Food Pattern, Food Selenium and Environmental Stress Regulating the Urinary Selenium in Tibetan Population

Tibetan Plateau, which was once a severe endemic area of Kashin-Beck disease (KBD), was low with selenium in the soil geochemical background and with harsh environment, thus resulting in selenium deficiency in local foods while high environmental-derived oxidative stress and inflammatory responses in human body. Diet was the major selenium source for humans, while external environment conditions could influence selenium consumption and disturb the selenium metabolism. This study explored the influence on urinary selenium of Tibetan population from the pespevtive of selenium intake, represented by food patterns and selenium concentration, and from the perspective of selenium metabolism caused by environmental stress. From 2019 to 2022, 572 food consumption questionnaires of Tibetan residents, matched urine samples, staple food samples, and local agricultural soil and water samples were collected. Environmental stressors, including absolute oxygen concentration, temperature-humidity index and ultraviolet radiation intensity were considered. Statistical analysis and Random Forest (RF) were used to explore the association, contribution importance and interactive effect of the factors above on urinary selenium concentrations. Urinary selenium concentrations of Tibetan residents were still generally low, declined with age whereas no difference was found between genders. In terms of food consumption patterns, dietary diversity score (DDS) and non-local food intake, poultry consumption frequency in particular were positively associated with urinary selenium, exerted a pro-linear relationship. Highland barley and wheat flour selenium concentrations showed positive impact on the urinary selenium concentrations, and the magnitude of impact was more obvious when the highland barley selenium concentration exceeded 0.04 µg/g, and the wheat flour selenium concentration was lower than 0.051 µg/g. The soil and water selenium concentrations also positively influenced the urinary selenium concentrations. Environmental stressors exerted distinct influencing curves on urinary selenium concentrations, with higher ultraviolet radiation intensity (UVRI) and lower environmental comfort induced by cold and dry conditions positively regulating urinary selenium concentrations, while oxygen concentration exhibited a marginal effect only when it reached a certain threshold. Food diversity, non-local food intake, staple food selenium concentrations and local agricultural selenium concentrations were all important factors for elevating the selenium status among Tibetan residents. Environmental stressors regulated the urinary selenium concentrations differently due to the divergent action pathways on the selenium depletion and metabolism. Correspondingly, increasing the food diversity through introducing non-local food, increasing the selenium level of local food and elevating the human selenium reference standards were suggested.