Diet quality of Norwegian children at 3 and 7 years: changes, predictors and longitudinal association with weight

Poor diet quality in early life can have long-term health effects, but the evidence is largely from cross-sectional studies. Our objective was to examine diet quality of Norwegian children by applying a-priori diet quality indices, identify early life determinants and examine prospective associations with overweight.

We included 34,074 preschoolers (3-year-olds) and 18,350 school-aged children (7-years-olds) from the prospective, population-based Norwegian Mother, Father and Child Cohort Study. Diet quality was assessed as (i) adherence to a Mediterranean diet, estimated by the food frequency-based Mediterranean Diet Score (fMDS, score range: 0-6) and (ii) by the diet quality index (DQI, score range: -33% to 100%), reflecting compliance to food-based dietary guidelines. In multivariate analyses we explored perinatal and childhood characteristics as potential determinants of diet quality. We used logistic regression to examine the associations between diet quality at 3 years and BMI status at 8 years, adjusting for relevant confounders and diet quality at 7 years.

One in three children had high MD adherence at 3 and 8 years, and DQI (mean 60%) at 3 and 7 years was strongly correlated (r = 0.48, p < 0.001). Short breastfeeding duration, physical activity and sleep duration and long screentime at 18 months were associated with 2-3% lower DQI at 3 years. At both ages, maternal diet quality was the strongest prospective predictor of DQI (beta = 5%, 95% CI = 4.7, 5.2 and beta = 3.1%, 95% CI = 2.8, 3.4), and screentime was the strongest cross-sectional predictor (beta = -5.2%, 95% CI = -5.9, -4.5 and beta = -4.1%, 95% CI = -5.0, -3.2). High DQI score at 3 years, but not MD adherence, was associated with a lower risk for overweight (including obesity) at 8 years, compared to low DQI (lower tertile) (adjusted OR = 0.77, 95% CI = 0.62, 0.96).

Our study provides evidences that high diet quality in early childhood may reduce the risk for overweight in later childhood, independent of the current dietary behaviors.