Soy research and expert insights
TRANS FAT FACT SHEETINTRODUCTION
During the 1960s and 1970s, consumers demanded that food companies eliminate fats such as lard, beef tallow and tropical oils (i.e. palm, palm kernel and coconut oils) from their products, in order to reduce saturated fat and cholesterol content. In many applications, the higher saturate oils were replaced
with partially hydrogenated vegetable oils. (Fully hydrogenated oils are very seldom used.) Hydrogenated oils have hydrogen atoms added to make the oil more stable, either solid at room temperature or still liquid but more resistant to oxidation. Without increasing dietary cholesterol or introducing high levels of saturated fat, hydrogenated oils offer more stability for certain food industry applications such as frying, baking and creating a desired texture in pastries, cookies and crackers.
However, recent studies have pointed to the possible negative health effects of trans fatty acids produced during the hydrogenation process, indicating that trans may behave like saturated fat in the body. Like saturated fat, trans fats raise LDL cholesterol (the "bad" cholesterol) levels when compared to unsaturated fats. But unlike saturated fats, trans fats may also lower HDL cholesterol (the "good" cholesterol) levels.
The average American eats a very small amount of trans fat compared to the amount of saturated fat consumed. Trans fat typically represents 2 to 4 percent of the American diet, while saturated fat represents approximately 11 to 12 percent.1 Health and nutrition professional organizations such as the American Dietetic Association (ADA) agree that limiting overall fat intake is the best strategy to lower saturated and trans fats.2
BACKGROUND ON FATS
The fats found in foods are essential to our diet. Fats supply the body with energy and essential fatty acids, promote the absorption of fat-soluble vitamins and provide insulation. Dietary Reference Intakes, issued by the Institute of Medicine (IOM) of the National Academies in 2002, recommend a range of 20 to 35 percent of total calories from fat to meet the body's daily energy and nutritional needs.3 Nutrition professionals generally suggest that our diets contain no more than 30 percent of calories from fat.4 In a 2000-calorie diet, 30 percent of calories from fat equates to almost 600 calories or 66 grams of fat per day.5
Many have hypothesized that fats with similar chemical structures may lead to similar health effects in the body. With trans fats, the hydrogen atoms exist on the opposite sides of the carbon chain. This causes the fatty acid to be a straighter chain, more like the straight chain of a saturated fatty acid than like either a monounsaturated or polyunsaturated fatty acid, which have bends in the chain where the carbon atoms have one hydrogen bonded to them instead of two.
Nature makes most mono- and polyunsaturated fatty acids in the cis form, meaning that the hydrogens that are bonded to the carbon atoms at the point of unsaturation are on the same side of the carbon chain. A small percentage of the fatty acids made in nature are made in the trans form, mainly in meat and dairy products and estimated to be less than 10 percent of the fatty acids present in these products. The other major source of trans fatty acids is partially hydrogenated vegetable oil. During the hydrogenation process, when hydrogen is added to make the fatty acids less unsaturated, some of the cis fatty acids will convert to the trans form.
HEALTH ISSUES RELATED TO TRANS FATTY ACIDS
Numerous research and epidemiological studies have been conducted over the past few years to try to determine the impact of trans fatty acids on cholesterol levels and coronary heart disease, with mixed results. One of the first studies to suggest a possible link between trans fatty acids and risk of heart disease was published in 1992. This study by Troisi, et al, found a correlation between increased consumption of trans fatty acids and an increase in LDL ("bad") cholesterol and decrease in HDL ("good") cholesterol.6 Troisi concluded that this could represent an increased risk of heart attacks. A review of dietary data from the Nurses' Health Study indicated that consumption of trans fatty acids was directly related to risk of coronary heart disease (CHD).7
More recently, a review of a number of studies also suggested that high levels of trans fatty acids in the diet appear to raise LDL cholesterol levels and reduce HDL levels8, but did not confirm an increase in CHD. A study on Dutch men found a positive correlation between trans fatty acid intake and the increase in CHD9; however, other scientists reviewing the study have questioned whether the results are from the consumption of trans fatty acids or from other forms of fats.10 The review of the Dutch study further indicates that the results of other epidemiological studies are inconclusive. In July 2002, the IOM issued a report concluding that trans fats boost LDL cholesterol levels more than saturated fat does, and diminishes HDL levels. The IOM did not set a recommended daily allowance for trans fats or establish safe upper levels, but recommended that people limit their intake as much as possible while eating an overall healthy diet.11
Separately, a 2006 literature review of 37 articles from 1997 to 2005 noted that other non-randomized, case-controlled studies have revealed a link between higher trans intake and heart disease outcomes.12 For instance, one study followed 78,778 women, free of heart disease and diabetes at baseline, for 20 years and found that trans intake was associated with an increased risk in CHD.13 The literature review also noted that the impact of trans fat intake on heart disease risk goes beyond the effect of high cholesterol, based on emerging research showing that trans also increases risk by adversely effecting endothelial function, inflammation, and LDL particle size. Studies have been conducted on healthy populations including those from the Nurses' Health Study14, 15, 16, 17 as well as populations with pre-existing hyperlipidemia and congestive heart failure.18,19
The American Dietetic Association recommends that patients with already high levels of LDL cholesterol limit their intake of foods high in trans fatty acids. Noting the effectiveness of medical nutrition therapy as a means to manage high blood cholesterol and reduce the factors associated with cardiovascular disease, the ADA accordingly developed a protocol for hyperlipidemia (high cholesterol) that includes a lifestyle goal of limiting foods high in trans fat.20 The studies examined in the ADA protocol were noted for their strong design, though doubts exist about their applicability to the general population, bias and adequacy of sample size in some of the studies. There are also inconsistencies in the results among the studies as a group.
Research at the University of Texas Southwestern Medical Center, reported in the Journal of the American Medical Association, compared the impact of a diet where all of the fat came from butter to one where the source of the fat was tub margarine.21 When 46 families went on the diet containing tub margarine,
80 percent of them had lower cholesterol levels than when following the diet containing butter. It should be noted that genetics also appeared to play a role, as parents whose cholesterol levels responded the most significantly to saturated fat also had children whose cholesterol levels responded the most strikingly.
TRANS FAT INTAKE LEVELS
The American Heart Association's Nutrition Committee advises that healthy Americans over the age of two limit saturated fat intake to <7% of total calories and limit intake of trans fats to <1% of total calories.22 Total fat intake should be between 20 and 35 percent of total calories.
The 2005 Dietary Guidelines for Americans, issued by the U. S. Department of Agriculture and Department of Health and Human Services suggest consuming a variety of nutrient-dense foods and beverages within and among the basic food groups while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol.23
Many food manufacturers have been working to reduce the amount of trans fatty acids in popular products by exploring new technologies and/or using soybean oil with improved fatty acid profiles for enhanced stability. As a result, a variety of cookies, crackers, potato chips, energy bars, popcorn and other snack foods now contain zero grams of trans fat for sensible snacking. As the following U.S. Food and Drug Administration chart illustrates, these product reformulations are particularly important since the advancements are in some of the largest product categories for typical trans fat consumption.
MAJOR FOOD SOURCES OF TRANS FAT FOR AMERICAN ADULTS 24
(Average Daily Trans Fat Intake is 5.8 Grams or 2.6 Percent of Calories)
BALANCING TRANS FATS IN A HEALTHFUL DIET
Most margarine products currently available in the marketplace, especially tub and squeeze/liquids, contain zero grams of trans fat. As a rule, the softer the margarine product, the fewer trans fatty acids it contains.25 The trans fatty acid levels in partially hydrogenated vegetable shortening used for baking and frying range from 14 to 18 percent, down from the 25 percent plus levels common in previous generations of shortenings.26
While most oil that is partially hydrogenated - canola, soybean and others - will contain trans fat, plain, non-hydrogenated soybean and other oils such as that used for salad dressing and mayonnaise do not contain any trans. (Nor do soy and soyfoods in and of themselves contain trans.) Soybean oil also offers one of the few non-fish sources rich in omega-3 fatty acids essential for various body functions.
In a 2006 study, consumers reported depending on soybean oil - commonly marketed as vegetable oil - as one of their two most frequent cooking oils, and
76 percent recognize it as a healthy choice.27
Public debates and discussions about the health effects of different types of fats have elevated general knowledge and awareness of dietary fats. Trans fatty acids represent a much smaller contribution to the overall diet than saturated fats, and new product formulations will make it even easier to limit intake of trans and saturated fats. Selecting a wide variety of healthful foods, incorporating fats in the diet in moderation and enjoying regular physical activity provide Americans with the building blocks for maintaining good health.
|TRANS FAT SOLUTIONS
Farmers, researchers and industry representatives are working together through a one-of-a-kind agricultural initiative, called QUALISOY™, with a primary goal of producing soybean oil that does not require hydrogenation and is even lower in saturated fat than current varieties. Some food manufacturers are already using the first of these enhanced soybean oils, a low linolenic variety, to produce food products with no trans fats.
- "Background on Dietary Fats & Fat Replacers," International Food Information Council. Online. 2005. http://www.ific.org/nutrition/fats/index.cfm.
- "Are Trans Fatty Acids Okay?" American Dietetic Association. Online.
- Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids, 2002, Institute of Medicine of the National Academies.
- "A Primer on Fats and Oils." American Dietetic Association Nutrition Fact Sheet, 2001.
- "To Get Lean, You Need Some Fat." Washington Post, February 12, 2002: HE02.
- Am. J. Clin. Nutr., 1992; 56: 1019-1024.
- Lancet, 1993; 341: 581-585.
- Fatty Acids in Foods and Their Health Implications 2nd edition, 2000; 667-686.
- Lancet, 2001; 357: 746-751.
- Lancet, 2001; 357: 732-733.
- "Trans fatty acids: Unsafe at any feed." Washington Post, July 16, 2002: HE03.
- Geriatrics Aging, 2006; 9(5): 358-364.
- Am J of Epidemiol, 2005; 161: 672-79.
- Am J Clin Nutr, 2004; 79: 606-12.
- Am J Clin Nutr, 2004; 79: 969-73.
- Metabolism, 2002; 12: 1534-7.
- Lipid Res, 2002; 43: 445-52.
- Am J Clin Nutr, 2004; 80: 1521-5.
- JADA, 2002 Jan; 102(1): 18-20.
- JAMA, 2000; 284: 2740-2747.
- Circulation. 2006 Jul 4;114(1): 82-96. Epub 2006 June 19.
- Dietary Guidelines for Americans 2005. US Department of Health and Human Services & US Department of Agriculture. 2005. Online. http://www.health.gov/dietaryguidelines/dga2005/report/HTML/D4_Fats.htm.
- U.S. Food and Drug Administration. 2003. Online.
- "Fun Facts and Figures." National Association of Margarine Manufacturers, 2001.
- Food Product Design, November 2001: 93-108.
- "Consumer Attitudes about Nutrition: Insights into Nutrition, Health and Soyfoods." United Soybean Board, 2006; 3.