Being the ultimate source of non-animal protein, soy has naturally high amounts of glycine. 100 g of these can contain up to 87.75 g of protein, 3.7 g of glycine, including varied amounts of iron, calcium, and zinc.
The skin alone of fryer-roaster types of turkey contains 3.34 g of glycine. Roasting it may increase this amount. Although the skin may contain high amounts of fat, it also contains 299 calories and 20.94 g of protein.