What’s the ‘skinny’ on trans fat?

As always, I feel that my primary purpose of this blog is to debunk myths and dissect nutritional oversimplifications.  It is in that vein that I am approaching today’s topic, trans fat.  Although I feel that the ban on trans fats by the FDA is a definite step in the right direction, I wish to posit that there is a deeper level of complexity to this topic, as tag lines and generalizations are not particularly useful in any discussion that is firmly grounded in science.  The fact is that not all “trans fats” are created equal.  Yes, I know, I can already “hear” the gasps from my readers as I type these scandalous words!  But that does not make my statement any less true.

Trans fat is one of the few components in food that is widely (and blindly) accepted by all as being unhealthy for us, and not without some legitimate cause.  Industrial trans fats are created by pumping hydrogen molecules into liquid vegetable oil, radically changing the chemical structure and causing the oil to become a solid fat that can potentially clog our arteries.  Trans fats are generally considered especially harmful because they raise total cholesterol while lowering HDL cholesterol, the so-called “good” cholesterol.  However, as we dig deeper, we uncover an important nuance inherent to trans fat that is often overlooked.  Naturally occurring trans fats in ruminant animal products are not at all harmful to our health, and may actually reduce the incidence of numerous chronic diseases states.  Natural trans fats are formed when rumen bacteria in the stomachs of ruminant animals (e.g. healthy non-CAFO cows, sheep, etc.) digest the grass that the animal has eaten, thus forming trans-rumenic and trans-vaccenic acid via biohydrogenation of polyunsaturated fats in the grass.  Conjugated linoleic acid, or CLA, is a trans-rumenic acid found abundantly in grass-fed meat and dairy products in particular.  It is also produced in our bodies from the conversion of trans-vaccenic acid (VA) from those same animal products.

Industrial trans fats however have critically different chemical structures than those of trans fats found in grass-fed beef and butter, namely the location of the molecular double bond.  And now that we’ve put on our propeller hats, let’s geek out even more!  CLA (Conjugated Linoleic Acid), a natural trans fat, contains both cis- and trans- bonds, whereas industrial trans fats have only trans bonds, which is a big problem mainly because this is not a molecular configuration that occurs in Nature, and if there is anything that I have harped on in this blog, it is that any unnatural edible food-like substance that we keep putting into our bodies will most likely slowly kill us over time.  These seemingly minor differences in chemical structure lead to significantly different effects in the human body, as has been demonstrated by numerous clinical and epidemiological studies.  While industrial trans fats have been shown to increase the risk of heart disease, cancer and obesity, CLA and naturally-occurring trans fats found in healthy animal products may actually decrease the risk of those same diseases.

The takeaway is this: the trans fat contained in a bag of Doritos circa 1995 is indeed “bad” for us, whereas the trans fat in good old Irish Kerrygold butter is in fact “good”.  So is it best for the FDA to ban industrial trans fats?  Absolutely!  But should we then avoid all trans fats, even if they are naturally-occurring?  Absolutely not!


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