Association between health literacy and dietary intake of sugar, fat and salt: a systematic review

Objectives: To collect and summarise all current data from observational studies, generating evidence of the association between health literacy (HL) and the dietary intake of sugar, salt and fat, to analyse intervention studies on the promotion of an appropriate dietary intake of the above-mentioned nutrients and to ascertain whether HL moderates the efficacy of such intervention. Design: A systematic literature search of analytical observational studies on the association between HL and dietary intake of sugar, salt and fat was performed in Medline and Scopus databases. Intervention studies on the promotion of healthy nutrition that concerned the intake of sugar, salt and fat were also assessed. Results: Of the eight observational studies included in this review, five investigated dietary intake of sugar, one focused on salt, one assessed sugar and salt and one analysed the fat intake. The results of the five studies assessing sugar were mixed: three found an association between low levels of HL and a high sugar intake, one found this association only for boys and two found no evidence of any association. The two studies assessing salt and the one assessing fat found no evidence of any association with HL. One intervention study on the sugar intake concluded that HL was not a significant moderator of the intervention's effectiveness. Conclusion: No evidence of any association between HL and salt and fat intake emerged, while for sugar, the results are mixed. More work is needed to better understand the moderating effects of HL on the outcomes of health promotion interventions.