Mustard seed oil is thought to help to stimulate the scalp to promote hair growth (see References 1). It contains extremely high levels of zinc and selenium. It is said that if the body has a lack of zinc or selenium, hair loss is more likely. Mustard seed oil also has a lot of beta carotene and is a good source of vitamins and nutrients, which help nourish your scalp. Beta carotene is converted into vitamin A, which helps normal hair growth by protecting hair fibers and promoting a healthy scalp.