Trans fatty acids: The Good, the Bad, and the Ugly by Sean O’Keefe

I have watched the changes in the food industry and consumer perceptions over the past 40 years with great interest. One of the changes that I find most fascinating is the change in perception of trans and saturated fatty acids that has occurred. When I speak to students today, they scratch their heads when I tell them “when I was your age, coconut oil was the devil’s milk and trans fatty acids were considered perfectly safe”. Scientific advancements often are the driving force behind consumer perceptions, and in the area of trans and fatty acids, this is certainly true.

Dr. Sean O’Keefe is at the other end of the pipeline that sent several Food Science undergrads from the University of Georgia to Virginia Tech for graduate studies It was through these connections that I developed a relationship on this blog with the website Don’t Eat the Pseudoscience. I became his Facebook friend and we disagreed about my perspective on ultra-processed foods. He suggested that I was giving the critics of these foods too much credibility. When I read the book Food Fights, I thought that he could provide some insights into beneficial aspects of food chemicals. I am happy to welcome Dr. O’Keefe and his commentary to my blog.   

 I first learned about food science by accident. I was rejected at the two marine biology programs that I had applied for after my Biology degree at Saint Francis Xavier. I had not considered other options . . . I wanted to follow the Calypso around the world, diving and studying marine life. Jacques Cousteau’s TV shows, stories of divers finding a treasure ship Le Chameau not far from Louisbourg harbor, and summer work on lobster boats had me interested in the sea. Living in Nova Scotia, we were surrounded by the sea. My mother inquired as to my plans. Perhaps the graduation gift of luggage was a hint, but I had no idea. She mentioned hearing of a Fisheries Technology program that just started at TUNS, Technical University of Nova Scotia in Halifax. I told her I was not interested. As mothers are wont to do, perhaps especially mothers of sons who ignore hints, she ignored me and made an appointment for me to meet them the next Monday.

I figured, what the heck, I’ll go up and talk. That was when I met “Dr. Bligh and Dyer” Graham Bligh and Bob Ackman, an event that changed my life. Ackman, at that time in 1981, has established himself as a world-renowned lipid chemist focusing on fatty acids. Marine fatty acids mainly, but anything that he could analyze with a gas chromatograph interested him. I asked him once when the GC was developed, and he told me with pride that he had made the third GC in the world when he was studying in London in the 1950s. He had been working at the Atlantic Fisheries Research Station and realized the serious problem of trying to analyze fish fatty acids using the old methods.

Ugly trans
Ugly trans

Bob had heard of AJP Martin’s machine that separated fatty acids, so he headed to London. His work on marine fatty acids lead to many developments in analysis and knowledge of omega 3 fatty acids, but he was the type of person who needed to know what all of the peaks were on a chromatogram, which leads us to one of the three sources of trans fatty acids. The ugly trans.  At Virginia Tech I’ve had the distinct pleasure of meeting Harold McNair many times, another giant in the field of chromatographic separations who studied in London in the 1950s, and whose knowledge is only matched by his incredible generosity, sharing his knowledge with others and support for students.

To discuss the ugly trans, we should first explain them all, the bad trans first. Normann first hydrogenated oleic acid in 1901, leading to patents and a developing industry converting liquid oils to plastic fats. The first shortening. Since trans fatty acids melt at higher temperatures than cis unsaturated oils, and lower than saturated fats, they can be used to replace largely saturated plastic fats such as butter to make margarine, a new plastic fat. Normann’s hydrogenated fat was enriched in trans fatty acids. So the double bonds changed from cis, the main form in biological systems, to trans. Not only this, but also the double bonds moved. So Normann’s catalytic hydrogenation resulted in trans with modified double bond configuration and position.

The ugly trans have a different origin. Rapeseed oil is from a small seed in the same family as mustard. It has been widely grown in Canada and became the main vegetable used there commercially. In the 1970s, research in France reported shocking evidence that erucic acid (22:1n-9), the main monounsaturated fatty acid in rapeseed oil, caused fat infiltration and cardiomyopathy in rats. This resulted in a huge concern in Canada as it was the most widely used vegetable oil. Because Ackman was the world expert in fatty acids, samples of rapeseed oil and new varieties of rapeseed oil that were the result of intensive plant breeding ended up in his laboratory. That is when Bob discovered the ugly trans.

The breeding on rapeseed oil was successful and the erucic acid decreased from ~50% to less than 3% in the new oils, now called LEAR, low erucic acid rapeseed oil. When “double low” varieties arrived, low in erucic acid and glucosinolates, the oil was renamed Canola. Bob’s research on these oils leads him to wonder what the extra small peaks were on the chromatograms of refined Canola oils that were not present in oils that he extracted in the lab himself. Those peaks, he later identified, were trans fatty acids. But not just any trans. Trans geometrical isomers of the essential fatty acids linoleic (18:2n-6) and linolenic acid (18:3n-6). They were geometrical isomers .. the trans bond positions did not move, but they changed configuration.

One of these acids, 18:3 cis9,cis12,trans15, was shown to be elongated and desaturated to isomers of EPA and DHA in the French lab of one of Bob’s PostDocs, Jean-Louis Sebedio. The structure of EPA with a trans17 bond is between arachidonic acid (20:4n-6) and “normal” EPA. Since EPA and AA have opposing effects in humans, the metabolic fate of the 17transEPA has been studied. It behaves more like AA than EPA in some studies. These trans fatty acids arising from deodorization are ugly because we know very little about them but we do know that the body does not see this trans15 18:3 to be different from “normal” 18:3n-3.

box of LandOLakes butter sticks
Good trans

This leaves the good trans. Good trans, you say, blasphemy. All trans are bad. Back to my first point about science changing consumer perceptions. By the mid-1980s, two landmark reports concluded that trans fatty acids in the diet were of little concern. It was not until the late 1980s that cracks formed in this opinion. A bit earlier, research on the health effects of meat found that meat and dairy products appeared to reduce the incidence of certain cancers. Good health effects of meat and butter? They have saturated fatty acids and cholesterol you say, and they do. But the search for the health promoting factors present in meat and dairy products led to the good trans fatty acids: CLA, the conjugated linoleic acids. These trans acids have been shown to reduce the risk of cancer, enhance the immune system, have weight reducing and anti-atherogenic effects. Good, right? Research showed that the rumen microflora are responsible for producing the good trans.

That leads us to the current thought on trans acids. Trans from ruminants are good. Trans from Norman’s catalytic hydrogenation are bad. And trans from deodorization processing of vegetable oils are ugly. Future research may clarify the situation and lead to different perceptions and conclusions. Nutritional knowledge is fluid … we should never forget that science changes our perceptions.

Sean O’Keefe was born in Nova Scotia, Canada and followed his parents taking his bachelors degree at Saint Francis Xavier University (StFXU). He received MS and PhD degrees from Technical University of Nova Scotia and Iowa State University. Following his PhD, he worked in Dijon France and then back in Halifax NS. He started his academic career at the University of Florida and later moved to Virginia Tech, where he has been for 20 years. He teaches courses Introduction to Food Science, Product Development, Brewing Science and Flavor Chemistry and conducts research on lipids and flavors. 

Next week: Food safety in the time of CoVID-19: managing risks in the food industry by Ben Chapman



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