Synthesis and metabolism of glycerol-3H triether, a nonabsorbable oil-phase marker for lipid absorption studies

A saturated mixed-chain glycerol triether, 1-hexadecyl-2,3-didodecyl glycerol (1-hexadecoxy-2,3-didodecoxypropane), was synthesized with (3)H at positions 9 and 10 or (14)C at position 1 of the hexadecyl moiety. In acute feeding experiments in rats, less than 0.2% of the triether was absorbed, based on lymph and fecal recoveries. Radioactivity was present exclusively as triether in feces, indicating that it was not degraded by digestive or bacterial enzymes. Chronic feeding experiments in rats confirmed the nonabsorbability of the triether and further indicated that it was nontoxic, did not influence the absorption of dietary fat, and mixed intimately with the fat present in colonic contents and feces. The triether that was absorbed was deposited as triether in adipose tissue, liver, and spleen. When administered intraperitoneally to mice, the triether was stored in the tissues and was not metabolized. When the triether was partitioned between an oil phase of triolein or fatty acid and monoglyceride, and an aqueous micellar phase, the triether remained exclusively in the oil phase. The triether appears to be an ideal nonabsorbable oil-phase marker for use in lipid absorption studies.     

Tritiated glycerol triether as an oil phase marker in man

3H-labeled glycerol triether has been suggested as a marker of the oil phase during digestion and absorption of a lipid test meal. This study examines the behavior of this isotope in the human alimentary tract. The results suggest that it is completely recovered from the gastrointestinal tract, and thus it remains solely with the oil phase of emulsions in vivo and with the oil phase of intestinal aspirates. (3)H-labeled glycerol triether may thus be an appropriate marker of the oil phase for use in human studies of lipid absorption.     

Intestinal absorption and lymphatic transport of cholesterol and beta-sitostanol in the rat.

The intestinal absorption of cholesterol and beta-sitostanol (the saturated analogue of beta-sitosterol) were measured and their absorptions compared in the presence and absence of cholestyramine. After test meals containing [(3)H]cholesterol and [(14)C]beta-sitostanol without added cholestyramine, 4-day fecal collections yielded an average of 51% of the fed cholesterol and 83% of the fed beta-sitostanol. In separate lymph transport studies without cholestyramine, 36% of the fed cholesterol was recovered in lymph in 24 hours compared to only 2% of the fed beta-sitostanol. Thus, while total recoveries of the two labeled compounds in feces plus lymph were nearly identical (51% + 36% = 87% for cholesterol and 83% + 2% = 85% for beta-sitostanol) their distribution in the two compartments was markedly different, reflecting the relative nonabsorbability of beta-sitostanol. Adding cholestyramine to the test meal caused fecal excretion of cholesterol to increase to 73%, independent of the dose of cholestyramine used. Cholestyramine had no effect on the fecal excretion of beta-sitostanol (average excretion after cholestyramine, 85%). The relative non-absorbability of beta-sitostanol compared to cholesterol is clearly evident in this study and leads us to suggest its possible use as a lipid-soluble, nonabsorbable reference compound for measurement of the absorption of cholesterol and other lipids. Further data are presented to justify its use for this purpose.-Hassan, A. S., and A. J. Rampone. Intestinal absorption and lymphatic transport of cholesterol and beta-sitostanol in the rat.     

Decreasing Effect of Chitosan on the Apparent Fat Digestibility by Rats Fed on a High-fat Diet

We investigated the effects of various dietary fibers or their likenesses on the apparent fat digestibility by rats fed on a high-fat diet. Each of 23 different fibers was added at 5% (w/w) to a purified diet containing 20% (w/w) corn oil. The rats were fed these diets for 2 weeks, and the feces were collected from each animal during the last 3 days. When compared with cellulose (control), 10 of the tested fibers significantly increased the fecal lipid excretion. Among these fibers, chitosan markedly increased the fecal lipid excretion and reduced the apparent fat digestibility to about a half relative to the control. The apparent protein digestibility was not greatly affected by chitosan. The fatty acid composition of the fecal lipids closely reflected that of the dietary fat. These results suggest that chitosan has potency for interfering with fat digestion and absorption in the intestinal tract, and for facilitating the excretion of dietary fat into the feces.     

Quantification of cholesterol absorption in man by fecal analysis after the feeding of a single isotope-labeled meal

The fecal excretion of cholesterol-4-(14)C and -sitosterol-22,23-(3)H has been studied in normal human subjects after they had ingested a single meal containing the radioactive substances. When 150 mg of -sitosterol, dispersed in the butter of a standard breakfast, was fed to 20 subjects the mean recovery of isotope in the feces was 90%. When plant sterols (70% -sitosterol, 30% campesterol) were fed together with cholesterol and used as an internal standard to correct for losses of cholesterol during intestinal transit and analytical procedures, excretion of dietary cholesterol was found to be 60-80%, irrespective of the amount fed over the range 150-1910 mg. If absorption of cholesterol is calculated from these figures, no saturation of the cholesterol absorption mechanism is indicated for the amounts of cholesterol fed in this investigation. The reason for the differences between these findings and those previously reported by other procedures is not clear, but may be related to the acute administration of a single dose of cholesterol in this study.     

Effect of diosgenin on lipid metabolism in rats.

The purpose of this study was to determine whether diosgenin suppresses cholesterol absorption in rats, and to examine relevant changes in cholesterol and bile acid metabolism. Diosgenin fed with the diet for 1 week inhibited cholesterol absorption as determined by the serum isotope ratio technique, as well as by measuring in the feces the amount of unabsorbed radioactivity from orally administered [3H]cholesterol. In addition, diosgenin suppressed the serum and liver uptake of radioactivity from co-administered [3H]cholesterol as well as the accumulation of liver cholesterol in the cholesterol-fed rat; diosgenin was substantially more active than cholestyramine or beta-sitosterol. In vitro, diosgenin had no effect on the activity of rat pancreatic esterase. Diosgenin decreased the elevated cholesterol in serum LDL and elevated cholesterol in the HDL fraction of cholesterol-fed rats; diosgenin had no effect on serum cholesterol in normocholesterolemic rats. In contrast to cholestyramine, diosgenin markedly increased neutral sterol excretion without altering bile acid excretion; in vitro, diosgenin had no effect on bile acid binding. Diosgenin treatment increased hepatic and intestinal cholesterol synthesis as well as the activity of hepatic HMG CoA reductase. This was accompanied by increased biliary concentration of cholesterol, but not of bile acids. Diosgenin had no effect on cholesterol synthesis when added to normal rat liver homogenates. It was concluded that diosgenin interferes with the absorption of cholesterol of both exogenous and endogenous origin; such interference is accompanied by derepressed, i.e., increased, rates of hepatic and intestinal cholesterol synthesis. The increased unabsorbed cholesterol together with enhanced secretion of cholesterol into bile resulted in increased excretion of neutral sterols without affecting the biliary and fecal excretion of bile acids.     

Measurement of starch absorption in humans

Although starch provides a large fraction of human caloric intake, there is limited information concerning the efficiency of intestinal absorption of this nutrient. Owing to the fermentation of starch by colonic bacteria, there is no quantitative test for starch absorption comparable to the fecal fat determination. The most accurate estimation of starch absorption has been obtained by intubating the terminal ileum and aspirating ileal contents following ingestion of a meal containing starch plus a nonabsorbable marker. Starch absorption is calculated from the ratio of starch:marker in the ileal aspirate relative to the ratio in the meal. Disadvantages of the technique are the requirement for ileal intubation and the possible adverse effect of intubation on the absorptive process. A more widely used technique to assess starch absorption involves measurement of breath hydrogen (H2) excretion after ingestion of starch. Malabsorbed starch is fermented by colonic bacteria with liberation of H2 that is absorbed and excreted in expired air. This test is simple and noninvasive and can provide quantitative measurements of starch malabsorption. Application of this technique has demonstrated that 5-10% of starch in wheat, potatoes, and corn is not absorbed by healthy subjects, while rice starch is nearly completely absorbed.     

Evaluation of the contribution of dietary cholesterol to hypercholesterolemia in diabetic rats and of sitosterol as a recovery standard for cholesterol absorption

The contribution of dietary cholesterol to hypercholesterolemia in diabetic rats fed chow ad libitum was evaluated. Diabetes was induced with streptozotocin, and the intake, absorption, and subsequent tissue distribution of dietary cholesterol were measured. Absorption was measured as the difference between [3H]cholesterol intake and fecal 3H-labeled neutral sterol excretion, using both [14C]sitosterol (added to diet) and [14C]cholesterol (added to feces) as recovery markers. [3H]Cholesterol absorption was underestimated by 1-3% using [14C]sitosterol as a recovery standard, due to the 7-8% absorption of sitosterol. After 3 weeks of diabetes, rats were hyperphagic, thereby increasing dietary cholesterol intake 2-fold. [3H]Cholesterol absorption was significantly increased from 69% in controls to 78% in diabetics, whereas [14C]sitosterol absorption was unaffected. With increased dietary cholesterol intake and decreased whole body cholesterol synthesis (Diabetes. 1983. 32: 811-819), influx from diet equaled for exceeded influx from synthesis. The amounts of 3H-labeled neutral sterol recovered from the small intestine, periphery, and plasma were increased 3- to 4-fold in the diabetic rats. Furthermore, the degree of hypercholesterolemia in diabetic rats was directly related to the fraction of plasma cholesterol derived from the diet. We conclude that the 2.3-fold increase in absorbed dietary cholesterol resulting from hyperphagia and, to a lesser extent, from increased fractional absorption, contributes to the hypercholesterolemia of diabetic rats fed chow ad libitum.     

Impact of β-cyclodextrin and resistant starch on bile acid metabolism and fecal steroid excretion in regard to their hypolipidemic action in hamsters1

To examine the impact on bile acid metabolism and fecal steroid excretion as a mechanism involved in the lipid-lowering action of β-cyclodextrin and resistant starch in comparison to cholestyramine, male golden Syrian hamsters were fed 0% (control), 8% or 12% of β-cyclodextrin or resistant starch or 1% cholestyramine. Resistant starch, β-cyclodextrin and cholestyramine significantly lowered plasma total cholesterol and triacylglycerol concentrations compared to control. Distinct changes in the bile acid profile of gallbladder bile were caused by resistant starch, β-cyclodextrin and cholestyramine. While cholestyramine significantly reduced chenodeoxycholate independently of its taurine–glycine conjugation, β-cyclodextrin and resistant starch decreased especially the percentage of taurochenodeoxycholate by ?75% and ?44%, respectively. As a result, the cholate:chenodeoxycholate ratio was significantly increased by 100% with β-cyclodextrin and by 550% with cholestyramine while resistant starch revealed no effect on this ratio. β-Cyclodextrin and resistant starch, not cholestyramine, significantly increased the glycine:taurine conjugation ratio demonstrating the predominance of glycine conjugated bile acids. Daily fecal excretion of bile acids was 4-times higher with 8% β-cyclodextrin and 19-times with 1% cholestyramine compared to control. β-Cyclodextrin and cholestyramine also induced a 2-fold increase in fecal neutral sterol excretion, demonstrating the sterol binding capacity of these two compounds. Resistant starch had only a modest effect on fecal bile acid excretion (80% increase) and no effect on excretion of neutral sterols, suggesting a weak interaction with intestinal steroid absorption. These data demonstrate the lipid-lowering potential of β-cyclodextrin and resistant starch. An impaired reabsorption of circulating bile acids and intestinal cholesterol absorption leading to an increase in fecal bile acid and neutral sterol excretion is most likely the primary mechanism responsible for the lipid-lowering action of β-cyclodextrin. In contrast, other mechanisms involving the alterations in the biliary bile acid profile or repressed hepatic lipogenesis, e.g., VLDL production, appear to be involved in the hypolipidemic effect of resistant starch.     

Absorption,endogenous excretion,and balance of zinc in growing rats on diets with various sugars replacing starch

The effect of partially replacing starch for various sugars on the apparent and true absorption, endogenous excretion, and balance of zinc was investigated in a study with growing rats. Six groups of five or six animals with an initial live weight of 39.4 +/- 2.7 g were fed diets that had the same Zn content (22 mg/kg), but differed in the sugar content: 1. Starch only (56%); 2. Glucose (15%); 3. Fructose (15%); 4. Sucrose (30%); 5. Galactose (15%); and 6. Lactose (30%). At the start of a 15-d fecal and urinary collection period, each animal was given an intramuscular injection of 380 kBq 65Zn for estimating endogenous Zn excretion by isotope dilution. The ratio of the specific activity of fecal Zn (after 12 d) to that of urinary Zn (after 9 d) was applied to reflect the ratio of endogenous to total fecal Zn collected from day 10 to 15. This ratio averaged 0.59, without significant differences among treatments. For this period, apparent and true absorption averaged 87.1 and 94.7% of Zn intake, respectively, and did not significantly differ among diets. Urinary excretion of 65Zn and of stable zinc by the galactose-fed rats was markedly higher than that by the other animals. Their Zn balance was, per unit weight gain, comparable with that of the other groups (30.7 vs 28.2 to 30.2 micrograms/g).     

Cholesterol absorption and turnover in hypercholesterolemic dogs

Cholesterol absorption was measured in chronically hypercholesterolemic dogs by four methods: the fecal recovery method of Borgstr?m (1969, J. Lipid Res. 10: 331-337), the dual isotope method of Zilversmit and Hughes (1974, J. Lipid Res. 15: 465-473), the recovery of cholesterol in thoracic duct lymph collected continuously for 16 hr after a meal, and the recovery of isotopic cholesterol from the liver and plasma 24 hr after the animals consumed an isotope-containing meal. The four methods showed excellent agreement and indicated that dogs fed a cholesterol-rich synthetic diet absorb 5.2 +/- 0.5 g (mean +/- SD) of cholesterol per day and that cholesterol absorption is reasonably constant from week to week in these animals. Separate estimates of cholesterol excretion indicated that these dogs excreted 4.7 +/- 0.5 g of cholesterol per day, and thus were at or near the steady-state with regard to cholesterol input-output. These data, taken together with a previous report (1981, J. Lipid Res. 22: 598-609), indicate that the canine liver can clear up to 300 mg of chylomicron cholesterol/hr, and support the concept that chylomicron remnants do not contribute significantly to the hypercholesterolemia in these animals.     

Effect of Soymilk Fermented with Lactobacillus plantarum P-8 on Lipid Metabolism and Fecal Microbiota in Experimental Hyperlipidemic Rats

We recently identified a novel probiotic strain Lactobacillus plantarum P-8 (L. plantarum P-8), which has been characterized in detail with regard to its probiotic potential. In the present study, soymilk fermented with L. plantarum P-8 was examined for its effects on diet-induced hyperlipidemia in Wistar rats. The experimental animals were divided into four groups: control group (C group), model group (M group), soymilk group (SM group) and fermented soymilk group (FSM group). The serum lipid levels, hepatic fat deposition, serum oxidative stress parameters, hepatic marker enzymes levels, organ indices, gut bacteria and fecal fat contents were analyzed. Fermented soymilk reduced the concentration of total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) in serum, with a significant elevation in high-density lipoprotein cholesterol (HDL) concentration. Our results also suggested the beneficial effects of fermented soymilk on the liver function, hyperlipidemia-induced oxidative stress and intestinal bacteria. Moreover, fermented soymilk could enhance the fecal excretion of TC, TG and bile acids. These findings demonstrated that soymilk fermented with L. plantarum P-8 was effective in improving the lipid metabolism in hyperlipidemic rats. The hypolipidemic effect of fermented soymilk was partly due to the inhibition of dietary fats absorption and regulation of fecal fats excretion mediated by gut bacteria.     

Copper absorption,endogenous excretion,and distribution in Sprague-Dawley and lean (Fa/Fa) Zucker rats

We previously observed a rapid reduction in plasma ceruloplasmin activity in lean Zucker (Fa/Fa) rats fed a marginal copper (Cu)-deficient diet compared to similarly fed obese Zucker (fa/fa) and lean Sprague-Dawley rats. In an effort to understand the mechanisms underlying this response, we utilized the isotope dilution method to investigate the absorption and excretion of Cu in lean Zucker rats fed control and marginal Cu diets. Sprague-Dawley (SD) and homozygous lean Zucker rats were fed either a Cu-adequate (Cont; 7.5 μg Cu/g diet) or a low Cu (Low; 1.1 μg Cu/g diet) casein-based diet for 23 d. Two weeks following initiation of the dietary treatment, each rat was injected intramuscularly (im) with 11.2 μCi of⁶⁷Cu. Urine and feces were collected daily. On the 9th d following isotope injection, rats were killed and tissues collected. Significant dietary effects were observed in the relative absorption and endogenous fecal excretion of⁶⁷Cu. The tissue distributions of nonisotopic Cu and⁶⁷Cu activity were also different between dietary treatments. Tissues from rats fed the low-Cu diet typically had high concentrations of⁶⁷Cu and low concentrations of nonisotopic Cu compared to controls. An increase in relative⁶⁷Cu absorption was evident for rats fed the low-Cu diet (57.2 and 39.3%, for SD Low, Zucker Low, respectively, and 17.9, and 28.5% SD Cont and Zucker Cont, respectively). Rats fed the low-Cu diet also had reductions in endogenous fecal excretion of⁶⁷Cu compared to their respective controls. Although strain effects were not evident for either percent Cu absorption or endogenous fecal Cu excretion, the relative adaptive changes appeared more marked for the Sprague-Dawley rats compared to the lean Zucker rats.     

Fat absorption in cystic fibrosis mice is impeded by defective lipolysis and post-lipolytic events

Cystic fibrosis (CF) is frequently associated with progressive loss of exocrine pancreas function, leading to incomplete digestion and absorption of dietary fat. Supplementing patients with pancreatic lipase reduces fat excretion, but it does not completely correct fat malabsorption, indicating that additional pathological processes affect lipolysis and/or uptake of lipolytic products. To delineate the role of such (post) lipolytic processes in CF-related fat malabsorption, we assessed fat absorption, lipolysis, and fatty acid uptake in two murine CF models by measuring fecal fat excretion and uptake of oleate- and triolein-derived lipid. Pancreatic and biliary function was investigated by determining lipase secretion and biliary bile salt (BS) secretion, respectively. A marked increase in fecal fat excretion was observed in cftr null mice but not in homozygous DeltaF508 mice. Fecal BS loss was enhanced in both CF models, but biliary BS secretion rates were similar. Uptake of free fatty acid was delayed in both CF models, but only in null mice was a specific reduction in lipolytic activity apparent, characterized by strongly reduced triglyceride absorption. Impaired lipolysis was not due to reduced pancreatic lipase secretion. Suppression of gastric acid secretion partially restored lipolytic activity and lipid uptake, indicating that incomplete neutralization of gastric acid impedes fat absorption. We conclude that fat malabsorption in cftr null mice is caused by impairment of lipolysis, which may result from aberrant duodenal pH regulation.     

Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal

The absorption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil triacylglycerols and fish oil ethyl esters consumed in a high-fat meal (44 g total fat) by male volunteers was measured and compared to values previously reported for consumption in a low-fat meal (8 g total fat). Absorption of EPA, but not of DHA, from fish oil triacylglycerols was significantly improved from 69% to 90% by co-ingestion with the high-fat meal. Absorption of both EPA and DHA from fish oil ethyl esters was increased three-fold, to about 60%, by co-ingestion with the high-fat meal, indicating that absorption of fatty acid ethyl esters is highly dependent on the amount of co-ingested fat.     

Antiobesity effect of recombinant human caseinomacropeptide in Sprague-Dawley rat

Caseinomacropeptide (CMP) is a glycopeptide of 64 amino acid residues derived from theC-terminal of mammalian milkk-casein. Recently, human CMP (hCMP) was produced from the recombinant yeastSaccharomyces cerevisiae. In this study, the antiobesity activity of the recombinant hCMP (rhCMP) was investigatedin vivo using Sprague-Dawley rats. The rhCMP did not affect the rats fed with a normal fat diet (fat content, 5.0%), but decreased the body weight gain of the rats fed with a high fat diet (fat content, 20%) by up to 19%. Autopsies revealed that the weights of the liver, kidney and adipose tissues decreased when the rats were given the rhCMP, which also reduced the lipid concentrations in the plasma and liver, but enhanced the fecal excretion of lipids. These results suggest that rhCMP prevent the accumulation of lipid by stimulating its fecal excretion, so could be used as a food supplement to alleviate the obesity problem caused by a high fat diet.     

Effects of diet on catabolism and excretion of (26-14C)cholesterol in rats.

The catabolism and excretion of [26-14C]cholesterol was studied in rats on semisynthetic and commercial diets low in fat or containing 15% butter or corn oil. Rats on the low fat commercial diet oxidized the labeled cholesterol to 14CO2 at more than twice the rate of those on the semisynthetic diet. Fecal excretion of labeled lipid was also somewhat higher with the commercial diet. The added fats had little effect on rate of oxidation of cholesterol but dietary corn oil stimulated fecal excretion of labeled lipid. The rate of loss of labeled cholesterol through oxidation and excretion showed a positive correlation with cholesterol biosynthesis, as measured previously by acetate incorporation into cholesterol in rats on the same kinds of diet. A simple method for efficient trapping and counting of 14CO2 was developed, which facilitated measurement of low levels of 14CO2 in expired air. Estimation of bile acid production from the rate of oxidation of [26-14C]cholesterol to expired 14CO2 and the specific activity of plasma cholesterol gave somewhat higher values than those obtained by other methods. Possible reasons for this difference are discussed.     

An improved multi-element measurement of mineral absorption in the piglet utilizing the fecal monitoring technique

The fecal monitoring technique for measuring the absorption of Zn, Mn, Se, and Fe was studied in eight male piglets (mean±SEM birthweight (bw)=1695±50 g) using high resolution gamma spectrometry. Four d old piglets were fed a complete liquid milk diet for five d prior to the orogastric administration of an isotope dose (⁷⁵Se,⁵⁴Mn,⁵⁹Fe, and⁶⁵Zn) equilibrated with the liquid milk diet.⁵¹CrCl₃ was used as a fecal marker but was found to be partially absorbed. Stool samples were collected daily for 15 d, counted, and then the daily fecal excretion was calculated. Results indicate that endogenous excretion for each of the isotopes was not constant but decreased exponentially with time. The pattern of endogenous excretion varied between elements. An improved method for calculating the endogenous excretion was therefore developed. This method is based on the pattern of endogenous excretion in three-four d old male piglets (mean±SEM bw=2060±75 g) injected intravenously with the same isotopes and on the level of endogenous excretion in orally fed animals in the postabsorptive phase of excretion. These findings have important implications for the estimation of endogenous excretion in future fecal monitoring absorption studies in order to minimize underestimation of true absorption.     

Effects of chitosan intake on fecal excretion of bisphenol A and di(2-ethyl)phthalate in rats

We evaluated the effects of chitosan intake on fecal excretion of bisphenol A (BPA) and di(2-ethyl)phthalate (DEHP) in rats. The rats were fed a chitosan diet (CHI group) or a control diet (control group) for 10 d and orally administrated BPA or DEHP (100, 500 mg/kg body weight, respectively) on day 4. Feces were collected and the rates of fecal excretion of BPA and DEHP were calculated. Fecal excretion rates of BPA and DEHP were significantly higher in the CHI group than in the control group. A significant negative correlation was observed between the fecal excretion rates of BPA and DEHP and apparent fat digestibility. Furthermore, the CHI group showed not only increased but also accelerated BPA excretion into the feces. In conclusion, we found that that chitosan intake significantly increased the fecal excretion of BPA, DEHP, and fat, suggesting that it might be useful for reducing adverse effects caused by lipophilic xenobiotics.     

Reduction in fecal excretion of Giardia cysts: effect of cholestasis and diet

Bile is a major growth factor for the proliferation of Giardia spp. trophozoites in the small intestine and, at high concentrations, stimulates encystment of trophozoites. This report demonstrates that surgical cholestasis to interrupt the flow of bile from liver to intestine or the use of bile-binding resins in the diet can both dramatically decrease the fecal excretion of Giardia muris cysts. Cholestasis produced a 3 log reduction in excretion of G. muris cysts within 24 hr of surgery and a 4 log reduction after 3 days. Sham controls showed no difference in cyst excretion from presurgical control values. Two isocaloric diets were studied: a control diet (N) of Purina mouse chow containing 5% celufil and an experimental diet (CR) containing 5% cholestyramine, a resin that binds bile. Compared with the N diet, the CR diet was associated with reductions in cyst excretion of 3 logs within 1 day. Despite lowered excretion of G. muris cysts in mice fed the cholestyramine diet, the trophozoite recovery from the duodenum was similar with both diets. Cyclic feeding of the CR diet and the N diet at 3-day intervals produced significant oscillations (changes of 3-4 logs) in fecal cyst shedding. The significant reductions in fecal excretion of cysts observed with agents that bind bile suggests that diets capable of binding bile might be a therapeutic means to minimize the fecal excretion of cysts and thereby may help to reduce the risk of spreading giardiasis through fecal-oral contamination.