Jenna Bell, a dietitian and triathlete with a PhD in exercise physiology, offers a primer on how to improve your gut microbiome, and why it even matters. Fermented drinks like kefir and kombucha are all the rage, and foods like yogurt, kimchi and sauerkraut are earning serious respect. In a conversation with host Robin Sussingham, Jenna explains the difference between pre- and probiotics, weighs in on supplements and reveals what she eats --and when!