My interest in olive oil began in 1984, when I joined The Miriam Hospital in Providence, Rhode Island, a major teaching affiliate of the Brown University medical school. The American Heart Association had just released a new set of diet guidelines which recommended that patients reduce the fat in their diet to no more than 30% of total calories. One of my tasks at the hospital was to test these guidelines by designing diets to decrease the risk of heart disease. From the beginning, I saw that as dietary fat decreased, the lipids of the patients were getting worse, with consistent increases in fasting triglycerides, and decreases in HDL (the so-called “good cholesterol”).
To understand why this was happening, I started exploring the literature on how dietary fat is related to a wide range of diseases. One of the first studies I read was the Seven Country Study led by Ancel Keys, an American epidemiologist who researched Mediterranean dietary regimes in the 1950s-1980s, and was one of the founders of the so-called “Mediterranean diet.” Keys looked at heart disease rates around the world and tried to relate them to various factors, including diet. I remember being intrigued to learn that the men on the island of Crete ate more than 40% fat, but their heart disease rate was over 80% lower than what was seen in the US. The diet fat for the men on Crete was mainly from olive oil, so I thought, “How can total fat in the diet be a health risk, if Mediterraneans eat so much olive oil and yet have low rates of heart disease?”
In subsequent years I became increasingly interested in olive oil, as I continued to read study after study that showed olive oil’s wide-ranging health benefits. Nutritional research studies routinely produce apparently conflicting results involving the same foods, often due to the study design, the participants used, or the food source of the nutrient. Yet somehow, the research on olive oil was different: studies involving olive oil have consistently revealed health benefits, and a relation to decreasing diseases. I found this fascinating, especially since at the time US health officials had begun to recommend low-fat diets to fight most chronic diseases, as well as for weight loss.
In fact, I have never supported the use of low-fat diets for any reason. In 1999 I co-authored a book for laypeople that presented the literature on low-fat diets, showing that they were neither healthy nor effective (Low-fat Lies, Lifeline Press, 1999). Low-fat diets aren’t effective for weight loss either: so long as you lower calories, the proportions of fat, protein and carbohydrates aren’t important for losing weight. What’s more, to keep weight down long-term, people have to stay on the diet, and for this to happen it helps a lot to like the diet. For me, in fact, the main problem with low-fat diets was the hunger that resulted from reducing dietary fat. Hunger is one of the main reasons people stop a weight loss diet.
Yet for reasons that I don’t fully understand, the media as well as many health officials and scientists jumped on the low-fat bandwagon, and somehow made “Mediterranean” synonymous with “fat.” I saw this in a conversation with my editor of Low-fat Lies. She asked me what diet I would recommend, and I said, “a Mediterranean diet.” Her response was, “Wouldn’t people gain weight on a high-fat diet like that?” What’s more, the label “Mediterranean diet” is widely misused, even by serious scientists. Some researchers term their diet “Mediterranean” if it includes canola oil, or has a ratio of monounsaturated to saturated fats similar to that in olive oil – even where the main source of monounsaturated fat isn’t olive oil at all, but red meat! Real Mediterraneans would never recognize such an olive-oil-free diet as their own.
I developed a weight-loss diet based on the basic eating principles observed around the Mediterranean by Ancel Keys and others, and widely practiced by Mediterranean populations today. To avoid confusion, however, I didn’t call it a “Mediterranean diet,” but a “plant-based olive oil diet” instead. It contained 2 to 3 tablespoons of extra virgin olive oil a day, which are used to cook vegetables, dress salads, dip bread, etc. Over 40% of the calories in the diet came from fat, primarily from the olive oil (as well as nuts). I thought that including olive oil at lunch and dinner would help to decrease hunger between the meals and as long as the calories were lowered, there would be weight loss. I recruited 10 women from the staff at Brown University and asked them to follow the diet for 8 weeks. From the first week of the diet they started to remark, “I am not hungry, and I am losing weight!” I invented new recipes so that they could make complete meals of olive oil, vegetables and a starch source (pasta, rice, potatoes, legumes), without having to include meat, poultry or seafood. (I don’t include meat, poultry or seafood in my recipes as these are not foods that will improve your health. In fact, their extra protein can actually lead to weight gain, as we do not store protein as protein, but break it down and store it as fat.)
My further research supported these initial findings. Around the year 2000 I set up two studies, one involving overweight people in a cardiac rehabilitation program (all had heart disease), and the other with Brown University employees who were overweight but otherwise healthy. For both studies, I randomly assigned half of the participants to my plant-based olive oil diet, and half to a conventional lower fat diet (< 30% fat). I was intrigued by the differences in the study meetings. The people on my diet were actually enthusiastic at each meeting, discussing different recipes they had tried and remarking on how delicious their meals were. Not so for the low-fat groups. One of the recurring comments from the group on my diet was again that they were not hungry and were losing weight. For both studies, my diet resulted in significantly greater weight loss than the lower fat diet. In a separate study, women on my plant-based olive oil diet lost more weight than with a lower fat diet. In addition, they had lower levels of triglycerides and higher HDL, ate significantly more vegetables, and their blood levels of carotenoids – plant pigments such as beta- and alpha-carotene and lycopene that have been linked to health benefits in humans – were significantly higher in my diet, meaning that they had more of these cancer-protective phytonutrients of these vegetables in their blood.
I teach nutrition at Brown University in the undergraduate program, and lecture on nutrition in the medical school. One of my undergraduate courses explores the literature on how food is related to chronic disease development and treatment, and the core food in the course is olive oil, because certain studies show that olive oil decreases the risk of all of the diseases we cover. This course is a lot of fun to teach, because I see students rapidly become more adept at understanding the health benefits of food, assessing the strengths and weaknesses of scientific studies, and comprehending how food can be used as medicine. It also keeps me current with the literature, especially studies of the health benefits of olive oil.
In addition to research and teaching with olive oil, I also use my olive oil diet in clinical work. In 2005 I started working with the chef of the hospital to develop recipes for the employee cafeteria, following my plant-based olive oil diet. The recipes all contained 2 tablespoons of olive oil, 2 servings of vegetables, together with whole-wheat pasta and brown rice. The meals were a success, and the chef dubbed them “Mary Meals.” Anthony Mega, MD, a medical oncologist at my hospital, liked them and subsequently asked me to develop a diet study for his patients with recurrent prostate cancer, who were being treated with androgen deprivation, a therapy that causes weight gain and the development of the Metabolic Syndrome (also known as “pre-diabetes”). We did a pilot study of 20 men who used my diet for weight loss. The average weight loss in 8 weeks was just over 11 pounds (6% of baseline weight). The majority of the men reported that they loved the diet, and were eating vegetables like spinach and broccoli that they had not eaten in years (if ever).
In several of my studies, participants had remarked on how inexpensive it was to eat my diet. I am on the board of the Rhode Island Community Food Bank, and asked the CEO if I could develop a study to see if food pantry clients who used my diet would spend less on groceries. The results of this study showed that they did in fact spend less when they used my recipes for 2 to 3 meals per week. They also improved their food security, diet quality and there was a significant weight loss for the group. This study refutes the notion that a healthy diet is expensive; it also shows that including extra virgin olive oil daily instead of meat/poultry or seafood is a very economical as well as healthy way to eat. I have also recently completed a small pilot study teaching 10- to 13-year-olds who are children of food bank clients to make meals with my recipes. The results are showing that the kids can easily make the recipes and the families are reporting eating more vegetables and whole grains, plus using extra virgin olive oil for several meals a week.
I am just starting a program to use my olive oil meals at McAuley House, a congregate meal site (a.k.a “soup kitchen”) that serves low-income and homeless individuals. The plan is to serve one olive oil meal a week and study their acceptability, cost, and ease of preparation as compared with the current meals. I’m now interviewing guests and working with the staff to lay the groundwork for our kick-off meal, which is on May 10th. I’ll be posting pictures from this event here on Truth in Olive Oil and on the McAuley House website.
I’ve been studying and working with extra virgin olive oil for thirty years, and am just beginning to sense how much we still can learn about it. Yet already I’ve come to believe that extra virgin olive oil is an amazing – indeed a near-miraculous – food. In future posts, I’ll be exploring some of its specific health benefits described in published studies, including my own research. I’ll also be detailing studies that I feel need to be done in the future, for which I’m pursuing funding. If you don’t believe it already, I hope to convince you with solid scientific evidence that including high-quality extra virgin olive oil in your diet will significantly decrease your risk of chronic disease.