Many microbes in the intestines are potentially pathogenic, which means they could cause disease in certain circumstances. Their potential for causing disease is controlled by immune cells, the physical barrier of the intestinal walls, and other resident microbes of the GI tract.[1][2]
In healthy people, the innate immune system controls Candida colonization by initiating the production of antimicrobial peptides (amino acid chains), and neutrophils (cells of the innate immune system) prevent Candida from escaping the GI tract and causing infection. Other microbes may communicate with the innate immune system to induce an antimicrobial response or produce metabolites, which suppress Candida growth.[2]
There is also some evidence that the GI tract in mammals induces specific characteristics in Candida that make it less likely to cause disease. In other words, it trades its virulence (or ability to cause disease) for better chances of survival in the human gut.[2]