We’ve mostly studied gut health. Something about modern diets is messing that up substantially. Some think it may be Roundup, others dish detergent, others some microbe we can’t culture on Petri dishes.
I find the dish detergent hypothesis more compelling than I used to - before moving to Australia. Here, I've noticed that almost nobody rinses the dishes after washing them (something I have always done). Curious what others do in different locations/cultures. Seems pretty obvious that consuming surfactants, triclosan, phthalates, alkaline agents, synthetic fragrances and dyes is not a great gut health strategy.