November 1, 1995
Translating the Mixed
By: Andrea Horwich Allen
When the presidents of three nutrition and science societies told the U.S. Food and Drug Administration that the jury was still out on trans fatty acids, they were making the nutritional understatement of the decade.
In a July 10, 1995, letter to FDA commissioner David Kessler, M.D., spokespersons for the three groups - the American Institute of Nutrition, the American Society for Clinical Nutrition, and the Institute of Food Technologists - recommended that FDA not make any regulatory changes that would require the labeling of trans fatty acids.
Not only is the scientific community divided on the relationship between trans fatty acid intake and incidence of coronary heart disease (CHD), the letter said, it also has yet to arrive at an accurate estimate of how much trans fatty acids the average American consumes.
"We strongly support research efforts to obtain the data necessary to answer the fundamental questions about the health effects of trans fatty acids," the letter added. "Until we are more secure in our knowledge and understanding of these substances, we believe it is prudent not to change policy governing food labeling, dietary guidance, and health claims."
Contrary to the advice offered in that letter, a change in labeling policy is just what the doctor ordered, according to Center for Science in the Public Interest. CSPI, a consumer advocacy group, petitioned FDA in February 1994 to require that trans fats be listed on food labels as saturated fats. The group also requested limitations on claims for foods containing significant amounts of trans fats so that nutrient claims such as "low in saturated fat" or "no cholesterol" could be made only if the product's combined levels of saturated fat and trans fat met FDA's criteria for saturated fat.
Finally, CSPI sought a ban on claims that foods are made with "100% vegetable oil" if they are, in fact, made with hydrogenated shortening.
FDA did not incorporate CSPI's recommendations into the food labeling regulations that became effective in May 1994. Still, the agency did stipulate that trans fatty acids could not be included in the voluntary listing of unsaturated fatty acids, and it imposed a limit on trans fatty acids in products making saturated-fat-tree claims.
Although CSPI applauded those minimal requirements, on June 13, 1995, the group filed a supplement to its original petition reiterating its recommendations. In an accompanying letter to Kessler, CSPI scientists pointed to new evidence that trans fat in partially hydrogenated oil increases LDL cholesterol compared with nonhydrogenated oils. (LDL refers to the low-density lipoprotein cholesterol nutritionists consider the "bad" cholesterol, as opposed to the high-density lipoprotein, or HDL, cholesterol considered to be "good.") "This evidence comes largely from well-designed feeding studies," the letter said.
What could cause this disagreement between CSPI - and the 11 scientists who co-signed the labeling petition supplement - on the one side, and other scientists who remain unconvinced that trans fats pose such a threat to the public health?
For one thing, researchers have yet to conduct a human clinical trial that demonstrates to everyone's satisfaction a link between trans fatty acids and CHD.
As early as the 1950s, researchers were linking trans fat intake to increased serum cholesterol levels, which is certainly a major risk factor in CHD. Relationships with cancer and other conditions have been suggested as well, although most of the studies - and the attendant publicity - have explored the CHD link.
The current interest in trans fats was ignited by a Dutch clinical study reported in 1990. In that study, researchers found that high intake of trans fatty acids correlated with increased LDL levels and decreased HDL levels.
One problem with the Dutch study was that subjects were given 33 grams of trans fats daily, which is three to six times more than most Americans consume. A more realistic study was done in 1992 by the U.S. Department of Agriculture for the Institute of Shortening and Edible Oils, and it was published in 1994 in the American Journal of Clinical Nutrition (AJCN).
In that trial, researchers found that a daily intake of 10 or 20 grams raised blood serum cholesterol levels as much as a diet high in saturated fats - or slightly less. According to USDA researcher Joseph Judd, though, that study was too small to indicate conclusively whether the effect was the same or less than that of saturated fats.
The bombshell that has generated all the recent coverage of trans fats in the consumer media was not a clinical trial at all. Rather, it was an epidemiological study by Walter Willett, M.D., Dr. P.H., and Alberto Ascherio, M.D., Dr. P.H., both of the Harvard School of Public Health.
The results of their research were published in the May 1994 American Journal of Public Health (AJPH). Based on data from the ongoing Harvard Nurses' Study, Willett and Ascherio reported a link between consumption of trans fats in hydrogenated margarines and shortenings with incidence of CHD. The higher the level of consumption, the higher the risk, according to the researchers, who attributed at least 30,000 deaths annually to trans fat intake.
Willett and Ascherio recommended strict limitations on partially hydrogenated fats in the U.S. food supply, or at least mandatory labeling disclosures for trans fats. Not surprisingly, the two Harvard nutrition professors also were among the scientists who co-signed the letter accompanying CSPI's supplemental labeling petition to FDA this year.
Continuing clinical data flow
The Harvard research was revisited and two other important studies were addressed in the Feb. 4, 1995, issue of The Lancet. The two additional studies investigated the relationship between the amount of trans fat in body fat, which reflects long-term trans fat intake, and two major clinical manifestations of CHD. Neither conclusively demonstrated such a link.
One of these was the multi-center EURAMIC study, which was conducted in seven European countries as well as Israel, and which was supported by the Commission of European Communities. Researchers compared the trans fats in the body fat of 671 men aged 70 or younger who had had a first acute heart attack (myocardial infarction, or MI), against that of 717 control subjects.
The researchers found no association overall between high trans concentrations and incidence of MI. However, they did note that the relative risk varied between countries, suggesting a "confounding" factor, according to the Lancet article.
"There is no convincing evidence that trans fatty acids are an important cause of CHD, although it is possible that at high levels of intake they interact with other risk factors for the disease," the article said.
The second study examined in The Lancet was the Southampton study, conducted in the United Kingdom and supported by the British Heart Foundation. Researchers examined the trans fats in the body fat of 66 men who had died from sudden heart attacks, having had no previous histories, against 286 healthy controls.
In this study, which measured trans isomers from both oleic and linoleic acids, the mean percentage of trans fatty acids expressed as a proportion of all fatty acids was "significantly lower than in healthy controls," the article said. There was no evidence of a relationship between sudden cardiac death and trans isomers from both acids combined; trans oleic acids were negatively associated with risk, and no association was found with trans linoleic acids.
CSPI scientists have challenged claims that these two studies disprove any link between trans fat intake and CHD. In their labeling petition supplement filed this year, Margo Wootan, D.Sc., and Lora Wilder, Sc.D., attributed a number of design flaws to the two studies.
Neither study measured the subjects' intake of saturated and monounsaturated fat, they noted. Regarding the British study, the CSPI scientists pointed out that "sudden cardiac death cases represent only a fraction of all coronary disease cases and cannot be considered representative of coronary disease in general."
Further, they said that the study was too small to detect an association if one did exist: "The fact that the study found no association between hypertension or diabetes and cardiac death underscores its lack of statistical power."
The EURAMIC researchers, they added, did find a tendency toward higher risk of acute myocardial infarction (AMI) at the higher levels of trans fat in the subjects' body fat - when they excluded the Spanish subjects because of their far lower levels of trans fat. Wootan and Wilder acknowledged that the trend did not reach statistical significance, but they pointed out that the authors said, "We cannot exclude the possibility that the contribution of trans fatty acids to risk of AMI is significant in countries with high intakes of trans fatty acids."
Reviewing the health links
At around the same time that the Lancet article was published, AJCN carried a letter from Sue Taylor, M.S., R.D., pointing to a flaw in recent studies that had shown a link between trans fat intake and CHD factors. Taylor, a spokeswoman for the National Association of Margarine Manufacturers, noted, "In clinical trials, trans fatty acids replaced cholesterol-lowering fatty acids (oleic and linoleic acids), thus giving the appearance of raising levels of (LDL) cholesterol.
"Moreover, studies in animals and humans have also shown that the effect of trans fatty acids on blood lipids is neutral, much like that of stearic acid," she added.
The intensity of the fracas surrounding trans fats has increased through the year, as has the number of papers, editorials and rebuttals appearing in nutrition journals. The most recent of these is a critical analysis of the credible research that has been conducted thus far, published as a special supplement to the September 1995 AJCN. The International Life Sciences Institute convened a panel of widely recognized authorities on trans fats to contribute to the analysis. Others, including Willett and the Dutch scientists, were invited by the journal to respond to the supplement in the September edition.
The expert panel reviewed research that covered all the bases: chemistry and physiology of trans fatty acids and dietary intake; epidemiological studies; animal studies; and clinical trials. The panel applied strict criteria in reviewing these studies, including strength of an association with CHD or CHD risk factors; consistency of findings among the studies; specificity of the results; and presence or absence of a dose-response relation.
Neither the review nor the responses provide the definitive clinical data still lacking in the trans fat puzzle. "This review places concerns regarding the effects of trans fatty acids on CHD risk factors into perspective and hopefully will be a catalyst for subsequent research," noted guest editor Penny Kris-Etherton, Ph.D., R.D., in her preface to the supplement.
Among the key questions that remain is whether the responses noted in some of the studies can be attributed to the addition of dietary trans fats - or to the fact that they replaced unsaturated fats known to be hypocholesterolemic, as Taylor noted earlier in the year. As nutritionists have pointed out, consumers are more likely to use trans fats as replacements for saturated, or hypercholesterolemic, fats.
"Both the independent and relative cholesterolemic effects of trans fatty acids remain to be established," wrote Kris Etherton, a nutrition professor at Pennsylvania State University, University Park. "Currently, it is not clear whether they are neutral or actually change plasma cholesterol concentrations and what their effects are compared with other fatty acids."
These are the questions that could be answered conclusively by a well designed, well-controlled clinical trial. Such a trial is in the discussion phase among industry, academic and government researchers. Until it is performed, though, a consensus has emerged that for anyone attempting to follow accepted recommendations for fat intake, trans fats will comprise only a small percentage of total calories anyway.
Addressing the issue
Most nutrition organizations, and the U.S. government, now recommend that no more than 30% of total calories be derived from fat, and that no more than one-third of that amount should come from saturated fat. However, most also agree that the average American is consuming closer to 34% or 36% of total calories from fat, and about 12% to 14% from saturated fat.
As for trans fats, they now make up 2% to 4% of total calories for most Americans. The actual percentage depends on how much shortening, oil, and fried food the individual consumes. Since frying fats have more trans fat than margarines, especially soft margarines, someone who is tempting fate by eating a lot of commercially fried foods is also consuming more trans fat than someone who eats a couple tablespoons of margarine, notes Neva Cochran, R.D., a spokeswoman for the American Dietetic Association. "Margarine is not the issue in this country," she adds.
Margo Denke, M.D., a professor and researcher at the Center for Human Nutrition at the University of Texas Southwestern Medical Center, Dallas, recently completed an "Internal Medicine Grand Rounds" report in which she assessed much of the current trans fat research.
According to Denke, who also served as one of the expert panelists on the September AJCN review, margarine accounts for only about one-third of all trans fat intake. She advises that consumers familiarize themselves with other sources of hydrogenated fats, but she adds that the best "heart-healthy" strategy is still to focus on reducing saturated fat intake.
Of course, the emphasis on saturated fats of the past decade or so is what led the food industry to replace animal-derived fats and tropical oils high in saturates with hydrogenated poly- and monounsaturates. An unfortunate outcome of this transition has been the current controversy over dietary trans fat. Food designers and ingredient suppliers have been quick to respond to nutrition concerns, and generous in their research and development investments, by continually creating and honing fat replacement ingredients and systems.
U.S. margarine manufacturers offer a full range of products with varying ratios of oil to water, and although these lower fat spreads don't meet the standards of identity for margarine, they are proving to be commercially viable alternatives. Some European and Canadian manufacturers have been using fats modified through interesterification to replace hydrogenated fats in vegetable oil spreads - but the process is by no means perfected, and it has yet to catch on among U.S. manufacturers.
The key to eliminating hydrogenation may be found through bioengineering. Calgene Inc., the Davis, CA, developer of the Flavr Savr tomato, has developed rapeseed plants that produce oils with more than 30% stearates, and others that produce oils that are 45% lower in saturates.
The former, which are now in field trials, would enable manufacturers to produce margarines and shortenings that require no hydrogenation. The others, which have been produced in the greenhouse, would result in salad oils and cooking oils with lower saturated fat contents. With the acquisition of Calgene by Monsanto Co., it's reasonable to expect further genetically engineered developments.
Meanwhile, considering that some two-thirds of dietary trans fats come from sources other than margarine, most food designers would do well to keep up with the debate. Health concerns are a growing factor in consumer demand - but taste and texture remain top priorities, as surveys consistently show. The food designer's challenge to develop products that meet all these criteria isn't an easy one.
One company that has risen to the challenge is Nabisco Inc., developers of the fat-free and fat-reduced SnackWell's products, as well as Salatrim, the fat replacer now being marketed by Pfizer Inc. Despite a firm commitment to fat-reduced foods, though, the company has by no means turned its back on full-fat food products.
"The way we look at it is that there's a full spectrum from the fat free to the really rich and indulgent," says Mark Dreher, Ph.D., Nabisco's director of nutrition. Choosing ingredients, including fats, for those products requires careful attention to a number of factors: functionality, stability, availability and cost. "It's a complex situation," Dreher notes.
Clear answers concerning trans fats would help simplify things, but not by much.
In Favor of Fat
The fact that the human body needs at least a certain amount of dietary fat in order to function is old news. Doctors and nutritionists have been laboring to make sure that message doesn't get lost in the frenzy to eradicate dietary fat.
With all the recent press that olive, flaxseed, and fish oils have garnered, one would think that nutrition professionals are reconsidering their advice to consume only 30% of calories from fat.
Think again. Those oils may indeed offer certain health benefits; at least they're the focus of some credible research. Most nutrition groups are standing firm, however, saying that the average American needs to cut dietary fat, not add it.
A case in point is the Mediterranean diet, heralded in the media during the 1960s as a major factor in the longevity of Cretan islanders, the subject of the long-term Seven Countries Study. The diet was translated into "pyramid" form by an organization called the Oldways Preservation & Exchange Trust, the Harvard School of Public Health, and the World Health Organization Regional Office for Europe.
Like the U.S. Department of Agriculture's Food Guide Pyramid, the Mediterranean pyramid places heavy emphasis on daily consumption of grain products, vegetables and fruits. Unlike the USDA pyramid, though, it separates legumes and nuts from animal protein sources, advocating daily consumption of the former and infrequent consumption of the latter. The most significant difference between the two is that the Mediterranean diet includes olive oil, and lots of it, whereas the USDA pyramid includes fats from multiple sources and in small amounts.
At first blush, that might seem a welcome change. Aside from the Seven Countries Study, other studies have linked consumption of olive oil to significant reductions in blood cholesterol. In one, Italian researchers showed an inverse association between intake of olive oil and blood cholesterol levels - not to mention glucose levels and systolic blood pressure. This would suggest a protective role for olive oil not only against heart disease, but against diabetes and hypertension, as well.
Researchers attribute these effects to the fact that olive oil is so high in monounsaturates like oleic acids. A study conducted at Veterans Administration Hospital in Dallas compared the effects of three different diets - typical American, Mediterranean and Asian - on the blood lipid levels of 11 patients, all of whom began the study with moderately high cholesterol levels. Scott Grundy, M.D., Ph.D., of the University of Texas Southwestern Medical Center, Dallas, developed liquid diets that were formulated to maintain specific balances between protein, carbohydrates and fat representative of the three different types of diets.
The patients on the American diet, which was about 40% fat and the highest in saturated fats, had higher than normal lipid levels after four weeks. Patients on the Asian diet, which was only about 20% fat, had an average 8% drop in total cholesterol, 15% in LDL cholesterol - and an unwelcome drop in HDL cholesterol. (LDL is the low-density lipoprotein cholesterol that contributes to atherosclerosis, and HDL, or the high-density lipoprotein, is an indicator that cholesterol is being cleared from the blood).
The patients on the Mediterranean diet equivalent consumed 40% of their total calories from fat, but 28% came from monounsaturates. That group showed an average drop in total cholesterol of 13% and in LDL cholesterol of 21%. Just as important, their HDL and triglyceride levels remained unchanged.
Grundy has been widely quoted over the past decade on the merits of monounsaturates. Although he has not advocated increasing dietary intake of total fats beyond currently accepted levels - 30% of total calories - he has recommended that monounsaturated fats make up a greater percentage than saturates or polyunsaturates.
Other researchers have called for actual increases in monounsaturate consumption. Indeed, a strict reading of the Mediterranean diet would place fat consumption at almost 40% of total calories. That's where many nutritionists draw the line.
"The real issue with the Mediterranean pyramid is that it does not necessarily emphasize reducing total fat in the diet, and that runs counter to U.S. dietary recommendations endorsed by virtually all health agencies," said Christine Bruhn, Ph.D., when the Mediterranean Pyramid was published in June 1994. Bruhn is the director of the Center for Consumer Research at the University of California, Davis, and is a past chair of the Institute of Food Technologists' nutrition division.
The Center for Science in the Public Interest, a consumer advocacy group, published an "Americanized" version of the Mediterranean diet in the December 1994 Nutrition Action Health Letter. Their revisions achieved a slightly lower fat content of about 35%. Still, the authors said a well-balanced, low fat diet based on a greater variety of foods would be preferable because it would provide more vitamins and minerals. Besides, they noted, the long-lived Cretans of the Seven Countries Study were considerably more active than most Americans - presumably making them better equipped to burn off more calories and fat grams.
Nor has the American Dietetic Association jumped on the bandwagon." We don't endorse that type of pyramid," says spokeswoman Neva Cochran, R.D. "We feel the Food Guide Pyramid is based on current scientific research."
Also, as Cochran, CSPI and many others point out, even olive oil contains some polyunsaturates and saturates. So, unless the "dieter" significantly reduces consumption of those fats, a large increase in olive oil, canola oil or any other oil rich in monounsaturates could pile on too many saturates and polyunsaturates.
Not that all saturates and polyunsaturates are to be shunned. For instance, stearic acid, a combination of medium to short-chain saturated fatty acids, has been shown by researchers at the University of Texas Southwestern Medical Center not to raise cholesterol levels.
A study conducted by Grundy and Margo Denke, M.D., showed that because of its stearic acid content, cocoa butter was only mildly cholesterolemic. Stearic acid is also prevalent in beef tallow, but because it did not prevent the saturated palmitic acid in the tallow from raising LDL levels, the researchers concluded that "beef fat must still be classified as a cholesterol-raising fat."
In addition, certain polyunsaturates have been found to offer health benefits. Among these are the omega-6 acids such as linoleic acid, which, like the monounsaturated oleic acids, have been shown to reduce total cholesterol and LDL levels. Omega-3 acids such as alpha-linolenic acid are thought to have preventive effects against heart disease, some cancers, hypertension and rheumatoid arthritis.
Vegetable oils like corn, safflower and sunflower are high in omega-6 acids, while the omega-3s are abundant in two of the trendiest sources: fish oil, and especially flaxseed. Epidemiological studies have suggested, but not proven, that diets rich in fish oil protect against coronary heart disease.
Although flaxseed is the media darling of the moment, scientists are still researching fish oil, as well. The nutritional benefits of both omega-3s and omega-6s have been exhaustively explored in many articles and books.
These are the essential fatty acids, so named because the body cannot manufacture them and must obtain them from other sources. Once ingested, they are then converted by the body to omega-6 and omega-3 fatty acids, respectively. Erasmus attributes myriad health problems, both physiological and behavioral, to deficiencies in either one, and he warns that the body needs a balance of both.
Of note to food designers, is his insistence that the oils be consumed as close to their natural state as possible, meaning minimally heated during pressing and minimally processed after that, in order to maintain the activity of their antioxidants and phytochemicals.
The same goes for olive oil. Although Erasmus sees no particular benefit to olive oil because it has few essential fatty acids, he notes that at least it's available in its extra-virgin, minimally processed state.
"One other thing about olive oil: It'll make you fat if you eat a lot of it," Erasmus says.
While the researchers carry out their debates over the nutritional myths and realities, that may well be the bottom line for many consumers when it comes to fats and oils.
You May Also Like
Advancing gender equity in the nutraceutical industrySep 25, 2023
CRN petition to FTC: RCTs aren’t required to substantiate ‘health-benefit’ claimsSep 22, 2023
Exercise recovery: Electrolytes, hydration and combating fatigue – SupplySide intensive webinarSep 22, 2023
Collagen peptide ingredient solutions for seniors’ changing needs – infographicSep 19, 2023