The Mediterranean Diet vs. a Completely Plant-Based Diet
Written by: Michael Greger M.D. FACLM on January 5th, 2017
Recent studies have shown that higher Mediterranean diet adherence scores are associated with a significant reduction of the risk of death, heart disease, cancer, and brain disease. The problem with such population studies is that people who eat healthier may also live healthier, and so how do we know it’s their diet? I explore this question in The Mediterranean Diet or a Whole Food Plant-Based Diet?.
As the American Heart Association position states, “Before advising people to follow a Mediterranean diet, we need more studies to find out whether the diet itself or other lifestyle factors account for the lower deaths from heart disease.” How do you do that? There are ways you can control for obvious things like smoking and exercise—which many of the studies did—but ideally you’d do an interventional trial, the gold standard of nutritional science. You change people’s diets while trying to keep everything else the same and see what happens.
We got that kind of trial 20 years ago with the famous Lyon Diet Heart Study where about 600 folks who had just had their first heart attack were randomized into two groups. The control group received no dietary advice, apart whatever their doctors were telling them, while the experimental group was told to eat more of a Mediterranean-type diet, supplemented with a canola-oil based spread to give them the plant-based omega-3’s they’d normally be getting from weeds and walnuts if they actually lived on a Greek isle in the 1950’s.
The Mediterranean diet group did end up taking some of the dietary advice to heart. They ate more bread, more fruit, less deli meat, less meat in general, and less butter and cream; other than that, no significant changes in diet were reported in terms of wine, olive oil, or fish consumption. So, they ate less saturated fat and cholesterol, more plant-based omega 3’s, but didn’t undergo huge dietary changes. Even so, at the end of about four years, 44 individuals from the control group had a second heart attack, either fatal or nonfatal, but only 14 suffered another attack in the group that changed their diet. So they went from having a 4% chance of having a heart attack every year down to 1%.
A cynic might say that while there was less death and disease, the Mediterranean diet continued to feed their heart disease, so much so that 14 of them suffered new heart attacks while on the diet. Yes, their disease progressed, but a lot less than the regular diet group (about four times less). But what if there was a diet that could stop or even reverse heart disease?
Dr. Caldwell Esselstyn and colleagues at the Cleveland Clinic recently published a case series of 198 consecutive patients with cardiovascular disease counseled to switch to a diet composed entirely of whole plant foods. Of the 198, 177 stuck to the diet, whereas the other 21 fell off the wagon, setting up kind of a natural experiment. What happened to the 21? This was such a sick group of patients that more than half suffered from either a fatal heart attack or needed angioplasty or a heart transplant. In that same time period of about four years, of the 177 that stuck to the plant-based diet, only one had a major event as a result of worsening disease. As Dean Ornish noted in his response to the latest trial, “a Mediterranean diet is better than what most people are consuming”…but even better may be a diet based on whole plant foods.
Dr. Esselstyn’s was not a randomized trial, so it can’t be directly compared to the Lyon study, and it included very determined patients. Not everyone is willing to dramatically change their diets, even if it may literally be a matter of life or death. In which case, rather than doing nothing, eating a more Mediterranean-type diet may cut risk for heart attack survivors by about two-thirds. Cutting 99% of risk would be better if Esselstyn’s results were replicated in a controlled trial, but even a 70% drop in risk could save tens of thousands of lives every year.