Abstract
Despite established links between the infant gut microbiome and health, how complementary feeding shapes colonization remains unclear. Using FoodSeq, a DNA-based dietary assessment technique, we surveyed food intake across 729 children (0-3 y) from North and Central America, Africa, and Asia. We detected 199 unique plant food sequences, with only eight staples shared across all countries. Despite this global variation, early-life diets followed a common trajectory: weaning stage emerged as the dominant dietary signature across populations. Crucially, dietary diversity did not correlate with gut microbial diversity. Instead, dietary diversity and weaning stage specifically predicted the abundance of adult-associated bacteria. Our findings support a two-stage maturation model: an initial milk-dominated phase, followed by a diet-responsive phase that yields adult-like communities. Monitoring and promoting plant dietary diversity may thus support timely microbiome maturation worldwide.