When visiting many of the Peruvian highlights, you need to take altitude into account. Yes, altitude can make you sick (and even kill you), but you can take steps to minimize those effects. Altitude also affects eating. It suppresses your appetite but, more importantly, because it is more difficult to cook at altitude, it can be harder for the traveller to find good food.
Did you know that water in Cusco doesn’t boil at 100 C, but at 88 degrees (191 F)?! Baking is also significantly affected by altitude (well, technically it is the air pressure, but let’s keep things simple). So in places like Cusco, cooking times and even ingredient proportions need to be changed. This will make you even more impressed when you find good food in the Andes!