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June 16, 2010
For years, the so-called Mediterranean diet has been promoted as a heart-healthy way of eating. Following a Mediterranean diet generally means consuming whole grains, fish, olive oil, nuts and seeds, and fruits and vegetables in abundance; dairy, eggs, and wine in low to moderate amounts; and red meat and concentrated sugars in low amounts. It is based on typical food consumption patterns in parts of the Mediterranean region — particularly areas of Greece — studied in the early 1960s, and it has been found in studies to be associated with a lower rate of heart disease. Studies have also shown it to be beneficial for diabetes control.
Now, however, a competitor has emerged: the Southern European Atlantic Diet, or SEAD. This diet refers to a style of eating common in northern Portugal and northwestern Spain, on the Atlantic coast. As reported in a Reuters article, researchers noticed that residents of this region experienced a low rate of death from heart disease and undertook a study to find out how big of a role the regional diet played in this phenomenon. The subjects were 820 people who had been hospitalized for a heart attack, as well as 2,196 people from the same geographic area who were randomly selected for the study. All participants filled out questionnaires focusing on their food habits in the previous year. Based on his responses, each participant was then rated as above or below the median consumption level in nine areas believed to constitute the pillars of the SEAD: cod fish, all other fresh fish, red meat and pork, dairy, legumes and vegetables, vegetable soup, potatoes, whole-grain bread, and wine. For each food category in which a participant had below-median consumption he was given a “zero,” and for each category with above-median consumption, a “one.” Each participant thus received a score on a nine-point scale reflecting adherence to the SEAD.
The researchers discovered that on average, a one-point increase on the SEAD scale was associated with a 10% reduction in heart attack risk. The heart attack risk of the top 25% of participants on the SEAD scale was 33% lower than the risk of the bottom 25%.
However, the researchers discovered that above-median consumption of two of their nine SEAD components — red meat and pork, and potatoes — increased rather than decreased the risk of heart attack. By reversing the scoring on these two categories — that is, giving a “zero” for above-median consumption and a “one” for below-median consumption — to create a new scale, they found an even greater dietary benefit. The top 25% of participants on this new scale had a heart attack risk 60% lower than that of the bottom 25% of participants.
This second part of the study indicates that the traditional SEAD is not necessarily the best diet for cardiovascular protection. Lower consumption of red meat and potatoes may in fact be responsible for the added benefit seen in the modified SEAD, but the study has several weaknesses that mean it may not. For example, other factors that were not measured — such as overall health-consciousness or following traditional ways of living — could have affected both the diet and the heart attack risk of participants.
It should also be emphasized that participants were scored only on whether their consumption in each food category was above or below the median. This means that any nonlinear effect — such as a risk of heart attack that increases both with very high or very low consumption of a food category — would not have come to light in the study, so no food category can be categorized as helpful in very large amounts or as so harmful that it should be heavily reduced or eliminated from the diet.
But if the modified version of the SEAD does, in fact, offer substantial protection against heart attacks, does it represent anything new in dietary advice? Could a lower overall glycemic index from the elimination of potatoes be partially responsible for the benefit? Do you see an overall pattern to be followed in both the Mediterranean diet and the SEAD (regular or modified)? Would you find either of these diets appetizing or easy to stick to? Leave a comment below!
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