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Context Dietary carotenoid intake is associated with vitamin A status and healthy visual and cognitive function in early life. To date, however, only limited population-level data on the concentrations of carotenoids in human milk or infant blood have been available to assess the dietary exposure of infants to carotenoids. Objective This systematic review seeks to define worldwide carotenoid concentrations in human milk and infant blood. Data Sources The PubMed, Embase, and Web of Science databases were searched for original research articles published before February 2021. Data Extraction Dietary carotenoid concentrations in human milk and in blood plasma or serum from healthy infants (≤1 year of age), along with study location, infant age, and lactation stage, were extracted. Means and 95%CIs were analyzed within and across variables. Data Analysis Publications on carotenoid concentrations in infant blood (47 publications, n = 4553 unique individuals) and human milk (65 publications, n = 2871 unique individuals) described populations from 22 and 31 countries, respectively. Carotenoid species concentrations ranged from 0.3 to 20 µg/dL in blood and from 0.1 to 30 µg/dL in human milk, with carotenoid concentrations generally decreasing in milk across lactation stages and increasing in blood with infant age. Conclusion Concentrations of the major dietary carotenoids—β-carotene, lycopene, lutein, β-cryptoxanthin, zeaxanthin, and α-carotene—have been reported in both infant blood and human milk across infant ages and lactation stages, with β-carotene, lutein, and lycopene tending to be more abundant than other carotenoids. Despite heterogeneous amounts of data available for each outcome, infants worldwide are exposed to a variety of dietary carotenoids. The estimates of dietary carotenoids in human milk and infant blood can facilitate the interpretation of future studies and the design of nutritionally relevant experiments on dietary carotenoids and infant health.

Background Skin carotenoid measurement by reflection spectroscopy (RS) offers a non-invasive biomarker of carotenoid intake, but feasibility, reliability, and validity are not established in infants. Objectives To determine feasibility and reliability of 4 month-old infant skin carotenoid score (SCS) measurement and its correlation with total carotenoid intake and plasma concentrations. Methods : SCSs were measured in a prospective, observational study by a modified, portable RS device at the index finger and heel of the foot in 4-months olds (n = 21). Infant plasma, human milk, and formula carotenoid concentrations were measured by HPLC-PDA, and carotenoid intake was estimated from 7-day food diaries corrected for actual milk carotenoid content. Mean SCS, time to acquire measurements, replicate intraclass correlations, and bivariate correlations between SCS, carotenoid intake, and plasma carotenoids were examined. Exploratory analyses of returning 6- (n = 12), and 8- (n = 9) month old infants were conducted. Results Mean ± SD finger and heel SCS in 4, 6, and 8-month-olds were 92 ± 57 and 92 ± 51; 109 ± 41 and 119 ± 44; and 161 ± 89 and 197 ± 128 units, respectively. Replicate SCS measurements were reliable, with high intra-correlation (≥0.70) within subject-visits. Four-month olds’ finger SCSs were correlated with carotenoid intake (rho = 0.48, P = 0.0033), and finger and heel SCS were correlated with total plasma carotenoid concentrations (rho = 0.71, P < 0.0001 and rho = 0.57, P = 0.0006, respectively). Eight-month olds’ finger and heel SCSs were correlated with total carotenoid intake (rho = 0.73, P < 0.001; rho = 0.58, P = 0.0014, respectively), while SCSs in 6-month olds’, in transition from exclusive milk to complementary feeding, did not correlate with plasma carotenoid or dietary carotenoids, despite correlation between plasma and dietary carotenoid intake (rho = 0.86, P = 0.0137). Mixed models suggest plasma total carotenoid concentration, age, carotenoid intake, and age*carotenoid intake, but not measurement site, are determinants of infant SCS. Conclusions Infant skin carotenoids are feasibly and reliably measured by RS, and may provide a biomarker of carotenoid intake in 4-month olds. ClinicalTrials.gov [NCT03996395].