Mustard and Mustard Oil Safety

The Full Story

Mustard is a flowering plant that has been grown and used as a condiment for thousands of years. The seeds and oil of the plant are recognized for their culinary value. Mustard plant seeds are blended with spices and vinegar to form commercially available mustard products. White mustard seeds are blended with turmeric to form yellow mustard, while Dijon mustard is crafted from mixtures of black or brown mustard seeds. Mustard’s bitter or pungent taste and aroma are due to the presence of a compound called allyl isothiocyanate, which is also found in other condiments including horseradish and wasabi.

Historically, mustard was used as a medicinal plant, since many biologically active compounds are found in the plant and its components. The Greek philosopher Pythagoras promoted the use of mustard as a treatment for scorpion bites, and Egyptians used mustard seeds when burying their kings. In modern times, mustard oil is used as a cooking and salad oil in Asian countries. There are two types of mustard oil: essential mustard oil is considered Generally Recognized As Safe (GRAS) and approved for food use by the United States Food and Drug Administration (FDA), while expressed mustard oil is not permitted for use as a food product by the FDA. The difference between these two oils, and the reason for the FDA ban on the expressed oil product, relates to the presence of erucic acid in expressed mustard oil.

Erucic acid is a fatty acid that is found in some types of mustard oil as well as its close cousin, rapeseed oil. In studies performed on rats and other animals in the 1970’s, the erucic acid found in rapeseed oil was found to cause heart and kidney diseases in the laboratory animals. Because of these studies, many countries prohibited the use of erucic acid in food products, although later trials showed that the harmful effects of erucic acids may be minimal in primates, including humans. Recent studies have demonstrated that erucic acid may actually have a beneficial activity in humans as an anti-inflammatory agent. Erucic acid, in combination with oleic acid, has also been used to treat a rare and often fatal genetic disorder called adrenoleukodystrophy. This condition is characterized by the abnormal accumulation of long-chain fatty acids in the brain and other tissues, and affected patients experience neurological deterioration that is often fatal within several years of diagnosis. The 1993 movie “Lorenzo’s Oil” told the story of a young boy named Lorenzo who was diagnosed with adrenoleukodystrophy in childhood. In the movie, Lorenzo’s family searched for a cure for their son, and discovered that erucic acid could be used to treat the disease. Unfortunately, in real life clinical trials, erucic acid was not found to cure adrenoleukodystrophy, and some patients who took the medication developed adverse effects including low platelet counts.

While mustard and mustard oil are generally safe when consumed orally, the allyl isothiocyanates present in these compounds can cause skin irritation. Bakers and restaurant workers have developed finger and hand rashes after handling mustard and radishes (which are part of the mustard family), and allergy testing revealed positive reactions to the isothiocyanates present in these plants. Some people have developed severe allergic reactions after consumption of mustard. In France, where mustard is extensively used as a condiment, it is the fourth most common cause of food allergies after milk, eggs, and peanuts. Since mustard is present in a variety of foods including salad dressings, pickles, and pesto sauce, individuals who are susceptible to food allergies should review ingredient labels carefully before eating these foods.

If you suspect poisoning from foods or essential oils, get help online at webPOISONCONTROL or call 1-800-222-1222. Both options are free, and available 24 hours a day.

Kelly Johnson-Arbor, MD
Medical Toxicologist