Very popular in Indian cuisine; The term mustard oil is used for two different oils that are made from mustard seeds: A fatty vegetable oil resulting from pressing the seeds,; An essential oil resulting from grinding the seeds, mixing them with water, and extracting the resulting volatile oil by distillation.

As with the canola oil GMO controversy, much internet chatter has conflicted its use due to its erucic acid content and toxic potential (consuming essential oil). Mustard seeds contain an enzyme called myrosinase and a glucosinolate called sinigrin. These two remain isolated while in the mustard seeds under normal conditions but react when the seeds are subjected to pressure and then put in the presence of water. SO:(whew) it is rising in popularity as a cooking oil, but we strongly recommend staying with products made from pressed seeds only and avoiding essential oils..

On a bright note, per Draxe:

1. Boosts Cardiac Health
Incorporating mustard oil into your diet may help protect against heart disease, according to a study in the April 2004 issue of the American Journal of Clinical Nutrition. The oil is rich in monounsaturated fats and polyunsaturated fats, both of which help lower bad cholesterol and raise good HDL cholesterol. Improving your cholesterol balance also helps lower triglycerides, or blood fat levels, which can in turn prevent obesity, kidney disease and hyperthyroidism, in addition to improving heart health.

2. Contains Antibacterial and Antifungal Properties
Mustard oil is thought to work as an antibacterial agent when taken both internally and externally and as an antifungal when used externally. Internally, it can fight bacteria infections in the colon, intestines and other parts of the digestive tract. Externally, it may be able to treat both bacterial and fungal infections when applied directly to the skin.

Researchers from the Armed Forces Institute, reporting in the October 2004 issue of the Journal of the College of Physicians and Surgeons, stated that a 1:1 mixture of honey and mustard oil is effective at killing dental bacteria and may be useful in root canal treatments. It may even help fight fungal and vaginal yeast infections by massaging your body with mustard oil due to the allyl isothocyanate found within it.

Draxe.com