PROJECT SUMMARY Valid biomarkers of dietary fruit & vegetable intake can improve our understanding of the linkages between infants’ and toddlers’ dietary intakes and health outcomes. Eating a variety of fruits & vegetables provides energy, vitamins, minerals, and non-nutrient bioactives, and is associated with health benefits across the lifespan. Introducing fruits & vegetables in infancy and toddlerhood supports their nutritional requirements and lays the foundation for a long-term healthy dietary pattern. However, it is challenging for researchers and organizations to easily and accurately monitor the fruit & vegetable intake of young children. A new application of reflection spectroscopy may offer a non-invasive means by which infant and toddler carotenoid and fruit & vegetable intake can be easily monitored. The technology measures the amount of carotenoids in the skin. Carotenoids are fat-soluble pigments found in red, orange, yellow, and dark-green fruits & vegetables. Some carotenoids convey pro-vitamin A activity, and are associated with visual and cognitive function and reduced risks of adverse cardiovascular outcomes and some cancers. However, whether skin carotenoid measurement is as reliable as the currently gold-standard measure of population fruit & vegetable intake, plasma carotenoid concentrations, must be determined. Further, whether carotenoid intake in young children is associated with visual function, a key bioactivity hypothesized for this population, is unknown. The purpose of this project is to evaluate the validity of skin carotenoid measurement for estimation of infant and toddler fruit & vegetable and carotenoid intake. Infants and toddlers will be longitudinally observed across solid food introduction and the agreement between skin carotenoid measures with plasma carotenoids and reported carotenoid and fruit & vegetable intake will be assessed. In a second study, the association between skin carotenoid measurement with toddlers’ carotenoid concentrations, plasma carotenoids, and reported fruit & vegetable and carotenoid intake will be observed at baseline, and then toddlers will be randomized to consume a controlled dietary carotenoid intervention for 4 weeks to define the sensitivity of skin carotenoid measurement to detect changes in dietary carotenoid intake. In a third study, we will define the associations of carotenoid intake with visual function in toddlers and infants. This project will both define whether reflection spectroscopy is a valid measure of infant and toddler fruit & vegetable intake and carotenoid intake, and will yield fundamental knowledge of the determinants of and biological correlates of infant and toddler dietary carotenoid exposure.