Mary Flynn, PhD, RD, is Associate Professor of Clinical Medicine at Brown University’s Alpert Medical School in Providence, Rhode Island. In her first contribution to Truth in Olive Oil, she covered some basic facts of olive oil health, and explained how she came to know, and then love, extra virgin olive oil for its health and nutritional properties. Here she shares some vital advice about cooking with extra virgin olive oil, based on her several decades of oil-related research and clinical trials. She also explodes some common olive oil myths, including the bizarre but persistent "don't cook with extra virgin olive oil" fallacy, and offers 3 of her olive oil-based recipes. Each month, Mary will donate another recipe to Truth in Olive Oil.
Eating and cooking with olive oil
I started to develop my plant-based olive oil diet in 2000, primarily including foods that would improve health and control weight. I saw extra virgin olive oil as a central part of this diet for several reasons. I knew it would improve health, but I also thought that using olive oil might increase vegetable intake – another key to good health – since it makes vegetables taste so much better. Also, I believed that using olive oil at meals would help people to eat less, because including fat in a meal makes the meal more satisfying and delays the onset of hunger after the meal. All fats do this, but olive oil is the best choice because it's a very healthy fat.
Extra virgin olive oil is the juice of the olive fruit. Like most unprocessed plant products, it contains a range of health-promoting phytonutrients. The phytonutrients in olive oil have been shown to decrease the oxidation of LDL (1) (which would lower heart disease risk) and DNA (2) (which would lower cancer risk). Other phytonutrients in olive oil have been shown to decrease blood levels of glucose and insulin (3); decrease blood pressure (4, 5); decrease blood coagulation (6); and decrease inflammation (7). This makes extra virgin olive oil very different from seed oils, like soybean, safflower, corn, and canola oil, which have undergone a refining process that destroys phytonutrients. Refined olive oil, typically labeled “olive oil” in stores, also lacks phytonutrients. (Take-away point: buy only extra virgin olive oil!)
I recommend the use of at least 3 tablespoons (45 ml) of extra virgin olive oil per day, most of which you’ll use to cook vegetables. In the studies cited previously, the health benefits of extra virgin olive oil consumption started at about 2 tablespoons a day, so using 3 tablespoons will ensure that you get these health benefits, and will likely increase your vegetable intake as well. The use of olive oil to prepare vegetables greatly improves the taste of vegetables, particularly those that are naturally bitter, like many leafy greens, or those that contain sulfur (the brassica family – broccoli, Brussel sprouts, cabbage, cauliflower, kale). I recommend 1 tablespoon of olive oil per cup of vegetables. In addition, brassica vegetables contain a phytonutrient family (glucosinolate) that has been shown to be cancer protective (8), but it is water soluble (9), so boiling or steaming these vegetables means you will not get the health benefits from this phytonutrient, since it will be lost in the cooking water. Cooking the brassica family in extra virgin olive oil therefore means that you get both the health benefits of olive oil itself and of the cancer-fighting phytonutrients in the vegetables. Plus using olive oil will make them taste so much better than boiling or steaming!
In the 12 years that I’ve employ my diet in my work, I have found, just as I’d hoped, that when my patients and study participants use more olive oil, they consume more vegetables (10, 11), a big plus for health. In addition, when they report using more than 3 tablespoons of olive oil a day – for example when summer vegetables are plentiful – they are still losing weight. I would guess there is some upper limit to how much you extra virgin olive oil you can consume before you start gaining weight, but I haven’t yet found it. In fact, I tell patients that they can never eat too much extra virgin olive oil. Sure, it’s a fat, but the benefits of extra virgin olive oil clearly outweigh its drawbacks – olive oil will improve your health.
Olive oil and vegetables
Vegetables, like olive oil, have long been associated with improved health. However, studies looking at the consumption of vegetables do not consistently show decreases in chronic diseases. There are at least as many studies showing no benefit as those indicating some disease protection from frequent consumption of vegetables. I believe this inconsistency may be attributable to the type of vegetable consumed in the studies, and to the way the vegetables are prepared. Certain plant products are clearly more health-protective than others, due to the phytonutrients they contain. Some of the healthiest, vegetables, which I recommend to my patients, include: all the brassica family – broccoli, Brussel sprouts, cabbage, cauliflower, kale; any vegetable with deep color, like carrots, peppers, winter squash; and anything leafy and green – spinach, collard greens, etc. I also recommend the use of frozen vegetables; in fact, I prefer them nutritionally over fresh as in many cases they are kept on the plant longer than what one would buy in a grocery store, so their phytonutrient is likely higher and they have the same vitamin content as store-bought fresh vegetables (12, 13). (I’ll write more on vegetables and health in an upcoming post.)
Low cost of meals that contain olive oil
I think it’s wrong, when considering the cost of olive oil, to consider it as another vegetable oil and compare its cost to theirs. Vegetables oils are chemically extracted from seeds and nuts and do not have health benefits remotely comparable to extra virgin olive oil, which is physically extracted from a fruit – the olive. If properly made, extra virgin olive oil is rich in many components that research has shown to produce manifold health benefits, and to be associated with a lower rate of chronic diseases. What’s more, many vegetable oils are high in polyunsaturated fats, which readily oxidize. I think a case could be made that vegetable oil consumption may actually increase your risk of chronic diseases.
Apart from the considerable health benefits of extra virgin olive oil, when you work out the cost of olive oil per tablespoon, it's actually quite inexpensive. A 17 fl. oz bottle of olive oil contains approximately 32 tablespoons, and a liter contains 64 tablespoons. Many extra virgin olive oils cost less than 30 cents per tablespoon, so my recommended dose of 3 tablespoons of oil per meal costs 90 cents. A health-promoting meal with plenty of olive oil therefore costs substantially less than one with meat, poultry or seafood – foods which in any case won’t improve your health.
“Raising the Bar on Nutrition” (RTB) is a program I developed for the Rhode Island Community Food Bank, after participants in my early research into my plant-based olive oil diet observed how inexpensive my diet was to follow. The recipes for RTB are based on my diet, but use foods commonly found in most food pantries, which are locations where low-income people can get free food. The average cost of my RTB recipes is $1.07 per serving (December 2011 pricing in Rhode Island), and all recipes include 1 to 2 tablespoons of olive oil per serving. RTB was tested as a research protocol using a 6-week cooking program for food pantry clients. Participants in the program had significant decreases in food insecurity, food costs, and body weight (10).
Canola oil is not a substitute for olive oil
Speaking of vegetable oils, I’m often asked about canola. U.S. health officials originally linked the health benefits of olive oil to its monounsaturated fat content, but since they didn’t think Americans would accept a dietary oil with pronounced flavor, like olive oil has, researchers at the University of Manitoba, Canada developed canola oil, which was naturally bred from the rapeseed plant (“canola” stands for “Canadian oil, low acid”). Canola oil is higher in monounsaturated fat than other seed oils, though not as high as olive oil, so the health benefits related to its lipid profile will be less than olive oil. Additionally, canola lacks numerous components contained in extra virgin olive oil which, as we’ve mentioned above, are linked to a range of health benefits. In fact, there are no studies showing health benefits from using canola oil. Bottles of canola oil often say “contains omega 3 fats”, which is true, but not the form of omega 3 that is known to improve health. Canola oil contains an 18-carbon form of omega 3, while health benefits have only been demonstrated with 20- and 22-carbon omega 3s. Humans convert only small amounts of the 18-carbon to the 20 carbon omega 3 compound (EPA) and even less to the 22- carbon compound (DHA) (14, 15), so the health claims concerning canola oil’s omega 3s may be misleading.
Olive oil and cooking
Nearly every time I lecture on olive oil, people ask whether heat destroys the oil, and whether they can cook with it. I don’t know who invented this misconception (seed-oil companies?), but I’d love to dispel it once and for all. High quality extra virgin olive oil can be heated to 420°F before it reaches smoke-point (ie begins to smoke and starts to form unhealthy compounds), which is higher than nearly every other vegetable oil. Olive oil is much more stable when heated compared to most vegetable oil (16, 17). Cooking with olive oil below the smoke-point does not destroy most of its health benefits, or make it less healthy – under normal cooking conditions, most of the therapeutic minor components are retained (18-20). Some studies have subjected olive oil to high temperatures (180°C/356°F) for long periods of time (from 90 minutes to over 20 hours). These conditions do tend to decrease the content of some phytonutrients, yet even under such extreme conditions, some phytonutrients remain (21).
This said, it is true that heating olive oil can modify or impair some of the flavor. So at least from a culinary point of view, and depending on your personal taste, it’s usually better to add high-quality olive oils to finish a dish, after cooking.
I’m also frequently asked if heating olive oil produces trans fats. Here again, the answer is No. Trans fats are created in an industrial process that adds hydrogens to the liquid oil (partial hydrogenation), making it semi-solid. This is how margarine is made (or at least was made, before trans fat were recognized as a health issue). Ordinary cooking, even at high heat, never produces trans fats.
Milder extra virgin olive oil is excellent in baking, especially since heating seems to decrease the bitter taste in some olive oils (20). I tell people to use an extra virgin oil like California Olive Ranch, which is relatively delicate in flavor, as well as economical. (A useful book on choosing different olive oils is The flavors of olive oil. A tasting guide and cookbook by Deborah Krasner (Simon and Schuster, New York 2002), which classifies oils according to taste - delicate and mild, fruity and fragrant, leafy and grassy, peppery - and also lists some oils by country of origin.) The oil gives muffins, quick breads, and even cookies an excellent texture, without any noticeable olive flavor. In fact, many of my patients tell me that my olive oil-based recipes for muffins and quick breads have a better texture than other recipes they've used which call for vegetable oil or margarine. In short, you can use extra virgin olive oil in any recipe that calls for liquid oil.
(Reprinted from The Pink Ribbon Diet by Mary Flynn and Nancy Verde Barr. Available from Da Capo Lifelong Books, an imprint of The Perseus Books Group. Copyright © 2010) (Photos by Francesca Mueller)
Here are three olive oil recipes that embody the health concepts of my plant-based olive oil diet. For more recipes and information, see my book The Pink Ribbon Diet.
Greek Style Vegetable Casserole
2 tablespoons extra virgin olive oil
¼ teaspoon dried red pepper flakes
¼ cup red onion (¼ of a small onion)
¼ cup diced celery (half of a stalk)
Salt and pepper
½ cup diced red or green pepper (half of 1 medium pepper)
1 cup cubed eggplant
1 cup zucchini slices (8 to 9 ounces)
1 cup canned, crushed tomatoes
1 bay leaf
¼ cup canned chickpeas, rinsed and drained
2 tablespoons feta
¾ cup cooked brown rice
Preheat the oven to 375°F.
Heat the olive oil on medium in a medium pan. Add the dried red pepper, then the onion and celery. Season with salt. Cook for 5 minutes.
Add the peppers, eggplant and zucchini. Cook for 5 minutes or until some of the oil is absorbed into the vegetables.
Add the tomato and bay leaf. Cook until the vegetables are bubbling (about 5 to 7 minutes).
Stir in the chickpeas and put the mixture in a casserole dish that holds the mixture in layer about 2 ½ to 3 inches deep.
Bake for 30 minutes. Remove from the oven; sprinkle the cheese over the top. Return to the oven and cook another 5 minutes or until the cheese melts.
Serve over the cooked rice.
This Pumpkin Bread is moist and flavorful—the perfect answer to a healthy breakfast especially for those who are used to eating high-calorie, negligible-nutrient muffins in the morning. Although the bread has some vegetable (the pumpkin), some fruit (raisins) and olive oil, it does not contain enough of any of them to include in the food count, so count the starch and consider the calories. You can cut the baked loaf into serving-size slices and freeze them individually. The slices will defrost quickly.
One 5 x 9-inch loaf pan, preferably non-stick or unglazed, ceramic stoneware. The stoneware gives the bread a particularly nice crust. If neither is available, brush the sides of the pan with olive oil so the bread will release easily.
1 ½ cups whole wheat flour
½ teaspoon salt
1 cup brown sugar
1 teaspoon baking soda
1 cup canned pumpkin
½ cup extra virgin olive oil
2 large eggs, beaten
¼ cup water
1 teaspoon cinnamon
½ cup walnut pieces
½ cup raisins
Preheat the oven to 350°F.
Measure the flour, salt, brown sugar and baking soda into a mixing bowl and stir with a fork to blend the ingredients together thoroughly. Be sure to break up any lumps in the brown sugar.
In a separate bowl, stir the remaining ingredients together until thoroughly blended. Gently stir the mixed dry ingredients into the pumpkin mixture just until combined. A plastic spatula works best. Do not over mix or the bread will not rise.
Pour into a loaf pan and bake 50 to 60 minutes or until a toothpick or cake tester inserted into the center comes out clean. Let the bread cool in the pan slightly, five or ten minutes, then turn it out onto a wire rack and cool thoroughly.
Makes 8 slices
Broccoli Wrap with Cheese
Can use other vegetables; can use other bread types; wraps tend to not absorb the olive oil but can pack in separate containers; this can also be made by roasting the broccoli for about 20 to 25 minutes in a 450F oven.
1 tablespoon extra virgin olive oil
1 cup fresh or frozen, chopped broccoli, defrosted
Salt and pepper
¼ cup ( 1 ounce) shredded cheddar
(optional: teaspoon sesame seeds)
1 whole wheat wrap (59 grams or about 2 ounces)
Heat the olive oil in a small skillet on medium. Stir in the broccoli. Season with salt. Reduce the heat to medium low and cook for 10 to 15 minutes or until the broccoli is softened.
Sprinkle the cheese over the cooked vegetables and allow the cheese to melt (2 to 3 minutes).
Place the wrap on a plate if eating now or on aluminum foil if packing to eat later. Use a rubber spatula to spread the cooked broccoli and cheese into a circle in the center of the wrap. Fold the bottom of the wrap up over the mixture; fold in the 2 sides. You can secure the wrap with a toothpick, if it is being eaten now. If packing for eating later, wrap tightly in aluminum foil.
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