Mustard seeds are the small round seeds of various mustard plants. The seeds are usually about 1 to 2 millimetres (0.039 to 0.079 in) in diameter and may be coloured from yellowish white to black. They are an important spice in many regional foods and may come from one of three different plants: black mustard (Brassica nigra), brown Indian mustard (B. juncea), or white/yellow mustard (B. hirta/Sinapis alba).
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. Studies are currently being conducted about mustard’s positive health benefits for menopausal women and migraine headaches.