Olive oil’s good, but only if you use it instead of butter

By: Dr. Joe Schwarcz

Sometime around 1500 BC, the island of Crete was shaken by a huge earthquake. Trying to placate the gods of the underworld who were shaking the earth, the natives lowered a supply of their most precious food into a deep well. And that is how in 1960 archeologists came to discover a large bowl of olives, well preserved by the cool temperatures, at the bottom of an ancient Cretan well. Did the inhabitants of Crete way back then know something about the health benefits of olives? Hard to say, but their descendants certainly seem to be a healthy bunch. At least that’s what famed epidemiologist Ancel Keys found in the 1960s when he examined disease patterns in different countries and attempted to relate these to lifestyle factors. Crete proved to be especially interesting because here people seemed to have a particularly long lifespan, low rates of heart disease and cancer and they routinely worked well into old age. Keys learned that the Cretan diet had been essentially the same for centuries, with its most basic element being virgin olive oil. That in itself of course did not mean much, as Keys realized, but he became more intrigued when he discovered that Cretans who had migrated to the United States suffered the same heart disease and cancer rates as the rest of the American population. Could diet be a factor?

Now when Keys analyzed his data further, a pattern began to emerge. Countries where a lot of saturated fat, as in meat and dairy products, was consumed had high rates of heart disease, whereas countries where liquid vegetable oils served as the main source of fat had a decidedly lower incidence of the disease. An explanation for this observation materialized when researchers discovered that heart disease rates were linked to the amount of cholesterol in the bloodstream, and that cholesterol levels in turn were determined by the fat composition of the diet. The critical feature seemed to be whether or not the fat molecules contained carbon-carbon double bonds in their structure. Those that did, the unsaturated fats, found in vegetable oils, lowered cholesterol while the saturated fats devoid of such bonds raised it.

As physicians learned of this relationship, they began to advise the public to alter their eating habits. Butter and lard were out, vegetable oils were in. And heart disease rates began to plummet. But you can’t spread vegetable oil on bread and you can’t make flaky pastry with it, so a compromise seemed to be in order. And the food industry knew just what to do. Producers geared up to react polyunsaturated fats with hydrogen gas to produce “partially saturated” solid fats, which were to be kinder to our coronary arteries than the infamous saturated ones. Margarine and vegetable shortening, widely promoted, as containing less saturated fat than butter, became dietary staples. Only later would we learn that hydrogenation introduces the notorious trans fatty acids, which, although still unsaturated, just may be worse for us than saturated fats. Hydrogenation thus blurred the link between consuming unsaturated fats and health benefits. Too bad, because those benefits are real, as long as we are talking about unsaturated fats without the scary trans fatty acids. Like olive oil.

Olive oil is a “monounsaturated fat,” which chemically speaking means it has one carbon-carbon double bond in its molecular structure. Saturated fats, as we have seen, are linked with heart disease and there is also some concern about a diet that is very high in polyunsaturates, seeing that in animal studies these promote the growth of colon and breast tumors. There is rational for this, polyunsaturated fats are more likely to give rise to those nasty species we call free radicals, which have been linked with all sorts of problems ranging from cancer to aging. As far as monounsaturated fats are concerned though, the news is good, especially when it comes to olive oil. While it doesn’t lower cholesterol better than polyunsaturates like corn or soy oil, it may offer benefits that these don’t. Like protection against cancer.

Back in 1995 the lay press got all excited about a study carried out in Greece, which implied that women who consumed olive oil more than once a day were able to significantly reduce their risk of breast cancer. Actually, the study was poorly carried out and relied on a single questionnaire to estimate dietary intake over the preceding year, a notoriously unreliable technique. But the study did have a significant effect. It stimulated more research into the possible protective effect of olive oil against cancer. At Northwestern University, for example, researchers treated human breast cancer cells with oleic acid, the main monounsaturated fat in olives. The dose used was akin to that found in the bloodstream of people whose diets are rich in olive oil. Interestingly, the acid halved the production of a protein, known as Her2/neu, which plays a key role in about a fifth of all breast cancers. But oleic acid may not be the only anti-cancer substance in olive oil. A study at the University of Ulster has just revealed that specific phenols, found in virgin olive oil, reduced the damage to DNA in cultured colorectal cells. Of course this is just a laboratory finding, but it does mesh with the observation of lower rates of colorectal cancer in Mediterranean countries where olive oil is widely consumed. Now add to this the recent finding that extra-virgin olive oil contains oleocanthal, an anti-inflammatory substance with pharmacological activity similar to that of ibuprofen (Advil), and olive oil begins to look even more attractive.

Many restaurants now recognize the appeal of olive oil and offer little dishes of it instead of butter on the table. A good idea. But the key phrase is “instead of.” Adding a couple of spoonfuls of olive oil a day to the diet is not the way to go, substituting it for saturated fats is. And if you want a further testimonial, just ask Madame Jeanne Calment. Actually you can’t. That’s because she died in 1997, at the age of 122, the oldest person ever. She attributed her longevity to port wine and olive oil. Mme. Calment also rubbed the oil on her skin and once quipped, “I’ve never had but one wrinkle, and I’m sitting on it.”
Dr. Joe Schwarcz, is director of McGill University’s Office for Science and Society. For a list of his books and publications please visit www.oss.mcgill.ca

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