Effects of Ramadan fasting on athletes' hematological indices: a systematic review.

OBJECTIVE: To evaluate the effects of Ramadan fasting on hematological data in athletes through a systematic appraisal of the literature. DESIGN: Systematic review Data sources: The entire content of two databases, PubMed/MEDLINE and Web of Science Eligibility criteria for selecting studies: Ramadanrelated measurements of any hematological indices in athletes were considered. Both single-group pre-post with and without a control group studies conducted in athletes and published in English language before December 31, 2018 were included. Study appraisal: The methodological quality of the studies identified was assessed using 'QualSyst'. RESULTS: Of nine selected articles, eight were of moderate quality and only one was of strong quality. The main problem to date has been a lack of appropriate controls. Compared to before Ramadan, hematocrit and hemoglobin values increased in three studies, decreased in one study and did not change in one study during Ramadan fasting. Another study reported increased hematocrit and a puzzling decrease of hemoglobin during as compared to before Ramadan fasting. In most studies, blood platelet counts and the limited number of immune function used to date remainedunchanged. CONCLUSIONS: All reported changes in hematological indices remained within the normal reference range of the laboratory. Therefore, regular training can continue safely during Ramadan fasting from a hematological view point.