I eat them but I haven't noticed that they help my gut. They contain probiotics but regular sauerkraut in the grocery store will not be fermented. Only certain brands that are sold refridgerated are actually fermented. They usually say "live organisms" on the jar. Bubbie pickles are fermented and sold in the refridgerator section at my grocery store.
You can ferment foods yourself. I recommend the book "Wild Fermentation" or "nourishing Traditions".