Frequently Asked Questions about the Trans Fat Index

Trans fats are unsaturated fats (i.e., fats with 1 or more double bonds) in which at least 1 of the double bonds is in the trans (instead of the more natural cis) configuration (see diagram below). Trans fats can occur naturally at fairly low levels in some meat and milk products, but most of the trans fats that Americans consume are industrially produced. That is, they are produced from liquid vegetable oils by the process of “hydrogenation”, which results in the creation of solid fats like shortening, margarine, etc.

Screen Shot 2014-02-28 at 8.35.22 AM

Examples of cis and trans-configured unsaturated fatty acids. Elaidic acid is the most common trans fatty acid in our food supply. Image from Mozaffarian D, et al. 2006, New England Journal of Medicine (click here for abstract).

Food industry began to produce margarines (which include trans fats) as a replacement for butter because the latter had been declared a health hazard due to its high saturated fat content. Industry needed an alternative for their frying and baking needs. Adding hydrogen to unsaturated oils created a semi-solid, trans fat product, e.g. Crisco, that was shelf-stable and made flakey baked goods and crispy fried chicken. Unfortunately, trans fats turned out to be worse than butter with regards to heart disease risk (See “Why are trans fats bad for my heart?”).  Now there is an effort to replace trans fats with alternatives, such as palm oil and, you guessed it, butter. The pendulum swings.

Processed foods, such stick margarine, baked goods, deep-fried fast foods, crackers and other pre-packaged snack foods, are our primary sources of industrially-produced trans fats. However, many of these types of foods are constantly being reformulated to reduce trans fat levels (See “What is being done to lower the trans fat content in foods?”).

Trans fats increase the risk for heart disease through negative effects on cardiovascular risk factors which leads to an increased risk for heart attacks.  Trans fats cause an increase in the “bad” (LDL) cholesterol, a reduction in the “good” (HDL) cholesterol, and worsens the total cholesterol:HDL-cholesterol ratio compared to cis-unsaturated and saturated fats.  Inflammatory makers, such as C-reactive protein and interleukin-6, were elevated in obese women with higher vs. lower intakes of trans fats. Endothelial function (blood vessel health) was worsened in clinical trials when subjects consumed trans fats in the place of monounsaturated fats or carbohydrates.


Higher trans fat levels in red blood cells was associated with a 47% increased risk for sudden cardiac death in a case-control study. Some studies also show an increased risk of diabetes in women who consumed more trans fats, but this is not as consistent as the heart disease data. It is estimated that eliminating trans fat from the food supply would avert between 6-19% of heart disease-related deaths per year, totaling up to 228,000 deaths.


This information is sourced from the article, “Trans Fatty Acids and Cardiovascular Disease,” published in The New England Journal of Medicine in 2006 by Dr. Dariush Mozaffarian et al. 2006. Please click here for access to the abstract of the paper.

Trans fats are an excellent product for baking and frying, but they are being removed from the food supply due to the discovery of their effect on heart disease risk. Indeed, the Food and Drug Administration removed the GRAS (Generally Recognized As Safe) status from trans fats in 2013, meaning that food processors must get permission to use trans fats in their foods. Many food processers have been removing and replacing trans fats from their products for years. The following graph shows the progress that has been made in lowering trans fat levels in foods with traditionally high levels. US consumers can expect these levels to drop further once the FDA ruling comes into effect.

Screen Shot 2014-02-28 at 11.16.31 AM

Average trans fatty acid (TFA) content from 2007 through 2011 of brand-name US supermarket food products that contained ≥0.5 g/serving trans fatty acids in 2007, by food categories. Data were not collected in 2009. All products listing 0 g trans fatty acids but still containing partially hydrogenated oils in the ingredients list were considered to still contain 0.25 g per serving of trans fatty acids. Image from Otite FO, et al. 2013, Prev Chronic Disease. To access the complete article, please click here.

The Nutrition Facts Panel on packaged foods lists the amount of trans fats per serving. If a serving of the food has less than 0.5 g of trans fat, then the manufacturer can list it as “0.” Non-packaged foods like bulk grains, cereals, candies; store-packaged meat; fresh fruits and vegetables do not have a Nutrition label and thus any trans fats in those foods will not be listed. The vast majority of trans fats in the US diet are found in packaged foods. The Nutrition Facts Panel example given here is the updated version, proposed by the FDA in 2014. Click here for more information.


The cut points were derived from a combination of two sets of data. First, based on over 27,000 samples analyzed at OmegaQuant Analytics over the last few years, we have an idea of the distribution of the Trans Fat Index in the US population.  Second, we used published data from Sun et al. (Circulation 2007;115:1858-1865) in the Nurses’ Health Study. These researchers measured levels of industrially-produced trans fats in red blood cell membranes and related those levels to risk for cardiovascular events. They found a statistically significant, direct relationship between the Trans Fat Index and heart disease – higher levels were associated with higher risk. Those women in the highest 25% of the population (4th quartile) were 2.8x as likely to have a cardiac event as women in the lowest quartile.


Based on these two data sets, we chose the lowest quartile in the Sun paper (1.0%) as the upper limit of the Desirable level, and we chose the highest quartile (1.65%) as the beginning of the lower limit of the Undesirable category. Individuals between 1% and 1.65% would be considered in the Intermediate zone. In the 27,000 sample data set from OmegaQuant, only about 13% of the population had a Desirable Trans Fat Index; 65% of the population had an Intermediate score; and 22% of the population was in the Undesirable range.

Graph TFI

Since we still need more data to really know what the “healthiest” level of trans fats would be, it is more important for the consumer to see a decrease in his/her Trans Fat Index after making healthier dietary choices than for the consumer to be in a specific risk group. In other words, lowering the Trans Fat Index from whatever level it is at the start shows good progress and would be expected to lower heart disease risk.