The message has been circulating for a few years now: trans fats = bad. It’s one of the rare times I find myself in alignment with conventional nutritional guidelines. (Of course, it’s not so simple, but I’ll unpack that one in a moment.) The fact is, manufacturers have done a better job sending the anti-trans fat message than public health agencies. Everywhere you turn in the grocery store the “No Trans Fat!” tag leaps out at you, complete with manic font and exclamation point, from hundreds of boxes, bags, and packages. (“Well, it must be healthy then!”) Unfortunately, the marketing push has crowded out the real science when it comes to the public’s engagement with the real issue. As you can guess, there’s more to the trans fat picture than the self-congratulatory manufacturer claims.
I know trans fats are unhealthy and I avoid them like the plague. But like so many things sometimes I need a little reminder why. (I regularly brush up my knowledge by visiting your site so that when a friend asks why I avoid grains I don’t say something like “Grains are bad because… something about lectins and phytates – can’t remember why… but they’re bad.”) Could you write up an easy to remember primer on what trans fats are and why are they unhealthy?
Thanks to Monica for this week’s question. Order up.
First, a brief update on the subject. Since 2006, when the FDA required food manufacturers to include trans fat content on nutritional labels, the prevalence of these partially hydrogenated oils has indeed changed. Shifted, really. Actually, these seedy little grease balls, devious criminals that they are, have gone undergone a strategic makeover and/or simply gone underground. They’re still operating among us, trust me – business as usual. But let’s break it down first.
What Are They?
“Shape shifters” is incidentally an apt way to describe trans fats. That’s exactly what the hydrogenation process involves. From a chemical standpoint, you take a decent enough unsaturated oil and add some hydrogen atoms. The process undoes the existing double carbon bonds of the unsaturated oil. By “saturating” the bonds with additional hydrogen, you saturate the oil. The result is a solid (at room temperature) but meltable, more stable fat.
As reader Sam adds (in the comment board): “Trans fats by definition are not fully saturated. They contain at least one double bond in the trans configuration. Unsaturated fats with cis double bond configurations have lower melting points than comparable saturated and trans fatty acids because the cis double bond causes a bend in the molecule, limiting intermolecular attractive forces. This bend is not present in saturated fats or unsaturated fats with only trans double bonds”
What Do They Do?
Seems simple enough, but all of a sudden the body doesn’t know what to make of the end product. The trans fats go on to incite havoc in cell metabolism. Research indicates trans fats cause comparatively more weight gain  than the same diet with monounsaturated fats and a redistribution of body fat tissue to the abdominal area, the riskiest place to carry extra padding. Additionally, they’re associated with inflammation  and atherosclerosis .
What Are They In?
Generally speaking, all the garbage a good Primal eating plan avoids: margarine, shortening, pastries, donuts, muffins, biscuits, cookies, cakes, frostings, pies, crackers, chips, bread, instant flavored coffee drinks, microwave popcorn, and the usual fast food suspects like fried chicken, chicken patty sandwiches, French fries, etc. Consider anything fried suspect.
How Are They Still Around?
The concern has even spurred local and state governments to regulate public consumption. New York City was the first in July of 2008, when the law that banned trans fats in city restaurants took effect. With the recent flip of the calendar, the State of California added itself to that list of regulators.
Although many restaurants and food manufacturers scrambled to create new formulations following the 2006 labeling rule, trans fats have all but disappeared. Some food producers, counting on consumers’ penchant for their products as-is, said label be damned and kept their formulation the same. (A quick rundown of fast food nutritional info or any frosting canister shows as much.) Other companies took advantage of the labeling loophole that allowed any content under .5 grams to be listed as zero. Considering that the American Heart Association suggests a 2 gram/day ceiling on trans fat intake (based on a 2000 calorie/day diet), it seems pretty likely that processed food consumers still have a solid chance of meeting that limit and then some. Ignorance may be bliss to these folks, but it’s not well-being.
Finally, trans fat content in many cases has simply morphed into what’s known as interesterified fats. Consider them trans fats’ partners in crime – a real Bonnie and Clyde duo. Essentially, interesterified fats provided manufacturers the same crispy, flaky, shelf stable benefits they were accustomed to while offering a convenient way to circumvent the new laws and labels. Interesterified fat combines unsaturated and the saturated fat stearic acid in a process that includes the same hydrogenation and a reshuffling of fatty acids. The result, like artificial trans fat, is a product that doesn’t exist in nature. Research shows  their impact to be even more insidious than trans fat. Think both insulin resistance and a negative shift in LDL/HDL ratio.
How Can You Avoid Them?
The best way is, of course, to avoid processed foods themselves. As far as labels go, check the trans fat content but also the ingredient list for words like partially hydrogenated, hydrogenated (which usually means “partially”), and high stearate, and stearic rich.
What’s Behind the Natural versus Industrial Trans Fats Comparison?
Perhaps you’ve heard that meat and dairy products contain trans fats as well. Technically, this is true, but the industrially produced trans fats aren’t to be conflated with the natural kind, called vaccenic acid. The digestion process, particularly the stomach bacteria, in ruminant animals naturally adds hydrogen. The result is a small amount of natural trans fat in the animals’ meat and milk that offers a number of benefits, including antiatherogenic effects . Conjugated linoleic acid (CLA), part of the family of naturally occurring trans fats, is a health powerhouse.
Unfortunately, about 80% of Americans’ trans fat intake is the artificial class . As is so often the case, there’s a tendency to throw the baby out with the bath water when it comes to nutritional guidelines. The rule here holds as it always does: the natural, Primal stuff nourishes the body, the artificial stuff undermines it. ‘Nuff said?
Be sure to weigh in with your thoughts. In the meantime, thanks for all the great questions and comments. Keep ‘em coming!