Without enough stomach acid, (aka HCL or Hydrochloric acid) protein, minerals, and vitamins are not properly broken down and end up going through the digestive tract undigested. This can cause a whole host of complications, including nutrient deficiency, and leaky gut (intestinal permeability).
Having enough stomach acid helps kill and neutralize pathogens, bacteria, and yeast. Having these get past the stomach can dysregulate the delicate microbiome balance in the body, resulting in too many bad bacteria, which can result in intestinal permeability, SIBO, and in some cases autoimmune disorders.