Most forms of medical advice, some of it stuck around for a long ass time (bloodletting and the idea of spirits and humors lasted several millennia), but I imagine that the vast majority of it is lost to time.

You don't even have to go all that far back to see this in action.

In the 90's, the universal medical advice was to avoid fats, sauces and dear lord never eat more than 2-3 eggs in a week or you'll have a coronary before 40.

You still shouldn't go overboard with fats and sauce which is made with fat, but the advice that you shouldn't eat more than 2-3 eggs in a week is entirely defunct now.

You can eat 2-3 eggs a day (which many people do without even knowing as eggs are used in a whole lot of things) without any medical disadvantages.