Looking around as I am shopping for stainless steel pots (e.g. for boiling soup), the majority of them have aluminum encapsulated base (for better heat distribution, etc). Is there any concern regarding aluminum possibly leaking into food, as aluminum is generally considered not 100% safe from that point of view?
No, "aluminum encapsulated" means the pan has a layer of aluminum bonded on to the exterior of the pan. The inner surface is stainless steel and perfectly safe because the aluminum never touches food.
This is just a less expensive version of copper-bottomed cookware. The copper is added for the same reason (heat distribution), but it's entirely on the exterior so never touches food.