Modified Mediterranean diet and survival

Editor—Cereda et al argue that lipid profile and blood pressure at baseline should be controlled for and that our study does not necessarily show a benefit of the Mediterranean diet (modified or not) among younger individuals. Blood lipids and blood pressure are determined by diet, alcohol intake, and physical activity, which have been evaluated in our study, as well as by poorly identified genetic factors. Blood lipids and blood pressure are therefore more likely to act as mediators of the effects of the evaluated factors rather than as confounders. Mediators, in contrast with confounders, should not be controlled for in the statistical analysis.¹ Suggestive evidence exists that the Mediterranean diet may also be beneficial among younger adults,² but we agree that this deserves further investigation.

Vos disagrees with the title “modified Mediterranean diet” and also cites references indicating that the benefit from polyunsaturated lipids may be limited to increased intake of omega 3 fatty acids and be unrelated to omega 6 fatty acids. With respect to his first point, the intention was to indicate that the diet we studied, although not strictly Mediterranean as characterised by the consumption of olive oil, still focuses on avoidance of saturated lipids, as traditionally done in the Mediterranean region. With respect to his second point, evidence exists that supports an important role of omega 3 fatty acids, but there is also evidence that vegetable lipids in general may have beneficial effects.³ As an aside, it is worth clarifying that the traditional Cretan diet, although strongly dependent on high olive oil intake, was never centred on fish consumption. In any case, epidemiological evidence provides the empirical background on the basis of which aetiological hypotheses have to be judged and perhaps modified.