Pak choy is one of the popular leafy-vegetables very low in calories. Nonetheless, it is very rich source of many vital phyto-nutrients, vitamins, minerals and health-benefiting anti-oxidants. 100 g of bok choy provides just 13 calories. It is one of the recommended vegetable in the zero calorie or negative calorie category of foods which when eaten would add no extra weight to the body but in-turn facilitate calorie burns and reduction of weight. Like other brasisca family vegetables, bok choy contains certain anti oxidant plant chemicals like thiocyanates, indole-3-carbinol, lutein, zeaxanthin, sulforaphane and isothiocyanates. Along with dietary fiber, vitamins these compounds help to protect against breast, colon, and prostate cancers and help reduce LDL or "bad cholesterol" levels in the blood. Fresh pak choi is an excellent source of water-soluble antioxidant, vitamin-C (ascorbic acid). 100 g provides 45 mg or 75 % of daily requirements of vitamin C. Regular consumption of foods rich in vitamin C helps body develop resistance against infectious agents and scavenge harmful, pro-inflammatory free radicals. It has more vitamin A, carotenes, and other flavonoid polyphenolic anti-oxidants than cabbage, cauliflower...etc. Just 100 g of fresh bok choy provides 4468 IU or 149% of daily-required levels vitamin A. Pak choi is very good source of vitamin K, provides about 38% of RDA levels. Vitamin-K has potential role in bone metabolism by promoting osteotrophic activity in bone cells. Therefore, enough vitamin K in the diet makes your bone stronger, healthier and delay osteoporosis. Further, vitamin-K also has established role in curing Alzheimer's disease patients by limiting neuronal damage in their brain. Fresh bok choy has many vital B-complex vitamins such as pyridoxine (vitamin B6), riboflavin, pantothenic acid (vitamin B5), pyridoxine, and thiamin (vitamin B-1). These vitamins are essential in the sense that our body requires them from external sources to replenish.
It also contains good amount of minerals like calcium, phosphorous, potassium, manganese, iron and magnesium. Potassium is an important component of cell and body fluids that helps controlling heart rate and blood pressure. Manganese is used by the body as a co-factor for the antioxidant enzyme, superoxide dismutase. Iron is required for the red blood cell formation.