Trans Fats in the Food Supply

Industrial trans fatty acids are unnatural fat molecules formed by a process called partial hydrogenation. (A small amount of a beneficial isomer of trans fat is found in meat fats and butter.) In the partial hydrogenation process, heated liquid oils are flooded with hydrogen gas in the presence of a nickel catalyst. This process causes a rearrangement of the hydrogen atoms in the fat molecule, moving one or more hydrogen atoms across to the other side of the molecule (trans means across), causing the polyunsaturated fat molecule, which is normally bent or wavy, to straighten out into a straight molecule. These straight molecules pack together easily, so they behave chemically like saturated fats. They are solid at room temperature and stable; the food processing industry prefers to use cheap partially hydrogenated fats rather than more expensive saturated animal fats or tropical oils for baked goods and fried foods.

In recent years, scientists have consistently pointed to the health dangers of dietary trans fats. In 2005, the National Academy of Sciences (NAS) stated “that dietary trans fatty acids are more deleterious with respect to coronary heart disease than saturated fatty acids.” In addition, trans fatty acids have been increasingly implicated as contributing to type-two diabetes, cancer, heart disease, auto-immune disease, tendon and bone degeneration, and problems with fertility and growth. Because of these facts and concerns, the NAS concluded there is no safe level of trans fat consumption. As a result of these recommendations, the FDA required labeling of trans fat content of food beginning January 1, 2008.

Faced with the new labeling requirement, the food industry has worked hard to minimize the levels of trans fats in processed foods. Many foods are touted as “trans fat free,” but in fact do contain trans fats. This is because food manufacturers are allowed to claim “zero trans fats” if the food contains .5 grams of trans fat or less per serving.

Often serving sizes are very small, so that consumers can end up eating quite a lot of trans fat if they eat several servings.

winter2011_knowyourfattable1TEST RESULTS

The Weston A. Price Foundation contracted with the Burnsides Research Laboratory (see page 35) at the University of Illinois to test trans fat levels in common grocery items. We found that trans fat levels generally conformed to amounts of trans fat on the labels (see Table 1), with all products labeled as “zero trans fats” containing less than 0.5 grams of trans fat per serving. Some of these serving sizes are very small, however: a serving size for chips is twenty-eight grams or just under two tablespoons. Someone eating a whole bag of potato or corn chips will be taking in quite a bit of trans fats. The serving size for Ritz crackers is one cracker.

Yet, overall, it can be seen that the food industry has greatly reduced the levels of trans fats in the food supply, In fact, Oreo cookies and Pepperidge Farm Goldfish crackers tested at zero; no trans fats found.

In liquid vegetable oils, the trans fat content is likely formed during deodorization, which involves a light hydrogenation process called “brush” hydrogenation.


We also tested these same products for levels of saturated, monounsaturated and polyunsaturated fatty acids. What we found were fairly high levels of saturated fat in these foods—saturated fat largely taking the place of trans fats, an ironic move since trans fats were first introduced into the market to take the place of saturated fat.

These saturated fats are coming from one of two sources: either naturally occurring saturated fat from palm oil, or manufactured saturated fats from fully hydrogenated vegetable oil (usually soybean oil). Full hydrogenation involves the same process as partial hydrogenation but the process goes on longer and more hydrogen is added.

The saturated fatty acids are then interesterified with monounsaturated and polyunsaturated fatty acids, creating triglycerides in which the arrangement of fatty acids results in the maximum benefit (stabilizing qualities) of the saturated fat. Interesterification moves these fatty acids around with the result that the interesterified fat has different melting and baking qualities. Fully hydrogenated oil is very hard, so only a small amount is needed—about 10 percent—to blend and interesterify with the liquid oil to produce a spreadable fat. (See

These interesterified oil blends may not contain trans fats but they have their own dangers, the main one stemming from the very high heat applied during the interesterification process. This ensures that the remaining unsaturated fatty acids will contain high levels of cancer-causing free radicals. Note, for example, that the trans-free Goldfish cracker contains high levels of omega-6 and a small portion of omega-3 fatty acids. These are bound to be rancid, full of free radicals after initial processing followed by interesterification. Country Crock “heart healthy” spread is very low in trans fats but exceptionally high in fragile omega-6 fatty acids.

Lesson to be learned: Buyer beware. Just because a product is labeled “trans free” does not mean it is healthy!


This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Winter 2011.

Sally Fallon Morell is the founding president of the Weston A. Price Foundation and founder of A Campaign for Real Milk. She is the author of the best-selling cookbook, Nourishing Traditions (with Mary G. Enig, PhD) and the Nourishing Traditions Book of Baby & Child Care (with Thomas S. Cowan, MD). She is also the author of Nourishing Broth (with Kaayla T. Daniel, PhD, CCN).

2 Responses to Trans Fats in the Food Supply

  1. Apple Wine says:

    Can the Body Break Down Stored Trans-Fats
    Can the body break down stored trans fat in adipose tissue? What do we know about trans fats stored in adipose tissue and the breakdown and removal of this fat from the body as compared to non-trans fat? Does this question make sense? Would strength training be just as effective at removing trans fat adipose tissue just as much as regular fat? If not, how much more difficult?

  2. applewine says:

    What about Hydroginated Oil
    Should any hydrogenated oil be avoided? Should canola oil be avoided since it is always hydrogenated? Legally I’d be interested in somebody creating a term that means food is 0 free of a list of a few main things that is really bad for you. Trans fat, hydrogenation, rancid causing processing and soybean oil. If I could have a word for that I’d start asking for it before ordering restaurant food. What are the top things that would fit this list?

Leave a reply

© 2015 The Weston A. Price Foundation for Wise Traditions in Food, Farming, and the Healing Arts.