Table 1.

Description of the PICOS criteria used to define the research question

Parameter	Description
Population	Included: adults and children   Excluded: none
Intervention/correlation	Correlation with plasma or serum carotenoid levels
Comparison	Not applicable, because observational studies and correlations were reviewed, rather than interventions
Outcome	Resonance Raman spectroscopy–assessed skin carotenoids
Study design	Cross-sectional studies describing the correlation between skin and plasma or serum carotenoids