Good question. There seems to be a couple schools of thought. #1. It appears that many times a candida yeast overgrowth can contribute to a weakening of the immune system. And as the immune system weakens it allows some of these other issues to overtake the body. #2. As the candida yeast “eat” they expel toxins that flow throughout the body contributing to bad issues. #3. Candida yeast can infiltrate the blood stream contributing to issues. But that being said it seems from dealing with literally thousands of people that if the candida yeast overgrowth in the intestinal tract is brought under control that many of these issues cease to become issues.