The Mediterranean diet has fascinated the public since it became famous more than a decade ago, and researchers continue to study it, hoping to understand the science behind it. For wine drinkers, of course, there's an added benefit—their favorite beverage is considered a lynchpin of a healthy lifestyle.
Still, just because the diet is popular doesn't mean there's universal agreement on whether it works or even how it works. Two new studies have only added to the confusion. A meta-analysis of Mediterranean diet research, published online in the British Medical Journal, shows a link between following the diet and a lower risk of major diseases and an early death. At the same time, another study argues that, at least when it comes to heart disease, maybe it's the wine alone, and not the diet, that promotes health.
First publicized by an American doctor stationed in Italy during World War II, the diet became famous after a Harvard study was published in 1995. The traditional diet, native to Mediterranean areas such as Italy, Greece and southern France, is characterized by a high intake of fresh fruit, vegetables, grains, nuts, cereals and fish and a low intake of meats, especially red, with olive oil as the principal source of fat. The moderate and daily intake of wine, usually red, is encouraged during meals.
Past studies have found a positive association between sticking closely to the eating regimen and increasing life expectancy, as well as lowering the risk of debilitating diseases such as type 2 diabetes and Alzheimer's disease.
For the British Medical Journal study, clinical nutrition researchers at the University of Florence in Italy wanted to see if a "defined Mediterranean diet" could work as an "effective preventative tool" for reducing the risk of major diseases. They examined the results of 12 international studies on the Mediterranean diet and its potential impact on the rates of heart disease, cancer, Alzheimer's disease and Parkinson's disease, in various populations.
Six of the analyzed studies dealt with populations living in countries with borders on the Mediterranean Sea. The other six were conducted in Australia, northern European nations or the United States. The meta-analysis collectively included data on more than 1.5 million participants.
The examined studies were far from uniform in rating participant adherence to the Mediterranean diet. For example, some classified chicken, pork and beef as one category of meat, while others separated out differing types of animal flesh. Nonetheless, all studies used a 9-point scoring system where the subject is given one point for closely following a single aspect of the diet while others are assigned a zero if they do not. The numbers are added at the end and those with a score of seven or more are considered to closely follow the diet.
During the followup periods of the various studies, which ranged from three to 18 years, 33,576 deaths were recorded. Tens of thousands of non-fatal cases of heart disease, cancer, Alzheimer's and Parkinson's were also reported. The Florence researchers compared these results against participants' Mediterranean diet scores and found that those who ranked seven points or higher showed a 13 percent lower risk of Alzheimer's and Parkinson's, a 9 percent lower risk of fatal heart disease and a 6 percent lower risk of cancer, compared to those who had low adherence scores. There was a 9 percent lower risk of early death from any cause.
According to lead researcher Francesco Sofi, one limitation to the study is the lack of a solid definition of moderate alcohol intake across all the studies. Nonetheless, he believes that wine is inextricable from the benefits seen in the studies. "Wine, especially red wine, is a key component of the dietary score for estimating the adherence to Mediterranean diet," he said.
But a study published in the September-October issue of the American Journal of Health Promotion reaches a slightly different conclusion: wine may be more important than the Mediterranean diet itself. Researchers in the department of preventive medicine and public health at the University of Navarra in Spain examined 3,825 seniors who were at risk for heart disease but had no history of heart disease yet.
For this study, the scientists wished to test the idea that wine drinkers enjoy a stronger protection against heart disease, in part, because of their eating habits, in this case, the Mediterranean diet. Furthermore, they wrote, "the hypothesis that wine intake provides healthier cardiovascular effects than alcohol from other sources is controversial."
In other words, should doctors tell patients at risk of heart disease to switch to wine or to strongly adhere to a Mediterranean diet? In order to answer this question, the researchers recruited volunteers who all had similar scores on the Mediterranean diet (in this case around 4 points on an 8-point scale). They theorized that if drinkers of various types of alcoholic beverages showed a similar risk of heart disease, then it's the diet that helps, not the type of drink.
Instead, according to lead author Francisco de Asis Carmona-Torre, the results suggest that wine drinkers who have an average adherence to the Mediterranean diet still display a lower risk of cardiovascular disease than drinkers of other alcoholic beverages with similar eating habits. This observation leads him to conclude that "it is very likely that wine itself is the protective element," and not the Mediterranean diet as a whole.