Why do my patients keep asking about apple cider vinegar? Why do so many young people drink kombucha? One reason is probiotics. It seems as though we're hearing a lot more about probiotics these days. In the refrigerated aisle, I've seen multiple products--yogurt, juice, miso, sauerkraut, kimchi--that loudly announce that they contain probiotics. Products I'd never heard about before-like kefir, a fermented milk beverage, and kombucha, a fermented tea beverage-suddenly seem t