The absorption of stearic acid from triacylglycerols: an inquiry and analysis

Although stearic acid is a saturated fatty acid, its influence on plasma cholesterol acid other health variables is neutral; possibly owing in part to poor absorption. Reduced absorption of stearic acid from particular triacylglycerols, cocoa butter and novel fats formulated with short- and long-chain acid triacylglycerol molecules (Salatrims) has been attributed to high intakes. However, the circumstances and causes of poor stearic acid digestion from triacylglycerols are unclear; published data were therefore collected and analysed, with emphasis on human studies. Of twenty-eight studies conducted in adults, most are in men (>90%). The assertion that reduced absorption is due to a high intake of stearoyl groups is not supported: dietary intakes of stearoyl of 0·05–0·65 g stearic acid equivalent/kg body weight (cf typical intake of 0·2 g stearic acid equivalent/kg body weight in the Western diet) indicate that the ‘true’ digestibility of stearoyl is 0·98 (SE 0·01) g/g, with apparent digestibility less than this value at low intakes owing to endogenous stearic acid excretion and to inter-publication variation of unidentified cause. The neutral health impact of stearic acid must be due to factors other than availability. Exceptions include cocoa butter, Salatrims and tristearin, for which digestibility is an additional factor. The efficiency with which human subjects digest stearoyl from cocoa butter still remains uncertain, while the digestion of total long-chain fat from this source is 0·89–0·95 g/g, high in comparison with 0·33 g/g for Salatrim 23CA and 0·15 g/g for tristearin in their prepared states. Salatrims contain the highest proportion of long-chain fatty acids that are stearic acid-rich other than tristearin, which is the main component of fully-hydrogenated soyabean and rapeseed oil. Analysis shows that apparent digestibility of stearic acid is associated with stearoyl density within the triacylglycerol molecule and that, in Salatrims, the occurrence of short-chain fatty acids in place of long-chain fatty acids increases this density. Soap formation appears not to be a major factor in the reduced digestion of stearic acid from tristearin under regular dietary circumstances, but both microcrystallinity and reduced digestibility of tri-, di- and monostearoylglycerols appears to be important. Solubilisation of high-melting-point tristearin in low-melting-point oils improves the digestibility of its stearic acid, particularly when emulsified or liquidized at above melting point. However, without such artificial aids, the digestive tracts of the rat, dog and man have a low capacity for emulsifying and digesting stearic acid from tristearin. Reduced digestibility of stearic acid from Salatrim 23CA also appears to be attributable to reduced digestibility of di- and monostearoylglycerols and is particularly due to remnants with the 1- or 3-stearoylglycerol intact after initial hydrolytic cleavage. Short-chain organic acid in Salatrim 23CA, which is readily hydrolysed, leaves such remnants. Unlike tristearin, Salatrim 23CA melts at body temperature and mixing it with low-melting-point oils is not expected to cause further disruption of microcrystalline structures to aid digestibility of its stearoyl groups. The low digestibility of stearoyl in Salatrim 23CA, together with the occurrence of short-chain organic acids in this product, account for its relatively low nutritional energy value (about 20 kJ (5 kcal)/g) compared with traditional fats (37 kJ (9 kcal)/g) and low fat value (<20:37 kJ/kJ; <5:9 kcal/kcal) relative to traditional fats. In part these differences are because of minor effects of Salatrim 23CA on the excretion of other fat and protein, due to the bulking properties of this poorly-digestible fat.

Related papers:

title: Stearic acid, clotting, and thrombosis.
abstract: Stearic acid causes hypercoagulability of the blood by activation of factor XII and by aggregation of blood platelets. Injection of unbound stearic acid (sodium salt) into the systemic circulation of dogs was followed by massive generalized thrombosis and sudden death. Similar infusions into birds, which are deficient in factor XII, did not cause hypercoagulability or thrombosis. The effects of the long-chain saturated fatty acids could be prevented by using albumin to bind the stearic acid at a molar ratio of free fatty acid (FFA) to albumin of < 2. The major issue is whether eating foods rich in stearic acid can cause a thrombogenic effect. We have no experimental evidence to support this concept. If a thrombogenic effect of long-chain saturated fatty acids exists in humans, it is most likely to occur as an aberration of fatty acid transport in which the FFA-albumin molar ratio exceeds 2 either as a result of very high plasma FFA concentrations from lipid mobilization or a low concentration of albumin in the blood as found in disease states such as the nephrotic syndrome.

title: Stearic acid metabolism and atherogenesis: history.
abstract: Studies conducted in dogs, rats, and hamsters show that stearic acid or stearic acid-rich glycerides are absorbed less efficiently than are lauric, myristic, and palmitic acids or their triglycerides. This observation may explain in part why stearic acid is less cholesterolemic than saturated fatty acids of shorter chain length. In rabbits, cocoa butter or other fats rich in stearic acid are less atherogenic than other saturated fatty acids. This finding is true for both cholesterol-containing and cholesterol-free diets.

title: Effect of long-chain fatty acids on low-density-lipoprotein-cholesterol metabolism.
abstract: The concentration of cholesterol in the low-density-lipoprotein (LDL) fraction of plasma is one of the major risk factors for coronary heart disease. Steady-state concentrations of LDL cholesterol in the plasma are determined primarily by the production rate and the rate of removal of LDL cholesterol from the circulation by receptor-dependent transport. The magnitude of these two processes is affected by the type of fatty acid in the diet. Saturated fatty acids with 14 and 16 carbon atoms suppress receptor-dependent LDL-cholesterol transport into the liver, increase the LDL-cholesterol production rate, and raise the plasma LDL-cholesterol concentration. The 9-cis 18:1 fatty acid restores receptor activity, lowers the production rate, and decreases the plasma LDL-cholesterol concentration. In contrast with these fatty acids, the 18:0 and 9-trans 18:1 fatty acids are biologically inactive and so do not change the circulating LDL-cholesterol concentration.

title: Review of triacylglycerol digestion, absorption and metabolism with respect to Salatrim triacylglycerols
abstract: The SALATRIM family of structured triacylglycerols is composed of fats containing acetic, propionic, butyric, and stearic acids esterified to a glycerol backbone. These triacylglycerols contain at least one short-chain fatty acid and stearic acid. The scientific literature shows that people are regularly exposed to SALATRIM components and SALATRIM-like structures from both dietary and metabolic sources. The digestion, absorption, and metabolism of SALATRIM fats are similar to those of other fats and proceed by well-kown mechanisms and metabolic pathways. These aspects of fats are reviewed with respect to SALATRIM structured triacylglycerols

title: Energy Value of a Fat High in Stearic Acid
abstract: A fat containing 92.1% stearic acid (tristearin) was evaluated for energy value using shortening (9 kcal/g) and mineral oil (0 kcal/g) as controls and young rats as the test model. Energy value was calculated based on efficiency of conversion of estimated gross energy intake to carcass energy over a 3-wk period. Rats fed the shortening-based diet deposited more than double the fat and significantly more protein in the carcass than rats fed the tristearin-based diet. Rats fed the tristearin-based diet deposited significantly more fat and protein than rats fed the mineral oil-based diet. Based on these observations, the estimated energy value of tristearin was calculated as 3 kcal/g.

title: Digestibility of cocoa butter and corn oil in human subjects: a preliminary study.
abstract: The comparative absorption of cocoa butter (25.5% C16:0, 34.4% C18:0, 34.4% C18:1, 3.4% C18:2) and corn oil (11.4% C16:0, 2.0% C18:0, 26.4% C18:1, 60.0% C18:2) was assessed in six healthy male subjects. During 3-d experimental diet periods, free-living subjects consumed either cocoa butter or corn oil as virtually the sole source of dietary fat, provided at 40% of the total energy intake in the form of specially formulated cookies. Fat absorption was determined by quantifying total fecal lipid excretion over the 3-d period. Total fecal lipid and fecal fatty acids were determined. The percentage of fat excreted was significantly higher (p less than or equal to 0.001) when subjects consumed the cocoa butter (10.8 +/- 3.2%) vs the corn oil (3.5 +/- 1.0%) diet. These results indicate that the digestibility of cocoa butter is significantly less than corn oil and may explain, in part, previous reports of a neutral effect of dietary cocoa butter on plasma cholesterol concentrations.

title: Effect of dietary stearic acid on plasma cholesterol and lipoprotein levels.
abstract: We studied the metabolic effects of stearic acid (18:0) on plasma lipoprotein levels in 11 subjects during three dietary periods of three weeks each. The three liquid-formula diets, which were used in random order, were high in palmitic acid (16:0), stearic acid, and oleic acid (18:1), respectively. Caloric intakes were the same during the three periods. As compared with the values observed when the subjects were on the high-palmitic-acid diet, plasma total cholesterol decreased by an average of 14 percent during consumption of the high-stearic-acid diet (P less than 0.005) and by 10 percent during consumption of the high-oleic-acid diet (P less than 0.02). Low-density lipoprotein cholesterol levels fell by 21 percent in subjects on the high-stearic-acid diet (P less than 0.005) and by 15 percent in subjects on the high-oleic-acid diet (P less than 0.005). No significant differences were observed in the plasma levels of triglycerides or high-density lipoprotein cholesterol among the three diets. Measurements of the intestinal absorption of palmitic, stearic, and oleic acids revealed essentially complete absorption of each during the three dietary periods. The oleic acid content of plasma triglycerides and cholesteryl esters increased significantly during the high-stearic-acid period, suggesting that stearic acid is rapidly converted to oleic acid. We conclude that stearic acid appears to be as effective as oleic acid in lowering plasma cholesterol levels when either replaces palmitic acid in the diet.

title: Metabolism of dietary stearic acid relative to other fatty acids in human subjects.
abstract: This paper reviews results obtained by stable-isotope-tracer methods for stearic acid (18:0) and palmitic acid (16:0) metabolism and the influence of dietary linoleic acid on the metabolism of these saturated fatty acids in humans subjects. The results, based on stable-isotope-tracer data, show that absorption of 18:0 is not significantly different from 16:0; percent desaturation of 18:0 to 9-cis 18:1 (9.2%) is 2.4 times higher than for 16:0 to 9-cis 16:1 (3.9%) and 9-desaturation is not greatly influenced by the amount of linoleic acid in typical US diets. Additionally, compared with 16:0, 18:0 incorporation is 30-40% lower for plasma triglyceride and cholesterol ester and approximately 40% higher for phosphatidylcholine; beta-oxidation of saturated fatty acids was slower than for unsaturated fatty acids and increasing the intake of dietary linoleic acid decreased beta-oxidation of saturated fatty acids. These results indicate that metabolic differences between 18:0 and 16:0 only partially explain the difference in the cholesterolemic effect reported for these saturated fatty acids.

title: Desaturation and interconversion of dietary stearic and palmitic acids in human plasma and lipoproteins.
abstract: Dietary saturated fatty acids are implicated as a risk factor for atherosclerosis. The conversion of the major dietary saturated fatty acids stearic acid (18:0) and palmitic acid (16:0) to monounsaturated fatty acids in whole plasma and lipoprotein fractions is reported for seven healthy adult humans over 6 d using [U-13C]stearic acid (18:0*) and [U-13C]palmitic acid (16:0*) and high-precision mass spectrometry. A tracer dose (28-32 mg) of 18:0* or 16:0* was loaded into an emulsion and orally administered before breakfast. Serial blood samples were collected on day 1 and fasting blood was drawn daily until day 7. Overall conversion of 18:0 to 18:1 was approximately 14%, whereas that of 18:0 to 16:0 was approximately 2% in plasma up to 144 h. Conversion of 16:0 to 16:1 was < 2%, whereas conversion of 16:0 to 18:0 was approximately 6%. No other fatty acid metabolites were detected for 18:0* or 16:0*. The conversion products were observed mainly in chylomicrons and very-low-density lipoproteins, indicating that the intestine and liver have comparable roles in desaturating 18:0 and 16:0. Overall, these data indicate that dietary 18:0 desaturation is severalfold greater than 16:0 desaturation. The low level (14%) of 18:0 desaturation in omnivorous adults may have little influence on blood lipid profiles relevant to atherosclerosis risk.

title: Short-term dietary calcium fortification increases fecal saturated fat content and reduces serum lipids in men.
abstract: The effect of dietary calcium on fecal fatty acid excretion and serum lipids was tested in a randomized, single-blind metabolic study in 13 healthy men with moderate hypercholesterolemia. A low calcium base diet containing 34% of energy from fat, 13% from saturated fatty acids, 240 mg cholesterol/d and 410 mg Ca/d was compared with a fortified version in which calcium citrate malate was added to orange juice, (550 mg) muffins (750 mg), and two tablets (500 mg) for a total calcium intake of 2200 mg/d. Fecal collections (72 h, d 8, 9, 10) and blood from fasting subjects for lipids and lipoproteins (d 9, 10, 11) were obtained. The percentage of dietary saturated fat excreted per day increased from 6 to 13% with calcium fortification. There was no change in fecal bile acid excretion. The high Ca diet significantly reduced total cholesterol 6% (5.99 to 5.66 mmol/L), LDL cholesterol 11% (4.13 to 3.67 mmol/L), and apolipoprotein B concentrations 7% when compared with the low Ca diet (P < 0.05). There was no change in HDL cholesterol or apolipoprotein A1 concentrations. Urinary calcium excretion increased from 146 to 230 mg/d when the high Ca diet was consumed. Calcium fortification was effective in lowering total and LDL cholesterol concentrations and may be an effective adjunct to cholesterol-lowering diet therapy.

title: Intestinal absorption of stearic acid after consumption of high fat meals in humans.
abstract: The intestinal absorption of stearic acid (18:0), relative to other fatty acids, was evaluated in a group of 10 normal volunteers. Subjects were fed two types of high fat meals; one contained a relatively high content of stearic acid and the other a relatively low content. Plasma chylomicrons were isolated at 2, 4, 6 and 8 h after ingestion of the meals. Fatty acid patterns of chylomicron lipids were determined, and relative intestinal absorption rates of each fatty acid were estimated by comparing the fatty acid composition of chylomicron lipids with that of the fat in the meals. Overall, for both meals the fatty acid pattern of chylomicron lipids was very similar to that of ingested fat. Percentages of palmitic acid (16:0) and stearic acid, relative to other fatty acids, were only slightly lower in chylomicron lipids than in the meal fat. These data suggest that intestinal absorbability of stearic acid is similar to that of palmitic acid, and both saturated fatty acids appear to be absorbed almost as well as oleic acid (16:1).

title: Effect of positional distribution on the absorption of the fatty acids of human milk and infant formulas.
abstract: A fat absorption study was conducted in rats to determine if the unusually high proportion of palmitic acid in the 2-position of triglycA©ridescould be related to the superior absorption of human milk fat. Digestion yields free fatty acids and 2-monoglycerides. The monoglycerides of the saturated fatty acids are more readily absorbed than the free acids. Tests run on a number of fats commonly fed to infants, showed that the high absorption of human milk fat, 94.6 (%), was equaled by a fat blend of a similar fatty acid composition with a high content of 2-palmitoyltriglyceride, 96.3, in contrast to one with low content, 89.9. Absorption of butterfat was 89.5, lard 92.4 and oleo 79.9. Individual fatty acid absorption was influenced by total fat absorption. A linear relationship between absorption and the proportion in the 2 position was demonstrated for palmitic, and to a lesser extent, for myristic and oleic, but net for stearic acid. Equations predicting fat absorption required emphasis of the product of stearic acid and palmitic acid esterified in the primary positions.

title: Studies in man of partially absorbed dietary fats.
abstract: A saturated long-chain triglyceride (SLCT) has been prepared by esterification with glycerol of the saturated long-chain fatty acid fraction of coconut oil, isolated by molecular distillation of the hydrolyzed oil. The resultant SLCT is comprised principally of stearate (89%) and palmitate (11%). The intestinal absorption of SLCT in man was compared with that of corn oil or a 1:1 mixture of SLCT and corn oil. Each fat or the mixture was incorporated in isocaloric amounts into a complete formula diet deriving 30% of its caloric content from fat, 55% from carbohydrate (dextrose), and 15% from protein (casein). The formula diets were administered in sequential feeding periods as the sole source of food. The results indicate that SLCT was poorly absorbed (31 to 39%) compared with virtually complete absorption of corn oil (98%). Fat absorption was improved when the dietary fat was an equal mixture of SLCT and corn oil. The poor absorption of SLCT was ascribed to its high melting point and related to impaired emulsification and micellar solubilization in the small intestine.

title: Effects of fats and fatty acids on blood lipids in humans: an overview.
abstract: Differences in dietary fatty acid structure induce marked differences in lipid and lipoprotein concentrations in plasma from fasting subjects. Under metabolic-ward conditions, replacement of carbohydrates by lauric, myristic, and palmitic acids raise both low-density-lipoprotein (LDL) and high-density-lipoprotein (HDL) cholesterol whereas stearic acid has little effect. Oleic and linoleic acids raise HDL and slightly lower LDL; all fatty acids lower fasting triglycerides when substituted for carbohydrates. Trans monounsaturates lower HDL and raise LDL and lipoprotein(a). The fatty acids in unhydrogenated fish oil potently lower triglycerides, with variable effects on LDL. Of the commercial fats, palm-kernel and coconut oil are the most hypercholesterolemic, followed by butter and palm oil. Replacement of hard fats rich in lauric, myristic, or palmitic acids or trans fatty acids by unsaturated oils will lower LDL, but replacement by carbohydrates will in addition decrease HDL and increase triglycerides. In free-living subjects, high-oil diets could lead to obesity, undoing the favorable effects on HDL and triglycerides.

title: Effects of fats high in stearic acid on lipid and lipoprotein concentrations in men.
abstract: The effects of beef tallow and cocoa butter, two fats with a high stearic acid content (C18:0), on serum lipid and lipoprotein concentrations were compared with the effects of butter fat and olive oil in 10 middle-aged men. Liquid-formula diets containing 40% of the calories from the test fat were fed in random order for 3 wk each, with lipoprotein concentrations measured on the last five days. Butter fat raised low-density lipoprotein (LDL) concentrations the most (4.23 +/- .15 mmol/L; mean +/- SE). Beef-tallow feeding resulted in significantly lower concentrations of LDL (4.03 +/- 0.18 mmol/L); cocoa butter resulted in even lower concentrations (3.82 +/- .15 mmol/L). The lowest concentration of LDL was observed with olive oil (3.62 +/- 0.18 mmol/L). Fecal excretion of fatty acids, after adjustment for fecal flow, indicated that oleic acid (C18:1) was 99% absorbed, palmitic acid (C16:0) was 96-97% absorbed, and stearic acid was 90-94% absorbed for the three fats containing significant amounts of stearic acid.

title: Effects of high- and low-fat diets on the bioavailability of selected fatty acids, including linoleic acid, in adult men
abstract: Thirty men, 34 to 61 years old, were fed four diets as follows: diet I — 43% of calories from fat (%FC) with a polyunsaturated to saturated fatty acid (P/S) ratio of 0.3; diet II −25% FC, P/S 0.3; diet III — 43% FC, P/S 1.0; diet IV — 25% FC, P/S 1.0 to study the effects of level and type of fat and of fiber intake on the excretion of selected fatty acids, including linoleic acid (LOA). Each of the four diets was fed for two 6-week periods (after 7-day pre-study and 21-day stabilization periods), with a random switchover at the end of the first 6-week period. Diets, urine, and feces were analyzed during the last 7 days of each period. Of the saturated fatty acids, stearic acid had the lowest apparent digestibility in all diets. The digestibility of oleic acid was high and was similar for all diet groups despite differences in intakes. LOA exeretion was slightly higher (0.81 and 0.86 g/day) with diets III and IV, in which men ate 44 and 24 g of LOA/day, than with diets I and II (0.46 and 0.56 g/day) in which men had 20 and 12 g LOA/day, respectively. Those amounts of LOA excreted represented, however, only a small protion of that eaten. LOA was slightly less digestible in diets II and IV (95.5% and 96.5%), in which the men ate more fiber (11.4 g/day), than in diets I and III (97.7% and 98.2%) in which the men ate less fiber. LOA digestibility was reduced by decreasing fat content of the diet in both high and low P/S diets. Whether those small differences are of physiological importance remains to be seen. Otherwise, this finding emphasizes the need for more research to investigate whether greater absolute amounts of LOA are required when low-fat diets are fed.

title: Clinical assessment of Salatrim, a reduced-calorie triacylglycerol
abstract: SALATRIM is a reduced-calorie fat composed of triacylglycerols containing mixtures of short-chain aliphatic acids and long-chain saturated fatty acids. Studies have been conducted in a clinical environment to confirm the predictable metabolism of ingested SALATRIM in humans. An acute tolerance test (study I) was conducted initially with a single ingestion (45 or 60 g) in a double-blind-crossover design with 10 subjects. The levels selected were chosen to significantly exceed expected exposure levels from consumption of foods containing SALATRIM

title: Composition of representative SALATRIM fat preparations
abstract: SALATRIM is a family of structured triacylglycerols containing at least one short-chain fatty acid and one saturated long-chain fatty acid (predominantly stearate) on each glycerol. The mixtures are prepared by the interesterification of hydrogenated vegetable oils such as soy or canola, with triacetin and/or tripropionin and/or tributyrin. Qualitative and quantitative analyses were conducted on five SALATRIM preparations. Qualitatively, several triacylglycerols are common to various members of the SALATRIM family. Approximately 90% of the total mass of the SALATRIM preparations is accounted for in positively identified triacylglycerol. Free fatty acids, phytosterols, and tocopherols account for an additional 0.4-0.8% of the mass of the SALATRIM

title: Caloric availability of SALATRIM in rats and humans
abstract: SALATRIM is a reduced-calorie fat substitute composed of structured triacylglycerols. These structured triacylglycerolB are composed of long-chain fatty acids (predominantly stearic) and short-chain aliphatic acids (acetic, propionic, and/or butyric). It has been demonstrated in rat studies and in a clinical study that SALATRIM with various combinations of these aliphatic acid and fatty acid side chains delivers fewer calories per gram than conventional triacylglycerols such as corn oil. The reduced calories are accounted for by the lower caloric value of the short-chain aliphatic acids and limited absorption of the stearic acid which is freed by enzymatic hydrolyse in the gastrointestinal tract. In caloric availability studies with rats SALATRIM was found to deliver between 4.5 and 6.0 kcal/g

title: Comparative study of endogenous fecal fatty acids in germ-free and conventional rats.
abstract: The effects of gastrointestinal flora on the quantitative and qualitative aspects of "endogenous" fecal fatty acid excretion were studied in the rat using germ-free (GF) and conventional (CVL) animals, lipid-free diet and open-tubular gas-liquid chromatography. Gastrointestinal flora slightly increased endogenous excretion of fatty acids. Analysis of fatty acids from different fecal lipid fractions showed that the presence of a microflora in the gastrointestinal tract extensively modified the qualitative aspects of endogenous fecal fatty acid spectra. In total endogenous fecal lipids, concentrations of mono and polyunsaturated fatty acids (from C16 to C22) were 3.5 times higher in GF rats, while concentrations of even-numbered and saturated fatty acids were 1.5 times higher in CVL rats. Odd-numbered fatty acids (from C11:10 to C2:0) represented 6.5% of total endogenous fecal fatty acids in CVL rats vensus 1.5% in GF rats. Branched-chain fatty acid (even-and-odd-numbered, iso and anteiso) concentrations were 12.9% in CVL rats versus 2.0% in GF rats. Results clearly showed that the gastrointestinal flora was the main source of odd-numbered fatty acids and branched-chain fatty acids in endogenous fecal lipids. However, a secondary source may also exist since these fatty acids represented 3.5% of the total endogenous fatty acids in GF rats.

title: The influence of diet on the quality of faecal fat in patients with and without steatorrhoea
abstract: By the use of gas-liquid chromatography it has been shown that the quality of the faecal fat in individuals without steatorrhoea is little affected by changes in the quality of the dietary fat. Large amounts of non-dietary fatty acids have been identified in the faeces both of patients with and without steatorrhoea. These have been identified as a number of isomers of oleic acid and hydroxystearic acids, particularly 10-hydroxystearic acid.

title: Absorption of individual fatty acids from long chain or medium chain triglycerides in very small infants.
abstract: Using stool samples previously obtained for a nutritional balance study of very small infants, the intake, excretion, and percent absorption (%A) of individual fatty acids were quantitated by gas-liquid chromatography in two groups of patients; one receiving a formula providing fat as long chain triglycerides (LCT), the other providing 40% fat as medium chain triglyceride (MCT). The total fat intake for each group was 7.22 g/kg/day (MCT group), 6.02 g/kg/day (LCT group) and the absorption was 6.79 g/kg/day (MCT group) and 5.41 g/kg/day (LCT group). The %A of individual acids was comparable in both groups being greater than 99% for MCT and being lowest (62%) for C18:0 FA. As a consequence, infants in the MCT-fed group had a better total %A of fat, 95.2 vs 89.9% and absorbed more fat than the LCT group.

title: Caprenin 3. Absorption and Caloric Value in Adult Humans
abstract: Caprenin is a triglyceride that contains primarily caprylic (C8:0), capric (C10:0), and behenic (C22:0) acids and modest amounts of arachidic (C20:0) and lignoceric (C24:0) acids. Using the fat-balance technique, the absorption of C20:0, C22:0, and C24:0 was measured in 20 healthy adult men and women aged 20–60 years consuming a chocolate-flavored caprenin confection. The absorption values for these very long-chain fatty acids (VLCFAs) were determined based on measurements of their dietary intake and fecal excretion during a 5-day treatment period and a 7-day posttreatment washout period after correcting for baseline excretion of VLCFAs. Each subject consumed 4.7 g C20:0, 52.8 g C22:0, and 0.84 g C24:0 from the test confection during the treatment. Absorption averaged 41.6% ± 3.6% (SEM) for C20:0, 28.8% ± 4.4% for C22:0, and 14.8% ± 3.9% for C24:0. Using a modification of the Atwater method, the physiological fuel value (caloric value) of caprenin was then calculated. This modified method takes into account the partial absorption of VLCFAs and the heat loss due to the metabolism of the medium-chain fatty acids C8:0 and C10:0. The results of this study demonstrate that the caloric value of caprenin is 5 kcal/g compared to the value of 9 kcal/g for other dietary triglycerides.

title: The absorbability by rats of various triglycerides of stearic and oleic acid and the effect of dietary calcium and magnesium.
abstract: Rats were fed diets in which the triglycerides contained oleate and stearate as the sole fatty acids. These fatty acids were esterified to specific positions on the glycerol molecule. The triglycerides were 1-stearoyl diolein (SOO), 2-stearoyl diolein (OSO), 2-oleoyl distearin (SOS), 1-oleoyl distearin (OSS), and triolein (OOO). The absorbability of the fatty acid component was measured by the fat balance technique. Two diets, one sufficient and the other deficient in calcium and magnesium, were used. The oleic acid of all of the triglycerides was absorbed almost completely. The following values for the absorbability of the stearate component in the presence and in the absence of the divalent cations were obtained: OSO 98 and 99; SOO 55 OAND 96; SOS 37 and 70; OSS 59 and 60. These patterns of absorbability are discussed in relation to the pathway of triglyceride digestion. If the stearic acid is esterified at the 2-position of the triglyceride, the resulting 2-monostearin is well absorbed. If it is esterified at the 1- or 3-position, it is released as free stearic acid, and in the presence of calcium and magnesium it is poorly absorbed.

title: In vivo metabolism of SALATRIM fats in the rat
abstract: SALATRIM fats are structured triacylglycerols that contain at least one short-chain fatty acid (SCFA) and a saturated long-chain fatty acid, usually stearic. SALATRIM (14)C-labeled in either acetate, propionate, stearate, or glycerol and triolein (14)C-labeled in either oleate or glycerol were administered to male rats by gavage. Rats were fed basal diet or basal diet containing 10 % (w/w) SALATRIM 23CA lot A014 for 14 days before administration of radio labeled fats. Acetate and propionate from SALATRIM are rapidly converted to carbon dioxide, which indicates the triacylglycerols are cleaved by lipases in the stomach and upper small intestine. The stearate of SALATRIM is hydrolyzed more slowly than the SCFA but almost identically to the oleate of triolein. Long-chain fatty acids of SALATRIM and triolein are predominantly metabolized to CO2. Stearic acid is more poorly absorbed than oleic acid. Of the absorbed stearate in fat stores, 57.2% had been converted to oleate. The biodisposition of glycerol from SALATRIM or triolein is essentially identical. The study supports the hypothesis that SALATRIM biodisposition is predictable and similar to that of other fats. Feeding SALATRIM 23CA lot A014 for 14 days did not significantly alter SALATRIM or triolein biodisposition.

title: Positional distribution of stearic acid and oleic acid in a triacylglycerol and dietary calcium concentration determines the apparent absorption of these fatty acids in rats.
abstract: In this study the effect of the positional distribution of stearic acid (18:0) and oleic acid (18:1) in a triacylglycerol on absorption of fat, energy and nutrients was investigated in young rats. In addition the effect of dietary calcium on these variables was studied. Forty rats were fed purified diets containing either a fat blend high in 2-oleoyl-distearate or a fat blend high in 1-oleoyl-distearate. Both diets were given at low (0.3 g/100 g) and high (1.0 g/100 g) dietary calcium concentrations. Total fat absorption, expressed as the percentage of fat intake, was significantly lower in rats fed 2-oleoyl-distearate compared with 1-oleoyl-distearate at both dietary calcium concentrations. When expressed as absolute figures, the lower fat absorption in rats fed 2-oleoyl-distearate compared with 1-oleoyl-distearate only reached statistical significance at the high dietary calcium concentration. The reduced absorption of total fat was mainly caused by the lower absorption of stearic acid. The percentage of, but not absolute, absorption of oleic acid and energy were lower in rats fed 2-oleoyl-distearate. Absolute and percentage of calcium absorption were lower in rats fed 2-oleoyl-distearate compared with 1-oleoyl-distearate. Absolute and percentage of magnesium absorption were not significantly affected by the positional distribution of stearic acid and oleic acid in the triacylglycerol, but were decreased at a high dietary calcium concentration. We concluded that the lowered stearic acid absorption from 2-oleoyl-distearate compared with 1-oleoyl-distearate might have been due to the greater formation of insoluble calcium and magnesium soaps in the intestine.

title: The effect of oral calcium on cholesterol metabolism.
abstract: The effects of calcium on cholesterol metabolism have been examined in 6 patients. The age of the subjects ranged from 61–73 years. Five of the patients were osteoporotic. The calcium was administered as organic salts (calcium glycerophosphate or calcium gluconogalactogluconate) and as dried skimmed milk. The results show that increased calcium in the organic form caused increased excretion of faecal bile acids and faecal total fat. There was no change in faecal neutral steroid output; increased faecal cholesterol was compensated by decreased coprostanol excretion. When the calcium was given in the form of skimmed milk, faecal bile acids and faecal fat remained elevated. Faecal excretion of cholesterol continued to rise and was accompanied by the return of faecal coprostanol output almost to the basal level, resulting in increased total neutral steroid excretion. The serum cholesterol and triglyceride levels showed little change from the basal levels during the calcium supplementation periods.

title: Energy values of unavailable carbohydrate and diets: an inquiry and analysis.
abstract: To determine digestible-energy values (DEVs) for unavailable carbohydrate (UC), an analysis was made of published data on 29 human diets with UC from several sources and intakes ranging from 4 to 93 g/d. A distinction was made between apparent DEVs, derived from UC intake and fecal loss, and partial DEVs, derived from energy intake and fecal loss. By use of a proposed calculation, partial DEVs ranged from -20 to +10 kJ/g (-4.8 to +2.4 kcal/g) in different diets; all values were below the corresponding apparent DEVs. Factors explaining this range, including analytical problems, are considered. Rather than finding discrepancies, both the partial DEVs and the energy available from the whole diet were found to be related to the apparent digestibility of UC (r = 0.88), the proportion of the diet estimated as UC (r = 0.73), and both combined (r = 0.98). Several food-energy evaluation systems are also assessed for accuracy and the implications of these observations for food-energy evaluation are discussed.

title: A comparison of absorption of glycerol tristearate and glycerol trioleate by rat small intestine.
abstract: Generally, fats rich in saturated fatty acids raise serum cholesterol, whereas fats rich in polyunsaturated fatty acids lower it. There appear to be exceptions; e.g., stearic acid (18:0)-rich fats have little or no effect on serum cholesterol concentrations. This apparent lack of cholesterolemic effect of stearic acid-rich fat could be because intestinal absorption of fat is poor or subsequent plasma and/or tissue metabolism of fat is different. To investigate mechanisms involved, we compared intestinal digestion, uptake, and lymphatic transport of glycerol tristearate (TS) and glycerol trioleate (TO, 18:1). Two groups of rats bearing intestinal lymph fistulas were used. TO rats were fed intraduodenally for 8 h at a constant rate a lipid emulsion of 25 mumols/h of TO (labeled with glycerol tri[9,10 (n)-3H]oleate), 7.8 mumols of egg phosphatidylcholine, and 57 mumols of sodium taurocholate in 3 ml of phosphate-buffered saline. TS rats were fed the same lipid emulsion except that TS replaced TO and the emulsion was labeled with glyceryl [1,3-14C]tristearate. The lymph triglyceride and radioactivity were determined. After infusion, the luminal and mucosal radioactive lipid content was analyzed. The results showed that there was significantly less lipid transported in the lymph of TS rats compared with TO rats. The results also showed a significant decrease in the absorption of TS as compared with TO. This was due in part to poor lipolysis. In addition, the lipid absorbed by the intestine of the TS rats was transported into lymph less efficiently than in TO rats.(ABSTRACT TRUNCATED AT 250 WORDS)

title: Effects of glycerol tripalmitate and glycerol trioleate on intestinal absorption of glycerol tristearate.
abstract: The goal of the present study was to determine 1) whether the poor digestion and absorption of glycerol tristearate (TS) that we observed previously is due to amount fed and 2) whether the digestion, absorption, and lymphatic transport of TS is affected by the presence of either a saturated fat [glycerol tripalmitate (TP)] or a monounsaturated fat [glycerol trioleate (TO)]. Three groups of intestinal lymph fistula rats were used. Group A was fed a lipid emulsion containing 12.5 mumol of TS (labeled as [glyceryl-1,3-14C]tristerate), 7.8 mumols of egg phosphatidylcholine, and 57 mumols of sodium taurocholate in 3 ml of phosphate-buffered saline per hour for 8 h. Group B rats were fed the same emulsion as group A, but with 12.5 mumols of TO added. Group C rats had 12.5 mumols of TP instead of TO added to the group A emulsion. The lymphatic radioactivity and triglyceride outputs were significantly lower in group A, with group C next and group B having the highest outputs. Significantly more TS remained in the lumen of the group A rats compared with groups B and C. The majority of the radioactivity in the lumen was still in the TS form in all three groups, indicating poor lipolysis. However, once the fatty acid and monoglyceride were absorbed, the reesterification process was similar in all three groups. When we studied the ability of the three groups of animals to transport the absorbed lipid into lymph (lymph transport index), both groups B and C were significantly better than group A rats.(ABSTRACT TRUNCATED AT 250 WORDS)

title: The metabolic balance technique: a critical reappraisal.
abstract: Twenty-six metabolic balance studies (MBS) of Ca, Mg, and P have been conducted in 11 postmenopausal women with osteoporosis and in 4 patients suffering from Paget's disease of bone. Subjects were given a liquid formula diet (LFD) matched as closely as possible to the patient's home diet. Studies lasted for 25 days, separated into 5-day periods by a carmine marker combines with Cr2O3 as continuous fecal marker. The balance studies were combined with a tracer technique using 47Ca to detect a possible loss of Ca by perspiration. The reliability of analytical methods necessary for mineral balances was tested. In 22 of the 26 MBS a steady state (SS) reflecting the patient's regular living conditions was demonstrated, while a non-SS situation possibly due to changes of physical activity was seen in four instances. The overall precision and accuracy of this balance method for Ca and P was found to be better than plus or minus 50 mg/day after four periods and plus or minus 40 mg/day after five periods, as related to an average daily intake of 920 mg Ca and 1230 mg P. For Mg (intake 190 mg/day), a precision of plus or minus 10 mg/day was recorded. The dermal loss of Ca was found to be less than 20 mg/day. As shown for Ca, Mg and P, the precision of a balance study is only little enhanced when the investigation is continued for more than four periods. At the present time is not possible to predict non-SS situations before starting such a study but a simple formula is proposed to detect those which were not performed under SS conditions.

title: Usefulness of chromic oxide as an internal standard for balance studies in formula-fed patients and for assessment of colonic function.
abstract: In 35 patients maintained solely on liquid formula diets, chromic oxide has been evaluated as an internal standard for balance studies that require stool collections. In 28 patients the excretion of chromic oxide was ideal: steady states were attained in which mean daily output was 90% (or more) of mean daily intake. In these patients corrections for fecal flow could validly be applied.In patients who excreted the marker ideally, the availability of chromic oxide balance data made possible the calculation of pool sizes and turnover rates of unexcreted intestinal content. These indexes bore little relationship to the usual clinical descriptions of bowel habits. In some patient who had daily bowel movements, pool sizes were very large and daily turnover was small, i.e., a large proportion of the colonic contents was not excreted for surprisingly long periods. It is critically important for investigators to recognize this possibility when carrying out balance studies for fecal constituents that may be altered by bacterial action within the gut lumen: for instance, in 6 patients a significant inverse correlation was found between daily fecal turnover and degradative losses of large amounts of dietary beta-sitosterol.7 of 35 patients failed to attain the ideal steady state of chromic oxide excretion. These patients would not have been singled out if an internal standard had not been used. In such patients balance studies that require analysis of fecal constituents must be interpreted with great caution, since the constituents in question may be handled in the same nonideal fashion as the internal standard.

title: Transit through the gut measured by analysis of a single stool.
abstract: A method is described for measuring transit time through the gut which requires the collection of only one stool. A dose of 20 radio-opaque markers is given to the subject on each of three consecutive days with breakfast, each dose of marker being of a different type. The first stool passed after rising on the fourth day is collected and its marker content analysed. The method has been validated in 15 subjects by comparing it on 36 occasions with mean transit time measured by a continuous marker technique (MTT-C). In 35 of these studies transit measured from a single stool (SST) and MTT-C were significantly correlated R = 0.78 P less than 0.001. In one study the designated stool contained none of the SST markers. An alternative way of validating the SST method is described by comparing it with the average of the three mean transit times from three separate doses of marker (MTT-S). The average MTT-S agreed very closely with MTT-C in 36 studies R = 0.94 P less than 0.001 and proved a satisfactory alternative method for validating transit techniques. In a total of 66 studies in 22 subjects average MTT-S correlated significantly with SST, R = 0.85 P less than 0.001.

title: Polyethylene glycol as a quantitative fecal marker in human nutrition experiments.
abstract: Data are summarized from five experiments in which polyethylene glycol (PEG) was fed to 51 subjects as a quantitative fecal marker. In three experiments PEG was fed continuously for 35 to 106 days. Preexperimental diet was assumed to have been completely excreted when the ratio of fecal PEG to fecal dry solids became constant. This took more than 7 days to occur in 50% of the subjects. Fecal recovery of PEG averaged only 93% of that consumed. PEG was a valid fecal marker for nitrogen, calcium, magnesium, iron, and zinc, but was less valid for sodium. In one experiment where PEG and chromic oxide (Cr2O3) were fed simultaneously, PEG was excreted faster on average than Cr2O3. In most subjects, small amounts of Cr2O3 were excreted sporadically for 42 days after Cr2O3 feeding had ceased. Inclusion of quantitative fecal markers permitted identification of the time when preexperimental diet had been completely eliminated, subjects who showed marked pooling of intestinal contents, and changes in the amount of fecal dry solids. However, an average fecal recovery of only 93% of the PEG or Cr2O3 consumed suggests that further work is needed before the recovery of either of these markers can be used with confidence for the correction of nutrient balance data.

title: Studies on transitory laxative effects of sorbitol and maltitol I: Estimation of 50% effective dose and maximum non-effective dose
abstract: The dose-response relationship between low-caloric sweetening agents, sorbitol and maltitol, administered orally in single doses, and the induction of diarrheal symptoms was investigated. Seven healthy male and 7 healthy female Japanese each in their twenties, thirties, and forties, respectively, or a total of 42 subjects were admitted to the study. The 50% laxative effective dose of sorbitol was estimated to be 0.4 g/kg for males and 1.0 g/kg for females and that of maltitol was estimated to be 0.8 g/kg for both males and females. The maximum non-effective dose of sorbitol was estimated to be 0.15 g/kg for males and 0.3 g/kg for females and that of maltitol was estimated to be 0.3 g/kg for both males and females.

title: Digestibility of cocoa butter from chocolate in humans: a comparison with corn-oil
abstract: To compare, in humans, the digestibility of moderate amounts of cocoa butter (30.7 g/d) consumed in the form of chocolate as part of a normal western diet with that of a well-absorbed fat (corn oil); and hence determine whether, by virtue of its apparent low absorption, cocoa butter can be considered to be a low calorie fat. Randomised, two-period crossover metabolic study, conducted under free-living conditions, but with strict control over food intake. Metabolic Unit, Nestlé Research Center Lausanne. Twelve healthy men were selected from volunteers at the Nestlé Research Center and all subjects completed the study. Two treatment periods of two weeks each: cocoa butter and control periods, with strict dietary control separated by a two week wash out period. No differences (P>0.05) were observed in faecal weight (wet or dry), faecal fat nor in defecation frequency between treatments (cocoa butter and corn oil). Cocoa butter at a dose of 30.7 g/d in the form of black chocolate, consumed between two meals, was found to have a similar digestibility to that of corn oil (99 % of corn oil digestibility).Conclusion: Cocoa butter, consumed as back chocolate within a normal mixed diet, has a high digestibility, similar to that of corn oil, and a digestible energy value of 37 kJ/g in man. Thus, cocoa butter cannot be considered to be a low-calorie fat. (2000) 54,

title: Suitability of traditional energy values for novel foods and food ingredients
abstract: Some novel foods and ingredients provide significantly less energy than traditional fats and carbohydrates. The use of energy conversion factors existing in food labelling regulations to determine the labelling requirements of foods that contain them can mislead consumers. The requirement to use factors limits the claims that can be made for such foods, even scientifically justifiable ones, and in turn inhibits the development of new products and processes to the ultimate detriment of both manufacturer and consumer. Where the energy value of a food ingredient lies outside the range of the variability for the traditional food ingredient, the scientifically determined value provides a more accurate description of the food ingredient energy value for nutrition labelling.