Food Lipids: Chemistry, Nutrition, and Biotechnology

inversely related to the degree of substitution or esterification (20,48). Because of
the molecular size of the fat substitutes and steric hindrance, the lipases cannot get
to the substrate, and subsequently the formation of the enzyme–substrate [ES] complex
required for lipase action on carbohydrate polyesters is prevented (11). Poor
digestibility and absorbability of carbohydrate polyesters indicate that these substances
supply few or zero calories; hence they are called low-calorie fat substitutes.
Olestra is an FDA-approved, zero-calorie fat substitute. Because olestra is the most
studied and the only synthetic lipid-based fat substitute approved, it is the focus of
most of the discussions.
A. Effect of Olestra on Serum Lipids and Weight Reduction
An early report by Crouse and Grundy (49) indicated that sucrose polyester (olestra)
interferes with the absorption of cholesterol because cholesterol is soluble in the fat
substitute. According to Grundy et al. (50), nondiabetic patients on a calorie-restricted
diet plus sucrose polyester (SPE) exhibited decreases in total cholesterol and
low density lipoprotein (LDL) cholesterol of 20% and 26%, respectively. Reduction
in serum cholesterol was at the expense of LDL-cholesterol. Diabetic patients with
hypertriacylglycerolemia caloric restriction showed a marked reduction in plasma
triacylglycerols with or without sucrose polyester consumption. Caloric restriction
apparently reduced cholesterol by reducing cholesterol synthesis. Sucrose polyester
has little effect on the concentration of HDL-cholesterol (47,51,52). LDL-cholesterol
is associated with the development of atherosclerotic plaques, while HDL-cholesterol
is associated with the prevention of atherosclerotic plaques. Patients with high cholesterol
levels are advised to lower their serum cholesterol levels by losing weight
and reducing both total fat intake (especially saturated fats) and cholesterol intake.
Sucrose polyester may also be useful in weight reduction (11,19,47). Other carbohydrate
polyesters can assist in the reduction of cholesterol levels (5,53–61). As
cholesterol enters the digestive tract, it dissolves into the carbohydrate polyester oil
phase and is excreted along with the carbohydrate polyester. Mellies et al. (53)
reported that in obese hypercholesterolemic outpatients, SPE induced significant reductions
in LDL-cholesterol beyond the effects of weight reduction. Glueck et al.
(54) found that substitution of SPE for dietary fats in hypocaloric diets in obese
women heterozygous for familial hypercholesterolemia resulted in 23% reduction of
LDL-cholesterol and in weight loss. Mattson and Jandacek (58) reported that [4- 14 C]
cholesterol injected into rats that were subsequently fed SPE diets appeared in the
feces of SPE-fed animals. Cholesterol absorption was reduced when 7 g of SPE was
fed twice a day to 20 normocholesterolemic male inpatients in a double-blind crossover
trial (56). It should be noted that Procter & Gamble did not pursue the approval
of olestra as a cholesterol-reducing agent.
B. Effect of Olestra on Macronutrients and Fat-Soluble Vitamins
Olestra does not affect the availability of macronutrients such as carbohydrates, triacylglycerols,
and proteins or that of micronutrients such as water-soluble vitamins,
olestra consumption was, however, found to increase the intake of carbohydrate but
without affecting total daily energy intake or usual patterns of hunger and fullness.
SPEs may affect the availability of some fat-soluble vitamins such as vitamins A,
D, E, and K, �-carotene, and lycopene (62), and cholesterol. In heavy snack eaters,
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.