A heritage cabbage green and relative to kale. With their giant green leaves that are nutrient rich, they are a great substitute for tortilla wraps! These are vitamin K bombs! Vitamin K acts as a modifier of bone matrix proteins, it improves calcium absorption, and it may reduce urinary excretion of calcium. One cup of boiled collard greens provides 770 micrograms of vitamin K. Collard greens also contain choline, an important neurotransmitter. Choline helps with mood, sleep, muscle movement, learning, and memory functions.