Concurrent validity of skin carotenoid status as a concentration biomarker of vegetable and fruit intake compared to multiple 24-h recalls and plasma carotenoid concentrations across one year: a cohort study

Table 2 Correlation coefficients^a and 95% confidence intervals of skin carotenoids, plasma carotenoids, and self-reported vegetable and fruit intake at baseline and across one year

	Total plasma carotenoids (μM/L)^d		VF (cup eq.)^b		Dietary carotenoids (mg/d)^b
	Baseline	Year	Baseline	Year	Baseline	Year
Reflection spectroscopy^c	0.70*** (0.53, 0.82)	0.65*** (0.46, 0.79)	0.27 (0.00, 0.51)	0.37** (0.10, 0.58)	0.10 (−0.18, 0.36)	0.24 (− 0.03, 0.48)
Resonance Raman spectroscopy^c	0.77*** (0.63, 0.86)	0.69*** (0.52, 0.81)	0.33* (0.06, 0.55)	0.37** (0.11, 0.59)	0.27 (0.00, 0.51)	0.29* (0.02, 0.52)
Total plasma carotenoids (μM/L)^d			0.27 (0.00, 0.51)	0.36** (0.10, 0.58)	0.24 (−0.03, 0.48)	0.33* (0.06, 0.55)
VF (cup eq.)^b					0.56*** (0.34, 0.72)	0.51*** (0.27, 0.69)

^aPairwise correlations at baseline were estimated using Pearson coefficients and full-year between-individual correlations were estimated using a mixed model
^bMeasured by the Automated Self-Administered 24-Hour (ASA24) Dietary Assessment Tool at 36 times over the year
^cMeasured at 12 times over the year
^dMeasured at 4 times over the year
Analyzed carotenoids were α- and β-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin
*Significant at P < 0.05
**Significant at P < 0.01
***Significant at P < 0.001

ISSN: 1475-2891