You can stack food/potion buffs, but only with the different types, in which there’s 4 types of it:
- Offensive buff foods (marked with a red sword icon)
- Defensive buff foods (marked with a blue shield icon)
- Stamina buff foods (marked with a yellow man icon)
- Elemental potions
So you can use 1 of each types of foods (offensive, defensive, & stamina), and also one type of elemental potions (either offensive or defensive).