Mustard oil is composed mostly of the fatty acids oleic acid, linoleic acid and erucic acid. At 5%, mustard seed oil has the lowest saturated fat content of the edible oils.

Due to its high content of erucic acid, which is considered noxious, mustard oil is not considered suitable for human consumption in the United States, Canada and the European Union, although mustard oil with a low content of erucic acid is available. In India, mustard oil is generally heated almost to smoking before it is used for cooking; this may be an attempt to reduce the content of noxious substances, and does reduce the strong smell and taste.

In North India, mustard oil is also used for rub-downs and massages (see ayurveda). To get around the restriction in Western countries, the oil is often sold "for external use only" in stores catering to Indian immigrants.

In India the restrictions on mustard oil are viewed as an attempt by foreign multi-national corporations to replace mustard oil with canola oil, a variety of rapeseed with a low erucic acid content. But for North Indians, mustard oil is not just a cooking medium but it is very much intricately interwoven with their culture. They have been using it for ages and dispute that there is enough evidence for the toxicity of erucic acid.

The global production of rapeseed and its oil is around 38-42 and 12-14 million tons. China (11-12 million tons), EU (10-13 million tons), Canada (6-7 million tons) and India (4-7 million tons) are the world's major producers. 4.5-6, 1.5 and 2.5 million tons of seed, oil and meal are traded globally.

Canada (2.5-3.5 million tons) and Australia (1.5 million tons) are major exporters, while Japan (2 million tons) and Mexico (1 million tons) are the major importers of seed. Canada is the major exporter of oil too. US is the major importer of oil.

India produces 4-7, 1-2, 2-4 million tons of seed, oil and mustard. India does not export or import seed and oil. Meal is exported. Rapeseed & mustard is cultivated in the rabi season (Oct-Nov to Feb-Mar). Production is highly dependent on the weather.

The major growing states are Rajasthan (40%), Uttar Pradesh (16%), Haryana/Punjab (15%). The oil content varies between 36-42%, with average oil recovery of 34-35%. The remaining is used as rapeseed meal cake.

India exports around 4 lakh tons of meal.