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Olive oil, and especially extra virgin olive oil, is all the rage on cooking shows and at finer dining establishments these days. It seems that good news regarding the benefits of olive oil for our health and wellness emerges almost daily. So it stands to reason that people would want to explore this ingredient for use in pet diets. In turn, several petfood companies have gladly obliged.
To the seasoned veterans of the petfood aisle, this may seem like a marketing gimmick whose sole intent is to leverage the halo effect from all the good press regarding olive oil’s benefits to human health. However, lest we be too quick to disparage this ingredient, there may just be a meaningful reason to consider olive oil in a pet’s diet.
The use of olive oil in human nutrition is most associated with the so-called Mediterranean diet, where fish and vegetable consumption is complemented by 25-50 mL per day of extra virgin olive oil. In this program, most of the health benefits associated with olive oil relate to its preventive effects on coronary artery disease. This is thought to be a function of the high monounsaturated fatty acid (principally oleic acid) content.
The relationship between high oleic acid oils and coronary artery disease is not a major nutrition/health concern for the dog or cat. So, if olive oil is to be beneficial for the pet beyond simply providing fat calories, there would need to be another justification for its use.
Unrefined olive oils, like extra virgin and virgin olive oil, possess a number of minor constituents (0.5% to 5%) that have noted effects on animal physiology. These include antioxidant compounds such as Î±-tocopherol (vitamin E), beta carotene and squalene, pigments from various chlorophyll derivatives and more than 36 unsaponifiable phenolic metabolites. The most prominent of these include hydroxytyrosol, tyrosol, oleuropean aglycone and oleocanthal. These phenolics have been reported to possess anti-microbial and anti-inflammatory properties (Cecerale, 2011). It is these properties that might be meaningful in pet diets.
There are a few published studies in which olive oil was fed to pets; unfortunately, the results have been mixed, and none really addressed the effects of these minor constituents in lieu of the fatty acid story. For example, use of olive oil in the diet as a remedy for canine atopy was found beneficial in combination with borage oil (Harvey, 1999) but not alone (Bond and Lloyd, 1992).
The addition of olive oil in the diet had a positive effect on digestibility when compared to sunflower oil for both dogs (Bellesta, 1991) and cats (Peachey, 1999). It might play a role in feline weight control by influencing energy intake and lipid oxidation in vivo (Jeusette, 2010). So, there does seem to be something worth considering, but clearly missing is any direct evidence regarding the effects the minor constituents in the virgin olive oils might have on animal health.
Olives are quite ancient in the realm of food and agriculture, with evidence of their use dating back to the early Bronze Age, some 5,000 years before the current era. They originated in the eastern Mediterranean coastal region in what are now the countries of Turkey, Syria, Lebanon, Palestine and Israel. Early uses were not so much for dietary consumption but rather for lamp oil, religious rituals, pharmaceutical ointments and soap production (Firestone, 2005; Vossen, 2007).
It may be obvious to most, but just to be clear, olive oil comes from olives, and olives grow on trees (Olea europaea L. sativa). They are grown on over 23 million acres around the world, with oil production second to table olives. Today, Spain, Italy and Greece account for more than 77% of the global olive oil output.
Growing olives is a decades-long venture, as olive trees take years to establish and live for hundreds of years. Today, olive orchards are tended by mechanical means, and the olives are harvested either by tree shakers or comb-type harvesters. The fruit must be harvested without breaking and processed quickly thereafter (within 24 hours) to avoid spoilage.
The first step in processing is to remove debris such as leaves and stems. Washing with water is avoided, if possible, as water complicates the extraction process and can lead to inferior oil products. The olives are crushed (pits included) to release the oil from cells and turned into a paste. Extraction of the oil from the paste is done by one of three methods: press, decanter-centrifuge or selective filtration. Once the oil is extracted, it is allowed to rest for several months to allow remaining particulate to settle and then packaged.
Standards for olive oil have become more uniform around the world. Grades are based primarily on process, flavor and chemical quality standards. Since 2010, the US has adopted standards (75 FR 22363) that are similar to those of the International Olive Oil Council.
The more expensive virgin olive oils are by definition extracted solely by mechanical or other physical means. Extra virgin olive oil and virgin olive oil may vary in color and flavor depending on region and type of mechanical extraction process. Purchase of these oils for pet diets will compete with the premium edible market. Verifying acceptability by the dog or cat should be the first line of consideration before their use.
The refined olive oils have been processed to remove the pigments (chlorophyll), waxes and unsaponifiables (phenolics). These refined oils are not likely of interest for petfood applications if one wants to take advantage of the minor attributes (i.e., the refining process strips them away).
The olive-pomace oils are obtained by solvent extraction of oil remaining in the spent pomace from the virgin olive oil extraction process. Since these oils are obtained by chemical extraction, they may contain small amounts of residues; they may also contain more chlorophyll and unsaponifiable components like the phenolics. So while less expensive, they have the potential to provide more value to a market that is not so concerned about a delicate olive flavor. However, to utilize these oils, one would want to verify that they did not negatively influence product shelf life or palatability.
Olive oil, like other vegetable oils, is a liquid at room temperature. It can be purchased in carboys and drums from various suppliers. While relatively stable, the oil should be stored in a cool, dry warehouse in a closed container prior to use. Extra antioxidant preservatives should not be necessary if the oil was handled properly during production; however, it is an oil and subject to oxidation if mishandled.
There are no upper limits on the use of olive oil in a pet diet, but considering price, it will likely be used sparingly. With amounts greater than 1%, one would want to affirm that the product/source chosen does not impart off-flavors or aromas that the dog or cat might reject.
At present, there is only a hint that olive oil could provide benefit in a pet diet. Digging deeper into the potential benefits of the minor constituents in the virgin olive oils could be a fruitful area for future research and product development. But for now, a hint of benefit may be all that is needed in this highly competitive market.