German Sauerkraut

German sauerkraut, lacto-fermented with 2% salt over 4-6 weeks, is the Western world's oldest probiotic food, producing distinct bacterial species. At 27 kilocalories per cup and $0.20 per serving when home-fermented, it outperforms the average commercial probiotic supplement in both cost and microbial diversity, while preserving vitamin C and generating K2 and GABA absent in raw cabbage.