The effect of olestra on systemic levels of oral contraceptives

Current concepts in the pharmacological management of obesity

The pharmacological management of obesity has gained increasing attention as new weight loss treatments are approved and a significant proportion of the public strives to lose weight. Obesity is associated with a high mortality rate, multiple chronic medical conditions, and carries an enormous financial burden. Obesity is a multifactorial condition, most often due to an imbalance in energy intake and expenditure. Despite the greater focus on management of obesity, weight loss remains a difficult goal to achieve. Obesity is a chronic medical condition that may require long term treatment, therefore the risks and benefits of all pharmacological agents must be carefully considered. Noradrenergic appetite suppressants (ie. phenyl-propanolamine, phentermine) result in weight loss but stimulatory effects limit their use. The serotonergic agents (fenfluramine, dexfenfluramine) were effective weight loss drugs, but were voluntarily withdrawn from the US market last year because of cardiovascular and pulmonary complications. The combination noradrenergic/serotonergic agent sibutramine is indicated for the management of obesity, particularly in the presence of other cardiovascular risk factors. Modest weight loss is achieved with sibutramine, although weight gain is significant after discontinuation. In addition, long term safety data are not yet available. The thermogenic combination of ephedrine plus caffeine is minimally effective, and adverse effects are usually transient. Other thermogenic agents, such as beta3-agonists, are still under investigation. Agents may alter digestion through lipase inhibition (orlistat) or fat substitution (olestra). Orlistat decreases systemic absorption of dietary fat, decreasing body weight and cholesterol. Olestra is a fat substitute that has been incorporated into snack foods. Olestra substitution for dietary fat has not been studied as a weight loss strategy, although olestra has no caloric value and may be beneficial. The use of orlistat and olestra may be limited by gastrointestinal adverse effects. Finally, the manipulation of leptin and neuropeptide Y are under investigation for the treatment of obesity. Pharmacological agents should be used as an aid to a structured diet and exercise regimen in the treatment of obesity. Weight loss agents may result in initial weight loss, but sustained weight loss is not always achieved even with continuation of treatment. The effect of weight loss obtained while using pharmacotherapeutic agents on morbidity and mortality has not been established. Therefore, diet and exercise should be the focus of any weight loss programme. There is a continued need for safe and effective pharmacotherapeutic agents for the treatment of obesity.

Review article: olestra and its gastrointestinal safety

Olestra is a fat substitute made from sucrose and vegetable oil. Olestra is neither digested nor absorbed, and therefore adds no calories or fat to the diet. Because the gut is the only organ that is exposed to olestra, the potential for olestra to affect gastrointestinal structure and function, and the absorption of nutrients from the gut, has been investigated. Histological evaluations performed after long-term feeding studies have shown no indications that olestra causes injury to the gastrointestinal mucosa. Olestra is not metabolized by the colonic microflora, and has no meaningful effects on the metabolic function of these organisms. Studies of gastrointestinal transit have shown that the consumption of olestra with food does not affect gastric emptying, or small or large bowel transit times. Olestra does not affect the absorption of macronutrients, water-soluble vitamins or minerals. It causes a dose-responsive decrease in the availability of the fat-soluble vitamins A, D, E and K; however, this potentially adverse effect is offset by the addition of vitamins to olestra-containing foods. Olestra has no consistent effect on the amount of total bile acids excreted in the faeces, and therefore probably has no significant effect on bile acid absorption. The occurrence of gastrointestinal symptoms, including diarrhoea, loose stools, gas and abdominal cramping, after consumption of olestra under ordinary snacking conditions is comparable to that following consumption of triglyceride-containing snacks.

Olestra: a new food additive

In 1987, Procter and Gamble Company (Cincinnati, Ohio) petitioned the US Food and Drug Administration (FDA) to amend the food additive regulations to allow sucrose esterified with fatty acids (olestra) to be used as a replacement for conventional fats. The petitioner later restricted its request for use in savory snacks. FDA considered evidence submitted by the petitioner, the opinions of experts, proceedings from the FDA Food Advisory Committee, and public discussion and concluded on January 25, 1996, that olestra was safe for use in savory snacks (eg, salty snacks such as potato chips, corn chips). Olestra is not toxic, carcinogenic, genotoxic, or teratogenic and is neither absorbed nor metabolized by the body, but may be associated with gastrointestinal tract symptoms such as cramping or loose stools. In addition, olestra affects the absorption of fat-soluble vitamins but does not affect the absorption of water-soluble nutrients. The petitioner's studies concluded that when olestra was consumed with foods containing vitamins A, D, E, or K, the fat substitute could have an effect on the absorption of these nutrients. Therefore, FDA is requiring that fat-soluble vitamins lost through absorption be added back to olestra as follows: 170 IU vitamin A per gram olestra, 12 IU vitamin D per gram olestra, 2.8 IU vitamin E per gram olestra, and 8 micrograms vitamin K per gram olestra. As part of the conditions of approval FDA is requiring that the food labels of products containing olestra disclose the vitamin compensation and the potential gastrointestinal effects. FDA is also requiring that further studies examining consumption patterns and the effects of olestra on human beings be conducted.

Update on the pharmacotherapy of obesity

OBJECTIVE

To review recent developments in the pharmacotherapy of obesity, including the agents currently approved for use in the management of obesity and those under development.

DATA SOURCES

A MEDLINE search from January 1990 to July 1997 was conducted to identify English literature available on the pharmacotherapy of obesity. The search was supplemented by a review of the bibliographies of identified literature.

STUDY SELECTION

All controlled and uncontrolled trials were reviewed. When available, double-blind, placebo-controlled trials were used preferentially.

DATA EXTRACTION

Agents were reviewed with regard to mechanism of action, clinical trial data regarding efficacy, adverse effects, pharmacokinetics, drug interactions, and contraindications where information was available. Study design, selected population, results, and adverse effect information were included.

DATA SYNTHESIS

The anorexiants currently available or under development for the management of obesity regulate food intake and satiety via the adrenergic and/or serotonergic pathways. Clinical trials have shown a 10-15% weight loss can typically be anticipated; however, little long-term safety and efficacy data are available. Adverse events tend to be mild and self-limiting, but serious adverse events can occur. Treatment options under development include thermogenic agents, digestive inhibitors, and analogs and antagonists of hormones that regulate food intake and satiety.

CONCLUSIONS

Several mechanisms to control weight are currently under investigation for the management of obesity. Since obesity is a chronic condition, further studies should be conducted to evaluate the long-term safety and efficacy of these agents and the role of combination therapy using different modalities.

Review and analysis of the effects of olestra, a dietary fat substitute, on gastrointestinal function and symptoms

Olestra, a dietary fat substitute, was recently made available to consumers in savory snacks in three cities. Early reports of gastrointestinal complaints attributed to olestra attracted media coverage and fostered confusion among physicians and consumers about the nature of olestra and its effects on the digestive system. We reviewed all published studies of olestra's gastrointestinal effects and all relevant unpublished studies submitted to the Food and Drug Administration. Each study was analyzed by a group of expert gastroenterologists and epidemiologists. The symptoms reported with olestra ingestion are similar to those reported with ingestion of fiber and sorbitol, although the mechanisms involved in changing stool characteristics differ among these food additives. Olestra's effects on stool habit and characteristics are due to its presence in the stool. Large amounts are more likely to induce gastrointestinal symptoms than small amounts. There is no evidence that olestra induces pathological change in bowel function: there is no increased fluid or electrolyte nor is there altered gastrointestinal motility or microflora. Olestra and triglyceride ingestion resulted in a similar frequency of symptoms in normal adults and children and in people with chronic inflammatory bowel disease in remission. Olestra traverses the digestive tract intact to become a stool additive. Some subjects develop a change in bowel habit and stool characteristics due to the presence of more olestra in the stool. These changes resemble those associated with ingestion of sorbitol and fiber.

Assessment of the nutritional effects of olestra

Olestra is a mixture of polyesters formed from sucrose and fatty acids derived from edible fats and oils. It is not absorbed or digested and can serve as a zero-calorie replacement for dietary fat. Because olestra is lipophilic and not absorbed, it has the potential to interfere with the absorption of other dietary components, especially lipophilic ones, when it is in the digestive tract with those components. A series of studies were conducted in the domestic pig and in healthy adult humans to define the nature and extent of olestra's effect on fat-soluble vitamins, selected water-soluble micronutrients, and macronutrients, and to demonstrate that the effects of olestra on the absorption of fat-soluble vitamins can be offset by adding extra amounts of the affected vitamins to olestra foods. Before conducting the human and pig studies, the intake of olestra from the consumption of snack foods made with olestra was estimated for various subgroups. The potential for olestra to affect the absorption of nonessential but potentially beneficial dietary phytochemicals was also assessed. In addition, an assessment of how consumption patterns influence the effect of olestra on the absorption of the highly lipophilic carotenoids was made. Finally, the results from the pig and human studies were used to assess the potential for olestra to affect the nutritional status of subgroups of the population who have particularly high nutrient needs or unique dietary patterns that may lead to large olestra-to-nutrient intake ratios.

Olestra, a nonabsorbed, noncaloric replacement for dietary fat: a review

Olestra has been shown to be safe for its intended use by extensive testing in animals and in humans. It is not digested or absorbed and has no effect on the structure or physiology of the GI tract, the only organ of the body that it contacts. Olestra can interfere with the absorption of other lipophilic substances from the GI tract. The interference occurs because a portion of those molecules that are sufficiently lipophilic partition into the nonabsorbed olestra and is carried out of the body. Whether olestra will interfere with the absorption of a specific molecule can be predicted from the octanol-water partition coefficient of the molecule, a parameter that can be measured or calculated from a knowledge of the structure of the molecule. Olestra does not affect the absorption or efficacy of oral drugs because, in general, they are not sufficiently lipophilic to partition into the olestra. Olestra does not affect the absorption of water-soluble micronutrients or the absorption and utilization of macronutrients. Olestra can reduce the absorption of the fat-soluble vitamins when olestra foods and the vitamins are coingested. These effects can be offset by adding specific amounts of the vitamins to foods made with olestra. Other than the carotenoids and vitamins A and E, olestra does not affect the absorption of potentially beneficial components of fruits and vegetables. The effects on the vitamins can be offset by adding the vitamins to olestra foods. The reduction in the absorption of carotenoids will be less than 6-10% when olestra snacks are eaten under free-living dietary patterns. Any effect this reduction has on vitamin A status can be offset by addition of vitamin A to the foods. The absorption of flavonoids, polyphenols, and most other phytochemicals in fruits and vegetables, which have been shown to provide beneficial health effects, will not be affected by olestra because they are not sufficiently lipophilic. Individuals consuming large quantities of olestra may experience mild or moderate common GI symptoms such as loose or soft stools, gas, or nausea, symptoms similar to those experienced with certain other foods or changed dietary habits. When olestra snack foods are eaten under free-living dietary patterns, the symptoms are not different from those experienced when eating full-fat snack products, in either incidence or severity. When they are experienced, the symptoms resolve in 1-2 days, but may recur. They do not worsen with continued or increased olestra consumption and pose no health risk to the consumer. Olestra products will carry an information label alerting consumers to the possibility of GI symptoms. Olestra foods provide an additional option to those individuals who want or need to lower their total energy intake and body weight. These individuals will find it easier to change dietary habits and to maintain healthful nutritional practices when they use olestra foods. For those who want or need to reduce fat intake but not lose weight, olestra foods can reduce fat intake without affecting energy. Because olestra foods have taste and other organoleptic properties that are similar to those of full-fat foods, individuals will find it easier to switch to low-fat diets.

Lipid-based fat substitutes

Fats and oils account for 38% of the total calories in the diet of Western populations, especially in the U.S. They provide the most concentrated source of energy, 9 kcal/g of a triacylglycerol molecule compared with 4 kcal/g provided by carbohydrate and protein. In response to consumer demands for low-calorie or calorie-free fats and their reluctance to give up the taste of fat, current research efforts have been directed toward the development of lipid-like fat substitutes. These fat substitutes contain the fatty acids found in conventional fats and oils, with all the physical and organoleptic properties of fats, but provide few or no calories in the diet. Some of the fat substitutes are modified triacylglycerols (glycerol backbone) with reduced digestion and absorption; others are digestible and nondigestible carbohydrate fatty acid esters and polyesters, respectively. Sucrose polyester (Olestra), a sucrose molecule esterified with six to either fatty acids, is the most studied of the lipid-based fat substitutes containing a carbohydrate backbone. If approved by the FDA, sucrose polyester will find application in almost all fat-containing foods. Specialty fats or fat substitutes targeted to certain individuals with special needs are being developed. Among these are the medium-chain triacylglycerols and structured lipids (glycerol backbone), or ¿nutraceuticals¿ with reduced absorption and medical applications. Enzyme biotechnology is another tool available to lipid chemists to selectively modify, esterify, transform, transesterify, and interesterify fats and oils or synthesize new lipids such as structured lipids of food, nutritional, and medical importance. These designer fats may be the trend in the future to produce medical lipids that do not occur normally in nature. The different types of lipid-based fat substitutes are reviewed with respect to their synthesis, analysis, metabolism, potential applications/uses, and the future of fat substitutes.

Safety evaluation of olestra, a nonabsorbed, fatlike fat replacement

Olestra is the mixture of the hexa-, hepta-, and octa-esters of sucrose with long-chain fatty acids from any edible oil. Its physical properties are comparable to those of triglycerides, but it is not digested by lipolytic enzymes or absorbed and therefore is noncaloric. Technically, it can replace fat in a wide variety of foods and can be used to make cooked, baked, and fried foods lower in fat and calories. A Food Additive Petition is under review by the FDA, which is comprised of results of extensive testing in animals and humans. The major areas of investigation are metabolism and absorption, chronic toxicity, mutagenicity, carcinogenicity, reproductive and developmental toxicity, safety for gastrointestinal tract, nutrition, and the potential for olestra to affect absorption of drugs. This testing involved studies in five different species of animals and over 30 clinical investigations. The results of this research support the safety of olestra for use in foods.