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• Infant diet assessment validity varies by dietary component and feeding stage. • Carotenoid intake estimates differ by milk carotenoid adjustment and approach. • Carotenoid intake estimates from 3 days of food diaries correlate with 7 days. Validated carotenoid assessment methods are needed to study infant carotenoid nutrition. This is a secondary analysis of repeated diet assessments of healthy participants collected at 4- (n = 21), 6- (n = 12), and 8- (n = 9) months of age in Houston, TX between April 2019 and June 2020. Intake was assessed with 3 assessment tools, analyzed with 3 nutrient databases, and underwent 3 adjustments to account for milk composition variability. We hypothesized that manual adjustment of milk carotenoid intake based on laboratory measurements would improve the validity of all assessment approaches and that using a database with greater coverage of infant food carotenoid compositions would improve accuracy. Generalized linear mixed models assessed associations between tool, nutrient database, age, and milk carotenoid adjustment variables with carotenoid, energy, fruit, and vegetable intakes. The effect of the number of food diary days on intake estimate precision was evaluated by testing the correlation between intake estimates derived from 1, 3, or 5, vs. 7 days. Visit age influenced energy intake estimates (p =.029), along with assessment tool (p =.020). Estimates of vegetable intake were influenced by tool (p =.009). Combined fruit and vegetable intake differed by nutrient database (p =.007). Carotenoid intake differed by age (p =<.0001), tool (p =.002), and nutrient database (p =.004). A minimum of 3 food diary days strongly correlated (rho = 0.79-1) with reference estimates across ages. Milk carotenoid adjustment was most influential in estimating 4-month olds' carotenoid intake, while nutrient database and tool were important for 6- and 8-month-olds', highlighting the dynamic nature of infant diet assessment validity across feeding stages. There are multiple methods available to assess infant carotenoid intake. This study finds that estimated infant carotenoid intake is influenced by child age, milk carotenoid adjustment method, nutrient database, and assessment tool. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Skin carotenoid measurement by reflection spectroscopy (RS) offers a noninvasive biomarker of carotenoid intake, but feasibility, reliability, and validity are not established in infants., Objectives: In this study we aimed to determine the feasibility and reliability of 4-mo-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 with a modified, portable RS device at the index finger and heel of the foot in 4-mo-olds (n = 21). Infant plasma, human milk, and formula carotenoid concentrations were measured by HPLC-photodiode array, and carotenoid intake was estimated from 7-d 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-mo-old (n = 9) infants were conducted., Results: Mean ± SD finger and heel SCSs in 4-, 6-, and 8-mo-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 intraclass correlation (≥0.70) of within-subject visit measurements. Finger SCSs in 4-mo-olds were correlated with carotenoid intake (ρ = 0.48, P = 0.0033), and finger and heel SCS were correlated with total plasma carotenoid concentrations (ρ = 0.71, P < 0.0001 and ρ = 0.57, P = 0.0006, respectively). Eight-mo-olds' finger and heel SCSs were correlated with total carotenoid intake (ρ = 0.73, P < 0.001; ρ = 0.58, P = 0.0014, respectively), whereas SCSs in 6-mo-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 (ρ = 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-mo-olds. This trial was registered at clinicaltrials.gov as NCT03996395., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society for Nutrition.)