Hydroxytyrosol: what it is and what its uses are
Hydroxytyrosol is a compound belonging to the class of polyphenols and it is, together with tyrosol, the most abundant phenol in olive oil.
Hydroxytyrosol is characterized by a powerful antioxidant action and numerous other beneficial properties.
Let’s find out what they are.
Olive oil: a healthy fat
The Mediterranean diet represents the expression of a healthy and complete food regimen from a nutritional point of view, based on the consistent consumption of foods rich in healthy nutrients, such as fish, fruit, vegetables, legumes and grain, and on a low consumption of foods rich in proteins (i.e. red meat) and saturated fats.
In the Mediterranean diet, olive oil (in particular extra virgin olive oil, EVO) is the main source of vegetable fats.
In the categorization of olive oil, the term “virgin” refers to the oil extracted solely through physical or mechanical means (in conditions that do not alter the oil) from the fruit of the olive tree (Olea europaea L.), which has not undergone any treatment other than washing, decanting, centrifugation and filtration.
Due to its beneficial properties, deriving from the high content of monounsaturated fatty acids (MUFA) and minor ingredients, particularly phenolic compounds, olive oil plays an important role in this dietary regimen.
Unlike other vegetable oils, olive oil contains high quantities of numerous active ingredients, including oleic acid (which represents the predominant monounsaturated fatty acid), polyphenols (hydroxytyrosol, tyrosol, oleuropein and flavonoids), which are responsible for organoleptic characteristics that distinguish olive oil (for instance the typical bitter taste), phytosterols, tocopherol (vitamin E), and squalene.
Compared to refined olive oils, virgin olive oil (including EVO oil) contains a greater amount of polyphenols.
As demonstrated by studies conducted in the laboratory (in vitro) and on animal/human subjects (in vivo), EVO oil:
- lowers blood pressure,
- improves the lipidic profile by increasing levels of good cholesterol (HDL cholesterol*) and reducing the levels of LDL cholesterol* (the dreaded “bad cholesterol”) and triglycerides,
- reduces oxidative stress,
- inhibits the oxidation of LDL cholesterol, thus making it unable to settle in the arteries.
*LDL: Low density lipoprotein; HDL: High density lipoprotein.
Furthermore, the fats included in the Mediterranean diet (including olive oil) have a positive effect against the cognitive decline associated with aging and the onset and progression of a number of neurodegenerative diseases.
The beneficial properties of olive oil are partly due to the antioxidant effect of phenolic compounds, in particular hydroxytyrosol, one of the most powerful phenolic compounds in olive oil. Let’s get to know it better.
What is hydroxytyrosol?
Hydroxytyrosol is a natural compound found in high concentrations in the leaves and fruit of the olive tree.
It belongs to the family of polyphenols, natural organic compounds containing one or more aromatic rings, found in fruits, vegetables, nuts and seeds, roots, bark, leaves of various plants, herbs, whole grain products, processed food (dark chocolate), tea, coffee and red wine.
During processing, part of this hydroxytyrosol is lost along with the waste of EVO oil residues (pomace and vegetation water) or during the production of refined olive oil. However, these residues are reused as natural ingredients by the food and cosmetics industries.
Hydroxytyrosol, considered the second most powerful antioxidant (after gallic acid), is obtained from a compound, oleuropein, through a chemical reaction produced by water (hydrolysis), and is present in olive oil and in edible olives in varying concentrations depending on various factors, including the latitude and altitude of the harvest, the olive variety and processing methods.
It is naturally present in the body, easily absorbed (enters the bloodstream in 15 or 20 minutes), and has no accumulation or toxicity problems (it is eliminated through the kidneys or digestive system approximately 6-8 hours after absorption).
Hydroxytyrosol has shown multiple beneficial properties, including:
- Antioxidant properties
- Antitumor action
- Prevention of osteoporosis
- Neuroprotective action
- Antimicrobial action
- Protective action of the skin and eyes.
Recent research has focused attention on the potential involvement of hydroxytyrosol and its metabolites also in the modulation of functions in the brain, where it may have a protective effect against oxidative stress.
This action could be due to the ability of this compound to accumulate in the brain, where it can reach concentrations useful for exerting a positive effect.
How the hydroxytyrosol in olive tree helps to counteract high cholesterol
Cholesterol is an important fat: it is in fact one of the main constituents of the cell membrane and participates in the production of vitamin D and other substances.
This synthesis happens mainly in our body, but part of it can be taken in through the diet.
Nonetheless, high concentrations of bad cholesterol can be dangerous, as they increase the chances of developing certain illnesses, such as heart attack and stroke.
Factors that can impact the increase in cholesterol levels include:
- unhealthy diet
- overweight and obesity
- physical inactivity
Prevention is key to keeping cholesterol under control: an effective preventive strategy to keep cholesterol levels under control involves a change in lifestyle, and should include:
- a healthy diet
- body weight control
- regular physical activity
- avoid/limit bad habits (i.e. smoking/drinking alcohol).
These changes can help reduce total cholesterol and the concentration of bad LDL cholesterol, increasing the concentration of good HDL cholesterol instead.
The phenols in olive oil – and especially hydroxytyrosol – have an effect on fat absorption (bad cholesterol and triglycerides) and on obesity (reducing the size of fat cells).
Inhibiting effects on cholesterol synthesis were also observed following the intake of hydroxytyrosol in combination with oleic acid.
A study (EUROLIVE) based on the administration of three similar types of olive oils, different only in phenolic content, revealed how the amount of phenols present in olive oil would seem to influence the increase in good cholesterol (HDL) levels.
Scientific evidence supports the positive effects of polyphenolic compounds also on type 2 diabetes, through a protective (against the action of glucose) and antioxidant action.
In 2012, the EFSA (European Food Safety Authority) recognized the role of hydroxytyrosol in protecting against the oxidation mechanism of LDL cholesterol by free radicals. In addition, the Ministry of Health has included hydroxytyrosol and polyphenols contained in olive oil in the list of substances with a nutritional or physiological effect.
Food supplements containing hydroxytyrosol
The intake of food supplements containing hydroxytyrosol for 1 month, observed in a study conducted on animal subjects, had beneficial consequences both on the lipidic profile and on antioxidant activity.
In addition, research on the effects of the pure formulation of hydroxytyrosol (in the form of a water-soluble powder) has shown that pure hydroxytyrosol causes a significant decrease in LDL cholesterol; the pure formula also proved to be safe and well tolerated.
The EFSA has recommended the consumption of hydroxytyrosol and its derivatives in the amount of 5 mg a day.
Adverse effects and side effects:
Regarding the recommended levels of use, the EFSA believes that the consumption of hydroxytyrosol-based products is safe and not unfavorable from a nutritional point of view.
Nonetheless, you ought to remember that in case of diabetes, the advisability of using a food supplement should be assessed with your doctor.
- Barrios V, Escobar C, Cicero AF, et al. Atheroscler Suppl. 2017;24:1-15.
- Berrougui H, Ikhlef S, Khalil A. Evid Based Complement Alternat Med. 2015;2015:208062.
- Colica C, Di Renzo L, Trombetta D, et al. Oxid Med Cell Longev. 2017;2017:2473495.
- Cox RA and García-Palmieri MR. Cholesterol, Triglycerides, and Associated Lipoproteins. In Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 3. Walker HK, Hall WD, Hurst JW, editors. NCBI Bookshelf.
- Echeverría F, Ortiz M, Valenzuela R, et al. Int J Mol Sci. 2017 Apr 28;18(5). pii: E930.
- European Food Safety Authority (EFSA). Panel on Dietetic Products, Nutrition and Allergies (NDA) – scientific opinion. EFSA Journal 2011;9(4):2033.
- European Food Safety Authority (EFSA). Safety of hydroxytyrosol as a novel food pursuant to Regulation (EC) No 258/97. EFSA Journal 2017;15(3):4728.
- González-Santiago M, Martín-Bautista E, Carrero JJ, et al.Atherosclerosis. 2006;188(1):35-42.
- Gorzynik-Debicka M, Przychodzen P, Cappello F, et al. Int J Mol Sci. 2018 Feb 28;19(3). pii: E686.
- International Olive Council – Designations and definitions of olive oils. Disponibile al link: http://www.internationaloliveoil.org/web/aa-ingles/oliveWorld/aceite.html. Ultimo accesso: Luglio 2019
- ISS-Epicentro. Colesterolo e Ipercolesterolemia. Disponibile al link: https://www.epicentro.iss.it/colesterolo/. Ultimo accesso: Luglio 2019
- Martínez L, Ros G, Nieto G. Medicines (Basel). 2018;5(1). pii: E13.
- Ministero della Salute – Linee guida per la prevenzione dell’aterosclerosi. Documento approvato dalla Commissione Consultiva per i prodotti destinati ad un’alimentazione particolare. Settembre 2004.
- Ministero della Salute. Altri nutrienti e altre sostanze ad effetto nutritivo o fisiologico (Revisione gennaio 2019).
- Peyrol J, Riva C, Amiot MJ. Nutrients. 2017;9(3). pii: E306.
- Priore P, Gnoni A, Natali F, et al. Oxid Med Cell Longev. 2017;2017:9076052.
- Romero C, Brenes M. J Agric Food Chem. 2012;60(36):9017-22.
- Serreli G, Deiana M. Antioxidants (Basel). 2018 Nov 22;7(12). pii: E170.
- Siefer S, Wacker R, Wihlem M, et al. J Nutri Med Diet Care. 2018;4(1):025.
- Volpe M. Documento di consenso e raccomandazioni per la prevenzione cardiovascolare in Italia. G Ital Cardiol. 2018; 18(1).
- Xiao JB, Högger P. Curr Med Chem. 2015;22(1):23-38.
- Yüksel Aydar A, Öncü Öner T and Fatma Üçok E. EC Nutrition. 2017; 11(4):147-57.