Mustard seeds also contain calcium, dietary fiber, iron, manganese, magnesium, niacin, phosphorus, protein, zinc, and selenium—a trace mineral that is an antioxidant that may offer protection against asthma, heart attacks, and some cancers.
Mustard plants come in several dozen varieties, all of which are rich in nutrients. Their leaves contain significant amounts of calcium, copper, and vitamins C, A, and K, while their seeds are particularly rich in fiber, selenium, magnesium, and manganese.