By Michael Yudell
Results of an important study out of Spain published last week in the prestigious New England Journal of Medicine suggests that a "Mediterranean Diet" supplemented by additional extra-virgin olive oil or nuts significantly lowered the risk of having a heart attack, stroke, or dying from heart disease.
Don't get me wrong. This is a valuable study, the largest of its kind to date. And it confirms earlier research showing that the Mediterranean Diet — a high intake of olive oil, nuts, vegetables, and cereals; moderate consumption of fish and chicken; low consumption of dairy, red and processed meats, and sweets; and drinking wine in moderation with meals — can be effective in moderating cardiovascular risks.
Here's what the researchers in Barcelona did: they enrolled 7,447 people between the ages of 55 and 80 with no history of heart disease but at risk for it. Risks included either type 2 diabetes or at least three of the following major risk factors: smoking, hypertension, elevated or low low-density lipoprotein cholesterol levels, overweight (or obesity), and a family history of premature coronary artery disease.
Participants were then randomly assigned into one of three dietary intervention groups: a Mediterranean Diet supplemented with extra-virgin olive oil (participants were given 1 liter of oil per week), a Mediterranean Diet supplemented with nuts (participants were given 15 grams of walnuts, 7.5 grams of hazelnuts, and 7.5 grams of almonds per week), or a low-fat diet (participants were not given any food supplements). The recommended low-fat diet called for at least three servings per day each of lean fish and seafood, low-fat dairy products, breads, potatoes, pastas and rice, fruits, and vegetables. The consumption of vegetable oils (including olive oil), sweets, nuts and fried snacks, red and processed meats, visible fat in meats and soups, fatty fish, spread fats, and sofrito were all discouraged.
Participants in the two Mediterranean Diet groups met quarterly with dietary screeners to determine adherence to their diets, while those in the low-fat group received yearly leaflets explaining how to stick to their diet. To evaluate adherence to the diets, Mediterranean dieters had their blood and urine tested for "biomarkers of compliance" —urine levels of hydroxytyrosol (olive oil byproduct) and plasma levels of alpha-linolenic acid (a nut byproduct). No such biomarkers were measured in the low-fat group.
Three years into the study the investigators realized, however, that the disparity in oversight between the Mediterranean and the low-fat groups was potentially biasing the study against the low-fat dieters. Thereafter, the study was changed to offer the same quarterly meetings and advice that the Mediterranean dieters had been getting.
The trial was stopped early, after nearly five years, when researchers found that the Mediterranean Dieters, supplemented with either extra-virgin olive oil or nuts, already had a "a substantial reduction in the risk of major cardiovascular events" (about 30%) that researchers believed was a result of their dietary changes.
So far so good, right?
Well, mostly. Study results seem to confirm what smaller studies have already shown —that there is a likely benefit to cardiovascular health from the Mediterranean Diet.
But the study's shortcomings and the media's promotion of its findings as an amazing new tool in the arsenal against heart disease should give us pause.
Here are a few important issues to consider (some of which the researchers acknowledge):
Another issue to consider, as Larry Husten at Forbes.com points out, is whether "we've made this issue far too complex." "Instead of getting lost in the weeds hunting for clues to a metabolic mystery," Husten posits, "perhaps we should think about diet more simply as a public health issue. Make healthy foods available to people. If people substitute walnuts or olive oil for a candy bar or French fries then they will benefit."
One final thought: the role that the media plays in the popularization of "life changing" studies, like the Mediterranean Diet study, is often counterproductive. When a study like this is published and unleashes a media torrent, the public may uncritically embrace the findings, only to eventually find out that the headlines did not match the research. When this happens, the public can grow weary, even cynical, of such claims.
Is there a better approach for translating scientific studies for popular consumption?
It may as yet be premature to invest your kid's college savings in Don's House O'Nuts or in olive oil futures. But science is a process, moving forward in fits and starts as it expands our understanding of the world around us and of ourselves. We don't need to oversell scientific discoveries — they shouldn't be sensationalized. Science is cool enough, and in the case of the Mediterranean Diet, tasty enough to withstand the rigors of discovery without the hype.