Can Some Trans Fats Be Healthy?
Trans fats are one of the few food components that are widely accepted as being unhealthy, and for good reason. Industrial trans fats are created by pumping hydrogen molecules into liquid vegetable oil, changing the chemical structure and causing the oil to become a solid fat. Trans fats are generally considered to be especially harmful because they raise total cholesterol while lowering HDL cholesterol. However, as usual with conventional nutrition advice, there is far more danger to trans fats than simply the effect they have on cholesterol ratios. Mark Sisson has written a helpful explanation as to why trans fats are best to be avoided.
However, it may surprise you to learn that many of the foods recommended on a Paleo or whole foods diet contain trans fats as well. Dairy fat and meats from grass eating “ruminant” animals contain significant amounts of trans fatty acids, and grass-fed animals actually have higher levels of these trans fats than grain fed animals. (1) In fact, your grass-fed steak contains about 0.5g-1.4g of trans fat per ounce (28.3g) of total fat. (2)
Does this mean we should avoid all grass-fed animal products, cut out red meat, and only eat fat-free dairy if we want to reduce our risk of heart disease? Not at all! These naturally occurring trans fats in ruminant animal products are not at all harmful to our health, and may actually reduce the development of many different chronic diseases.
CLA: How is it different than industrial trans fats?
Naturally occurring trans fats are formed when rumen bacteria in the stomachs of ruminant animals (cows, sheep, etc.) digest the grass the animal has eaten and form trans-rumenic and trans-vaccenic acid via biohydrogenation of polyunsaturated fats in the grass. Conjugated linoleic acid, or CLA, is a trans-rumenic acid that is found abundantly in grass-fed meat and dairy products, and to a lesser degree in grain-fed products. It is also produced in our bodies from the conversion of trans-vaccenic acid (VA) from those same animal products.
Industrial trans fats have slightly different chemical structures than those trans fats found in beef and butter (specifically, the location of the double bond). CLA also has contains both cis- and trans- bonds, whereas most industrial trans fats have only trans bonds. But these minor differences in structure lead to majorly different effects in the body, as has been shown in many clinical and epidemiological studies. (3) While industrial trans fats are shown to increase the risk of heart disease, cancer, and obesity, CLA and other trans fats found naturally in animal products are actually thought to decrease the risk of those diseases.