Bok choy or pak choi is a type of Chinese cabbage. Chinensis varieties do not form heads and have smooth, dark green leaf blades instead, forming a cluster reminiscent of mustard greens or celery. Health Benefits of Bok Choy. Containing a wealth of vitamins C, A, and K, and excellent sources of calcium, magnesium, potassium, manganese, and iron, bok choy deserves its reputation as a powerhouse among vegetables. Other vitamins and minerals include phosphorus, zinc, sodium, copper, manganese, selenium, niacin, folate, choline, beta-carotene, and vitamin K. Bok choy ranks sixth on the Aggregate Nutrient Density Index (ANDI) for fruits and vegetables.