Kale is a cruciferous vegetable that is a member of the mustard family, Brassicaceae. It is an excellent source of vitamin A, vitamin C, vitamin K and manganese, as well as a source of dietary fiber, thiamin, riboflavin, folate, iron, magnesium, phosphorus, vitamin B6, calcium, potassium and copper 1. Many of these nutrients have antioxidant activities.
Recent attention has been devoted to an additional component of cruciferous vegetables, namely, the glucosinolates. Glucosinolates are sulfur-containing compounds that can be broken down in the human gastrointestinal tract. Isothiocyanates, including sulforaphane, are the metabolites of glucosinolates that can then be absorbed through the intestine 2. Kale has a moderate to high glucosinolate content when compared with other cruciferous vegetables 3.