Lifeway Kefir Lifeway Kefir is a tart and tangy cultured milk smoothie. It's high in protein and calcium and has 12 live and active probiotic kefir cultures. Learn more about Lifeway Kefir. Lifeway Kefir is a tart and tangy cultured milk smoothie. It's high in protein and calcium and has 12 live and active probiotic kefir cultures.