Trans Fatty Acids

Foods High in Trans Fats

Synthetic or industrial trans fats can be added to various foods (Picture 2, Chart 1).

Picture 2. Examples of foods with added (industrial) trans fats

Chart 1. List of Common Foods High in Trans Fats
Food	Trans fats (g)
French fries (1 serving)	0-6.1*
Vegetable shortening (1 tbsp, 13 g)	2-5.5
Breaded chicken nuggets (1 serving)	0-5*
Partially hydrogenated oil (1 tbsp, 14 g)	0.5-4.5*
Pies (1 serving)	2-4.7*
Vanaspati ghee [vegetable ghee used in South Asia] (1 tbs, 14 g) [22,23]	0.5-4
Margarine, hard (stick) (1 tbsp, 14 g)	0.5-3.5
Cheeseburger, hamburger (200-400 g)	1-3*
Pancakes (1 serving)	0.1-3
Doughnuts (1 serving)	0.1-2.7
Cake (1 piece, 144 g)	2
Other: Spreads, nondairy coffee cream, salad dressings Commercially baked products: biscuits, brownies, cakes, cookies, crackers, muffins Deep-fried fast food products and packaged snack foods: fried chicken, microwave popcorn, potato chips, tortilla chips, granola bar Candies, confectioner coating, peanut butter Burrito Frozen products: breaded fish sticks, cinnamon rolls, meatballs, pie crusts, pizza dough, ready-made frosting, waffles Dry mixes: Cake, pancakes, mac mixes Soft (tub) margarines Sunflower seeds (oil roasted)	0-2 g/serving

* Some fast food chains and restaurants in the United States have stopped using trans fats, so certain foods listed in the chart as high in trans fats may actually have almost no trans fats ^[29]. The amount of trans fats in foods can vary greatly among brands; you may find exact data on the producers’ websites.
Sources: USDA.gov ^[2], The New England Journal of Medicine (data from 2002) ^[18]

Food Products Without Artificial Trans Fats

When producers do not use trans fats in the food processing, all their foods, including those in Chart 1, can be free of artificial trans fats. Zero trans fat French fries, potato chips, chicken nuggets, pies, margarines and shortening are available. You can usually find the amount of trans fats in foods on producers’ websites.

In the United States, food products that contain less than 0.5 g trans fat are considered trans fat free ^[28]. Below is a list of foods that that contain practically zero artificial and natural trans fats (<0.2 g/serving) ^[2]:

• PLANT FOODS:
  • Vegetable oils: canola (non-hydrogenated version of low-erucic-acid rapeseed oil), corn, cottonseed, hazelnut, linseed, olive, peanut, rice-bran, safflower, sesame, soybean, sunflower and walnut oil (except when they are “partially hydrogenated”)
  • Coconut, palm and palm-kernel oil
  • Certain margarines and margarine-like spreads (there should be no “trans fats” on Nutrition Facts labels and no “partially hydrogenated oil” or Ingredients labels)
  • Most breakfast cereals
  • Nuts and seeds
  • Legumes
  • Fruits
  • Vegetables
  • Most candies
• ANIMAL FOODS:
  • Fish and other seafood
  • Most yogurts and ice creams
  • Eggs
  • Mayonnaise
  • Milk chocolate

Are natural or ruminant trans fats harmful?

According to 3 systematic reviews (2006, 2011), there is no association between the intake of natural trans fats and coronary heart disease ^[12,18,21]. The potential health benefits of conjugated linolenic acid (CLA) found in milk have not been proven so far ^[21].

Trans fats occur naturally occur in red meat: beef, lamb and veal (up to 2 g/3 oz) and, in smaller amounts (<0.5 g/serving), in pork, poultry, cheese (American pasteurized, cheddar, mozzarella, Mexican quesadilla), milk and butter ^[2].

Reheating Oils and Formation of Trans Fats

In few baking and stir-frying experiments, ordinary heating of vegetable oils, like canola oil, to up to 527 °F (275 °C), did not significantly increase the amount of trans fatty acids ^[38,39]. It is not only heating but adding hydrogen to oils in the presence of a catalyst, like nickel, that converts cis unsaturated fats to trans fats ^[40].

Cooking at relatively low temperatures (325-375° F or 163-191° C) can actually spoil certain oils, such as extra virgin olive oil, but this is because of formation of free fatty acids, which have a bad taste, and not due to formation of trans fatty acids.

The Effect of Industrial Trans Fats on Blood Cholesterol Levels

Trans fats increase the blood levels of:

• Total cholesterol ^{[3,4-V9,6,18]}
• LDL cholesterol ^{[3,4-V9,6,18]} and small dense LDL particles ^[18] but probably not oxidized LDL cholesterol levels ^[37]
• Total/HDL cholesterol ratio ^[3,6,18]
• Triglycerides ^[5,18,36]
• Lipoprotein Lp(a) ^[18,36]

All of the above changes in blood lipid are associated with increased risk of coronary heart disease ^[18].

Harmful Effects of Trans Fats

Trans Fats, Inflammation and Atherosclerosis

There is CONFLICTING EVIDENCE about the effect of trans fats on systemic inflammation: in one interventional study, trans fats increased markers of inflammation ^[52] but in another one did not ^[49]. There is another conflict in observational studies: in 2 reviews of the Nurses Health Study I, two different groups of researchers have found different markers of inflammation ^[53,54,55].

Based on 2 observational studies in individuals with documented atherosclerosis of the coronary arteries, there is LIMITED EVIDENCE that intake of trans fats is associated with atherosclerosis, which is the main cause of coronary heart disease ^[47,48].

Trans Fats and Coronary Heart Disease and Stroke

According to several studies, systematic reviews and meta analyses, high trans fat intake increases the risk of coronary heart disease:

• According to two 2009 systematic reviews, there is convincing evidence that intake of trans fats increases the risk of coronary heart disease ^[16,17].
• According to a opinion of European Food safety Authority from 2007, there is association between higher intakes of  trans fats and coronary heart disease ^[36].
• According to one 2006 review of studies, an increase of trans fat intake by 2% of calorie intake (5 g trans fat in a 2,000 Cal diet) is associated with 23% increase in incidence of coronary heart disease ^[19].
• According to 2 reviews (1993, 1997) of the Nurses Health Study, consumption of trans fats (margarine, biscuits, cakes, white bread) may be associated with coronary heart disease in women ^[14,15].
• According to one 1999 review, trans fats increase the risk of coronary heart disease ^[19].

Some studies have found only weak or no association between high trans fat intake and heart disease, though:

• According to one 2011 systematic review and meta analysis of studies, there is only small, insignificant association between intake of industrial trans fats and chronic heart disease ^[12].
• In the Health Professionals Follow-Up Study (1986-1992), trans fat intake, when adjusted for dietary fiber and total fat intake, was negatively associated (0.93) with a risk of fatal coronary heart disease ^[9], while in one prospective Finnish study (1985-1988), trans fat intake was associated with increased risk of coronary heart disease regardless of fiber intake ^[57].
• In the 1995 EURAMIC study in several European countries and Israel, trans fat intake (estimated from the trans fat content of the body fat) in men who had heart attack was not greater than in men who did not have heart attack ^[10].
• In another 1995 study, individuals who have died from sudden cardiac death due to coronary heart disease did not have greater amounts of trans fats in their body fat than healthy live individuals ^[11].

Trans Fats and Diabetes 2

There is INSUFFICIENT EVIDENCE about trans fatty acids as a risk factor for diabetes 2 ^[7,8,18,36].

Trans Fats and Cancer

There is NO CONSISTENT EVIDENCE about the association between trans fat intake and cancer ^[31,36].

• In one prospective study in men (1982-1995) ^[32], but not in another one (1994-2003) ^[34], trans fat intake was associated with increased risk of prostate cancer. Note, that at the time of the studies, the average trans fat consumption was much higher than today.
• In one prospective study in women (1989-2002), trans fat intake was supposedly associated with increased risk of breast cancer ^[33].

Trans Fats and Other Health Risks

• According to one 2014 systematic review of observational studies, intake of trans fats is associated with increased risk of Alzheimer disease ^[13].
• According to one prospective study in married women (1991-1999), high intake of trans fats may increase the risk of ovarian infertility ^[35].
• There seems to be no association between trans fat intake and allergies, high blood pressure or thrombosis ^[36].

How much trans fats is too much?

According to one 2006 review of studies, as low as 2 grams of trans fats per day can increase the risk of coronary heart disease ^[19]. American Heart Association recommends to limit trans fats to less than 1% of energy intake, that is less than 2 g of trans fats in a 2,000 Calorie diet ^[25]. Dietary Guidelines for Americans 2010 by US Department of Agriculture recommend avoiding trans fats as much as possible ^[20].

FDA and Trans Fats

According to the US Food and Drug Administration (FDA) regulation, all foods that contain 0.5 grams or more trans fat per serving have trans fat listed on the Nutrition Facts labels ^[28]. FDA has also removed trans fats and partially hydrogenated soybean and cottonseed oil from the list of Generally Recognized As Safe (GRAS) food ingredients ^[1,43], which means they may become illegal in the United States in near future. On the other hand, partially hydrogenated menhaden oil ^[1,50] and partially hydrogenated version of low-erucic-acid rapeseed oil (LEAR), known as canola oil ^[1,51] are still listed as GRAS.

Trans Fat Ban

In Europe, trans fats are “nearly banned” in Denmark, Austria, Hungary, Iceland, Norway and Switzerland ^[44]. In general, the use of trans fats in Western Europe has declined, while in Eastern Europe may still be high ^[30].

In the United States, in the New York City ^[45] and California ^[46], trans fats are banned in restaurants.

Related Nutrients

• Fats
• Saturated Fats
• Cholesterol
• Dietary Fiber
• Proteins