Olive oil, the product of olive fruit extraction, is the pillar of Mediterranean diet and its consumption is well known to provide multiple benefits to our health (e.g. for the cardiovascular system). Olive oil is nowadays highlighted and marketed as a “superfood” for human health not only due to its lipid profile (e.g. high oleic acid and low saturates), but also due to its high content in micronutrients such as squalene and polyphenols. The latter powerful antioxidants are in many cases advertised almost as an “elixir” that promise to relieve us against multiple diseases and health problems. Which of these advertised health claims have a scientific basis and how many of them are promises or just guesses?

Over the last two decades, olive oil has concentrated scientific attention not only in the Mediterranean area, but all around the world due to its beneficial effects in human health. This trend is mainly driven by its content in polyphenols. Hydroxytyrosol, tyrosol, oleuropein, eleocanthal, oleacein and other polyphenols with exotic names may not being well known to general public yet, but they already appear in the product labels in the shelves of supermarkets and pharmacies, promising to provide multiple benefits to consumers.

Polyphenols pass from the olive tree to olive fruit, olive oil and olive processing by-products (olive tree leaves and olive mill wastewater). Recent biochemical, pharmacological and other studies have shown that polyphenols possess strong radical scavenging capacities and can play an important role in protecting against oxidative damages and cellular aging. By far the most investigated olive oil polyphenol is hydroxytyrosol. Studies have been conducted in both cells and animals, whereas its antioxidant effect is nowadays taken for granted. Besides, hydroxytyrosol is currently in early clinical trials as a dietary supplement for patients with multiple sclerosis and as a measure preventing breast cancer in women with a relevant genetic predisposition. Oleuropein, which is mainly contained in the olive tree leaves, has also been investigated a lot. Oleocanthal, a tyrosol derivative whose ant-inflammatory role found similar to that of the drug ibuprofen in 2005, have also shown important bioactivities (e.g. against Alzheimer’s disease, several cancers etc), although most studies have been performed in cells and few of them in animals; thus it has not yet been fully evaluated.

Despite the so far promising results, the main weakness for these investigations is that their outcomes are to a great extent not systematically addressed. Olive oil is an extremely complex mixture of ingredients and thus it is not clear if findings based on experiments conducted with free compounds (e.g. hydroxytytorosol and oleuropein that exist in minute quantities in olive oil) can be extended to actual major constituents and olive oil (a natural product with great variability in composition). The problem of the levels of individual bioactive compounds in olive oil and the possible combined effects of various classes of bioactive compounds have not yet answered. In addition, the vast majority of the available studies have so far been conducted either in vitro or in vivo. Very few of them have been performed to reliable clinical trials in humans. The latter constitute the necessary test to prove the efficacy and safety of a component.

The health claim of polyphenols in olive oil and its ambiguous interpretation

Those consumers, who are observant and check more olive oil labels, have mentioned that some of them indicate that olive oil contains substances that shield the human body against various health problems. Besides, since 2012, olive oil can be labeled with a health claim approved of the European Authority for Food Safety (EFSA) and is strictly defined by the European Commission regulation 432/2012 as follows: “Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress”. However, this claim can only be used for olive oils containing at least 5 mg of hydroxytyrosol and its derivatives (e.g. oleuropein complex and tyrosol) per 20 g of olive oil. In addition, the label must provide information to the consumer that the beneficial effect is obtained with a daily intake of 20 g of olive oil (about one and a half spoon).

This European Regulation is somehow ambiguous since the list of hydroxytyrosol derivatives is not referred and the determination method is not defined. The official determination method of International Olive Oil Council is based on high performance liquid chromatography (HPLC) with UV detection. This ambiguity generates implications in the market. On one hand, some phenols are named as hydroxytyrosol derivatives, while others that are actually derivatives are sometimes advertised for activities that are not approved. At the same time, some commercialized olive oils indicate other false benefits that do not comply with EFSA rules.

Polyphenols from olive mill wastewater: A great or a stifled opportunity?

The situation becomes even more complicated taken into account that olive mill wastewater is richer in polyphenols compared to olive oil. This fact led researcher to consider this waste stream as a cheap source of antioxidants. Indeed, the first animal experiments and a couple of hu¬man studies have confirmed the bioactivity of extracts derived from this source and subsequently relevant dietary supplements appeared in the market (e.g. Hidrox, OlivActive, Oleaselect, Opextan, Prolivols, Phenolea Complex and others).

To this line, many commercial products involving hydroxytyrosol are marketed already in the U.S.A. where FDA granted Generally-Recognized-As-Safe status and allowed their usage as antioxidants in baked goods, beverages, cereals and other foods at a level of up to 3000 mg/Kg. In Europe, EFSA handles health claims of hydroxytyrosol-containing products in a preserved manner and has tightened up the way in which companies can advertise health benefits. Indeed, health claims have only been approved for olive oils rich in hydroxytyrosol. If you recover hydroxytyrosol from olive mill wastewater and fortify a food product (e.g. bakery products) or even an olive oil, the health claim is not valid. This policy is driven by the need of protecting consumers from claims that lack of scientific depth and evidence.

However, the significantly different approach of market release between FDA and EFSA influences substantially olive oil industry growth in EU. Demonstration of proven health benefits is very costly for the companies activated in the field. This fact creates implications for stifling innovation in the field, as the obtainment of the required data is not affordable and most companies (typically start-ups with low funding) cannot afford them. Besides, the risk of claims rejection by the corresponding authority is too high.

Olives, olive oil and olive mill processing by-products are NOT YET sources of medicines

With all of these ambiguities and unknown parameters (solid evidence in clinical trials is yet to be gathered), still no one can claim the development of medicines from olive oil components.  Olive oil is a superior food providing health benefits, whereas extracts derived from olive oil processing by-products can be considered as powerful nutritional supplements. However, both are neither medicine nor can be considered as sources for the development of medicines. This is something to be highlighted and may prove (or not) over the next years. The current scientific evidence suggests that choosing an extra virgin olive oil rich in polyphenols would contribute to the dietary intake of micronutrients in quantities that have been correlated with a reduced risk of developing coronary heart disease.

Nevertheless, since polyphenols are more and more linked to the quality of olive oil and human health, they will continue to drive innovations and advances in the market. Thereby, it is only a matter of time that researchers will clarify the potential health benefits of the relevant compounds and extracts. Subsequently, authorities around the world will stand over the above issues and harmonize specifications, e.g. by setting qualitative limits for polyphenols according to well-defined determination methods, defining in details the derivatives of hydroxytyrosol and providing a way out for the polyphenols recovered from olive oil processing by-products.

Olive Mill Waste: Recent Advances for Sustainable Management addresses today’s most relevant topics in olive oil industry sustainable management. Emphasizing recent advisable practices, the book explores the potential of reutilizing OMW to power the mill itself, the reuse of OMW as soil amendment, aerobic biological treatment of OMW and compost production, the case study of OMW within the biorefinery concept, the recovery of bioactive compounds from OMW, and their applications in food products and cosmetics.

Recent research efforts have concluded that the successful management of OMW focuses on three main routes: (a) reuse of water, (b) reuse of polyphenols, and (c) reuse of nutrients. Following this consideration, the book covers sustainable practices in the olive oil industry, revealing opportunities for reutilizing the water of OMW within the process or as s soil amendment.

At the same time, it explores all the possibilities of recovering polyphenols and reutilizing them in target products, such as foods and cosmetics. In addition, the book presents successful cases of industrial OMW valorization through real world experiences.

Key Features

• Covers the most recent advances in the field of olive mill waste management following sustainability principles
• Fills the gap of transfer knowledge between academia and industry
• Explores the advantages, disadvantages and real potential of processes and products in the market

Read more articles from Charis Galanakis, Galanakis Laboratories

Charis M. Galanakis is an interdisciplinary scientist with a fast-expanding work that balances between food and environment, industry, and academia. His research targets mainly the separation and recovery of functional macro- and micromolecules from different food by-products, as well as their implementation as additives in food and other products. He is the research and innovation director of Galanakis Laboratories (Chania, Greece) and the coordinator of Food Waste Recovery Group of ISEKI Food Association (Vienna, Austria).

He serves as an editorial board member and subject editor of Food and Bioproducts Processing and Food Research International, and he has edited 6 books from Academic Press: Food Waste Recovery: Processing Technologies and Industrial Techniques (2015), Innovation Strategies in the Food Industry: Tools for implementation (2016) and Nutraceutical and Functional Food Components: Effects of Innovative Processing Techniques (2017), Olive Mill Waste: Recent advances for the Sustainable Management (2017), Handbook of Grape Processing By-Products: Sustainable Solutions (2017) and Handbook of Coffee Processing By-Products: Sustainable Applications (2017).

See his full portfolio of books here.

Follow Dr. Galanakis via Twitter – @CharisGalanakis, LinkedIn or ResearchGate.

Join the Food Waste Recovery Group on LinkedIn or the Food Waste Recovery Page on Facebook.

Charis’ latest books are available to order on the Elsevier Store. Use discount code STC317 at checkout and save up to 30% on your very own copy!