I did a bunch of research into what could reduce gut permeability in the heat and what could reduce gut permeability in athletes overall, and it turns out that something called colostrum is pretty much the number one way to do that. For example, there was one recent randomized control trial on healthy adults—they showed that 1 gram a day of colostrum for 20 days reduced levels of stool zonulin. Stool zonulin is the gold standard marker of gut lining permeability.