Mediterranean Diet Inversely Associated With the Incidence of Metabolic Syndrome: the SUN Prospective Cohort: Response to Tortosa et al.

We read with interest the article of Tortosa et al. (1) describing an inverse association between adherence to a Mediterranean dietary pattern and the cumulative incidence of metabolic syndrome in a cohort study involving 2,563 Spanish university graduates followed prospectively for 6 years. This study adds to the mounting epidemiological evidence indicating that adherence to a healthy lifestyle, including healthy dietary patterns, is associated with reduced incidence and prevalence of metabolic syndrome (2,3). The probability of participants with higher adherence (score 6-9) having metabolic syndrome was 80% less than that of participants with poor adherence (score 0–2). However, there are some inconsistencies in Table 1 (1) regarding the authors’ statement that participants with the highest score had lower levels of all components of the syndrome after 6 years of follow-up except for plasma glucose. This is incorrect because both systolic and diastolic blood pressure were also higher in these participants. Ironically, the only value that was significantly different across participants was waist circumference; within a 0.5-cm difference seems to lie all the significance of the study. It seems surprising that these small differences lead to an odds ratio of 0.2 (95% CI 0.06–0.63). One speculation may be that participants who were initially free of metabolic syndrome and risk factors were in fact very close to the cut-off values for diagnosis, so the small differences present at 6 years may have switched the balance. In practical terms, we are speaking of about 56 participants who developed the syndrome within the years of follow-up. Finally, epidemiological studies, both cross-sectional and prospective, are hypothesis-generating and do not prove a cause and effect relationship. However, there are some interventional studies, which the authors failed to mention, that clearly indicate that healthy food patterns, including a Mediterraneanstyle diet, resolve the metabolic syndrome in patients who had the syndrome at baseline in a proportion oscillating from 20 to 48% (4–6). This is good evidence for a role of healthy dietary patterns, which currently include the Mediterranean dietary pattern, in the prevention and treatment of the metabolic syndrome.