US panel says no amount of trans fat is safe

Last Updated: 2002-07-11 10:01:03 -0400 (Reuters Health)

By Todd Zwillich

WASHINGTON (Reuters Health) - Pastry and fried food lovers beware: there is no level of trans fatty acids that is safe to consume, a report from the Institute of Medicine concluded.

The report is likely to lead the US Food and Drug Administration (FDA) to go ahead with stalled plans to order manufacturers to disclose the trans fatty acid content of foods on packaging.

An expert panel at the Institute of Medicine issued a detailed review of research into trans fatty acids, the class of fat found in abundance in stick margarine, hydrogenated vegetable shortening and foods that contain them.

Though the panel had the option to declare a safe upper limit of daily trans fatty acid consumption, it declined to do so. "It is recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet," the report concludes.

Trans fatty acids are known to increase blood levels of low density lipoprotein (LDL), so-called "bad" cholesterol, while lowering levels of high density lipoprotein (HDL), known as "good" cholesterol. A blood profile containing high LDL and low HDL is a strong risk factor for heart disease.

Trans fatty acids are common in foods containing shortening, including pastries and fried foods, and are found in lower levels in dairy products and meats.

FDA proposed ordering the labeling of trans fatty acid levels on food packages in 1999 but held off finalizing the regulation until the Institute of Medicine issued its report. The agency is likely to go ahead with a rule ordering the labeling, according to press reports.

The Center for Science in the Public Interest first petitioned FDA for the labeling changes in 1994. Margo Wootan, the group's director for nutrition policy, said in a statement that the agency should now require manufacturers to display trans fatty acid values next to saturated fat levels.

"The report leaves the FDA with only one choice," she said.

Trans fat worse for heart than saturated fat

By Suzanne Rostler

NEW YORK, Jul 12 (Reuters Health) - When choosing between a thick juicy steak and a heaping plate of French fries, the meat just might be the healthier option, a study from the Netherlands suggests.

The study measured the effect of trans fat, found in fried foods and processed foods such as cookies, crackers and pastries, and of saturated fat, found in meat, butter and some dairy products, on blood vessel function and cholesterol levels.

Researchers fed 29 healthy, nonsmoking adults two different diets. The "Trans-diet" contained 9.2% of total calories from trans fat and the "Sat-diet" diet contained the same proportion of calories from saturated fat. Individuals followed the diets for 4 weeks, and then switched to the other diet for 4 weeks.

Dr. Nicole M. de Roos, of Wageningen University, and her colleagues studied participants' blood vessel function by measuring how readily the vessels dilated in response to blood flow. Relatively poor dilation is a marker of heart disease risk.

According to the results, the trans-fat diet reduced this blood vessel function by 29% and lowered HDL ("good")-cholesterol levels by about one fifth, compared with the saturated-fat diet. Previous research has shown that trans fats, like saturated fats, also raise LDL ("bad")-cholesterol levels.

"This suggests that trans fatty acids increase the risk of heart disease more than the intake of saturated fats," the researchers conclude.

In an interview with Reuters Health, de Roos said that companies manufacturing foods such as doughnuts and cookies should report how much trans fat is found in the item on the label. Additionally, restaurants could use liquid vegetable oils, which do not contain much trans fat, rather than solid "hydrogenated" fats to fry foods. Hydrogenated fats are oils that undergo a process to make them solid at room temperature.

"The major sources of trans fats in our diet are the ready-made baked goods and fried fast foods," de Roos explained. "These foods are not labeled, so the consumer does not know how much trans fat he gets."

Trans fat accounts for 4% to 7% of dietary fat intake in the US and The Netherlands, according to the report in the July issue of Atherosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.

To reduce the amount of trans fats in the diet, the American Heart Association recommends that consumers cook with unhydrogenated oils such as canola or olive oil and choose processed foods made with these oils rather than with hydrogenated or saturated fat.

Low-fat margarine, a minor source of trans fat, should be used instead of butter, which contains both trans and saturated fats. Liquid or tub margarines are preferable to stick varieties.

SOURCE: Atherosclerosis, Thrombosis and Vascular Biology 2001;21:00-00.

Copyright © 2001 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.

So does anyone know where we can find an online calculator that shows trans fats? I looked at USDA and, if they are shown, I don't know how to identify them.

;-Deb

Hi Deb,

Actually, I've never heard of a trans fat breakdown anywhere.

Dr Eades in Protein Power LP says on p. 61 that trans fat is "an unnatural, processed fat" and is "widely used for baking, turning up in all kinds of processed foods" "largest contributors ... are white bread, rolls, crackers, doughnuts, cookies, and cakes."

p. 80 includes french fries, potato chips, margarines, salad oils, bakery goods, corn chips, and candies. "sandwich cookies, vanilla wafers, animal crackers, and honey graham crackers."

The one ingredient to look for on all labels to find trans fat is "Partially hydrogenated vegetable oil" (meaning also partially hydrogenated soy oil and partially hydrogenated corn oil, etc.)

Vegetable oils that are in clear, plastic bottles and that do not need to be refrigerated are almost always partially hydrogenated. They shoot the oil full of hydrogen atoms. This makes the oil more rigid, increases its shelf-life to almost unlimited, and makes an unnatural oil. So unless the oil needs to be in a dark glass bottle, they've preserved it by altering the fat to an unnatural trans fat. Our bodies use these rigid unnatural oils in our cells and it hurts everything from our immune system to our cholesterol levels.

Stick margarine is pure trans fat. The article saying low-fat margarine is better than butter is only saying this because they are afraid of butter's saturated fat and because a low-fat spread will have less trans fat because it has less fat altogether. But you can be that the small amount of fat it has is 100% trans fat.

I believe these articles are wrong in saying meat and dairy have trans fat. Since everything I've read shows that trans fat is a man-made fat, I don't see how this can be true. This is my next avenue for research.

This is one of the trans fat studies done to prove saturated fat was safer than trans fat.

J Nutr 2001 Feb;131(2):242-5

Consumption of a solid fat rich in lauric acid results in a more favorable serum lipid profile in healthy men and women than consumption of a solid fat rich in trans-fatty acids.

de Roos N, Schouten E, Katan M.


Solid fats are used in food manufacturing to provide texture and firmness to foods. Such fats are rich in either saturated or trans-fatty acids, both of which increase the risk of coronary heart disease. Epidemiological and experimental studies suggest that trans-fatty acids increase risk more than do saturates because they lower serum high density lipoprotein (HDL) cholesterol. However, there appear to be differences between saturates in their effect on HDL cholesterol. We investigated whether the consumption of a solid fat rich in lauric acid (C12:0) would result in a more favorable blood lipid profile than the consumption of a solid fat rich in trans-fatty acids. We fed 32 healthy men and women two controlled diets in a 2 x 4-wk randomized crossover design. The diets consisted of a background diet supplemented with margarines. In the trans-diet, 9.2% of energy was provided by trans-fatty acids and 12.9% by saturated fatty acids. In the Sat-diet, energy intake was 0% from trans-fatty acids and 22.9% from saturated fatty acids. Lauric acid composed one third of all saturates in the Sat-diet. Serum HDL cholesterol was 0.36 mmol/L lower at the end of the trans-diet than at the end of the Sat-diet (95% confidence interval, -0.46 to -0.26), whereas serum low density lipoprotein cholesterol and triglyceride concentrations remained stable. Serum total cholesterol was 0.31 mmol/L (95% confidence interval, -0.48 to -0.14) lower at the end of the trans-diet than at the end of the Sat-diet. Consumption of a solid fat rich in lauric acid gives a more favorable serum lipoprotein pattern than consumption of partially hydrogenated soybean oil rich in trans-fatty acids. Thus, solid fats rich in lauric acids, such as tropical fats, appear to be preferable to trans-fats in food manufacturing, where hard fats are indispensable.

Another trans fat study. Our friend Willet is in on this one:

Circulation 1994 Jan;89(1):94-101

Comment in:
Circulation. 1994 Nov;90(5):2568-9; discussion 2573-7.

Trans-fatty acids intake and risk of myocardial infarction.

Ascherio A, Hennekens CH, Buring JE, Master C, Stampfer MJ, Willett WC.

Department of Nutrition, Harvard School of Public Health, Boston, MA 02115.

BACKGROUND: Concern that trans-fatty acids formed in the partial hydrogenation of vegetable oils may increase the risk of coronary disease has existed for several decades, but direct evidence on this relation in humans is limited. METHODS AND RESULTS: With a case-control design, we studied the association between intake of trans-fatty acids and a first acute myocardial infarction among 239 patients admitted to one of six hospitals in the Boston area and 282 population control subjects. Intake of trans-fatty acids was estimated using a previously validated food frequency questionnaire. After adjustment for age, sex, and energy intake, intake of trans-fatty acids was directly related to risk of myocardial infarction (relative risk for highest compared with lowest quintile, 2.44; 95% confidence interval, 1.42, 4.19; for trend P < .0001). This relation remained highly significant after adjustment for established coronary risk factors, multivitamin use, and intake of saturated fat, monounsaturated fat, linoleic acid, dietary cholesterol, vitamins E and C, carotene, and fiber. Intake of margarine--the major source of trans-isomers--was significantly associated with risk of myocardial infarction. CONCLUSIONS: These data support the hypothesis that intake of partially hydrogenated vegetable oils may contribute to the risk of myocardial infarction.

I think this is the study (1st post) the USDA based it's decision on, to require trans fats declared in food lables. Press release posted here:

http://forum.lowcarber.org/showthre...&threadid=50159

Wa'il

Regarding trans fat in meat and dairy: Technically, there shouldn't be any trans fat in meat and dairy. However, if the meat has been cooked in margarine or deep fried in partially hydrogenated vegetable oil, then it has trans fat. Also, a mother who eats french fries and donuts during pregnancy will have trans fat in her breast milk. Theoretically, dairy could also have trans fat if the cows were fed it somehow.

However, meat and dairy are not the things to worry about when it comes to trans fat. Trans fats do not naturally occur in meat and dairy. The real culprit in the trans fat scenario is carbohydrates that have been processed i.e. junk foods and some oils. Cut these out and you've cut out most of the trans fat in your diet. As far as the trans fat and oil connection, canola and olive oil appear to be the best.

Found the study from the Netherlands quoted from the above article:

Lancet 2001 Mar 10;357(9258):746-51

Comment in:
Lancet. 2001 Mar 10;357(9258):732-3.

Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study .

Oomen CM, Ocke MC, Feskens EJ, van Erp-Baart MA, Kok FJ, Kromhout D.

Department of Chronic Diseases Epidemiology, National Institute of Public Health and the Environment, Bilthoven, The Netherlands. claudia.oomen~rivm.nl

BACKGROUND: Evidence on the relation between trans fatty acid intake and coronary heart disease is limited. We investigated this relation in a Dutch population with a fairly high trans fatty acid intake, including trans fatty acids from partly hydrogenated fish oils. METHODS: We prospectively studied 667 men of the Zutphen Elderly Study aged 64-84 years and free of coronary heart disease at baseline. We used dietary surveys to establish the participants' food consumption patterns. Information on risk factors and diet was obtained in 1985, 1990, and 1995. After 10 years of follow-up from 1985-95, there were 98 cases of fatal or non-fatal coronary heart disease. FINDINGS: Between 1985 and 1995, average trans fatty acid intake decreased from 4.3% to 1.9% of energy. After adjustment for age, body mass index, smoking, and dietary covariates, trans fatty acid intake at baseline was positively associated with the 10-year risk of coronary heart disease. The relative risk for a difference of 2% of energy in trans fatty acid intake at baseline was 1.28 (95% CI 1.01-1.61). INTERPRETATION: A high intake of trans fatty acids (all types of isomers) contributes to the risk of coronary heart disease. The substantial decrease in trans fatty acid intake, mainly due to industrial lowering of trans contents in Dutch edible fats, could therefore have had a large public-health impact.

Okay, there is a naturally occurring type of trans fat in dairy. However, although this is called "trans fat" it is different from the kind synthetically produced in processed junk foods.

Biol Res 1999;32(4):273-87

Trans fatty acid isomers in human health and in the food industry.

Valenzuela A, Morgado N.

Laboratorio de Lipidos y Antioxidantes, INTA, Universidad de Chile, Santiago, Chile. avalenzu~uec.inta.uchile.cl

Trans fatty acids are unsaturated fatty acids with at least one double bond in the trans configuration. These fatty acids occur naturally in dairy and other natural fats and in some plants. However, industrial hydrogenation of vegetable or marine oils is largely the main source of trans fatty acids in our diet. The metabolic effect of trans isomers are today a matter of controversy generating diverse extreme positions in light of biochemical, nutritional, and epidemiological studies. Trans fatty acids also have been implicated in the etiology of various metabolic and functional disorders, but the main concern about its health effects arose because the structural similarity of these isomers to saturated fatty acids, the lack of specific metabolic functions, and its competition with essential fatty acids. The ingestion of trans fatty acids increases low density lipoprotein (LDL) to a degree similar to that of saturated fats, but it also reduces high density lipoproteins (HDL), therefore trans isomers are considered more atherogenic than saturated fatty acids. Trans isomers increase lipoprotein(a), a non-dietary-related risk of atherogenesis, to levels higher than the corresponding chain-length saturated fatty acid. There is little evidence that trans fatty acids are related to cancer risk at any of the major cancer sites. Considerable improvement has been obtained with respect to the metabolic effect of trans fatty acids due the development of analytical procedures to evaluate the different isomers in both biological and food samples. The oleochemical food industries have developed several strategies to reduce the trans content of hydrogenated oils, and now margarine and other hydrogenated-derived products containing low trans or virtually zero trans are available and can be obtained in the retail market. The present review provides an outline of the present status of trans fatty acids including origin, analytical procedures, estimated ingestion, metabolic effects, efforts to reduce trans isomers in our diet, and considerations for future prospects on trans isomers.

Sorry if I'm giving anyone brain-overload. I thought it was important to show that meat and dairy contained relatively low amounts of trans fat.

J Cardiopulm Rehabil 2000 May-Jun;20(3):143-6

Dietary trans fatty acid.

Lichtenstein AH.

Lipid Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA. Lichtenstein~HNRC.Tufts.edu

Trans fatty acids are unsaturated fatty acids that contain at least one double bond in the trans configuration. In the diet they occur at relatively low levels in meat and dairy products as a by-product of fermentation in ruminant animals or in hydrogenated fats as a consequence of the hydrogenation process. In general, dietary hydrogenated fat/trans fatty acids have been reported to increase LDL cholesterol levels relative to oil in the natural state or cis fatty acids. In contrast, dietary hydrogenated fat/trans fatty acids have been reported have to have little effect or decrease HDL cholesterol levels, the later observation restricted to relatively high intakes of trans fatty acids. These two effects result in higher, therefore less favorable, total or LDL cholesterol/HDL cholesterol ratios. Significant increases in Lp(a) levels have been reported after consumption of diets relatively high in trans fatty acids compared with either unsaturated or saturated fatty acids. However, the magnitude of the change is for the most part small and the physiological significance of this observation has yet to be resolved. Data related to the mechanism by which hydrogenated fat/trans fatty acids alter serum lipid levels and other risk factors for cardiovascular disease are in the nascent stages. At this time it would appear prudent that public health recommendations should be aimed at encouraging the moderate consumption of products low in saturated fat or minimally hydrogenated. Trans fatty acids intake should not be stressed at the expense of saturated fat but should augment it.

Not at all, you're doing a great job

Wa'il

Thanks Wa'il,

Your replies to me always make me smile!

As some of you know, I've been in biochemistry hell this summer, and TFAs are one of the things that were covered in the course. Here's what my notes say about them:

Fatty acids are long-chain carboxylic acids. If they are saturated it means they are saturated with hydrogens, and there are no double or triple bonds in the molecule. (this is basic organic chemistry). Palmitic acid, steric acid are examples of saturated fatty acids. Obviously, then, an unsaturated fat or acid is NOT completely saturated with hydrogen and has at least one double bond in it. Oleic acid would be an example of an unsaturated acid. Linoleic acid has two double bonds. The double bonds are usually "cis" in formation, and are often three units apart on the carbon chain of the molecule. When we partially hydrogenate an unsaturated acid, it leads to cis/trans isomerization, and we end up with trans conformations, which give us trans-fatty acids. As anyone who has taken basic o-chem knows, cis and trans molecules look similar but behave very differently. The melting point of a cis-isomer is lower than a trans isomer, because the cis conformation puts a "kink" in the molecule and prevents tight packing. The trans conformation packs more easily, more energy must be applied to disrupt this good packing, and hence, trans isomers are more solid and have higher melting points than cis isomers.

Basically, what I take from all of this is that it's not nice to fool Mother Nature -- when we partially hydrogenate, we screw up the conformation of the molecule in the aforementioned way and get a molecule that behaves very differently.

Can meat and dairy and oils have TFAs...? Yes, because animals can be fed foods with TFAs in them. And as I understand it, sometimes it just happens. (without our help) But if we avoid refined foods and fats, we should be in pretty good shape.

From this class and my reading, I tend to believe that going crazy on saturated fats is not a great idea. Cholesterol, for example, is a flat, rigid molecule that has little flexibility. When it gets into our cell membranes, this rigidity can cause problems with diffusion and fluidity in the membrane. The same tight packing mentioned before decreases membrane fluidity. Cholesterol molecules are big, so they slow things down...things kind of have to move around it!

OK, that's enough biochem for one day...I can see your eyes glazing over.

Joanie, you know your stuff! Thanks!

As far as saturated fats, I loved what Dr. Eades said in Protein Power LP p. 66:

"Polyunsaturated fats keep the membranes supple; saturated fats (along with cholesterol) provide the structural stability of the bilayer membrane. If we have the right mix, then we have optimal fluidity with just the right amount of stability. How do we get this optimal mix? By the consumption of the right ratio of saturated to unsaturated fats? Not entirely. Fortunately the body has the ability to transform the fats we eat--and the fats we make from ccarbohydrate--into the fats we need.

"Specific enzymes in the mitochondria can lengthen and even add a double bond to a saturated fat and make it a monounsaturated fat. These enzymes, called elongases and desaturases, are incredibly important in the modification of fatty acids, especiallly the polyunsatured fatty acids."

I love that our bodies can change saturated fat to unsaturated fat. I wondered why I haven't died before now due to never eating fish in my life and eating mostly saturated fat and trans fat. Not that I recommend such a diet, but our bodies are marvelous. They made my prime rib into olive oil! (by extension of course, not literally) The only kind of fat our body can't make is omega-6 and omega-3.

Also, most of our cholesterol is produced by the liver (about 80%). Eating cholesterol has little to do with this.