Association Between Fruit and Vegetable Intake and Skin Carotenoid Levels Among Japanese Adults in the Workplace

Background/Objectives: Skin carotenoid measurements have been proposed as an indicator to reflect of fruit and vegetable intake, but evidence from occupational settings remains limited. The primary aim of this study was to assess the association between fruit and vegetable intake and skin carotenoid levels in the workplace. The secondary aim was to examine the association of skin carotenoid levels with blood glucose levels and blood pressure (BP). Methods: This cross-sectional study included Japanese workers aged ≥20 years between 2022 and 2023. Skin carotenoid levels were measured, dietary intake was assessed using self-administered questionnaires, and data from workplace health check-up records were collected. Multiple regression analysis was conducted to examine the association between skin carotenoid levels and fruit and vegetable intake in 210 participants. Associations between skin carotenoid levels and log-transformed glycated haemoglobin (HbA1c), fasting blood glucose (FBG), systolic BP, and diastolic BP levels were examined in 162, 158, and 183 participants, respectively. Results: Skin carotenoid levels were positively associated with the number of vegetable dishes consumed and the frequency of fruit intake. A slight positive association was observed with HbA1c levels (partial regression coefficient = 0.00012), whereas no associations were found with FBG or BP. Conclusions: Skin carotenoid levels reflect self-reported fruit and vegetable intake, supporting their potential use as a non-invasive dietary assessment tool in workplace nutrition education. However, the associations observed with HbA1c were very small and of limited clinical significance, and the results should be interpreted with caution.