Diet is the answer and they thrive better in acidic environments but can exist in an alkaline one as well. It depends on what parasite we're talking about. Some can easily be killed, others can not. In most of us, they exist because we have more than one issue. It could be we don't have an optimal GI flora, our pH is slightly acidic, or we have multiple pathogens that weaken our immune response. One thing is certain, eating the proper foods will help with every issue we have. It may not be curative, but our symptoms will diminish. I have eaten properly and it is extremely difficult. I don't believe I could maintain it long term. But there was no doubt it made a huge difference in my symptoms.