3 Problems About the Latest Mediterranean Diet Study
A UCLA Distinguished Professor Emeritus Dr James Barnard is taking a closer look at the recent study on the heart benefits of the Mediterranean Diet and identifying 3 problems with the study.
We’ll start by talking about what’s good about the newly published study* that garnered headlines like “Mediterranean Diet Shown To Ward Off Heart Attack and Stroke.”
The study affirmed the benefits of a healthy diet even for people already taking medications for high cholesterol, blood pressure, or diabetes.
The takeaway: Drugs have benefits. Drugs plus diet have even more benefits.
And there’s no question that a Mediterranean-style diet (fruits, vegetables, legumes, fish, whole grain, nuts, olive oil, wine) is healthier than a typically American diet, full of fast food and other artery-cloggers like cheese, butter, red meat, processed meats, refined flour, sugar, and salt.
Now to the problems (and there are many) with this study. We’ll focus on three major ones.
• The study followed 7,447 people with heart disease risks who were randomly assigned to either Mediterranean-style diets or a low-fat diet, but the low-fat diet was not low in fat. Not even close. The people in the “low-fat” group started out with a diet that was 39% fat. They decreased fat intake to 37%.
So, the authors weren’t really comparing a Mediterranean diet to a low-fat diet. It’s much more accurate to say they were comparing a Mediterranean diet with a fatty American-style diet. And sure enough, a lot of the foods the so-called “low-fat” group was eating were heart-damaging foods like red meat, commercially baked goods full of refined flour and fat, and sugary sodas.
• Some argued that the people in the “low-fat” group were unsuccessful in reducing their fat intake because a low-fat diet is too difficult to maintain, but it could also be argued that the scientists conducting this study never really gave the “low-fat” diet group a chance.
During the first half of the study, the people assigned to the Mediterranean diet received intensive education in eating well, including regular visits with registered dietitians. The people in the “low-fat” group got one visit. That’s it. It was the equivalent of a doctor’s visit in which the doctor hands you a pamphlet with what to eat, and what not to eat, and essentially says, “Good luck.”
Moreover, the “low-fat” diet that the scientists designed excluded an important food proven to protect against heart disease, a food that is a part of many low-fat plans, including the Pritikin Program – omega 3-rich fatty fish. The subjects in the study were discouraged from eating fatty fish like salmon.
And ironically, this “low-fat” diet devised by the scientists had no limits on some foods known to increase heart disease risk, like soft drinks.
• The scientists summarized that the Mediterranean diet “reduced the incidence of major cardiovascular events” compared to a low-fat diet, and media articles led with announcements like “30% of heart attacks, strokes, and deaths from heart disease were prevented.”
But in the study itself, the scientists reported no significant reductions in heart attacks or cardiovascular-related deaths among the Mediterranean dieters. They wrote, "Only the comparison of stroke risk reached statistical significance."
So how did they jump from stroke reductions to all reductions in cardiovascular risk? Well, it’s easy when you know how to play with numbers. They pooled all the data on heart attacks, strokes, and deaths, and the numbers on strokes were high enough so that the average of the three looked good.
It appears that the scientists were doing everything they could to make the Mediterranean diet the winner. Why? We don’t know for sure, but consider this:
The olive oil, nut, and wine/alcohol industries were very involved in this study. Two olive oil companies supplied all the olive oil. Two nut companies supplied all the nuts. The lead author, Dr. Ramon Estruch, has served on the board and received lecture fees from wine groups like the Research Foundation on Wine and Nutrition and the European Foundation for Alcohol Research.
The other authors of the study have deep ties with other olive oil, nut, and wine groups such as the California Walnut Commission, the International Nut and Dried Fruit Council, the Mediterranean Diet Foundation, and an wine/alcohol public relations group in Spain called Cerveceros de España.
Yes, it could be argued that these scientists had a vested interest in making the Mediterranean diet look as good as it possibly could. By contrast, there was no financial interest in making the “low-fat” diet look good.
What would have been a far better study is one in which a Mediterranean diet was compared with a truly healthy low-fat plan like Pritikin.
Pritikin includes all the excellent elements of a Mediterranean diet (fruits, vegetables, whole grains, legumes, fish) as well as the ability to shed excess weight (something the subjects in the Mediterranean study did not achieve) because on Pritikin calorie-dense foods like oil and nuts are kept to a minimum.
So strong are the data affirming the heart-healthy benefits of the Pritikin Program that Medicare is now covering it for people with a history of cardiovascular disease.
The Pritikin Program combines daily exercise with an eating plan that emphasizes:
• Hearty consumption of fruits, vegetables, whole grains, and legumes like beans
• Moderate intake of fat-free dairy products and lean animal protein like fish, skinless poultry, and bison
• Little or no intake of added sugars, saturated fats, trans fat, and sodium (no more than 1,500 mg of sodium a day).
Is this a low-fat diet? Yes. Average intake is about 10 to 15% fat.
But more importantly, it’s an extremely healthy diet, proven in more than 100 studies over the past three decades to dramatically reduce virtually every modifiable risk factor for cardiovascular disease, including LDL bad cholesterol, trigylcerides, blood glucose, insulin, hypertension, inflammatory markers like C-reactive protein, and excess weight/obesity.
A study comparing this type of healthy, low-fat diet with the Mediterranean diet would have been a study that deserved headlines. Not the study that was published this week.
Written by James Barnard, PhD, UCLA Distinguished Professor Emeritus, Department of Integrative Biology and Physiology
* New England Journal of Medicine, February 25, 2013; DOI: 10.1056/NEJMoa1200303
Also see Dr. Gayl Canfield's story discussing the pros and cons of the Mediterranean Diet. What each follower of this diet should know about the advantages and disadvantages of this plan.
Do you use Mediterranean food in your diet? If yes how often? Let us know in the comment sections please.