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The Mad Gastronomist

Hey Fatty!: The Truth About Trans Fats

By Mike Iacoviello | 3.19.07

I was eating lunch recently at the greasy burger joint around the corner from work when I noticed a new sign in the window: a proud announcement of the fact that the restaurant now used trans-fat-free oil for all their cooking. I didn’t really understand how this sign was supposed to make me feel any better about the damage that I was about to do to myself, what with my usual order of an Italian beef/sausage combo (dry/hot, for those that care) with a corn dog on the side. Trans fats or no trans fats, that shit tastes too good to not be taking hours off my life. I then came to the realization that “zero trans fats” has become the new buzz label for the healthily inclined. Trans fats have replaced “carbs” as both the villain of public health and the newest scapegoat for why America is so damn fat and unhealthy. After investigating trans fats further, I can’t say that this reputation is wholly undeserved; but as with most media health crazes, neither is the story as cut and dry (or cut and greasy) as we’d like to think.

Fat comes in two different dietary forms, saturated and unsaturated, a difference that sadly requires organic chemistry to explain. Saturation refers to the state of hydrogenation, or the amount of available hydrogen slots that are filled, of the fatty acid chain that dangles off the fat molecule’s glycerol backbone: saturated fats have all the available hydrogen slots filled and none of the carbons have double bonds. As the hydrogens are plucked off the fatty acid chain, double bonds between the carbon atoms are created and the fat is considered unsaturated. Now, to really give ourselves unpleasant flashbacks to organic chemistry, remember that double bonds can be in either the cis (the hydrogens are on the same side of the bond) or trans (the hydrogens are on opposite sides of the bond) conformation and the orientation of these bonds affects the structural and physical properties of the fat molecule. Saturated fatty-acid chains are nice and straight and favor lining up in an organized fashion. These fats are solid at room temperature, an important characteristic for their use in food, as we’ll see later. The cis orientation of unsaturated fats introduces a kink in the fatty acid chain (Figure 1) which makes the interactions with other molecules a bit clumsier and lowers the melting point such that cis-unsaturated fats are liquid at room temperature. Rotating the double bond into the trans conformation straightens the chains out and results in an unsaturated fat that acts more like a saturated fat in that it is semi-solid at room temperature. Nature seems to favor the cis conformation of unsaturated fats; in fact, the only naturally occurring source of trans fat that we consume comes from dairy products and meat from cows, sheep, and other ruminants (that is, animals that chew a cud). It is produced by bacteria in their stomachs and only accounts for a negligible percentage of our total intake of animal fat, usually about 0.5% of total energy intake. The vast majority of trans fatty acids that we consume come from industrially-produced products in the form of margarines, deep-fried fast foods, bakery products and packaged snack foods.

The brief history of industrial trans fatty acids begins around 1900 when it was found that unsaturated vegetable oils can be catalytically hydrogenated to form semi-solid fats. This is known as “hardening” in industry jargon and it results in a malleable fat that is solid at room temperature, but melts when baked or eaten. Crisco hit the market in 1911 and mass food manufacturing hasn’t looked back since.

Partial hydrogenation of vegetable oils opened up many doors for the producers of food products. Removal of part or all the double bonds improved the stability and decreased the rancidity. This means that the trans fat oil used in restaurants to fry food needed to be changed less and baked goods that used trans fat had a longer shelf life. The list of utilizable raw material was also expanded to include liquid oils that were previously unusable due to their propensity for spoiling or lack of hardness. With this process also came the ability to create “designer” fats with specific textural, functional and sensory properties by manipulation of the reaction conditions. In short, food manufacturers fell in love with hydrogenation because they were able to produce their products cheaper and keep them on the shelf longer without worry of them spoiling.

In the mid 50’s, when people were waking up and beginning to care about how the food they ate related to their health, science was uncovering the link between saturated fats and coronary heart disease (CHD). The table was set for trans fat products (which, remember, are technically unsaturated) to become the “healthy alternative” to saturated fats, and homes all across America began shunning butter in favor of margarine. It took until 1990 for the research to come out and convince the right people that trans fat products are not only just as bad for you as saturated fats -- whoops, they’re worse. Saturated fats are bad because they are known to increase the amount of low-density lipoprotein (LDL, or bad cholesterol). In addition to increasing LDL, trans fats also decrease levels of high density lipoprotein (HDL, or good cholesterol). Even though total cholesterol may not be changed by trans fat, the delicate balance of good vs. bad cholesterol is definitely perturbed in a decidedly non-heart-healthy way. Furthermore, the detrimental effects of trans fat are not limited to changes in cholesterol levels. The prevalence of CHD attributed to consumption of trans fat is greater than what would be predicted by the effect on cholesterol. This overlay of CHD is presumably caused by other heart killing and artery hardening factors that are independent of cholesterol, such as activation of inflammatory responses and disruption of endothelial cell function. By some estimations, on a per calorie basis, trans fats increase the risk of CHD more than any other macronutrient. Eating just 2 grams of trans fat a day can increase the risk of CHD by as much as 20%. Yikes!

For all the detrimental health effects of trans fats, there are zero reports of positive health benefits. It seems that at this point all the positive benefits of trans fats are realized by the food manufacturing industry in the form of increased profits, which is one reason why it might be taking so long for change to happen. The trans fat jig has been up, scientifically, since around 2001, but it has taken until recently for the FDA, public health officials, and more importantly food providers to take responsibility and action. Beginning January of 2006, the FDA is requiring that nutritional labels for all food and supplements include the content of trans fat. While this seems like a good first step, the labels aren’t required to report the whole truth – the cutoff for reporting is 0.5g of trans fat per serving. Anything less and the label is allowed a convenient round-down, and the product can be reported as having zero trans fat (typically billed as ZERO! TRANS! FAT!). Suppose you have 3 or 4 servings of a product that you believe to be zero trans fat; surprise, you may have inadvertently ingested as much as 2 grams of trans fat, which is, as discussed, consumption at potentially harmful levels. Interestingly, what these labels don’t say is as incriminating as what they do. Unlike most other ingredients, the trans fat listing doesn’t include a recommended percent daily value. This exclusion is an implicit admission by the FDA, acknowledging that trans fats are unhealthy at any level; however, for some reason they still allow them in the food supply. To me, this is tantamount to allowing arsenic, cyanide, or any other common poison into my food and is unacceptable.

The New York City Board of Health seems to agree with me, seeing as just a few months ago they passed a trans fat ban in restaurants that requires full compliance by July 2008. A similar ban has been proposed for Chicago and the whole country of Canada, while Denmark has been trans-fat-free since 2003. This move has understandably encountered serious opposition from the restaurant industry, as trans fats have become very well integrated into the food preparation system. Recipes will need to be changed, and equipment possibly updated. Slowly but surely, though, the big boys of the fast food industry are coming around. Wendy’s got rid of trans fat cooking oil in late 2006, KFC and Taco Bell committed to being free of trans fat by April of ’07. McDonalds, however, has been dragging their feet on the issue. They previously pledged to be free of trans fat in their restaurants by 2003, but only recently have they decided on an oil that they say doesn’t compromise their signature taste. They still haven’t committed to a date to make the switch, only that they’re “phasing it in”. Pretty weak, if you ask me. Hell, even the Girl Scouts got rid of trans fat in their cookies. I hate the idea of Johnny Law reaching his filthy paw into my stomach as much as the next guy (I think the recent fois gras ban in Chicago is a bit of an overstep of authority, for example), however, in the case of trans fats, I don’t think there is any alternative if you follow the epidemiological arrows.

To be sure, trans fats are unhealthy, but it’s worth reminding the public that they aren’t the only unhealthy substance out there. One of the dangers of putting too much blame on trans fats alone is that as they are phased out they will most likely be replaced by good old saturated fat, which is only a marginal upgrade in healthfulness. I can take a shit in a box and label it “zero trans fat” in big bold letters, but if you choose to eat it you’re still eating a turd – and I can’t believe that anyone would want to eat a turd. The factors conspiring against us living long healthful lives are many and monitoring only one is an open invitation for trouble. Proper labeling and comprehensive bans of restaurant use of trans fats is a beginning, but your health and keeping yourself alive is a matter of personal responsibility. So, put down that Big Mac, fatty, and grab yourself an apple.


Mozaffarian D, Katan MB, Ascherio A, Stampfer MJ, Willett WC. 2006. Trans fatty acids and cardiovascular disease. N Engl J Med. 354(15): 1601-13.

Willett WC. 2006. The scientific basis for TFA regulations – is it sufficient? Comments from the USA. Atheroscler Suppl. 7(2): 69-71.

Korver O, Katan MB. 2006. The elimination of trans fats from spreads: how science helped to turn an industry around. Nutr Rev. 64(6): 275-9.

The Mad Gastronomist

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