Skin Carotenoid Status and Diet Quality in Professional Rugby League Players: An Exploratory Longitudinal Study

Background/Objectives: Diet quality is relevant to athlete health and recovery, yet practical methods for assessing dietary patterns in elite sporting environments remain limited. This exploratory study aimed to examine the relationship between skin carotenoid status and diet quality in male professional National Rugby League players. Methods: Skin carotenoids were assessed at three time points throughout the NRL season: pre-, mid-, and end-season. The Veggie Meter® was used to assess carotenoids alongside a single 24 h dietary recall at each time point. Dietary data for each player were scored using the Healthy Eating Index for Australian Adults 2013 (HEIFA-2013) to calculate a score out of 100. Correlations were explored via Pearson correlation coefficients, and linear mixed models were used to compare data over the season. Results: Correlations between carotenoid status and diet quality score varied across time points: pre-season, r = 0.297, 95% CI −0.094 to 0.608, p = 0.196; mid-season, r = 0.451, 95% CI 0.108 to 0.698, p = 0.012; and end-season, r = 0.335, 95% CI −0.036 to 0.625, p = 0.076. Mean carotenoid scores did not differ significantly across the season: 294 in pre-season (n = 27), 314 in mid-season (n = 30), and 318 in end-season (n = 29), p = 0.16. Mean HEIFA-2013 scores also did not differ significantly across the season: 66.4 in pre-season, 64.6 in mid-season, and 62.6 in end-season, p = 0.38. Conclusions: This exploratory study provides preliminary evidence that skin carotenoid status may reflect aspects of diet quality in elite NRL players, although associations varied across time points and only reached statistical significance at mid-season. Non-invasive tools such as the Veggie Meter® may complement traditional dietary assessment methods, although further validation is required in larger, adequately powered studies of elite athletes.