Tuesday, February 26, 2013

Is The Mediterranean Diet Really All That?

This study about supposed benefits of a Mediterranean diet is making news:

Primary Prevention of Cardiovascular Disease with a Mediterranean Diet, New England Journal of Medicine, 25 February 2013

7447 people "with no cardiovascular disease at enrollment" were randomly assigned to one of 3 diets. After ~4.8 years into the study:
  • 96 people assigned to the Mediterranean diet plus olive oil (about 4 tablespoons/day) group experienced a major cardiovascular event.
  • 83 people assigned to the Mediterranean diet plus nuts (about 1 ounce/day mixed - 15 g walnuts, 7.5 g almonds, 7.5 g hazelnuts) group experienced a major cardiovascular event.
  • 109 people assigned to the control diet (advised to reduce fat but didn't) experienced a major cardiovascular event.

Why did 179 people who had no cardiovascular disease (CVD) prior to entry into this study experience heart attacks or strokes after eating a Mediterranean diet supplemented with olive oil or nuts? It sounds like what they were doing before they started supplementing their diets with olive oil and nuts protected them more from CVD, since they apparently developed it only after partaking in the study.

Dr. Esselstyn had much better success with his plant-based, oil-free diet and his patients did have CVD:
"The patients in Dr. Esselstyn’s initial study came to him with advanced coronary artery disease. Despite the aggressive treatment they received, among them bypasses and angioplasties, 5 of the original group were told by their cardiologists they had less than a year to live. Within months on Dr. Esselstyn’s program, their cholesterol levels, angina symptoms, and blood flow improved dramatically. Twelve years later 17 compliant patients had no further cardiac events. Adherent patients survived beyond twenty years free of symptoms."
Back to the present study ... There was a 30% reduction in risk (of a "major cardiovascular event" but only stroke reached significance) for eating the Mediterranean diet, but this article from the New York Times said:
"Those assigned to a low-fat diet did not lower their fat intake very much. So the study wound up comparing the usual modern diet, with its regular consumption of red meat, sodas and commercial baked goods, with a diet that shunned all that."
The authors said so much:
"We acknowledge that, even though participants in the control group received advice to reduce fat intake, changes in total fat were small."
Perhaps the benefit was due to eliminating red meat, soda, commercial baked goods, and dairy (the control group was advised to consume 3 or more servings of dairy a day, the Mediterranean diet groups were not) and not due to eating olive oil or nuts. It's hard to say since the authors did not divulge what participants in each group ended up eating. (Update: I was wrong about this. I just reviewed the supplemental materials. Here are some additional facts:
  • The control group, which had been advised to eat a low-fat diet, was eating 37% of their calories from fat. The low-fat diet community says a low-fat diet gets 10-12% of its calories from fat. The American Heart Association says a low-fat diet is <30% fat. By any standard, this was not a low-fat diet.
  • Both Mediterranean diet groups ate more vegetables, fruits, legumes, wine, and seafood than the control group. (Table S5, p<0.05).
  • The Mediterranean diet groups did not reduce risk for heart attack, death from cardiovascular causes, or death from any cause. "Only the comparisons of stroke risk reached statistical significance."

Given Esselstyn's scorecard, people eating the Mediterranean diets in this study could have reduced their CVD risk further by reducing intake of processed fats (including olive oil) and nuts.

This study was conceived and conducted in Spain. The olive oil and nuts given to participants were supplied by producers in Spain, who were probably very happy to see the results lauding oil and nuts' benefits published in a prestigious journal. Also, the authors of this study report the following conflicts of interest:
  • Research Foundation on Wine and Nutrition
  • Beer and Health Foundation
  • European Foundation for Alcohol Research
  • California Walnut Commission
  • International Nut and Dried Fruit Council
  • Mediterranean Diet Foundation
  • OmegaForte
That's a photo of my olive oil and walnut. I like both, but I don't eat anything near the amounts in this study.


caulfieldkid said...

Are you sure that's olive oil? :)


RB said...

Most reports didn't discuss the fruit and vegetable consumption on the Mediterranean diet and lack of red meat. The report noted "the traditional Mediterranean diet is characterized by a high intake of olive oil, fruit, nuts, vegetables, and cereals; a moderate intake of fish and poultry; a low intake of dairy products, red meat, processed meats, and sweets; and wine in moderation, consumed with meals."

I think the Mediterranean diet would be improved by reducing the amount of fat from any source including olive oil.

I thought most of the media did a poor job of reporting this story and left the impression that a lot of olive oil, nuts and wine in the diet was a good thing. I think they did the public a great disservice. I suppose reporting fruits and vegetables are important in a healthy diet is not what the press thinks the public wants to hear. Just eat fat and be happy. Good PR for olive oil.

Bix said...

I'm not sure!

Anonymous said...

Bix, I'm not sure that Mediterranean diet exist at all out of books and scientific papers. For example, there are many differences in the intake of different nutrients between people living here (Italy). For sure there is a common use of olive oil, brad and pasta. Meat and fish consumption is variable between individuals (and places depending on the distance from sea) and fruit and vegetable load too. To me, the term Med Diet refers more to the use of olive oil and cereals in the diet rather than a fixed balance between macronutrients including fish and meat. Alessandro

Bix said...

Love your perspective, Alessandro. I've always had difficulty characterizing the Mediterranean diet, besides maybe the lack of fast food.

Reijo Laatikainen said...

Results are in line with the meta-analyses of prospective cohorts and short term surrogate marker studies. Can you show the better data on any diet?

Ornish diet may work well for some. But the fact is that as a clinician you run into problems if your only tool is the Ornish. Only handful of the patients you see are able to or willing to change the diet so dramatically. Plant based diets are the right path, anyway.

Bix said...

Reijo, I agree with you that if your only tool is Ornish, you're quite limited.

Bix said...

I've been pouring over these supplemental materials. Great stuff. For instance ... they all ate about the same amount of red meat and soda and pastries, but the Mediterranean groups did eat significantly more fruits, vegetables, beans, wine, and seafood. Honestly, I think that's the real lesson in this... But I'm only shadowing RB now :)

Anonymous said...

So the Mediterranean diet doesn't reduce heart attacks? Why aren't the news media reporting that? How could they get it so wrong!

Angela and Melinda said...

The NYT said the ~7500 Spaniards in the study were "subjects at high risk of heart disease": "Heart disease experts said the study was a triumph because it showed that a diet was powerful in reducing heart disease risk, and it did so using the most rigorous methods. Scientists randomly assigned 7,447 people in Spain who were overweight, were smokers, or had diabetes or other risk factors for heart disease to follow the Mediterranean diet or a low-fat one." Another benefit they mentioned was that more people enjoyed the Mediterranean diet than the low-fat diet. I admire people (like you, Bix & some of you others!) who can eat only plant foods and little-to-no oil, but I just can't do it myself, so I'm happy to know there's a helpful alternative. Just my opinion of course.

Angela and Melinda said...

The diet does eschew red meats and even downplays white meats in recommending what *not* to eat: "Of course, there are also foods to avoid or consume in limited quantities. They include cream, butter, margarine, pâté, lunch meats, French fries, potato chips, sugared sodas or other drinks with sugar added, as well as pastries and baked goods like cakes, cookies and doughnuts. Try to steer clear of what the researchers call “industrial desserts,” which they defined as puddings, custards and other desserts that are not homemade. Eat white meat like chicken or turkey without the skin instead of red meat or processed meats like sausages."

Bix said...

Being at risk for cardiovascular disease (CVD) is not the same as being diagnosed with cardiovascular disease. Even if the participants eating the Mediterranean diet DID have CVD, which we were told they didn't, why did their disease progress to a major heart event? At the same rate as those in the control group! (Table 3.)

In this study, the Mediterranean diet did not reduce risk for heart attack, death from cardiovascular causes, or death from any cause. Please see Table 3.

As you know, I am not a vegan.

Bix said...

This study was published in the New England Journal of Medicine.

The former editor-in-chief of The New England Journal of Medicine, Dr. Marcia Angell, said in 2009:

"It is simply no longer possible to believe much of the clinical research that is published, or to rely on the judgment of trusted physicians or authoritative medical guidelines. I take no pleasure in this conclusion, which I reached slowly and reluctantly over my two decades as an editor of The New England Journal of Medicine."

Angela and Melinda said...

I do remember vividly that comment by the NEJM editor and have cited it often. Thanks for bringing it up again, Bix, so now I have the correct quote!

Excuse me for confusing you with a vegan--I thought you were. Mea culpa.

If no published research can be trusted, how does one decide whether to believe Esselstyn (sp?), Ornish, Barnard, Campbell,the authors of the NEJM study, or any of the others? They're all making a profit, either from their books or from advancing up the academic ladder (publish or perish).

Looking at the Mediterranean foodway historically, it would have originated back in ancient times or even prehistoric times, when few people travelled and folks ate what they had available. So the coastal areas around the Medit. ate fish, veggies, lots of fruit, olives, foraged greens, etc. Nowadays, food supplies are far more diverse, so really only anthropologists can reconstruct what a foodway originally was. Same problem with the Paleo diet, which I think people completely miscontrue nowadays (not that it's how I eat, but I know some pretty hardcore Paleo folks who brook no criticism of their diet).