Originated in the Mediterranean region, these seeds are usually harvested just prior to them becoming ripe and bursting. Besides, they are hard and round, with a color ranging from beige or yellow to light brown. White mustard seeds can be used whole for pickling or toasted for use in dishes. And when ground and mixed with other ingredients, a paste or more standard condiment can be produced. Nutritionally, mustard seeds are a very good source of selenium and omega-3 fatty acids. They also contain generous amounts of healthy phytonutrients, which can prove valuable against various cancers such as the bladder, colon, and cervical cancer.