Health Risks from Processed Foods and The Dangers of Trans Fats

Dr. Mary Enig Interviewed By Richard A. Passwater, Ph.D.

Mary G. Enig, Ph.D., a nutritionist widely known for her research on the nutritional aspects of fats and oils, is a consultant, clinician, and the Director of the Nutritional Sciences Division of Enig Associates, Inc., Silver Spring, Maryland. She received her PhD in Nutritional Sciences from the University of Maryland, College Park in 1984, taught a graduate course in nutrient-drug interactions for the University’s Graduate Program in Nutritional Sciences, and held a Faculty Research Associateship from 1984 through 1991 with the Lipids Research Group in the Department of Chemistry and Biochemistry. Dr. Enig is a Fellow of the American College of Nutrition, and a member of the American Institute of Nutrition. Her many years of experience as a “bench chemist” in the analysis of food fats and oils, provides a foundation for her active roles in food labeling and composition issues at the federal and state levels.

Dr. Enig is a Consulting Editor to the “Journal of the American College of Nutrition” and formerly served as a Contributing Editor to “Clinical Nutrition.” She has published 14 scientific papers on the subject of food fats and oils, several chapters on nutrition for books, and presented over 35 scientific papers on food and nutrition topics. She is the President of the Maryland Nutritionists Association, past President of the Coalition of Nutritionists of Maryland and was appointed by the Governor in 1986 to the Maryland State Advisory Council on Nutrition and served as the Chairman of the Health Subcommittee until the Council was disbanded in 1988.

I first learned of Dr. Mary Enig’s research from a 1978 report in the Federation Proceedings. We met shortly after that, and since I had written about trans fats several times in Supernutrition, we had common concerns about the effect that these trans fats from processed foods were having. We were both concerned particularly about the misconception that processed margarine was better than natural butter.

In several visits by Dr. Mary Enig to the Solgar Nutritional Research Center I quickly learned that she was an exacting scientist who is not afraid to speak out and who supports good nutrition, not just going along with the establishment’s party line. While studying for her Ph.D. at the University of Maryland, often she would first respond with the “correct” answer that was expected, and then she would explain why new research indicated “alternatives,” such as optimal vitamin and mineral nourishment, provided a better answer. It is not easy be credentialed by the “system,” while your own research shows other facts.

In her 1978 report, Dr. Enig challenged the speculation concerning the relationship of dietary fat and cancer causation. She concluded that correlations between the increase in per capita dietary fat intake and total cancer mortality over a sixty-year period show significant positive correlations for total fat and vegetable fat, and negative correlation for animal fat. That is the cancer rate is higher when the amount of vegetable fat or total fat is higher in the diet, but the cancer rate is lower when there there is more animal fat in the diet. These findings were unpopular then as they are today, but they are still correct. It is convenient to blame everything on red meat and animal fat, and believe that vegetable oil is the great dietary salvation-even if it is partially hydrogenated. At least that is what the vegetable oil people would like everyone to believe.

Now, we are not saying that lots of dietary fat is good for you and that vegetables are not good. Eating vegetables, fruits and other whole foods is very desirable. However, that is not the same as eating partially-hydrogenated vegetable oils. Americans eat too much fat (especially partially hydrogenated vegetable oils) and not enough fruits and vegetables. The problem is that the typical American is not eating enough whole foods, but instead, is eating too much partially-hydrogenated vegetable oil-a fractionated food-that has been made into “funny foods” such as margarine or added to baked goods. Such “funny foods” are far differentthan real whole foods

Hydrogenation ruins the nutritional value of vegetable oils! Why would anyone want to ruin the nutrition value of vegetable oils? The purpose of hydrogenation is to solidify an oil so that it can be made to resemble real foods such as butter. The hydrogenation process imparts desirable features such as spreadability, texture, “mouth feel,” and increased shelf life to naturally liquid vegetable oils. In the hydrogenation process, vegetable oil is reacted under pressure with hydrogen gas at 250 – 400oF for several hours in the presence of a catalyst such as nickel or platinum. However, this industrial process cannot control where the hydrogen atoms are added to the “unsaturated” double bonds. Randomly adding hydrogen atoms to polyunsaturated fats converts natural food components into many compounds, some of which have never seen before by man until partially hydrogenated fats were manufactured.

Some of the several dozens of altered compounds created in the manufacture of partially-hydrogenated fats are “trans” fatty acids. Fatty acids are the building blocks of fats, much like amino acids are the building blocks of proteins. Other new compounds accidentally synthesized include fatty acids having double bonds translocated to new and un-natural positions, and various molecular fragments. Many of these altered compounds are detrimental to health.

Since “trans” fats are so detrimental to our health. permit me to briefly review the relevance of distinguishing between “trans” and .ati” fats before chatting with Dr. Enig. Recently, in the September issue, in the interview with Dr. Jim Clark and Mr. Lance Schilipalius, we discussed “trans” isomers of carotenoids. “Trans” means the same thing here. “Cis” and “trans” isomers refer to how identical atoms are added to double bonds. When the atoms are added to the same side of the double bond, the compound is called “cis” and the molecule is bent because of the crowding of the atoms on one side. When the atoms are added on opposite sides of the double bond, the compound is called “trans” and molecule is “space-balanced” and straightened. The shape of a molecule is important because enzymes and their substrates-the molecules enzymes act upon-must fit together like a key in a lock.

Dr. Enig will discuss this during the interview, but the important thing to remember is that natural polyunsaturated fatty acids are “cis” compounds and are bent. Partial hydrogenation produces many un-natural “trans” fats, which are straight and not intended for use in the human body. You don’t have to understand the difference between “trans” and “cis,” but it is important that you know that there is a difference because, as Dr. Enig will explain, it can affect your health.

Passwater: Dr. Enig, a lot of people are interested in “trans” fats now. You have been researching them since 1977. How are trans fats harmful to us?

Enig: More than a decade of research at the University of Maryland, as well as research that was being done at other institutions, showed that consumption of trans fatty acids from partially hydrogenated (a process that adds hydrogen to solidify or harden) vegetable fats and oils had many adverse effects in health areas such as heart disease, cancer, diabetes, immunity, reproduction and lactation, and obesity. It is rather easy today to come up with a long list of these adverse effects from the published research done by many scientists around the world, as well as the researchers at the University of Maryland.

The reason there is so much recent interest is that during the past three years there has been a number of major research reports published in prestigious medical journals that caught the attention of the press. These and earlier reports had shown, for example, that consumption of trans fatty acids lower the “good” HDL cholesterol in a dose response manner (the higher the trans fat level in the diet, the lower the HDL level in the blood) and raise the atherogenic lipoprotein(a) in humans as well as raising the “bad” LDL cholesterol and total blood cholesterol levels by 20-30 milligram-percent. These studies have usually been shown in independent non-industry studies. Perhaps the most significant event though was the report from researchers at Harvard University, who evaluated more than 85,000 women in a long-term prospective study and found that there was a significantly higher intake of trans fatty acids in those individuals who developed heart disease.

As regards to the question of cancer, trans fatty acids induce adverse alterations in the activities of the important enzyme system that metabolizes chemical carcinogens and drugs (medications), i. e., the mixed-function oxidase cytochromes P-448/450. The initial research in this area was done by the Maryland group in collaboration with the U. S. Food and Drug Administration, and was followed by the more extensive evaluation that I did for my Ph.D. dissertation; several groups around the country and the world also reported the same or similar results. Several groups around the world reported a higher intake of partially hydrogenated fats in those individuals who have developed cancer.

Both primate and human studies have shown inappropriate handling of blood sugar; trans fatty acids decrease the response of the red blood cell to insulin, thus having a potentially undesirablacidfect in diabetics. Theed smate research was initiated at Maryland in collaboration with the U. S. Department of Agriculture and the National Institutes of Health, and the human research is from the University of Pittsburgh and quite recent.

One major concern is that trans fatty acids adversely affect immune response by lowering efficiency of B cell response and increasing proliferation of T cells. This was shown in research done at Maryland using a mouse model and although there are reports from clinicians that there are problems of immune dysfunction in humans it still needs to be evaluated systematically in humans.

Recent research from outside the U. S. has indicated that trans fatty acids interfere with reproductive attributes and of concern is the finding that trans fatty acids lower the amount of cream (volume) in milk from lactating females in all species studies including humans, thus lowering the overall quality available to the infant. The latter research was done at Maryland by my colleague Dr. Beverly Teter.

Basically, trans fatty acids cause alterations to numerous physiological functions of biological membranes that are known to be critical for cell homeostasis, e.g., appropriate membrane transport and membrane fluidity, and these fatty acid isomers produce alterations in adipose cell size, cell number, lipid class and fatty acid composition.

Passwater: Now that trans fats are becoming of more interest, the term may still just be a buzz word to many of our readers. Would you explain just what are trans fats? Where do they come from? How are they formed?

Enig: To understand what trans fatty acids are you have to understand what fatty acids are. Fatty acids are basically chains of carbon with a carboxyl group (COOH) at one end that can react (e.g., combine) with another molecule. When fatty acids are in fats or oils they are combined with glycerol in the proportions of three fatty acid molecules to one glycerol molecule and p=cenform triacylglycerols or in common terminology, triglycerides.

Fatty acids come in different chain lengths ranging from three carbons long (propionic acid) to 24 carbons long (lignoceric acid). These fatty acids are either “saturated” (with an adequate number of hydrogen atoms) and chemically stable, or they are “unsaturated” (missing adequate hydrogens) and chemically unstable. If a fatty acid is missing two hydrogens, it is called a monounsaturated fatty acid, and in place of the two hydrogens, the adjacent carbons “double” bond to each other. If the fatty acid is missing four or six or more hydrogens, it is called a polyunsaturated fatty acid, and it is even more unstable than the monounsaturated fatty acid. Because the double bonds in naturally occurring plant oil fatty acids are curved with a “cis” configuration, the fatty acids cannot pack into a crystal form at normal temperatures so their presence produces a liquid oil. Saturated fatty acids have a straight configuration and can pack into a solid crystal at normal temperatures.

If the unsaturated fatty acids are altered by partial hydrogenation to straighten the chains so that they have some of the physical packing properties of saturated fatty acids they have had their “cis” double bond changed to a “trans” double bond and they turn a technically mostly unsaturated oil into a solid fat. The trans fatty acids are the same length and weight as the original “cis” fatty acid they were formed from, and although they have the same number of carbons, hydrogens, and oxygens they are shaped differently in space. The term that is used is that they are “isomers.” The problem arises when a large number of the trans fatty acids are consumed from foods and they are deposited in those parts of the cell membranes that are supposed to have either saturated fatty acids or “cis” unsaturated fatty acids; under these circumstances the trans fatty acids essentially foul up the “machinery.”

Although the trans fatty acids are chemically “monounsaturated” or “polyunsaturated” they are considered so different from the “cis” monounsaturated or polyunsaturated fatty acids that they cannot be legally designated, e.g., monounsaturated for purposes of labeling. Most of the trans fatty acids produced by the partial hydrogenation process are chemically monounsaturates.

There have always been small amounts of one kind of trans fatty acids in the human diet from the ruminant fats (dairy, sheep, goat, deer, buffalo, antelope, etc.) because the microorganisms in the rumen try to get rid of the polyunsaturated fatty acids that are found in the plant foods eaten by these animals. In the early days of trans fatty acid research, the researchers assumed that the trans fatty acids found in ruminant fats were no different than those produced by partial hydrogenation in the factory. But the studies showed that not only was the amount much smaller (e.g., the fat in butter might be 2-3% of the ruminant trans), the effect on the “machinery” in the cell membranes was not different than without the trans. Yet all studies feeding the trans produced by partially hydrogenating the vegetable oils showed the adverse effect on the cell “machinery.”

Passwater: Why are trans fats a problem?

Enig: The various mechanisms through which the trans fatty acids disrupt function are related in part to the ability of trans fatty acids to inhibit the function of membrane related enzymes such as the delta-6 desaturase resulting in decreased conversion of e.g., linoleic acid to gamma-linolenic acid or arachidonic acid; interference with the necessary conversion of omega-3 fatty acids to their elongated tissue omega-3 fatty acids; and escalation of the adverse effects of essential fatty acid deficiency. This latter effect was shown especially by the work of Dr. Holman and his colleagues at the Hormel Institute at the University of Minnesota, the other effects have been shown by many researchers including the University of Maryland researchers.

Passwater: What were your early findings and what got you interested in this area of research?

Enig: My initial published research in 1978 when I was at the University of Maryland showed that trans fatty acids, which were increasing in the food supply at the time and which had not been catalogued in any of the food data tables, were the very factors that explained the positive statistical relationship between the increase in cancer mortality and vegetable fat consumption in the U. S.

It was clear from the literature that once the trans fatty acids were identified as products of partial hydrogenation and studies were engaged in, there were a number of earlier researchers who questioned the biological safety of the trans fatty acids viz a viz their relationship to both cancer and heart disease. In fact, Dr. Ancel Keys had originally claimed that the partially hydrogenated vegetable oils with their trans fatty acids were the culprits in heart disease. This was in 1958, and the edible oils industry was very swift in their squelching of that information; they shifted the emphasis to “saturated” fat and started the phoney attack on meat and dairy fats.

Passwater: What have others added to your findings?

Enig: As you have noted in some of your writings, we at the University of Maryland were not the first to raise the issue of trans fatty acids and adverse health effects; Dr. Fred Kummerow from the University of Illinois, Dr. George Mann from Vanderbilt University, and Dr. Edward Pinckney with the American Medical Association had sounded the alarm many years before my plunge into the foray. In fact, I had drawn heavily on the research findings of Dr. Kummerow and the informative writing of Dr. Mann when I first started to investigate what was known about health effects of trans fatty acids at the time. Our research findings have been duplicated by others, but more importantly other independent researchers have extended and explained many of our findings and concerns.

The Case of the Phantom Fat The Dangers of Trans Fat

First it was cholesterol, then saturated fat. Now trans fatty acids are the latest dietary demon. Like those nutrients, trans fats raise blood cholesterol levels and significantly increase the risk of premature heart disease. Trans fat has been nicknamed “phantom fat” because the Food and Drug Administration does not require it to be listed on food labels. As a result, even health-conscious consumers are often unaware that hundreds of popular foods-from margarine, baked crackers and biscuits to cookies, fish sticks and french fries-pack significant amounts of trans fatty acids.

Much of this fat comes from liquid vegetable oils that have been converted to solids because they stay fresh longer than conventional shortenings. On average, Americans consume about five grams of trans fat per day, accounting for about 3 percent of their total calories, according to a 1999 study in the Journal of the American Dietetic Association. While that may sound tiny, research has linked even small amounts of trans fat to an increased risk of heart disease. A 1994 Harvard University study found more than twice the risk of heart attacks among those who ate partially hydrogenated oils, which are high in trans fat, compared with those who consumed little trans fat. Several large studies in the United States and elsewhere, including the Nurses Health Study, also show a strong link between premature death and consumption of foods high in trans fatty acids.

Trans fats are unique in that they affect blood lipids in every way that is harmful. This hidden fat raises low-density lipoprotein (LDL) the harmful form of cholesterol and lowers protective high-density lipoprotein ?Those who try to reduce trans fat will find it tough because most food labels don’t have the information that you need to do that. Nutritional labels on prepared foods list the total grams of fat in products and that total does include trans fat, but there is no separate line showing, as they do with saturated fats, the actual amount of trans fats. The FDA, however, proposed in November that food manufacturers begin including trans fat on labels. The 90-day public comment period won’t end until mid-February and two food companies have already requested a 90-day extension. When the comment period ends, it could take about two years for any new rule to go into effect.

Under the proposed regulation, trans fat would be folded into the saturated fat gram count, since both raise the risk of heart disease. An asterisk would direct the consumers to the bottom of the label where they could find a reference listing the exact amount of trans fat included in the food. If the proposal goes forward, trans fat would also be part of the nutritional information that the FDA considers when it gives foods such rankings as “lean,” “extra lean,” “reduced saturated fat” or “low saturated fat.” Low-cholesterol foods that now sometimes contain significant amounts of trans fatty acid would be required to contain less than two grams of saturated fat and trans fat per serving combined.

The FDA estimates that these labeling changes would prompt changes in eating habits that would save at least $1 billion in annual health care costs by preventing 6,400 cases of heart disease per year and at least 2,1satueaths. Others say the benefits could be even greater. Trans fatty acids are responsible for about 30,000 premature deaths per year.

The Stealth Fat

Why the sudden concern about trans fats? Beef and high-fat dairy products have always contained minuscule amounts of trans fat, which is produced in the gastrointestinal lining of cattle. But in the 20th century, food manufacturers discovered the stability and long shelf life of trans fat. During the past 50 years, trans fat has become one of the most common ingredients in both grocery store food and restaurant fare. Trans fats are produced when food manufacturers take liquid vegetable oils, heat them and add metal catalysts and hydrogen to the mix. Called partial hydrogenation, this process produces hardened vegetable oils that remain solid at room temperature. They can then be made into shortening and margarine and are less likely to spoil.

With the proliferation of prepared foods in recent years, it’s a small wonder that a long and varied list of products now contains hidden trans fat. Food surveys suggest that the typical American eats about 34 grams a day of saturated and trans fat combined, well over the recommended daily intake of 20 grams of saturated fat for an average 2,000 calorie-a-day diet. A close look shows clearly how the numbers creep up. Think that biscuit with three grams of saturated fat on the label isn’t too bad? Add in the four grams of trans fatty acid and it jumps to seven grams of artery-clogging fat. Peruse the label of those chocolate chip cookies that boast only two grams of saturated fat per serving. Surprise! They contain double the amount of fat when the trans fat is taken into account. Ditto for the fish sticks, which tout just three grams of saturated fat per serving but actually pack another five grams of hidden trans fat. Same goes for some of the most popular brands of baked crackers, which boast just one gram of saturated fat on their labels but contain an extra two grams of trans fat. And that piece of apple pie? It has seven grams of saturated fat in the crust, but contains another seven grams of trans fat per serving.

In the dairy case, there’s more confusion between butter and margarine. Butter contains no trans fatty acids. Each tablespoon of butter still has seven grams of saturated fat – or roughly a third of the recommended daily intake. Many margarines, particularly stick margarines, are low in saturated fat, providing just two to three grams per tablespoon, but they come loaded with trans fat, sometimes as much as three additional grams per tablespoon. Stick margarines are almost as bad as butter, but the tub margarines are much better and the lower-fat tub margarines are much, much better.

Calculating Trans Fat In Your Food

Until a final rule is made, however, consumers can only guess how much trans fat most foods contain. The easiest way to check is usually to read the ingredient list. If partially hydrogenated oils or fats appear, the food has trans fat. But knowing how much is difficult – unless the label happens to list monounsaturated and polyunsaturated fat grams, which are not required but are sometimes included on the label. Even then, consumers need to calculate the amount of trans fat by adding grams of polyunsaturated, monounsaturated and saturated fat and subtracting that sum from the total fat listed on the label. The difference is a ballpark estimate of trans fat. For example, Oreos have seven grams of total fat in a serving. The saturated fat, polyunsaturated and monounsaturated fat add up to five grams. The difference is two grams, and most of that is trans fat. Wheat Thins have six grams of total fat and only three grams are accounted for in the saturated, polyunsaturated and monounsaturated fat counts. That leaves three grams of fat and most of that is trans fat.

The Washington Post January 12, 2000

DR. ValeOLA’S COMM7s m3A The move to have manufacturers label the amount of trans fat is an important step in the right direction. I am pleased that the FDA has taken the initiative to do this. I am at the same time disappointed that it will not be implemented for over two years. Trans fat is really one of the worst, although good tasting, foods you can eat. Trans fat is the reason you should rarely, if ever, eat French fries, as the fat in them is nearly 100% trans fat.


The value of hardened (trans) unsaturated fats in our food supply is probably best exemplified by the glazed doughnut. At room temperature, a glazed doughnut can be easily eaten with one hand, but warmed up it requires two hands and a napkin. That’s what trans fats can do for us: they keep our pastries firm and our margarine stiff at room temperature. Trans fats are generally found in absolutely unnecessary foods like doughnuts and margarines. Trans fats are produced when polyunsaturated vegetable fats are artificially hydrogenated, a process that increases both their firmness and their resistance to oxidative spoilage. About 5 to 10 percent of the fat in our American diet and about 5 percent of the fat stored in our American adipose tissue is trans unsaturated fat

It is the type of dietary fat and not the total amount of fat consumed that affect a person’s risk of coronary heart disease. The findings may have an impact on current recommendations by United States health officials that the daily total dietary intake of fat in general not exceed 30% of total calories consumed.

This study focused on the cardiac risk of several types of fat: saturated fat, found in meats and dairy foods; trans unsaturated fat, the “hardened” fat found in margarine and fast foods; monounsaturated fat, as occurs in olive and canola oils; and polyunsaturated fat, as found in corn and soybean oils. The main finding is that it’s the type of fat that’s most important for the risk of heart disease — that it’s not the total amount of fat because there are ‘good’ fats and ‘bad’ fats, much like ‘good’ cholesterol and ‘bad’ cholesterol. Higher intake of trans unsaturated fat is associated with increased risk of heart disease.

This is the first major epidemiologic study to look at all the major fats and total fats — to put all the fats together in one prospective study. The researchers calculated a 17% greater risk of coronary disease from dietary saturated fat compared with the same caloric intake from carbohydrates. BUT, trans unsaturated fats were associated with the highest heart risk — almost twice that (93%) of carbohydrates.

This large effect is probably explained by the impact of trans unsaturated fat on blood lipid levels, its interference with fatty-acid metabolism, and its ability to elevate triglycerides — a type of blood fat. But the risk percentages of the other fats ran in the opposite direction. As compared with the equivalent energy intake from carbohydrates, the heart disease risk was 19% lower for monounsaturated fats and 38% lower for polyunsaturated fats among the nurses followed in the study.

In addition, the researchers note that the high-carbohydrate diet recommended by some heart disease prevention programs, which are intended to lower LDL (“bad”) cholesterol levels also lower the (“good”) HDL levels. According to the report, replacing 5 percent of energy from saturated fat with unsaturated fat leads to a 42% lower risk of heart disease. And replacing 2 percent of energy formerly eaten in the form of trans unsaturated fat with unhydrogenated, unsaturated fat drops heart risk by 53%.

The New England Journal of Medicine ( November 20, 1997;337:1491-1499)

DR. MERCOLA’S COMMENT: It is interesting to note that saturated fat has an increased risk of heart disease. The increase is small though. It is my belief that the risk is secondary to other factors. Generally saturated fat is from animal products that have been raised commercially. This means the animals have been given estrogen and other hormones, antibiotics and fed grains that contain pesticides which accumulate in the fat and are transferred directly to the individuals who eat them. They also eat large amounts of grain which does cause a shift in the percentage of saturated fat in their tissues.

I believe that if one eats animals fed organic food and large amounts of grasses rather than grains like corn and they are not given chemicals to enhance their growth their meat will have much lower levels of saturated fat and it will not be as harmful. There is absolutely no question in my mind that butter is much healthier than margarine and healthy meat and poultry for most people will promote health rather than cause disease.

Organic eggs have far lower levels of saturated fat than non organic eggs. This is primarily due to the fact that the chickens are fed grains. Just as in humans, the grains and high carbohydrate diet will force the chickens to increase their insulin levels. High levels of insulin will cause the liver to make saturated fats. This happens in chickens and humans and is one of the main reasons why carbohydrates like bread, pasta, cereal, fruit, rice, potatoes and cereals should be limited if one wants to avoid heart disease and cancer.

I find it fascinating that this study shows that even commercially raised sources of saturated fat only increased heart disease risk by 17% while the trans fat increased the risk by 93%. The factor that is not reviewed in this report is the tremendous increase in cancer that occurs with trans fat ingestion that other studies clearly document

One must also be careful when using the other fats. I would not recommend most of the polyunsaturated fats. As mentioned last week, canola oil, although a monounsatrate should be avoided. Most commercially available oils are highly processed and should not be consumed. The best oil would be extra virgin olive oil in glass. The glass should be opaque or the bottle should be stored away from light to avoid any oxidation of the fats in the oil from light. Of course flax oil, if one can tolerate is one of the best polyunsaturated oils.

All corn and soy oils should be avoided and not consumed. For certain individuals sesame oil is excellent as it can inhibit the formation of arachidonic acid, which is a fat that is major precursor of inflammation. Other oils, obtained from the health food store and cold pressed which might be useful are safflower, sunflower, almond, and organic peanut oil. Organic coconut oil would be the best oil to cook with as it is completely saturated and NO trans fats can be made from it.

There is a effort underway to have the government indicate the percentage of trans fat on the food labels. That measure will likely occur in the next few years. In the meantime it is relatively easy to avoid these incredibly dangerous poisons. One just needs to search for the term partially hydrogenated oil on the list of ingredients as that will ALWAYS indicate trans fats are present in that food, the only question will be how much. But there is no safe levels of the dangerous chemicals and they should all be avoided.


Margarines and shortenings are the products of modern technology based on chemical and physicochemical reactions which modify the chemical composition of the parent fats and oils. This introduces into the human diet fatty acids not found in naturally occurring untreated vegetable oils. These new fatty acids have the same carbon-chain length and the same number of double bonds as the natural compounds. They are positional isomers when the double bonds are at different locations on the fatty acid chain and geometrical isomers when the molecule has the trans configuration around the double bonds.

The physical and chemical properties of shortenings and margarines largely depend on the degree of hydrogenation of the vegetable oils which are high in unsaturated fatty acids. Partial hydrogenation reduces the degree of unsaturation of vegetable oils and gives them physical and chemical properties more acceptable to the food industry and for baking in particular. Thus the three major unsaturated fatty acids (linoleic, linolenic and oleic acids) are drastically changed with the production of many new chemical isomers, the properties of which are still unknown but potentially hazardous in the long-term such that the oblivious general public is participating in an uncontrolled long-term experiment.

The digestion, absorption, transport and catabolism of fatty acids containing trans unsaturation differ little from the cis counterparts, but because of differences in molecular shape and some physicochemical properties, it has been suggested they should be treated in much the same manner as saturated fatty acids. The hypercholesterolemic effect is variable but even when positive it is apparently of shorter duration. The effect on blood cholesterol or LDL is not of paramount importance but the direct or indirect effect on atherogenesis is unknown. The effect of possible changes on cellular metabolism and cell membrane function is also unknown and the possibility remains that the trans fatty acids may have a much more indirect metabolic effect that could hinder the resilience of the arterial wall and its reparative capacity.

The nature and quantity of these trans isomers are unpredictable and again unknown. The high content of trans isomers in margarine, shortening and salad oils produced commercially and consumed in our diets is of concern. Whereas polyunsaturated fatty acids consumed by cattle are biohydrogenated, thereby increasing the degree of saturation, milk, butterfat and meat as a result contantakydrogenated saturated fatty acids and monounsaturated fatty acids. The low trans fatty acid content of butterfat and ruminant body fat has been recognized for some time. The suggestion is that they are probably more natural foods for humans than artificially manufactured trans fatty acids, the physiological or pathological effects of which in the long-term cannot be deduced.

Up to 12 g per capita of trans fatty acids are consumed in the USA per day”‘ and the level may be as high as 27.6 g. Of this 95.2% comes from partially hydrogenated vegetable oils and only 4.8% from animal fat. There is also a considerable intake when prepackaged crispy and tasty tidbits such as crackers and other snacks are consumed. Unfortunately these trans fatty acids are often included in the category of saturated fatty acids for the purposes of nutrition statistics, and nutrition labeling and mislabeling is frequent . There is evidence that trans fatty acids are metabolized much more slowly and less effectively than the cis isomers. In experimental animals, the fetus contains very little trans fatty acid either due to the placental barrier or preferential use but the trans isomers are transferred to the milk. The concentrations of trans isomers are always lower in the brain than in other organs. Their possible effects on the human physiology are unknown but they could affect plasma membrane fragility and physiology and cell function throughout the body. The preference for cis isomers in natural synthesis of fatty acids and of the brain suggests that the trans fatty acids may be detrimental but suggested links have been made between both cancer and hypercholesterolemla. The evidence is that trans fatty acids elevate serum LDL levels and lower HDL cholesterol and yet current dietary recommendations frequently advocate the use of margarine rather than butter.