Reply to X Chen et al

Abstract

We thank Chen et al. for their interest in reading our work entitled “Effects of a Paleolithic Diet on Cardiovascular Disease Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” In that study (1), we evaluated the effects of a Paleolithic diet on cardiovascular disease risk factors using data from randomized controlled trials. However, Chen et al. raised some questions that must be addressed. According to their classification regarding possible questions, we answer those questions in the same order accordingly: Discrepancies in effect sizes reported: In the study of Irish et al. (2), only the baseline data, but not after-intervention data, were reported in Table 1. Only the percentage change in the mean was reported in the Result section, meaning that this percentage cannot be used to calculate the SE. Therefore, data on C-reactive protein were extracted from Figure 5E in that article using Plot Digitizer (http://plotdigitizer.sourceforge.net/). This kind of figure-based estimation is a routine procedure to derive the means and their variations. In all included studies in our meta-analysis, the unit of lipids was mmol/L except for the study of Masharani et al. (3) and the unit conversion from mg/dL to mmol/L was performed for this study. Therefore, the correct unit of lipids is mmol/L, whereas unfortunately it has been reported in mg/dL for lipid markers. The effect size of −0.20 mmol/L for triglycerides is correct. However, the findings from reanalysis did not tangibly change from those reported in the article [weighted mean difference (WMD) = −0.22 mmol/L; 95% CI: −0.43, −0.02 mmol/L; P = 0.031 compared with WMD = −0.24 mmol/L; 95% CI: −0.46, −0.01 mmol/L; P = 0.037] (Figure 4B). We thank Chen et al. for their precise point. As observed in Figure 4B, we used a mean difference of −0.14 for the study of Genoni et al. (4). In fact, the effect size of −0.41, which is seen in Table 1, was written by mistake. Unfortunately, this is a typing error in Table 1; however, the effect size used for the meta-analysis is right. and e) It can be seen in Figure 2C (BMI) that we used an effect size of −1.8 from the study of Mellberg et al. (5) and −0.8 from the study of Boers et al. (6), but these were swapped by mistake (−0.8 for Mellberg et al.’s study and −1.8 for Boers et al.’s study in Table 1); unfortunately this is a typing error in Table 1. In fact the effect sizes reported in Figure 2C are righ