Letter to the Editor
Recently, we read with great interest the article by Si et al. (2017). The authors performed a meta-analysis of 27 observational studies to explore the association between dietary patterns and risk of endometrial cancer (EC). It is an interesting study. Nevertheless, we would like to raise several concerns related to this paper.
Traditionally, the association of single nutrients or foods with EC has been widely studied. Because foods and nutrients are never eaten in isolation and their effects are likely to be interacted, a main limitation of this method is the little correlations between intakes of various nutrients or food items. To resolve the limitations of this method, the studies of dietary patterns emerged, which comprehensively consider the combined effects of foods or nutrients on the etiology of disease (Hou et al., 2015). Our search identified that there are about 73 studies investigating the association of single food items and risk of EC, while, there are only five studies (McCann et al., 2001; Dalvi et al., 2007; Biel et al., 2011; Bravi et al., 2015; Canchola et al., 2015) exploring the association of dietary patterns derived by factor analysis or principal component analysis with EC. The meta-analysis by Si et al. (2017) considered single food items as dietary pattern. For instance, they considered meat intake in the studies by Genkinger et al. (2012), Shu et al. (1993), and Arem et al. (2013) as western dietary pattern and combined the results of these studies with the results of the studies by McCann et al. (2001) and Dalvi et al. (2007), which examined the association of a western pattern characterized by a higher intake of meats, sweets and desserts, soft drinks, refined grains, high-fat dairy products, and lower loading of fruits, vegetables, and dietary fibers with the risk of EC. It is obvious that meat intake is only one of the components of a western pattern and could not be considered as a western dietary pattern. Similar method was followed for healthy dietary pattern in this meta-analysis, which is not methodologically correct. Thus, we believe that bias is introduced to the results of the study by Si et al. (2017) because of an inappropriate methodology.
In summary, the findings of the study by Si et al. (2017) should be interpreted with caution. It would be valuable if the authors could provide a new, more accurate estimation of the pooled risk estimate after taking into account this limitation.
Conflicts of interest
There are no conflicts of interest.
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