After kidney donation there is no special diet to follow, nor special diet restrictions. Your remaining kidney should handle everything fine, and you can return to normal diet.
Right after surgery, of course, your appetite will be wacky for a while, and many donors have trouble with constipation in the days after donation, but things get back to normal soon.
Naturally, you will want to follow the healthful diet recommendations that are recommended for EVERYBODY to help maintain good kidney health (avoid getting over-weight, eat your veggies, take it easy on salt, etc.)
Many donors find tht they are more sensitive to alcohol in the weeks/months after surgery, so if you drink you should be cautious when you start again, as a small drink may have the effects that a large drink used to have.
best wishes,
Fr. Pat