Try to rest to increase your red and white cells in the altitude.
Eat light and small portions throughout the day, this helps to avoid bad digestion in the altitude.
Drink lots of water to avoid dehydration and altitude sickness.
Diarrhea is a common problem in Peru. If you get it, avoid dehydration by drinking Gatorade, electro light or salt in water (rehydration salt) as soon as possible. After that, start to introduce white foods such as rice.