From what I’ve learned through this Forum and other websites about kefir is that one receives the best of it’s properties when it is made directly at home which is not hard to do after you get the hang of it. I too was concerned to even attempt kefir due to my lactose intolerance, but I’ve been making it myself and have not had any intolerance. In fact I love it! The reason it’s advised to make it yourself is that the store bought brands are pasturized which kills any beneficial bacteria in kefir. Then they add it back and sell it saying it has beneficial bacteria.
If you are interested in how to make kefir, check out U-tube videos, Cultures For Health, Dom’s website, and google “kefir production”. That’s how I learned about it. There is a lot of info. available. Also, you may be able to obtain starter grains through someone in your area if you go on the Weston A. Price Foundation.
I didn’t answer your specific question but I hope this is helpful to you.