Sergio, I'm an OBGYN but I have been studying nutrition for the past 3 years (on the side). What I can tell you about stevia (so far) is that, considering all artificial sweeteners, it appears to be the safest choice. If you decide to use the powdered version, you must know it's 95% sucrose (which is just a fancy way of saying sugar - it's the chemical name of sugar, actually) and 5% stevia. Now the liquid version is indeed mostly stevia (and some preservative), so I would recommend you stick to that one. Aspartame has shown to alter the microbiome (a huge "zoo" of microorganisms we host in our bodies - i.e gastrointestinal tract, urinary tract, etc - They do wonderful things for us!) and sucralose has been linked to certain forms of leukemia (although the evidence is not robust). I hope this information proves useful. I'd be more than happy to answer any other concerns you have on this and other nutritional topics. Take care.