Tehran University of Medical Sciences Journal of Nutritional Sciences and Dietetics 6 1 2020 01 18 47 54 Mohammad Hozoori Qom University of Medical Sciences Korosh djafarian Clinical Nutrition Department, Nutrition and Diet Therapy College, Tehran University of Medical Sciences, Tehran, Iran. Zohreh Sheikhi-Zadeh Qom University of Medical Sciences Mohaddeseh Asafari MSc, Deputy of Food and Drug, Arak University of Medical Sciences, Arak, Iran Orcid ID: 0000-0002-2021-6226 2020 04 09 2021 01 18 Abstract: Objective: There is limited number of study on dietary supplements use in most gyms clubs. The aims of current study were to assess supplement intake in athletes who exercise regularly in gyms in the city of Qom, Iran, and to determine the knowledge, attitude, and practice regarding dietary supplement. Methods: We conducted a cross-sectional study among 300 athletes who were randomly selected from 18 sport clubs of Qom city between November 2015 and March 2016. A self-administered questionnaire containing 34 questions was used to evaluate the socio-demographic characteristic, knowledge, attitude, and practices of athletes on dietary supplements. Validity and reliability of questionnaire determined through panel of experts and Cronbach’s alpha (N=24, α=0.79) respectively. Results: Our results showed that 28% of women, and 62% of men had the history of supplement usage (42 percent of all participants). Male were more likely to take supplements than females (p<0.01). The results of knowledge questions showed that more than half of the questions (56.3%) were answered correctly. Although, coaches was the main source of information on dietary supplements (43%), but significant difference was shown between men and women. Conclusion: The results of this study were reported that nearly half (42%) of athletes used dietary supplement. The overall scores indicated that dietary supplements knowledge of these athletes is not enough for healthy decision making. The source of information and dietary supplement practices of athletes were strongly affected by gender. Keywords: Dietary Supplements, Knowledge, athlete, Coaches. https://jnsd.tums.ac.ir/index.php/jnsd/article/view/300 https://jnsd.tums.ac.ir/index.php/jnsd/article/download/300/246