Yellow mustard seed is one of the forty mustard varieties and is known as the mildest tasting mustard variety. It is a spice generally grown in regions with a Mediterranean climate. This spice, which has a history of approximately 5000 years, is used both in the kitchen and as a medicinal plant. Yellow mustard seed contains selenium, magnesium, Omega-3 and fatty acids. With its rich content, it can help regulate sleep patterns and be good for loss of appetite.