A systematic review update of athletes' nutrition knowledge and association with dietary intake.

Athletes' dietary intakes sometimes do not meet sports nutrition guidelines. Nutrition knowledge (NK) is one factor that may influence dietary intake, but NK measurement tools are often outdated or unvalidated, and results regarding athletes' NK are equivocal. The aims of this systematic review were to update previous systematic reviews by examining athletes' NK and to assess the relationship between athletes' general NK, sport NK and dietary intake. MEDLINE, CINAHL, Scopus, SPORTDiscus, Web of Science and Cochrane were searched for studies published between November 2015 and November 2020 that provided a quantitative measure of NK and described the NK tool used. Twenty-eight studies were included, study quality was assessed using JBI checklists and data on NK score and diet intake was extracted. Eight studies utilised validated, up-to-date NK measurement tools. Mean general and sport NK% scores varied between 40·2% ± 12·4 and 70 % ± 9. Mean protein and carbohydrate consumption was 1·1-3·4 g/kg.bw/d and 2·4-4·6 g/kg.bw/d, respectively. Weak-to-moderate, positive associations were found between NK and positive dietary behaviours. Due to a wide variety of NK measurement tools used, it is difficult to synthesise results to determine overall NK in athletes. Overall, there appears to be a low standard of knowledge. Quality of measurement tools for NK has improved but remains an issue. Future studies should use relevant, current validated NK tools or validate tools in their study population. More research is needed into the relationship between NK and other modifiable factors influencing dietary intake.