Assalaamu alaikum,
(smile) Mmm... I have wondered about kefir, myself. I used to drink it until one day, I found some rather old kefir in my fridge that was unopened, and it seemed ok, so I drank it. But it tasted rather odd, and I could smell the alcohol on my breath a little while after drinking it (the body gets rid of some of the alcohol through the lungs). It also gave me a headache and made me feel unpleasantly odd. So I decided not to drink it again.
(smile) Perhaps just avoiding
old kefir would be all that is necessary... but how to know exactly when is too old? As the alcohol content can
sometimes be quite high (enough to have an effect), it seems to me that kefir is a bit of a grey zone.
There are other ways of getting "good" bacteria into your gut. Not only are there
probiotics (such as plain yoghurt), but there are also
prebiotics, that are foods that encourage the growth of "good" bacteria in your gut. Prebiotics contain non-digestible (by humans. But food for the "good" bacteria) carbohydrates. For a quick intro, try this link:
http://www.mayoclinic.org/healthy-li...s/faq-20058065
May Allah, the Oft-Forgiving, Guide us in our choices.