Table olives consist of almost 75% water, 12-25% oil, with the rest being made up of sugars (2 – 3%), fibre, organic acids, vitamins (Vit E) and minerals. Of the minerals, potassium is present in the highest concentration. The EU dietary guide quotes table olives as a good source of zinc, which the body requires as a micronutrient.

Most emphasis to date has been placed on the oil content of table olives when discussing the healthy aspects of olives. Making up such a large percentage of the mass of the olive, especially the ripe black olive, this is indeed one of the most important factors. Yet researchers and nutritionists are becoming more aware of the major role played by the olive phenolics in many other areas of human health.

Latest Research Results

In many areas, fruit and vegetables – including grapes and olives – are continuously exposed to environmental stress like UV radiation and high temperatures and therefore need a variety of compounds to maintain their integrity, like the phenolics.

The protective effects of a Mediterannean diet have been attributed to the low saturated fat content – and the high proportion of monounsaturated fat – yet more recent evidence has underlined the importance of plant foods and the regular use of olive oil. The classic risk factors for coronary heart disease (CHD) such as serum cholesterol and high blood pressure are not very different in the populations of the Mediterranean basin when compared to the Western and North European countries. In fact, several studies do not unequivocally link CHD incidence and fat intake. This evidence has led to the formulation of an antioxidant/atherosclerosis hypothesis which has stimulated many studies on the role of antioxidants in the protection from CHD observed in the Mediterranean area.

The Role of the Monounsaturated Fatty Acids (MUFA)

Of the fatty acids in olive oil, the monounsaturated fatty acid, oleic acid, accounts for 56% – 84% of the total fatty acids. These MUFAs have an extremely positive effect on the cholesterol balance in the body, by lowering the low density lipoproteins (LDL) while increasing the high density lipoproteins (HDL). In addition, the monounsatured fatty acids also assist in controlling blood sugar levels, which in turn control the insulin levels, and this is extremely important in the prevention of the onset of diabetes, which is becoming more prevalent in Western society.

The Role of the Olive Phenolics

Research has demonstrated that olive phenolics are powerful antioxidants both in vitro and in vivo, and possess potent biological activities that could partially account for the observed healthy effect of the Mediterranean diet. The juice of the olive, also known as olive oil, is a delicious source of these antioxidants. These substances are called polyphenols and contribute largely to the taste and aroma of olives.

The amounts of these compounds in olives depend on several factors, including cultivar, maturation and climate. The amounts usually decrease as the fruit over-ripens, yet, in warmer climates where the fruit tends to ripen faster, the olives are richer in phenols. Unfortunately there is currently a dearth of appropriate methodology for the qualitative and quantitative evaluation of phenolic compounds in olives and oil.

The secoiridoid (also known as glycoside) oleuropein, is the bitter principle in olives, and Panizzi reported as early as 1960 on the hypotensive properties of this complex phenol. In the olive fruit these complex phenols are present in a polar, hydrophylic (water soluble) form, which in extracted olive oil it is in a form more liposoluble. Oleuropein inhibits the oxidation of LDL, inhibits platelet aggregation and has been shown to have a scavenging effect with respect to hypochlorous acid. Hypochlorous acid is a potent oxidant produced in vivo at inflammation sites, and a major component of chlorine-based bleaches used in the food industry. This phenolic also increases blood plasma antioxidant capacity.

In addition, the olive oil contains a recently discovered compound called oleocanthol, which acts like Ibuprofen, the anti-inflammatory agent. “Structurally it’s not similar, but pharmacologically, it’s very similar” says Paul Breslin (Nature:437, p45, Sept 2005). This too helps to explain why the Mediterranean Diet protects against heart disease, cancer and Alzheimers Disease.

Recently the consumption of functional probiotic foods has been increasing in conjunction with increasing awarenewss of their beneficial effects. Amongst these are the promotion of gastrointestinal tract (GIT) health and disease prevention, especially colon cancer. These health-promoting foods are now being used to treat various ailments and diseases. They have been shown to prevent food allergies, alleviate the symptoms of lactose intolerance and counteract hypercholesterolemia. Regular intake of probiotic foods inhibits pathogens.

To date, most of these foods have been milk-related, but now attention is being turned towards non-dairy foods that could contribute to a regular consumption by those with lactose intolerance or those who have a diet which lacks of milk-derived products. To colonise the GIT, probiotic strains need to be ingested as large populations on a daily basis. They should therefore be included in the normal dietary products of the consumer.

During the natural fermentation of olives, the main role players are a group of bacteria called lactic acid bacteria. The main strains are Lactobacillus plantarum, Lactobacillus casei and Leuconostoc mesenteroides, with many minor strains also playing a vital part in the final flavour profile. Regular consumption of naturally fermented olives is therefore a valuable source of GIT colonising bacteria. A research group in Bari, Italy, has proposed that olives be used as a new probiotic food – the olives are to be used as a vehicle for incorporating bifidobacteria and lactobacilli strains into our diets (Appl Environ Microbiol. 71(8): 4233-4240, 2005).

To summarise

The health benefits of table olives:

  • Their oil content of 12 – 25%, and therefore all the health benefits of olive oil – the cheapest way to ingest olive oil
  • Their mineral (potassium and zinc) and vitamin (especially Vitamin E) content
  • The major protective role played by the olive phenolics
  • Oleuropein has a proven hypotensive effect.
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