, consumption of hydroxytyrosol-supplemented biscuits (5.25mg HT) was associated with a reduction in postprandial oxidized–LDL concentrations compared with unsupplemented biscuits (Mateos et al 2016). However a recent 8 week intervention trial with 45 mg per day hydroxytyrosol found no significant reduction in oxidised LDL. [Lopez- Huertas et al 2017]
There are consistent data on the beneficial effects of extra virgin olive oil on markers of lipid peroxidation, including oxidized-LDL <ref>{{cite journal|pmid=15939067}}</ref>. It seems likely that the protection against oxidative stress is mediated by olive phenolics. Evidence from human studies however is very limited. In a small (n=13) , acute, randomized, crossover, double-blind study, consumption of hydroxytyrosol-supplemented biscuits (5.25mg HT) was associated with a reduction in postprandial oxidized–LDL concentrations compared with unsupplemented biscuits (Mateos et al 2016)<ref>{{cite journal|pmid=27006237}}</ref>. However a recent 8 week intervention trial with 45 mg per day hydroxytyrosol found no significant reduction in oxidised LDL <ref>{{cite journal|pmid=28063380}}</ref> .

Blood glucose control:
Blood glucose control:
De Bock et al. 2013 conducted a randomized, double-blind, placebo controlled crossover trial trial that demonstrated supplementation with olive leaf extract for 12 weeks (equivalent to 51.1 mg oleuropein and 9.7mg hydroxytyrosol per day) improved insulin sensitivity by 15% and improved in pancreatic β-cell function 28% compared with placebo treatment in overweight middle-aged men syndrome (n = 46) at risk of risk of developing metabolic [2]. OLE supplementation led to a 14% decrease in insulin AUC and 6% decrease in glucose AUC and increased fasting interleukin-6, IGFBP-1, and IGFBP-2 concentrations.
De Bock et al. 2013 conducted a randomized, double-blind, placebo controlled crossover trial trial that demonstrated supplementation with olive leaf extract for 12 weeks (equivalent to 51.1 mg oleuropein and 9.7mg hydroxytyrosol per day) improved insulin sensitivity by 15% and improved in pancreatic β-cell function 28% compared with placebo treatment in overweight middle-aged men syndrome (n = 46) at risk of risk of developing metabolic <ref>{{cite journal|pmid=23516412}}</ref>. OLE supplementation led to a 14% decrease in insulin AUC and 6% decrease in glucose AUC and increased fasting interleukin-6, IGFBP-1, and IGFBP-2 concentrations.
A second a randomized, double-blind, placebo intervention study in type-2 diabetic patients (n=79) consuming 500 mg OLE per day for 14 weeks, showed that compared with placebo OLE significantly reduced glycated haemoglobin (HbA1c) and fasting plasma insulin levels indicating improved long-term glucose control [3].
A second a randomized, double-blind, placebo intervention study in type-2 diabetic patients (n=79) consuming 500 mg OLE per day for 14 weeks, showed that compared with placebo OLE significantly reduced glycated haemoglobin (HbA1c) and fasting plasma insulin levels indicating improved long-term glucose control <ref>{{cite journal|pmid=22512698}}</ref>.


==Soaps and cosmetics==
==Soaps and cosmetics==

Revision as of 11:40, 28 August 2017

Leaves from an olive tree in Portugal

Olive leaf is the leaf of the olive tree (Olea europaea). Although olive oil is well known for its flavor and health benefits, the leaf has been used medicinally in various times and places.[1] Olive leaf and olive leaf extracts (OLE), are now marketed as anti-aging, immunostimulator, antioxidant, cardio protective, blood sugar regulating, anti-inflammatory and antibiotic agents. There is strong evidence from randomised, controlled, clinical trials in humans to support beneficial effects of OLE on cardiovascular risk factors and glucose metabolism. For the other potential uses, although there is some supportive in vitro and preclinical evidence (i.e., bioassays), clinical evidence in humans is limited.

Food fraud

Olive leaves are sometimes chopped and added to oregano by unscrupulous producers and processors.[citation needed]

Leaf characteristics

The silvery green leaves are oblong, measuring 4–10 centimetres (1.6–3.9 in) long and 1–3 centimetres (0.39–1.2 in) wide. When consumed, leaves have an astringent bitter taste.

Olive leaf products

Several olive leaf products are available on the market, including powdered dried olive leaves and olive leaf extracts (OLE). The majority of clinical trials supporting the health benefits of olive leaf have been conducted with olive leaf extracts rather than powdered dried olive leaves.

Active compounds

The positive biological effects of OLE are attributed to its high polyphenol content. These olive phenolics are much more concentrated in the leaves compared with olive fruit or olive oil: 1450 mg total phenolics/100 g fresh leaf vs. 110 mg/100 g fruit and 23 mg/100 ml extra virgin olive oil (EVOO) [2]The primary active compounds in unprocessed olive leaf are believed to be the antioxidants oleuropein and hydroxytyrosol, as well as several other polyphenols and flavonoids, including luteolin, rutin, caffeic acid, catechin and apigenin.[3] oleocanthal.[citation needed] Elenolic acid is a component of olive oil and olive leaf extract. It can be considered as a marker for maturation of olives. Oleuropein, together with other closely related compounds such as 10-hydroxyoleuropein, ligstroside and 10-hydroxyligstroside, are tyrosol esters of elenolic acid. The phenolic composition of OLE varies according to plant variety, harvesting season and method, leaf maturity, storage conditions and extraction method.

Health benefits of OLE

Historical uses

Historically the benefits of olive leaves have been widely touted, and been used by various cultures for both medicinal and nutritional uses. [4] In the Mediterranean region, olive leaves have been used for the treatment of complaints including cough, colds and flu, high blood pressure, inflammation, arthritis, fever and high blood sugar.[5]

Antioxidant

Plants in the Mediterranean have developed high levels of antioxidants as a protection mechanism against environmental stressors.[6] Olive leaf extract is a potent antioxidant, and in 2007 a study evaluated 55 medicinal herbs and discovered that the olive leaf had one of the highest levels of antioxidants tested.[7]

Fresh Olive Leaf Extract is known to contain over 100 phytochemicals, with at least 12 already showing antioxidant properties. [8] Oleuropein and hydroxytyrosol are the most well known antioxidants in Olive Leaf Extract, and give the tonic its signature bitter taste.

Immune support

Olive leaf has been traditionally believed to help with colds and flu, with anecdotal evidence also suggesting that cold sores and urinary tract infections issues improved with the use of olive leaf.

Olive leaf has also been suggested to support innate immunity through their interactions with macrophages. Olive leaf has been suggested to stimulate macrophages and increase the production of nitric oxide. Therefore by increasing the effectiveness of macrophages, the immune systems first line of defense against pathogens is also protected. [9][10][11]

Cardiovascular effects and blood glucose control

Numerous high quality randomized, double blind, placebo controlled trials in healthy subjects and patients, have demonstrated that consumption of olive leaf extracts has beneficial effects on cardiovascular risk factors (blood pressure, cholesterol, blood lipids and inflammatory markers) and glucose metabolism (insulin resistance, plasma glucose and insulin levels, HbA1c and other biomarkers). These studies and their findings are discussed in a review article on the beneficial effects of OLE on metabolic syndromes published in 2017 [12]

Cardiovascular protection: OLE appears to lower cardiovascular disease risk via multiple mechanisms: anti-atherosclerotic, hypotensive, antioxidant, anti-inflammatory, hypocholesterolaemic and hypolipidaemic.

Blood pressure: There is extensive evidence from well-conducted dietary intervention studies that consumption of polyphenol-rich extra virgin olive oil compared with refined olive oil or other low polyphenol vegetable oils, is associated with improvements in blood pressure in hypertensive and pre-hypertensive volunteers.[13][14][15]. These studies suggest that the hypotensive effects of the extra virgin olive oil may principally be due to the polyphenolic compounds in the olive oil rather than its fat composition. These beneficial polyphenols are concentrated in the leaves of the olive trees: 100g of fresh olive leaves contains around 60 times more of these beneficial compounds than 100 ml of extra virgin olive oil.[16] Several randomized double-blind, controlled, studies with OLE supplements provide strong support for hypotensive and other beneficial cardiovascular effects of polyphenols. One such study randomised 40 borderline hypertensive subjects to consume either 500 mg or 1000 mg of OLE daily (equivalent to 104 or 208 mg oleuropein respectively) for 8 weeks. It found a dose-dependent reduction in systolic blood pressure (mean of 6 and 13 mmHg for lower and higher doses) [7].[17]. In an 8 week, randomized, double-blind, active drug-controlled clinical trial, stage-1 hypertensive patients (n = 46) received either 1000 mg OLE (199 mg oleuropein) or the hypotensive drug captopril. Significant reductions compared with baseline in systolic and diastolic BP were seen with OLE supplementation at a magnitude similar to the captopril control group [18]. Lockyer et al. conducted a 6-week, randomized double-blind, placebo-controlled, crossover trial with OLE (equivalent to 136 mg oleuropein and 6 mg hydroxytyrosol) in 60 prehypertensive subjects. The study demonstrated clinically significant reductions in 24 h systolic and diastolic BP of 3-4 mmHg was observed [9][19]. In addition, significant reductions in total cholesterol, LDL-cholesterol, triglycerides and IL-8 were observed in this study. A randomised, double-blind, placebo-controlled, cross-over, acute intervention trial in 18 healthy volunteers showed that a single dose of OLE (51 mg oleuropein and10mg hydroxytyrosol) improved vascular function as measured by DVP-stiffness index and increased IL-8 production [20]. This study together with that of Ziyyat et al 1997[21] suggest that olive polyphenols act on the endothelium of the blood vessels, improving their flexibility, thereby allowing more blood to flow through and subsequently lowering blood pressure.

Cholesterol and blood lipids The evidence for the anti-hyperlipidaemic effects of olive phenolics is not as strong as it is for its anti-hypertensive effects. Nevertheless, several randomized placebo controlled controlled clinical studies with OLE have reported beneficial responses in plasma lipids including total cholesterol, LDL-cholesterol and triglycerides. Perrinjaquet-Moccetti et al.[7][22], Sasulit et al.[23], Lockyer et al.[24] and Fonollá J et al [25] reported significant reductions in total cholesterol, LDL-cholesterol and triglyceride levels in human volunteers, although such improvements in lipid profiles after OLE supplementation were not observed by De Bock et al but this study used a lower total daily dose of OLE [26]. There are consistent data on the beneficial effects of extra virgin olive oil on markers of lipid peroxidation, including oxidized-LDL [27]. It seems likely that the protection against oxidative stress is mediated by olive phenolics. Evidence from human studies however is very limited. In a small (n=13) , acute, randomized, crossover, double-blind study, consumption of hydroxytyrosol-supplemented biscuits (5.25mg HT) was associated with a reduction in postprandial oxidized–LDL concentrations compared with unsupplemented biscuits (Mateos et al 2016)[28]. However a recent 8 week intervention trial with 45 mg per day hydroxytyrosol found no significant reduction in oxidised LDL [29] .

Blood glucose control: De Bock et al. 2013 conducted a randomized, double-blind, placebo controlled crossover trial trial that demonstrated supplementation with olive leaf extract for 12 weeks (equivalent to 51.1 mg oleuropein and 9.7mg hydroxytyrosol per day) improved insulin sensitivity by 15% and improved in pancreatic β-cell function 28% compared with placebo treatment in overweight middle-aged men syndrome (n = 46) at risk of risk of developing metabolic [30]. OLE supplementation led to a 14% decrease in insulin AUC and 6% decrease in glucose AUC and increased fasting interleukin-6, IGFBP-1, and IGFBP-2 concentrations. A second a randomized, double-blind, placebo intervention study in type-2 diabetic patients (n=79) consuming 500 mg OLE per day for 14 weeks, showed that compared with placebo OLE significantly reduced glycated haemoglobin (HbA1c) and fasting plasma insulin levels indicating improved long-term glucose control [31].

Soaps and cosmetics

Olive leaf extracts are sometimes used in skin creams and other cosmetics for application to the skin. Olive leaf extract has been shown to provide antioxidant and antibacterial effects that can prolong the shelf life of cosmetic preparations. [32]

Notes

  1. ^ Kilham, Chris, Healing Power of Olive Leaf, January 23, 2013, FoxNews.com
  2. ^ . PMID 26951205. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  3. ^ Benavente-Garcia, O., Castillo, J., Lorente, J., Ortuno, A., Del Rio, J. (2000). Antioxidant activity of phenolics extracted from Olea Europa L. leaves. Food Chemistry, 68:457-462
  4. ^ Quigley, Gerald Olive Leaf Extract: Nature's Secret to Wellness
  5. ^ Pinelli, P., Galardi, C., Mulinacci, N., Vincieri, F., Tattini, ., Romani, A (2000). Quali-quantitative analysis and antioxidant activity of different polyphenolic extracts from Olea europea L. Leaves. Journal of Commodity Science, 39(2): 71-83
  6. ^ Vivioli, F., Bellomo, G. &Galli, C. (1998). Free radical-scavenging properties of olive oil polyphenols. Biochemical and Biophysical Research Communications, 247:60-64
  7. ^ Wojcikowksi, K., Stevenson, L., Leach, D., Wohlmuth, H., Gobe, G. (2007). Antioxidant capacity of 55 medicinal herbs traditionally used to treat the urinary system: A comparison using a sequential three-solvent extraction process. The Journal of Alternative and Complementary Medicine, 12(1): 103-109.
  8. ^ Benavente-Garcia, O., Castillo, J., Lorente, J., Ortuno, A., Del Rio, J. (2000). Antioxidant activity of phenolics extracted from Olea Europa L. leaves. Food Chemistry, 68:457-462
  9. ^ Visioli, F. & Galli, C. (1998). Olive oil phenols and their potential effects on human health. Journal of Agricultural and Food Chemistry, 46(10):4292-4296
  10. ^ Carluccio, M., Massaro, M., Scoditti, E. &De Caterina, R. (2007). Vasculoprotective potential of olive oil components. Molecular Nutrition and Food Research, 51(10): 1225-1234
  11. ^ Visioli, F., Bellosta, S. & Galli, C. (1998). Oleuropein, the bitter principle of olives, enhances nitric oxide production by mouse macrophages. Life Sciences, 62(6): 541-546
  12. ^ . PMID 28661446. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  13. ^ . PMID 26251666. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  14. ^ . PMID 15939067. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  15. ^ . PMID 10737284. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  16. ^ . PMID 26951205. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  17. ^ . PMID 18729245. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  18. ^ . PMID 21036583. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  19. ^ . PMID 26951205. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  20. ^ . PMID 26051429. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  21. ^ Ziyyat, A., Legaayer, A., Mekhfi, H., Dassouli, A., Serhrouchni, M,, Benjelloun, W. (1997) Phytotherapy of hypertension and diabetes in oriental Morocco. Journal of Ethnopharmacology, 58(1): 45-54
  22. ^ . PMID 18729245. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  23. ^ . PMID 21036583. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  24. ^ . PMID 26951205. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  25. ^ . doi:10.1016/S1567-5688(10)70859-X. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  26. ^ . PMID 23516412. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  27. ^ . PMID 15939067. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  28. ^ . PMID 27006237. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  29. ^ . PMID 28063380. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  30. ^ . PMID 23516412. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  31. ^ . PMID 22512698. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  32. ^ Natural Antioxidants, Antibacterials From Olive Leaf Extracts Used In Cosmetics, Pharmaceutical, And Food Industries Fuad Al-rimawi, Prof., Imad Odeh, Abdallah Bisher, Hiba Yateem, and Mohammad Taraweh Qatar Foundation Annual Research Conference Proceedings 2014, HBPP0116. http://www.qscience.com/doi/abs/10.5339/qfarc.2014.HBPP0116
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