Letter To The Journal.

The paper "Short-term Mediterranean Diet Improves Endurance Exercise Performance: A Randomized-Sequence Crossover Trial" (1), which was published in the Journal of the American College of Nutrition is based on the results of 11 individuals who each ran twice on a treadmill. The authors report that there was 6% decrease in the time required to run 5k after eating a Mediterranean diet for 4 days before the second run. The interpretation of the data is complicated by the small sample size and the fact that the results are highly skewed. The authors state that means and standard deviation of the two sets of data are "(27.09 ± 3.55 vs. 28.59 ± 3.21;  = 0.030)", thereby implying that the test is a comparison of the means. However, the p refers to the result for a paired t-test. The authors discuss the several limitations of this study, but these limitations focus on the diets. They do not discuss how the fact that the testing is not blind may affect the results. It is stated that "recreationally active" 20-60 tear olds were recruited for this study "from the general population in metropolitan St. Louis, MO". However, the runners tested had a tight range of run times (27.09 ± 3.55), age (28 ± 3), and BMI (24.6 ± 3.2). This hardly seems like a random sample of this group.