david gregory, thank you very much. so you have heard democrats push medicare for all. dr. sanjay gupta tells us what it is and how much it could cost next. >> first, how your diet can boost your immune system? today's food as fuel from jacquelyn howard. studies linked having good gut health with boosting immunity. all natural yogurts are a good source of probiotics. garlic can have a powerful effect on your immune system. it is a source of selenium which is good for cell damage. it can be found in broccoli, sardines and enriched breads. go for bone broth. broths like the one in chicken soup can help ease symptoms of infection. to keep your immune system strong think zinc. zinc can be found in seafood like oysters which are high in the mineral. of course, vitamin c.