Shahabeddin Rezaei1,2, Ahmed Abdulahi Abdurahman3, Maryam Mahmoudi1,4,5. 1. Department of Cellular and Molecular Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. 2. Students' Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran. 3. Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences International Campus, Tehran, Iran. 4. Pediatric Gastroenterology and Hepatology Research Center, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran. 5. Dietitians and Nutrition Experts Team (DiNET), Universal Scientific Education and Research Network (USERN), Tehran, Iran.
Dear Editor,We have recently read with great interest the article, “Tumor cells growth and survival time with the ketogenic diet (KD) in animal models: A systematic review” that was written by Khodadadi et al.[1] The topic of the study is interesting and the authors tried to shed light on the probable beneficial effect of KD in cancer through retrieving animal studies. We would like to correct some aspects of this study. First, we would like to correct the definition of KetoCal in this paper. The authors stated that KetoCal is a new KD; however, it is incorrect. KetoCal is one KD formula that was designed to ease the implementation of the KD.[2] Historically, the KD has mainly four kinds namely classical KD, modified Atkins diet, medium-chain triglyceride diet, and low glycemic index treatment.[2] This formula has designed for classical KD.[2]In addition, the search strategy of this study is not well established. First, the authors merely used the abbreviation of KD in their search strategy. Therefore, they missed the articles that did not use the abbreviation form of KD. Second, the authors did not use MeSH terms in PubMed search. When we use MeSH terms, PubMed searches pertinent papers.[3] Therefore, several relevant papers were ignored in this study. Third, their search result in Scopus yielded less publication than their search in PubMed, and it is not rational. Scopus is the most comprehensive literature database.[4] Consequently, the result of Scopus should be more than PubMed. We searched Scopus with the keywords that were mentioned in the paper namely “KD” and “Neoplasm” or “cancer” or “tumor” and limited our result to 2014. Our search result was 8,154 citations. While in the Khodadadi et al. study, they limited their search to November 2015 and the result was 25.Finally, the study selection of this study has some errors. First, in the flowchart of study selection, according to the preferred reporting items for systematic reviews and meta-analyses,[5] duplicates should be removed before the screening; however, in this review, the authors removed duplicates after screening which is mistaken. Second, the authors illustrated that they included 268 papers. After discarding 107 unrelated citations, they indicated that 155 citations remained; however, 161 citations should remain. Moreover, the numbers of the next steps are incorrect.