The Marvelous Misunderstanding of Miss Mustard Oil

Today’s post, the second in our series from student’s in MET ML 619, The Science of Food and Cooking, with Professor Valerie Ryan, is submitted by gastronomy student Julian Plovnik.

Last January, I accepted a job with a company whose focus centered around the delivery of authentic, homemade food to hungry customers across the country, with dishes being made predominantly by immigrant populations living in major U.S. cities. I was fortunate enough to be in a role that facilitated a lot of 1-on-1 interaction with the cooks on our platform, allowing me the opportunity to ask them questions about their backgrounds, national cuisines, and specific culinary traditions. Conversations often included winding trips down memory lane, emotional stories about each cook’s journey to the U.S., and obviously lots of talk about food.  It was not out of the ordinary for me to learn something new each day. In fact, it was rare for me not to. From ingredients like jaggery, galangal, and kaffir lime, I was constantly being introduced to food and foodways that lived outside of my daily life experiences.

For the most part, I was never surprised by anything I learned. There was no reason for me to question specific techniques or dishes that some of the cooks on the platform wanted to prepare. That is, until I was asked by one woman what seemed to be a very simple question at the time. “I’m not allowed to use mustard oil in my dishes, correct?” Unsure of exactly what she was asking, I asked her why that would be the case. “Well,” she said, “because it’s illegal”. I was confused. I had never heard of mustard oil before and I definitely hadn’t heard of an illegal cooking oil before. What could possibly be illegal about it? Was it highly combustable? Were there new sanctions on Pakistan that I hadn’t heard about? Maybe it was toxic to pets. Nevertheless, I assured her I would look into her question and get back to her.

Mustard oil is a bright, pungent oil made from pressing the seeds of the mustard plant to release an oil that is relished in many countries for its unique spiciness and high smoking point of 480F (Sharma, 2020). It’s most popularly used as a cooking oil or condiment in the cuisines of East and Central Asian countries such as China, Bangladesh, and India, but also appears in some dishes in Russian and other Baltic cuisines. It’s particularly popular in the northern state of West Bengal in India, where it’s used in dishes such as achaars, a pickled condiment used to add an acidic spice to a wide variety of dishes. One difference that you might see as you traverse Asia is the type of mustard seed being used to make mustard oil. In India, black mustard seeds from the plant Brassica nigra are used to make the oil, while brown mustard seeds from Brassica juncea are more commonly used in China and Russian oils (2020). However, the controversy behind mustard oil lies deeper into the biology of the mustard plant and Brassicaceae family in general, specifically with a long-chain fatty acid called erucic acid.

Erucic acid is a naturally-occuring, non-branched, monounsaturated fatty acid with 22 carbons and a cis-configured double bond on the 13th carbon (Vetter et al., 2020). The Brassicacea family of plants, often referred to as the Cruciferae or mustard family (Šamec et al., 2019) includes vegetables that are highly consumed all across the world, such as broccoli, Brussels sprouts, cabbages, and of course mustard greens. Additionally due to their high fat content, many species of fish, such as wild salmon, also contain measurable levels of erucic acid (Vetter et al., 2020). While mustard oil is comprised of a variety of fatty acids, erucic acid can sometimes comprise up to 50% of an oil’s fatty acid composition, causing it to be a liquid at room temperature  (Wendlinger et al., 2013). It’s because of this high concentration of erucic acid in the fatty acid composition that makes mustard oil such a controversial ingredient, as many of the other members of the Brassicaceae family tend to have much lower overall levels.

Fig. 1. Chemical structure (two variants) of erucic acid including carbon labeling (Vetter et al., 2013)

Discussion around the potential toxicity of erucic acid first began in the 1950’s when research began to surface showing a potential link between high levels of erucic acid consumption in rats and the development of myocardial lipidosis and heart lesions (2013). In one of the studies, fully refined rapeseed oils (another oil with a high concentration of erucic acid) containing different amounts of erucic acid from 1.6% to 22.3% were fed, at 20% by weight of diet, to weanling male and female rats for periods up to 112 days.. Myocardial lipidosi, a temporary, reversible heart condition was seen in rats that had been fed oxidized and unoxidized rapeseed oil containing 22.3% erucic acid, moderate with rapeseed oil containing 4.3% erucic acid and very slight in rats fed rapeseed oil containing 1.6% erucic acid (2013). Its most serious detrimental health effects were determined to be high triacylglycerol accumulation in the heart due to insufficient oxidation, which could possibly result in a reduced ability for the heart muscle to function (2013). In other words, the lower the concentration of erucic acid in the rapeseed oil a rat was fed, the less likely they were to develop heart conditions.

At the same time that these studies were being produced, work was being done by scientists and manufacturers in Canada to develop a “heart healthy” cooking oil that was low in erucic acid. Through careful breeding processes, the group of scientists were able to produce rapeseed plants with low levels of erucic acid. The oil, later to be named canola oil (can- for Canada, -ola which stands for “oil, low acid”) soon became a commercialized, easily marketable hit with both the public and science community alike (Fisher, 2020). The question then became, is the risk worth the reward?

The regulations on mustard oil began in 1976 when the EU introduced a maximum level of 5% erucic acid contribution to the total fatty acids in edible oils and added fats (Vetter et al., 2020). 16 years later, the U.S. followed suit in the 1990’s when the FDA banned the import and sale of mustard oil as foodstuffs (Sen, 2011). External uses of the product, such as for massage oil, were still viewed as acceptable. Most recently in 2016, the FDA released Import Alert #26-04 which stated that “[M]ustard oil is not permitted for use as a vegetable oil. It may contain 20 to 40% erucic acid, which has been shown to cause nutritional deficiencies and cardiac lesions in test animals” (U.S. Food & Drug Administration, 2016). Additionally, the European Food Safety Authority (EFSA) released a report in 2016 suggesting the decrease of the acceptable maximum level from 5% down to 2% of the total fatty acid composition (Vetter et al., 2020).

All in all, things haven’t looked good for mustard oil and its devoted fans since the 1950’s, despite there not being any presence of evidence or work towards researching that high concentrations of erucic acid would have negative health consequences on human beings, not just lab rats. When I first learned about the banning of mustard oil, I was fairly frustrated. The use of this type of incomplete research on laws and regulations can have widespread negative effects on the greater population if not properly reexamined over time. With so many Southeast Asian cuisines relying on the inclusion of mustard oil to create some of their most beloved dishes, a banning of the substance inherently creates a lack of accessibility for specific populations that immigrate to any country where the ingredient is banned. While yes, mustard oil can still be sold in stores, it must don a “For External Use Only” label on it in order to be purchased, forcing a narrative on its consumers that they as an entire population eat ingredients that are not deemed to be edible by greater science. When these consequences are then balanced with the fact that the laws and regulations around mustard oil were based off of decades-old research that was performed on laboratory rats, the ends in no way seem to justify the means.

While there has been some progress towards a better understanding of the importance of mustard oil (the very first refined, single-ingredient mustard oil called recently became approved by the FDA in 2016 (U.S. Food & Drug Administration, 2016)), there still is much work to be done in understanding the cultural and societal consequences in banning particular foodstuffs and ingredients, specifically when the research is outdated or incomplete. What can be learned from mustard oil’s struggle for acceptance is an overall better understanding of the holistic impacts on food safety decisions and what they inherently say about a specific culture, cuisine, or population.

Works Cited

Charlton, K M, A H Corner, K Davey, J K Kramer, S Mahadevan, and F D Sauer. “Cardiac Lesions in Rats Fed Rapeseed Oils.” Canadian journal of comparative medicine : Revue canadienne de medecine comparee. U.S. National Library of Medicine, July 1975.

“Erucic Acid a Possible Health Risk for Highly Exposed Children.” European Food Safety Authority. Accessed March 25, 2022.,occur%20at%20slightly%20higher%20doses.

Fisher, Ben. “The Real Reason Mustard Oil Is Banned for Cooking Purposes in the U.S.” Mashed, July 22, 2020.

“Import Alert 26-04.” Food and Drug Administration, November 18, 2016.

Sen, Indrani. “American Chefs Discover Mustard Oil.” The New York Times. The New York Times, November 1, 2011.

Sharma, Nik. “The Truth about Mustard Oil: Behind the ‘for External Use Only’ Label.” Serious Eats. Serious Eats, September 11, 2020.

Vetter, Walter, Vanessa Darwisch, and Katja Lehnert. “Erucic Acid in Brassicaceae and Salmon – an Evaluation of the New Proposed Limits of Erucic Acid in Food.” NFS Journal 19 (2020): 9–15.

Vles, R. O., G. M. Bijster, and W. G. Timmer. “Nutritional Evaluation of Low-Erucic-Acid Rapeseed Oils.” SpringerLink. Springer Berlin Heidelberg, January 1, 1978.

Šamec, Dunja, and Branka Salopek-Sondi. “Cruciferous (Brassicaceae) Vegetables.” Nonvitamin and Nonmineral Nutritional Supplements. Academic Press, October 5, 2018.

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