The body has its own ph control mechanism. If you eat or drink lots of acidic foods, the body works to balance the ph accordingly. Though there is controversy around this area, skeptics will say that it doesnt matter what you eat or drink as the ph will always change throughout the body. However, water ionising experts claim that the more alkaline food or drink you consume the higher ratio of alkalinity your body will be making you healthier and more immune to viruses etc. Draw your own conclusions. I don't hold any particularly credibility but as a researcher I think that the more alkaline that is consumed the less burden on the body to re-alkalise itself, so high more alkaline foods are better.
Im sure even air ionizers wouldnt sell if they couldnt be justified.