On the new Mediterranean Diet Study: Proceed with Caution

I’ve been reading about the excitement in the medical community over the results of the first sustained clinical study of the effects of switching to the much touted Mediterranean diet for those at high risk for cardiac disease.  You can read the results in detail at the the New England Journal of Medicine website (NEJM.org).  You’ll recall that this diet abounds in olive oil, nuts, beans, vegetables and fish.  Whether participants took statins, were diabetic, or hypertensive, or overweight, the results across the board showed a 30% reduction in heart attacks, stroke, and death.

The study, encompassing 7,447 people in Spain, employed two diet regimens:  the Mediterranean and a low fat diet.  Up to now, evidence for the efficacy of the Mediterranean diet has been inconclusive, while the low fat approach hasn’t been shown to be effective in previous studies, primarily because many people find it hard to stay with.

Unfortunately, appearance, as in so many things, may not be the reality, given the human tendency, even in the sciences, to make unwarranted associations; for example, while the medical establishment has pummeled cholesterol as the primary villain in cardiac disease and urged us to cut down on organic meats, the truth is that only about 20% of our total cholesterol derives from our food.  That helps explain why nearly half of those suffering heart attacks have low LDL levels.  Inflammation, not cholesterol, is more likely a primary instigator.

While olive oil, a staple of the Mediterranean diet, is widely believed to reduce inflammation, thus promoting a healthy heart, it actually impairs endothelial function like most oils and should be avoided.  I have to scratch my head sometimes at the absurdity of health authorities telling us to reduce saturated fat foods, then waxing enthusiastic about olive oil, which is 14% saturated fat!  Ironically, canola and flax seed oil are better for you because of their greater omega-3 content, though still to be avoided.  (See Vogel RA. Corretti MC. Plotnick GD. The postprandial effect of components of the Mediterranean diet on endothelial function. Journal of the American  College of Cardiology. 36(5):1455-60, 2000 Nov 1).

Behind the diet’s success lies its plethora of vegetable, fish, whole grains and, yes, red wine.  In any event, the new research doesn’t halt or reverse heart disease because it doesn’t limit oils. On the other hand, low fat diets (10 % max) do succeed when consistently followed. The problem is getting people to stick with a sharply reduced fat diet ( i. e., vegan), an admitted weakness in the just concluded study. Not incidentally, those on the low fat diet were, for a time, not given the ample support those on the Mediterranean diet enjoyed, which in my view suggests bias or pedestrian methodology from the very outset.

What’s more, the study’s low fat group consumption was a mere 37%, and not the 10% of truly low fat diets shown to prevent and reverse heart disease. It should be noted, as well, that many of the study’s proponents have ties to food interests, including the Spanish government.

But let’s look at the facts about the original Lyon Heart Study (1995), which utilized the Mediterranean diet, specifically Cretan version, for its research findings, launching near universal medical endorsement along with a tsunami of new cookbooks. Mortality rates from heart disease declined by 70% among those on the Cretan diet vs those on a normally prescribed diet for reducing coronary risk.

In retrospect, the facts are that the Lyon diet actually reduced total fat consumption from the 40% in the Cretan diet to 30% and limited dairy intake and meats, while emphasizing salads, vegetables and grains.

But then why did the Cretans enjoy a lower mortality rate, considering their higher fat in-take?  For one thing, they still ate a largely plant diet and worked very hard.  For another, the study found that canola oil with its high omega-3 fatty acids was a significant  factor, not olive oil, which has a low omega-3 content.  Omega-3 fatty acids reduce inflammation whereas omega-6 fatty acids can increase it.

However, what the media ignores is that by the end of the Lyon Diet Heart Study, nearly four years after its start, fully 25% of the subjects on the Mediterranean Diet had either died or undergone a cardiovascular event.

If you’re like me, you’ve grown tired of medical flip-flops.  In some circles, physicians like Dr. Walter Willett at Harvard’s school of Public Health have been promoting unlimited quantities of so called “good fats.” The truth is that fats play a leading role in fostering heart disease through weight gain. Saturated fat can mount up and is especially dangerous.  Olive oil is rich in the latter.  The clincher for me, at least, is the Vogel study I alluded to earlier.

The bottom line, as in so many areas of life, is to be wary of new enthusiasms in medicine that have their vogue, only to fade quickly–in part, because they’ve often proven dangerous. The Mediterranean diet goes right in its emphasis on whole grains, vegetables, and omega-3 fatty acids.  It goes wrong when we misuse it to overeat or
overload with fats of any kind.

A low fat diet at 10% of total calories combined with unrefined foods and low glycemic load remains the pathway to optimal digestive and coronary health. When adhered to, its potential to reverse heart disease has been demonstrated consistently, something the Mediterranean diet per se cannot claim.


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