Americans' growing preference for reduced-fat diets has food manufacturers cooking up new substances to replace most, if not all, of the fat in a food.
Some of these fat substitutes, with trade names such as Simplesse and Avicel, already are on the market and being used in a variety of foods, including cheese, chips, frozen desserts, and candy. Others remain in development. At least one--olestra--is under FDA review.
The idea behind all these substitutes is to reduce a food's fat and calories while maintaining the texture provided by fat. They often fall short, however. While most contain fewer calories than fat, they don't withstand the cooking temperatures that natural fats do.
Olestra appears to be an exception. Because olestra is formed by chemical combination of sucrose (sugar) with fatty acids, it has properties similar to those of a naturally occurring fat. But, unlike the natural products, this synthetic substitute provides no calories or saturated fat because it is undigestible: It passes through the digestive tract but is not absorbed into the body.
As promising as that sounds, olestra and similar fat substitutes that may come along in the future raise new concerns: What effect can they have on the gastrointestinal system if they are not absorbed? Can they affect absorption of fat-soluble vitamins? Can they interfere with absorption of other nutrients or with drugs? What particular effects might they have in people with conditions that affect nutrition, such as intestinal disease?
Unlike other food additives, which make up only a minute amount of the diet, fat substitutes, such as olestra, have the potential to make up a substantial portion of the diet because they replace fat, a major dietary component. This raises another concern: how best to determine if there are possible toxic effects from such fat substitutes. The usual method for studying toxicity of food additives--giving upwards of 100 times the likely human intake of the substance to laboratory animals--is impractical for fat substitutes like olestra. It is not possible to feed laboratory animals the large amount of fat substitutes that would be required to conduct a traditional toxicology test as is done with other food additives to determine safety.
FDA's Center for Food Safety and Applied Nutrition (CFSAN) is exploring these concerns in its review of a food additive petition for olestra. The manufacturer, Procter and Gamble of Cincinnati, is seeking approval to use olestra in salty or sharp-tasting snacks, such as potato chips, cheese puffs, and crackers. This is the first and only filed petition for a fat-based fat substitute now before the agency. P&G filed the petition in 1987.
Fat in the Diet
Replacing fat in the diet is not as easy as it may sound. Contrary to public perception, natural fats actually have many useful roles in the diet. They are one of the nutrient categories essential for proper growth and development and maintenance of good health. They carry the fat-soluble vitamins A, D, E, and K and aid in their absorption in the intestine. They are the only source of linoleic acid, an essential fatty acid. And they are an especially important source of calories for people who are underweight and for infants and toddlers, who have the highest energy needs per kilogram of body weight of any age group.
Fat also plays important roles in food preparation and consumption. It gives taste, consistency, stability, and palatability to foods.
On the other hand, too much fat in the diet can be harmful. Fat is calorie-dense: It contains 9 calories per gram, compared to 4 calories per gram for protein and carbohydrates. So eating a lot of fat can result in excess calorie in take, which in turn can perhaps lead to undesirable weight gain.
Fat intake also is linked to several chronic diseases. There is some evidence of a link between high intakes of fat and a possible increased risk of certain cancers, such as breast, colon and prostate cancers. There also is a link between high intakes of saturated fat and cholesterol and an increased risk of coronary heart disease.
The Dietary Guidelines for Americans recommend that fat intake be limited to 30 percent or less of calories and saturated fat to less than 10 percent.
Many Americans are trying to reduce their fat intake. According to a survey by the Calorie Control Council--an association of low-calorie and diet food manufacturers--nearly two-thirds of the adult U.S. population consume low- or reduced-fat or reduced-calorie foods and beverages, and two-thirds also believe there is a need for food ingredients that replace fat.
Manufacturers are responding by adding more and more reduced-fat foods to their product lines. These products often contain fat substitutes already approved by FDA.
Fat Substitutes
Fat substitutes can be carbohydrate-, protein- or fat-based.
The first type to reach the market contained carbohydrate as the main ingredient. Avicel, for example, is a cellulose gel introduced in the mid-1960s by FMC Corp., and N-Oil is a tapioca dextrin introduced in the early 1980s by National Starch and Chemical Co. These types of fat substitutes are used in a variety of foods today, including lunch meats, salad dressings, frozen desserts, table spreads, dips, baked goods, and candy.
Protein-based fat substitutes entered the market in the early 1990s. There are two that have been affirmed as "generally recognized as safe" (GRAS): microparticulated proteins from egg white or dairy protein and whey protein concentrate. Microparticulation is a process in which the protein is shaped into microscopic round particles that roll easily over one another. These fat substitutes give a better sensation in the mouth--"mouth feel" in industry parlance--than the carbohydrate-based ones and can be used in some cooked foods. However, they're not suitable for frying.
Olestra
Olestra is a fat-based fat substitute. Unlike the other fat substitutes, it provides zero calories. This is due to its unique configuration. Most fat substitutes mimic the molecular shape of fat--one molecule of glycerol attached to three molecules of fatty acids. With olestra, the glycerol molecule is replaced with sucrose and has six, seven or eight fatty acids attached. The fatty acids can come from a variety of vegetable oils, such as soybean, corn, palm, coconut, and cottonseed oils. The idea is that with this many fatty acids, digestive enzymes can't get to the sucrose center in the time it takes for the substance to move through the digestive tract. The sucrose center is where breakdown of the substance for absorption into the body would take place.
P&G first sought FDA approval for olestra--as a drug--in 1975. The company filed an investigational new drug application after early human studies showed that olestra lowered blood cholesterol. But additional studies showed that it did not sufficiently reduce cholesterol to warrant its use as a drug. In 1988, P&G withdrew the application.
In 1987, the company filed a food additive petition for the approval of the use of olestra as a calorie-free replacement for fat in shortening and cooking oil. In 1990, it amended the petition to limit olestra's use to 100 percent replacement for conventional fats in the preparation of savory snacks, such as potato chips, cheese puffs, and crackers.
P&G also is seeking approval for olestra in Canada and the United Kingdom.
Olestra Studies
Since 1987, P&G has submitted to FDA more than 150 studies on olestra's safety. These include:
To help CFSAN resolve some of the issues raised by the olestra petition, the center, in spring 1995, established a team made up of senior managers from CFSAN and FDA's Center for Veterinary Medicine, which was included because of its expertise in reviewing animal studies. The group was charged with reviewing safety data and recommending a decision to the center director on the olestra petition. In addition, CFSAN arranged for the members to discuss the data with its expert consultants from academia and with experts from other government agencies.
CFSAN sought additional input from FDA's Food Advisory Committee, which met Nov. 17, 1995, to discuss the olestra petition. A committee working group met Nov. 14 through 16 to review the safety data on olestra and to consider whether all safety issues had been adequately addressed.
The working group considered four areas: olestra's chemistry and consumption, toxicology and potential interference with drug absorption, gastrointestinal effects and labeling, and nutritional effects. For each area, the working group was asked to decide whether all relevant issues had been identified, whether there were sufficient data to address these issues, and whether there was a "reasonable certainty of no harm" from the proposed use of olestra. The working group unanimously concluded that, in all four areas, the relevant issues had been identified and the data were sufficient to address the relevant issues. Most of the working group also agreed that the data provided a reasonable certainty of no harm from olestra.
However, the group recommended that products containing olestra bear a label statement about the food's potential to cause intestinal discomfort or a laxative effect, without suggesting that the product is intended for use as a laxative.
Also, the committee agreed that while olestra has no effect on water-soluble nutrients, it should be formulated to contain vitamins A, D, E, and K to avoid their depletion in people who eat olestra-containing foods. Although the working group considered carotenoid depletion by olestra, most members said they were reasonably certain that no harm will result from the effect of olestra on carotenoids.
During the Nov. 17 meeting, the full Food Advisory Committee discussed the working group's conclusions. Most committee members concurred with the working group's findings and agreed that there is a reasonable certainty of no harm from olestra's proposed uses. The committee's comments, as well as those of the working group, will be passed on to FDA for its consideration in making a decision on the olestra petition.
Advisory committee recommendations are not binding on FDA but are carefully considered by the agency.
This is a mirror of the page formerly at <http://www.fda.gov:80/opacom/backgrounders/olestra.html>