I actually make it at home as Kefir isn't sold in my country :). I couldn't yet take a call on whether its a placebo or not. My partner says its placebo effect too but I don't think so.

I bought the grains locally and use them to ferment milk for 24 hours (I live near equator so you might have to adjust for your climate). I strain the kefir - seperate out the grains - add some milk and store in the refrigerator for a week (so basically I make it once a week). I store the seperated kefir again in the refrigerator. I take one cup after lunch and one before sleeping (without any additives or even sugar).