Skin carotenoid status (SCS) measured by resonance Raman spectroscopy (RRS) may serve as an emerging alternative measurement for dietary carotenoid, fruit and vegetable (FV) intake although its application had not been assessed in a middle-aged and older population in Asia. This cross-sectional study aims to concurrently examine the use of SCS and plasma carotenoids to measure FV and carotenoid intake in a middle-aged and older population, taking into consideration potential socio-demographic and nutritional confounders. The study recruited 103 middle-aged and older adults (mean age: 58 years) in Singapore. Dietary carotenoids and FV, plasma carotenoid concentration and SCS were measured using 3-d food records, HPLC and a biophotonic scanner which utilised RRS, respectively. Adjusted for statistically defined socio-demographic covariates sex, age, BMI, prescription medication and cigarette smoking, plasma carotenoids and SCS showed positive associations with dietary total carotenoids (β plasma: 0·020 (95 % CI 0·000, 0·040) µmol/l/mg, P = 0·05; β skin: 265 (95 % CI 23, 506) arbitrary units/mg, P = 0·03) and FV (β plasma: 0·076 (95 % CI 0·021, 0·132) µmol/l per FV serving, P = 0·008; β skin: 1036 (95 % CI 363, 1708) arbitrary units/FV serving, P = 0·003). The associations of SCS with dietary carotenoid and FV intake were null with the inclusion of dietary PUFA, fibre and vitamin C as nutritional covariates (P > 0·05). This suggests a potential influence of these nutritional factors on carotenoid circulation and deposition in the skin. In conclusion, SCS, similar to plasma carotenoids, may serve as a biomarker for both dietary carotenoid and FV intake in a middle-aged and older Singaporean population.

A number of studies have examined dietary patterns in various populations. However, to study to what extent such patterns capture meaningful differences in consumption of foods is of interest. In the present study, we identified important dietary patterns in Norwegian postmenopausal women (age 50–69 years, n 361), and evaluated these patterns by examining their associations with plasma carotenoids. Diet was assessed by a 253-item FFQ. These 253 food items were categorised into forty-six food groups, and dietary patterns were identified using principal component analysis. We used the partial correlation coefficient (radj) and multiple linear regression analysis to examine the associations between the dietary patterns and the plasma carotenoids α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene and zeaxanthin. Overall, four dietary patterns were identified: the ‘Western’; ‘Vegetarian’; ‘Continental’; ‘High-protein’. The ‘Western’ dietary pattern scores were significantly inversely correlated with plasma lutein, zeaxanthin, lycopene and total carotenoids ( − 0·25 ≤ radj≤ − 0·13). The ‘Vegetarian’ dietary pattern scores were significantly positively correlated with all the plasma carotenoids (0·15 ≤ radj≤ 0·24). The ‘Continental’ dietary pattern scores were significantly inversely correlated with plasma lutein and α-carotene (radj= − 0·13). No significant association between the ‘High-protein’ dietary pattern scores and the plasma carotenoids was found. In conclusion, the healthy dietary pattern, the ‘Vegetarian’ pattern, is associated with a more favourable profile of the plasma carotenoids than our unhealthy dietary patterns, the ‘Western’ and ‘Continental’ patterns.

Since collection of 24 h urine samples is very time consuming and difficult to obtain, epidemiological studies typically only obtain spot urine samples. The aim of the present study was to evaluate whether flavonoids and enterolactone in overnight urine could substitute flavonoids and enterolactone in 24 h urine as an alternative and more feasible biomarker of fruit, vegetable and beverage intake. A total of 191 individuals in the Inter99 cohort in Denmark completed the validation study. Concentrations of nine urinary flavonoid aglycones (quercetin, isorhamnetin, tamarixetin, kaempferol, hesperetin, naringenin, eriodictyol, phloretin and apigenin) and enterolactone were determined in overnight and 24 h urine samples, and their validity as biomarkers of fruit, vegetable and beverage intake was evaluated in relation to two independent reference methods (Inter99 FFQ data and plasma carotenoids) by using the method of triads. The intakes of fruit, juice, vegetables and tea reported in the FFQ were reflected by the flavonoid biomarker both in overnight and 24 h urine samples. Validity coefficients for the flavonoid biomarker in overnight urine ranged from 0·39 to 0·49, while the corresponding validity coefficients for the biomarker in 24 h urine ranged from 0·43 to 0·66. Although the validity coefficients were lower for overnight urine than for the 24 h urine flavonoid biomarker, they were still of acceptable magnitude. In conclusion, the results indicate that flavonoids and enterolactone in overnight urine samples may be used as a more feasible biomarker than 24 h urine for the assessment and validation of fruit, juice, vegetable and tea intakes in epidemiological studies.