Very confusing since that study was about preserved vegetables! yes you can buy kimchi and some fermented veggies in a bottle BUT that is not the real deal. If you make your own fermented veggies, it is beneficial.
I believe sauerkraut has too much sodium (salt) to be recommended but if you can factor the salt in and reduce in other areas. I actually use less added salt by eating food with sauerkraut and sumac, plus I get the benefits of both too.
Prebiotics are troublesome for anyone who is prone to IBS (I developed mild IBS last year – long story) – so had to avoid prebiotic foods. The Water Kefir I drink I tolerate well however, but it is a polysaccharide solution the grains are in.