ABSTRACT Objectives Intestinal function is an important but often overlooked aspect of human biological variation, with the intestines serving as both a barrier against external pathogens/contaminants and the primary conduit of nutrient extraction from food. Impaired intestinal function among children is viewed as a key contributor to growth faltering globally. However, few studies have investigated children's intestinal function in rural settings or beyond infancy. To address this limitation, we conducted a pilot study to describe the intestinal function of school‐age Indigenous Shuar children of Amazonian Ecuador and to assess the feasibility of implementing the widely utilized lactulose:mannitol (L:M) test of absorption and permeability with this group. Methods The urinary L:M test was performed with 23 rural‐living Shuar children aged 4–12 years. Ultra‐performance liquid chromatograph–high‐resolution mass spectrometry was used to determine L:M ratios, lactulose recovery, and mannitol recovery. Age and sex patterns were investigated using linear regression models. Results Children's mean L:M ratio was 0.33 ± 0.32, a ratio comparable to values reported for children in other low‐ and middle‐income settings. 35%–91% of children were categorized as having impaired intestinal function using common cut‐off values. Children's lactulose (0.14% ± 0.17%) and mannitol (2.60% ± 2.22%) recoveries did not differ by sex but increased with age ( p < 0.05) and indicated diminished intestinal absorptive capacity and increased permeability. Conclusions Intestinal function appears to be considerably impaired among school‐age Shuar children living in a low‐resource, rural setting. Children living in unsanitary, non‐industrialized contexts may routinely experience intestinal permeability‐related immune activation and malabsorption‐related energy/nutrient loss. More research is needed to explore the breadth of global variation in children's intestinal function and to investigate its many evolutionary and public health implications.
Pfaff‐Nash et al. (Sun,) studied this question.