How 'Healthy' Is Olive Oil?
What is the source of olive oil?
The olive (Olea europea) is one of the oldest known cultivated trees and was grown in Crete as long ago as 3,000 BC. Although the olive tree has its origins in the Mediterranean area, many other parts of the world have also been found suitable for its cultivation, including the USA and South Africa. Olive oil is obtained from the fruit of the olive tree. The oval-shaped fruit contains between 35-70% oil, depending on the variety and on production conditions. The oil has a characteristic greenish-yellow colour, depending on variety and age of fruits and a unique but variable flavour and aroma that makes it popular in many countries.
How is olive oil recovered?
Virgin olive oil is typically described as "cold pressed" (although, increasingly, centrigfugation is used to separate the oil from the fruit) and not altered in any significant way, unlike most other vegetable oils that are conventionally refined by the use of small quantities of chemicals and high temperature heat treatments - in both cases carried out under vacuum, ensuring minimal reaction with atmospheric oxygen. This means the oil is consumed in a "close-to-natural" state.
After harvesting, the surface of the olives is cleaned. The olives and pits are then ground to a paste and the oil is extracted by hydraulic presses or separated from the paste by high-speed centrifuges that spin out the oil. The variation in oil colour may be due to the time of harvest or to the variety of olive. Green olives, processed earlier in the season, yield greener-coloured oils.
The best olive oil is mechanically extracted while the fruits are fresh, thereby minimising the development of free fatty acids through enzymatic action; it is not subjected to high processing temperatures; and it has a low free fatty acid value, although typically higher than that of refined vegetable oils. However, a range of olive oils of different qualities are available.
What are the grades of olive oil?
Extra Virgin Olive Oil: This is oil of the finest taste and aroma with a free fatty acid (FFA) value of less than 1%. Extra virgin olive oil accounts for less than 10% of olive oil produced.
Virgin Olive Oil: This oil is obtained by pressing or centrifugation and has a good characteristic flavour and aroma. It has an FFA level of less than 2% for oil labelled "Virgin" and an FFA value of between 2% and 3.3% for products labelled "Ordinary Virgin".
Lampante Virgin Olive Oil: Oil with defective flavour and FFA of more than 3.3%.
Olive Oil: A low cost blend of cheap refined and virgin olive oil with a maximum FFA of 1.5%.
Refined Olive Oil: Virgin olive oils with high free fatty acid values and flavour defects are subjected to the standard refining process used for most vegetable oils, during which free fatty acids are greatly reduced to a maximum of 0.5%. (Compared to less than 0,2% for "conventional" cooking oils)
Pomace Oil: Oil that has not been removed from the pulp (pomace) can be extracted using solvents and steam. This oil is inferior in flavour and aroma and is mainly used for industrial purposes.
Note: Rather like the Californian wine industry some 50 years ago, very different views have arisen regarding what constitute meaningful standards for olive oil with numerous "new world" producers outside of Europe (including the US, South America, Australia and South Africa) insisting that the traditionalists (particularly Italy) are endeavouring to support out-of-date practices rather than more modern approaches which are claimed to result in superior olive oil.
Why all the interest in olive oil?
The interest shown in olive oil by the public can probably be attributed to three topical issues that have received attention in the media, namely: the Mediterranean diet; 'natural, traditional and health foods'; and the claimed health benefits of monounsaturated fats.
- The Mediterranean Diet
This diet is ideally one in which desirable amounts of grain cereal products, fresh fruit and vegetables, fish and olive oil are eaten. Some studies have indicated that this could be a reason why the incidence of heart disease in Western Europe was found to be lowest in the diets of the Mediterranean people. It has been suggested that the Mediterranean diet is possibly very close to an ideal, balanced diet. Equally important reasons for heart health though, may simply have been due to people in this less affluent and sunnier part of Europe, eating less, eating more simply and getting more outdoor exercise.
- 'Natural, traditional and health foods'
Because some olive oil is extracted and bottled with minimal treatment and is not subjected to standard refining processes - including heating, deodorisation and solvent extraction; it is often regarded by consumers as being healthier or superior to other oils. However, the nutritional benefit of the reduced processing of virgin olive oil is probably insignificant in a balanced diet.
- Monounsaturated fat
Research shows that in an affluent society that tends to overeat, a common problem is not only the over-consumption of fats (meaning both fats and oils), but also the over-consumption of fats of the saturated type. Ideally, the total fat component in a diet should provide less than 30% of an individual's energy requirement. It has been suggested that this fat should consist of an equal proportion of the three different types of fat (namely saturated, monounsaturated and polyunsaturated). Olive oil has attracted attention because consumers are urged to cut back on saturated fats and improve the ratio of mono and poly unsaturated fat in the diet. Olive oil is an excellent source of monounsaturated fat (containing up to 85% monounsaturates) and is, accordingly, widely promoted. However, it is more important to consume fats in the correct overall amounts and ratios than to focus on a particular type.
What does scientific evidence suggest?
Studies show that olive oil can have beneficial effects in the blood with regard to cholesterol (both levels and ratio of 'good' to 'bad' cholesterol), glucose, antioxidant levels and clotting factors. However, in these studies, the consumption of olive oil as the main source fat is generally implied and no direct comparisons are done to evaluate the properties of other oils of vegetable origin which, in the correct amounts and ratios, could have much the same benefits.
What is the shelf life of olive oil?
The shelf life of olive oil depends on the olive variety from which the oil is derived, the quality of the olives when pressed and, most importantly, the storage conditions after processing and bottling. Light causes marked deterioration of oil especially when stored in warm places and in the presence of air. In such extreme cases the lifespan of the oil can be as short as three months. However, olive oil stored in sealed tins or glass bottles and kept in the dark under cool, dry conditions, can have a storage life of two years or longer.
Is it really olive oil?
The only way to confirm whether the type of oil in a bottle or tin matches what is claimed on the label is to have it tested for authenticity by a reputable laboratory. As an expensive commodity, olive oil is prone to adulteration. Since it cannot be produced cheaply, low cost olive oil should be viewed with suspicion. Less expensive oils may be coloured and sometimes flavoured and sold as olive oil. "Virgin" olive oil is also sometimes mixed with cheaper refined olive oil - read the label! The best option for consumers is to purchase well-known brands.
What is the FACS message?
Consumers should not interpret the high profile media coverage of olive oil to mean that it should automatically be added to a diet (which may already be too high in fat), nor that the oil should replace a more affordable (of the order of 1/10th of the price) and desirable unsaturated fat, such as sunflower, canola, groundnut (peanut), cottonseed, maize or similar vegetable oil, as a salad or cooking oil. The most appropriate course of action would be, firstly, to ensure that overall fat consumption levels are acceptable, that is, that fat does not provide more than 25-30% of the total number of kilojoules consumed in the daily diet. Recommended daily consumption of fat:
About 97g/day as part of the total fat from all sources, for moderately active 'average' men - mass approx 79 kg.
Secondly, ensure that not more than 30% of the energy or kilojoules from the fat component of the diet is 'saturated' - that which is mainly found in fatty meat, butter, fatty dairy products (cheese) and products containing elevated quantities of palm oil, palm kernel oil, coconut oil and cocoa butter (such as some fried snacks, biscuits, chocolates, chocolate substitutes, etc).
About 73g/day for 'average' women - mass approx 63kg.
A rough guide
As a very rough guide to help consumers determine their saturated fat intake, the following can be expected to contain about 50% saturated fat: beef fat, mutton fat, butter, coconut oil, palm oil and palm kernel oil. Similarly, chicken and pork fat can be expected to be about 30% saturated. Cocoa butter, the fat found in chocolate, can be as high as 60% saturated.
Once proper fat consumption levels and ratios have been achieved, olive oil may then be introduced into the diet. For optimum nutrition it can be used on a rotational basis, with other less expensive vegetable oils such as sunflower, maize, canola, cottonseed, peanut and soya, each of which has its own particular contribution to make to a balanced diet.
Reviewed for FACS by AMa (2016)