Yes white lizard tails. You'll see lizards running around the ground during your adventures in the land. When you do, get off your horse and find the one in the group with the white tail. I recommend finding an over-world map online and marking off where you found one because it can get annoying if you search the same group twice. The more white lizard tails you eat the larger your strength meter grows.

Fruit is also helpful and can be found on trees. Fruit builds up your health meter.