The problems of sugar consumption notwithstanding, many nutrition experts believe that the most important health problems in the United States today stem from Americans' high intake of fats. Many Americans consume 40 percent or more of their daily dietary calories in the form of fats. The FDA, the American Heart Association, and other health agencies, however, recommend diets containing no more than about 30 percent of calories from fats (and less than 10 percent from saturated fats),
Concern about fat consumption arises because diets high in fat are highly correlated with a variety of cardiovascular disorders, including high blood pressure, atherosclerosis ("hardening of the arteries"), heart attack, coronary heart disease, congestive heart failure, and stroke. Cardiovascular disorders are currently the leading cause of death in the United States. The American Heart Association estimates that 61.8 million Americans have cardiovascular disease, resulting in more deaths in the United States than the next seven causes (including all forms of cancer) combined. It is hardly surprising, then, that food scientists are interested in developing synthetic foods that mimic the desirable characteristics of fats and eliminate all or most of their disadvantages.
Fats are a member of the biochemical family known as lipids. The lipids include a wide variety of compounds present in living organisms that are grouped together on the basis of a single physical property: They are soluble in organic solvents such as benzene, ether, chloroform, and carbon tetrachloride but are insoluble in water.
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Chemical structures of a typical triglyceride and caprenin |
Fats and oils are chemically similar lipids that consist of glyc-erol, a trihydric (three - OH groups) alcohol, esterified with one or more fatty acids. The only difference between fats and oils is their physical state (fats are solid and oils are liquid) and the degree of unsaturation (the number of double bonds present) of the fatty acids they contain. The chemical structure of a typical fat is shown on page 79.
The three-carbon backbone at the left of the molecule is the remnant of the glycerol molecule from which the fat is formed. The three long-chain segments attached to the backbone are the remnants of the fatty acid from which it is formed. The fat shown here is also called a triglyceride because it has three (tri-) fatty acid remnants (-glyceride). Some fats contain only one fatty acid remnant (mono-glycerides) and some contain only two fatty acid remnants (diglyc-erides). Fats that contain fatty acid remnants with double bonds are called unsaturated fats, while those that contain only single bonds are saturated fats.
A diet high in fat poses at least two risks to one's health. First, fats produce a relatively large amount of energy when metabolized, nine calories per gram, compared with four calories per gram for carbohydrates, like sugar and starch. Second, saturated fats are believed to be responsible for an increase in blood cholesterol levels which, in turn, have been implicated with an increased risk for heart disease.
The primary goal of food chemists in their search for synthetic fats is to modify lipid molecules so that they provide most of the sensory advantages possessed by fatty foods, the characteristics that make people want to eat fats, while reducing the risks posed by such molecules. The term structured lipid (SL) has been invented to describe lipids in which the position and character of fatty acid remnants in a lipid molecule have been altered from those found in the molecule's natural state.
One example of a structured lipid is a product known as caprenin, developed by Procter & Gamble (now P&G). As shown in the diagram on page 79, the caprenin molecule consists of the usual glycerol background to which are attached fatty acid remnants of 8, 10, and 22 carbon atoms, remnants corresponding to caprylic (C7H15COOH), capric (C9H19COOH), and behenic (C21H43COOH) acids. No molecule of this kind exists in nature, so it can legitimately be called a structured lipid. When this molecule is digested, the behenic acid formed is not metabolized but is absorbed by the body. Since only the glycer-ol, capric acid, and caprylic acid molecules formed are metabolized, fewer calories (5 calories per gram) are released compared with those obtained from a natural fat.
In 1991, Procter & Gamble filed a petition with the FDA, requesting that caprenin be considered a GRAS substance and that it be made available for commercial use. The SL's first application is in a proposed new candy bar, Mars Milky Way II, where caprenin replaces the cocoa butter used in the original version of the candy. On September 18, 2000, Procter & Gamble withdrew its GRAS petition, indicating that it might resubmit the application at a later date.
Another structured lipid product that has become commercially available is salatrim, developed by the Nabisco Foods Group. This SL is somewhat different from caprenin in that it consists of a mixture of glycerides containing four fatty acid fragments, rather than the three found in caprenin. The four fatty acids contain 2, 3, 4, and 18 carbon atoms. The comparable fatty acids are ethanoic (CH3COOH), propanoic (C2H5COOH), butanoic (C3H9COOH), and stearic (C17H35COOH) acids. Salatrim's molecular structure gives it its name: Its molecules contain short - and long-chain acyl triglycer-ide molecules. Like caprenin, it has about half the calorie content of natural fats.
Nabisco notified the FDA in 1994 of its intention to seek approval for the use of salatrim as a GRAS substance. The introduction of GRAS substances in the marketplace involves a somewhat different approval process than that of other food additives. If a company's own research indicates that a new compound has no health effects on humans, it may notify the FDA that the compound can be considered "generally recognized as safe" (GRAS) and begin to market the compound commercially. The compound then remains on the FDA-approved GRAS list as long as objections are not raised or research presented to the FDA suggesting that the compound has been incorrectly classified as GRAS.
Thus, Nabisco began marketing salatrim under the brand name Benefat® shortly after notifying the FDA of the compound's GRAS status. It has thus far been used primarily in confectionery products, including chocolate chips and candies. A number of other SL products have been developed or are currently being studied in the United States and abroad. These include Structolipid (Pharmacia &
Upjohn AB, Sweden), Captex 810D (Abitec Corporation), Bohenin (Fuji Oil Company), and Neobee (Stepan Food Company).
Some nutrition groups have expressed concerns about the use of products such as caprenin and salatrim, arguing that data are insufficient to allow their release to the general public. In 1998, for example, the Center for Science in the Public Interest (CSPI) asked the FDA to deny Nabisco's petition to have salatrim listed as a GRAS substance. The CSPI pointed out that Nabisco had conducted only one short (28-day) study on the product, and this study had found some negative short-term effects of the product. The FDA has thus far not acted on either the original petition or CSPI's letter of complaint.
An entirely different approach in the production of a synthetic fat is olestra, perhaps the most famous fat substitute yet developed. Olestra was discovered in 1968 by Robert Volpenheim and Fred Mattson, researchers at Procter & Gamble's Miami Valley Laboratories. Volpenheim and Mattson were engaged in a project to develop a new kind of fat that could be digested more easily by premature babies. Instead, they came across a new compound that had many of the properties of a fat but that passed through the human body without being digested.
Olestra belongs to a group of compounds known as sucrose polyesters. These are compounds in which two or more hydroxyl groups in the sucrose molecule have been replaced by fatty acid fragments. Olestra is a mixture of the hexa-, hepta-, and octa-fatty acid esters of sucrose. In the diagram on page 83, each of the structures marked "FA" represents a fatty acid fragment substituted for a hydroxyl group on the sucrose molecule.
The molecule is so large that enzymes that normally digest sucrose (sucrases) have no access to the bonds on which they normally operate. As a result, the molecule passes through the human digestive system without being digested, absorbed, or metabolized.
The market appeal of olestra, then, is that it tastes like fat, but it contains no nutritional calories. For example, a one-ounce bag of potato chips normally contains about 10 grams of fat and 150 Calories. A comparable bag of chips made with olestra contains nearly the same amount of fat, 9 grams, but only 70 Calories (from constituents other than the fat). Olestra is marketed under the trade name Olean.
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Olestra
@ Infobase Publishing
Chemical structure of olestra
Like other synthetic foods, olestra has a complex regulatory history. It began in 1975 when Procter & Gamble petitioned the FDA to approve olestra as a drug. The company took this approach because the compound seemed to be effective in lowering blood cholesterol. When the company was unable to provide sufficient evidence for this claim, however, it changed course. In 1987, Procter & Gamble submitted a new petition with the FDA, asking it to approve olestra as a food additive that could be substituted for up to 35 percent of the fats used in home cooking and 75 percent of the fats used in commercial food processing.
At this point the regulatory story becomes really complicated. P&G's original patent on olestra was due to expire in 1988, making it impossible for the company to complete its FDA application before losing its patent rights. Ultimately, it took a special act of Congress to extend P&G's patent and allow it to complete its application process with the FDA.
The FDA finally acted on P&G's petitions on January 24, 1996, when it granted approval for the use of olestra in a limited variety of commercial products, including potato chips, crackers, and tortilla chips. P&G and other food companies soon began marketing a variety of new commercial products containing olestra, including Fat Free Pringles, Wow Potato Chips, and Ruffles, Lay's, Doritos, and Tostitos MAX chips. A long-term goal of P&G is to obtain FDA approval to use the product in many other types of foods as well, including doughnuts, cakes, cookies, pastries, pies, ice cream, french fries, fried chicken and fried seafood, grilled meats and vegetables, margarines, and cheeses.Almost since olestra was first discovered, however, P&G has had to deal with complaints by public interest groups about possible health effects of the new substance. Shortly after the company filed its first petition with the FDA in 1987, the CSPI suggested in a letter to the FDA that P&G's testing of the new product was inadequate and failed to address health concerns. Over the next two decades, CSPI, other consumer groups, and many individuals continued to express concerns about the safety of olestra.
Critics attribute a variety of gastrointestinal complaints to the consumption of olestra. Symptoms cited include bloating, diarrhea, cramps, loose stools, and urgency of defecation. In addition, olestra apparently has the tendency to bind to certain essential biochemi-cals, preventing the human body from absorbing them. Among these biochemicals are fat-soluble vitamins (A, D, E, and K) and carotenoids, such as beta-carotene, lycopene, lutein, and zeaxanthin. In an attempt to resolve this problem, the FDA now requires food producers to add fat-soluble vitamins to products containing olestra.
The debate over olestra and other synthetic foods has hardly been resolved. Companies that manufacture artificial sweeteners and fat substitutes continue to promote the safety and health values of their products, arguing that their more extensive use can help improve the nutritional diets of the average American. At the same time, many organizations and individuals point out that the vastly increased availability of synthetic diet foods (such as aspartame, saccharin, caprenin, and olestra) has had no discernible impact on that very problem. As these supposedly nutritionally sound synthetic foods have become more available, the average American's nutritional health has continued to deteriorate, with more and more people confronting the very problems of weight that those foods were supposed to help solve. For example, the Center for Disease Control and Prevention's 2003-2004 National Health and Nutrition Examination Survey (NHANES) found that 66.3 percent of all adults studied could be classified as overweight and 32.2 percent as obese. These figures represent an increase of 18 percent and 40 percent, respectively, over similar data collected in a 1994 NHANES survey.
Food chemists have developed a number of synthetic foods with the potential for improving the quality of food available to Americans and people around the world. Artificial sweeteners and fat substitutes can be useful for diabetics, people who are trying to lose weight, and others concerned about maintaining a healthy diet. At the same time, this is not to ignore the potential health risks for
some people who may be allergic to such products and may develop other health problems by using them.
The flurry of research on synthetic foods appears to have abated to some extent in the last decade. Relatively few artificial sweeteners and fat substitutes have appeared on the market during that time. But research on such products has certainly not come to an end. Food chemists will continue to search for new products with which to augment and improve peoples' diets.
Introduction
The History Of Food Modification
Food Additives
Synthetic Foods
