Stearic Acid Is Well Absorbed from Short- and Long-Acyl-Chain Triacylglycerol in an Acute Test Meal

ORIGINAL ARTICLE Stearic acid is well absorbed from short- and long-acyl-chain triacylglycerol in an acute test meal

S Tuomasjukka1, M Viitanen2 and H Kallio1

1Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland and 2Geriatrics, University of Turku, Turku, Finland

Objective: Absorption of stearic acid from natural oils has been shown to be efficient, but it is claimed to be lower from short- and long-acyl-chain triacylyglycerol molecules (Salatrim). The aim was to measure the apparent absorption of stearic acid from Salatrim fat in an acute test meal. Design: Double–blind crossover study. Subjects: Ten healthy male volunteers, of whom eight completed the study. Methods: The subjects were studied on two occasions after consumption of a single high-fat meal either without (control) or with 30 g of Salatrim. Fecal samples were collected for 96 h after the meal and the fat was extracted for analysis of the content and composition of free and esterified long-chain fatty acids. Results: Baseline fecal fat was 5.672.6 g/day increasing to 10.474.9 g/day after addition of Salatrim (P ¼ 0.001). During the whole collection period, the baseline fecal free and esterified fatty acids were 2.672.3 and 0.870.7 g, respectively. After Salatrim meal the corresponding figures increased to 5.973.6 g (P ¼ 0.001) and 1.5 (71.2) g (P ¼ 0.003), respectively. The total fecal stearic acid after control meal was 0.9770.9 g. Consumption of Salatrim with 16.770.5 g of stearic acid increased the content to 3.1271.6 g (Po0.001), with apparent absorption of 87%. Conclusions: The apparent absorption of stearic acid does not differ from its absorption from natural fats. The status of Salatrim as a low-energy fat substitute needs to be re-evaluated. Sponsorship: University of Turku. European Journal of Clinical Nutrition (2007) 61, 1352–1358; doi:10.1038/sj.ejcn.1602658; published online 14 February 2007

Keywords: stearic acid; Salatrim; structured triacylglycerol; absorption

Introduction energy derived from the short-chain acetic, propionic and butyric acids (3.5, 5.0 and 6.0 kcal/g) compared with Structured triacylglycerols with short and long acyl chains conventional long-chain fatty acids (e.g., stearic acid (Salatrim) are being used as reduced calorie fat in confec- 9 kcal/g, respectively) (Weast, 1993) and on the claimed tionary and bakery products. In each Salatrim molecule there reduced absorption of saturated long-chain stearic acid is at least one short-chain fatty acid and at least one long- (Hayes et al., 1994). chain saturated fatty acid (usually stearic acid) (Anonymous, The early suggestions of low absorption of stearic acid 2002a). The claim of a reduced caloric content is based on (Mattson, 1959; Mattson et al., 1979) have recently been the properties of the components: on the lower combustible questioned. The absorption of stearic acid from natural fats and oil is currently estimated to lie between 86 and 98% (Denke and Grundy, 1991; Dougherty et al., 1995; Baer et al., Correspondence: S Tuomasjukka, Department of Biochemistry and Food 2003). This is in conflict with the reported 63% absorption of Chemistry, University of Turku, Turku 20014, Finland. et al E-mail: [email protected] stearic acid from Salatrim (Finley ., 1994). Contributors: ST and HK were responsible for the design of the study. ST and It is possible that in Salatrim, the combination of short- MV organized and run the study. ST collected and analyzed the data and and long-chain fatty acids in the same molecule results in interpreted the results. All authors participated in discussion of the results. ST only a partial hydrolysis by the pancreatic lipase and a was the main writer of the manuscript. Received 9 October 2006; revised 13 December 2006; accepted 19 December formation of poorly digestible mono- and distearoylglycerols 2006; published online 14 February 2007 (Livesey, 2000). This could result with partially hydrolyzed Stearic acid absorption from Salatrim S Tuomasjukka et al 1353 Salatrim molecules with esterified stearic acid excreted in the provided on an ad libitum basis, but the subjects were advised feces. The aim of this study was to measure the apparent to follow their normal eating habits with respect to eating absorption of stearic acid from Salatrim consumed with a times and amount consumed. Drinking was not controlled high-fat meal, and to measure the distribution of stearic acid except for alcohol (not allowed during the test period). between the free and the esterified fractions. The test meal hamburgers (mean weight 324712 g) were obtained from a fast-food restaurant (Hesburger, Turku, Finland) ready to eat. About 1,0080 IU vitamin D (Devitol, Subjects and methods Orion, Turku, Finland) in 5.0 g of soybean oil was added to both meals to study vitamin D absorption (results not Subjects presented here) and Salatrim fat was spread on hamburger Ten healthy males were recruited for the study. The buns at Salatrim test. Hamburgers were heated in a micro- exclusion criteria included a family history of cardiovascular wave oven before consumption. disease or diabetes, body mass index (BMI) o19 or 425, Representative samples of the controlled diet (pizzas and plasma cholesterol 45.0 mmol/l, plasma triacylglycerol hamburgers) were pooled separately, homogenized and 42.0 mmol/l, current use of prescription drugs and an freeze-dried for subsequent protein, carbohydrate and fat immoderate consumption of alcohol. The mean values and analyses. Protein was analyzed by the Kjeldahl method using s.d. for clinical data of the subjects were: age 19.971.6 correction factor of 6.25. Available carbohydrate was ana- (years); BMI 21.270.6 (kg/m2); triacylglycerols 0.870.3 lyzed with an enzymatic kit (Megazymes, Bray, Ireland) and (mmol/l); cholesterol 3.770.3 (mmol/l); s-HDL 1.470.2 lipids were chloroform-extracted from lyophilized samples (mmol/l); s-LDL 2.070.4 (mmol/l). One subject was not able with Soxhlett. Test meal lipids and long-chain fatty acids to participate in one test period for personal reasons not were analyzed in the same way as from the fecal samples. related to the study and one subject showed a deviating pattern in the fecal fat excretion, resulting with eight subjects included in the final data. Informed consent was Fecal samples obtained from each participant. The study protocol was The subjects collected fecal samples from 0800 h on day 2 for approved by the Ethical Committee of the University a maximum of 96 h. A coloring agent was used for estimating Hospital of Turku, Finland. transit time. Quantitative samples were collected with the Kendall Precision Commode Specimen Collection System (Tyco Healthcare, Helsinki, Finland). Samples were frozen Study design and stored at À201C. Feces were lyophilized, transferred to The study had a non-randomized, double–blind cross-over plastic bags and thoroughly homogenized after crushing. design. Fecal fat content and composition after two meals A representative sample of lyophilized feces (13 g, 9–37% consisting of either hamburgers (control test meal, period 1) of total feces) from the transit time period (varying between or hamburgers combined with 30 g of Salatrim (Benefat B-R, 24 and 96 h) was first Soxhlett-extracted with chloroform for Danisco, Copenhagen, Denmark) (Salatrim test meal, period 5 h, then acidified with HCl, lyophilized and extracted again 2) were measured on two occasions 4 weeks apart. for another 5 h. Total lipid yield was measured gravimetri- The controlled diet was started on day 1 at noon. The cally. The extractability of the Salatrim fat was checked with evening meal was consumed at 2000 h. On day 2, the a spiked sample. Internal standard (triheptadecanoate, subjects attended the trial site at 0800 h after a 12-h fast. Sigma, St Louis, MO, USA) for quantification was added to Adherence to the instructions was checked verbally. The test both extracts. The esterified fatty acids were analyzed by meal was consumed within 10 min, after which the subjects methylation of the first extract by sodium methoxide abstained from all food (water allowed). A pizza meal was (Christie, 1982), and total fatty acids by methylation of both served 7.5 h later, after which the subjects were free to leave. extracts by boron trifluoride (Morrison and Smith, 1964). The controlled diet was continued until the end of day 2. The methyl esters were analyzed by gas chromatography Gastrointestinal tolerance was surveyed with a question- with a flame ionization detector (Perkin–Elmer Auto- naire. system, Boston, MA, USA) with a J&W DB23 column (60 m Â 0.32 mm i.d., 0.25 mm film (Agilent, Folsom, CA, USA)). Non-esterified fatty acids were calculated by subtract- Diet and test meals ing the esterified from the total fatty acids. The controlled diet consisted of frozen pizzas (La¨nnen Excreted fecal lipids were first measured from the whole Tehtaat, Sa¨kyla¨, Finland and Dr Oetker, Bielefeld, Germany) sample collection period, which varied individually and were obtained from a local grocery store and test meals. The pizzas then expressed as g/day by dividing total yield by collection were screened to make sure they had a roughly equal time. The absorption of stearic acid from Salatrim was carbohydrate-to-fat ratio. Two subjects who did not have calculated by subtracting the control period fat excretion sufficient cold storage were provided with non-frozen ready- (g/day) from the Salatrim period fat excretion (g/day), to-eat pizzas with similar nutritional content. Food was multiplied by sample collection time.

European Journal of Clinical Nutrition Stearic acid absorption from Salatrim S Tuomasjukka et al 1354 Statistical analysis Table 2 Fatty acid composition and content in the test meals Each subject consumed two test meals in non-random order, Fatty acid Control test meal Salatrim test meal and served as his own control. Paired samples t-test was used for testing the differences in fecal fat, total, esterified and g % g % non-esterified fatty acid fractions, and individual fatty acids. 7 7 7 7 A statistical difference at Po0.05 was deemed significant. 14:0 0.8 0.0 1.5 0.0 0.8 0.0 1.1 0.0 16:0 7.170.1 13.070.1 8.370.0 10.970.1 Analyses were carried out with SPSS (Chicago, IL, USA). 16:1(n-7) 0.870.0 1.570.0 0.870.0 1.170.0 Values are expressed as the mean of eight determinations. All 18:0 3.870.3 6.970.4 20.570.5 26.870.3 data were log-transformed before analysis. 18:1(n-9) 26.970.3 49.370.4 28.970.1 37.970.4 18:1(n-7) 1.370.0 2.470.0 1.470.0 1.870.0 18:2(n-6) 9.270.1 16.970.2 9.970.0 12.970.1 18:3(n-3) 3.770.0 6.770.1 3.970.0 5.170.0 Results 20:0 0.270.0 0.470.0 0.670.0 0.870.0 22:0 0.070.0 0.070.0 0.170.0 0.270.0 7 7 7 7 Diet Other 0.8 0.3 1.4 0.6 1.1 0.3 1.5 0.4 The nutrient composition of the controlled diet is presented Total 54.570.9 100.0 76.370.9 100.0 in Table 1. During the control period, the dietary fat was estimated to consist of 29% saturated (SFA), 50% mono- Values are presented as a mean of three analyses (7s.d.). unsaturated (MUFA) and 21% polyunsaturated fatty acids (PUFA) with palmitic (19%), stearic (6%), oleic (47%), Table 3 Total fecal lipids and fatty acids after the control and Salatrim linoleic (15%) and a-linolenic (5%) acids as the major fatty meals during the collection period (varying between 24 and 96 h) acids. During the Salatrim period, SFA, MUFA and PUFA Control test meal Salatrim test meal Increase content were 34, 46 and 20%, respectively, with 18% palmitic, 13% stearic, 43% oleic, 14% linoleic and 5% g % 7 7 a-linolenic acids. In 30 g of Salatrim, 1.2 0.0 g (5.7 0.2% 7 7 a 7 7 Total lipids (g)9.95.3 18.1 7.6 8.2 4.9 82.1 of all long-chain fatty acids) palmitic acid, 16.7 0.5 g Free FA (g)2.672.3 5.973.6a 3.372.2 127.8 (76.670.9%) stearic acid, 2.070.1 g (9.370.1%) oleic acid % of total lipids 23.1710.7 30.877.4 and 0.770.0 g (3.070.1%) linoleic acid were measured, with Esterified FA (g)0.870.7 1.571.2a 0.7070.6 87.7 7 7 a total 21.870.9 g of long-chain fatty acids (72.873.0% of % of total lipids 7.4 4.1 8.0 4.4 Total FA (g)3.472.8 7.474.1a 4.072.4 118.3 Salatrim net weight). The total test meal fat composition is % of total lipids 30.5711.1 38.977.2 shown in Table 2. Values are presented as a mean of eight subjects (7 s.d.). FA, fatty acids. aSignificantly different from control, Po0.01. Fecal fat The gastrointestinal transit time varied between 1 and 3 days and did not differ between the test meals. After the Salatrim possibility of temporary gastrointestinal disturbance could meal, the fecal fat content increased in all but one subject, not be screened out, and the subject’s data was excluded whose daily fecal fat content decreased by 1.2 g. The subject’s from the analysis as a precaution. defecation frequency was very low and the fecal weight was The total lipids and esterified and non-esterified fatty acids high after the Salatrim meal, indicating long transit time. from the whole fecal collection period are presented in The fatty acid profile of the fecal samples (collected for 96 h), Table 3. The free and esterified fatty acids increased however, showed an increase in the stearic acid content, significantly after the Salatrim meal (increase of 128% similar with other subjects after the Salatrim meal. Even (P ¼ 0.001) and 88% (P ¼ 0.003), respectively). Unsaponifi- though the subject’s fecal weight, fecal fat content and ables (excluding fatty acids) accounted for 69.5 and 61.1% of defecation frequency were normal after the control meal, a the lipid extracts from control and Salatrim periods, respectively. Table 1 Estimated nutrient composition of the controlled diet on the The average fecal total lipid content after the control test days preceding the test (day 1) and on the test day (day 2) meal was 5.672.6 g/day and it increased to 10.472.9 g/day after the Salatrim test meal (P ¼ 0.001). During the whole Day 1a Day 2 collection period, ingestion of a single 30 g dose of structured Control period Salatrim period b triacylglycerol increased the total fecal-fat content by 7 Energy (kJ) 9912 10 101 10 731–10 851b 8.2 4.9 g (P ¼ 0.001). Protein (g) 111 110 110 Available carbohydrate (g) 261 212 212 Fat (g) 100 127 157 Fecal fatty acids aSimilar diets during both control and Salatrim periods. The fecal fatty acid composition is shown in Table 4. After bBased on estimated 21–25 kJ/g of Salatrim fat (Anonymous, 2002b). the control test meal, the major fecal fatty acids were

European Journal of Clinical Nutrition Stearic acid absorption from Salatrim S Tuomasjukka et al 1355 70.0 58.4 % 16:0 100.0 À

À 60.0 18:0 18:1(n-9) 0.10.1 51.4 382.3 0.6 87.7 0.40.2 86.6 47.7 0.0 0.0 0.0 46.0 0.0 166.0 50.0 18:2(n-6) 7 7 7 7 7 7 7 7 7 g other

0.01 40.0 À

30.0 % 47.0 0.01 À 20.0 0.9 111.51.0 210.9 0.06 0.22 2.2 127.8 0.70 0.20.1 65.4 0.24 6.90.0 230.30.0 0.14 812.5 0.00 0.0 0.2 50.2 0.04 7 7 7 7 7 7 7 7 7

g 10.0 %the increase of overcontrol period 0.02

À 0.0 % 17.2 Figure 1 Fatty acid profile of the additional fecal fat in the free and À esterified fractions after Salatrim meal. Values are calculated from the average increase of eight subjects. 0.9 104.61.0 221.2 0.96 1.92 2.4 118.3 3.3 0.50.3 75.30.0 31.2 0.21 0.0 0.01 181.20.0 263.2 0.06 0.03 0.2 61.2 0.11 7 7 7 7 7 7 7 7 7 g 4.00 0.01 saturated palmitic (28.9%) and stearic acids (28.7%) and À unsaturated oleic (17.6%) and linoleic acids (15.7%). Palmitic

% and stearic acids were mainly present in their free form (88.4 11.418.8 1.02 2.15

b a a and 94.0%, respectively), whereas oleic and linoleic acids 0.50.4 34.50.1 29.7 0.45 0.0 0.16 1.5 0.0 0.2 0.0 0.06 0.03 1.2 0.1 0.1 0.1 0.1 0.15 were equally distributed (53.2 and 45.0% in free form, g 7 7 7 7 7 7 7 7 7 respectively). Palmitic and especially stearic acids were present in a clearly higher percentage than in the diet. Consumption of 30 g of Salatrim increased the amount of % all the major fatty acids in the feces. The increase in palmitic and stearic acids were mainly in free form (0.9670.9 g 0.7 1.51 0.3 34.70.3 0.52 37.70.0 0.45 0.0 1.9 0.02 0.0 0.7 0.00 0.7 0.00 0.1 14.10.0 0.17 7.3 0.28 0.0 0.0 0.06 7 7 7 7 7 7 7 7 7 7 g (P ¼ 0.005) and 1.92 1.0 g (Po0.001)). A minor, but significant, increase of them was observed in the esterified fatty 0.80 acids fraction. Oleic acid increased in both free and esterified % 8.9 0.28 1.5 0.01 form (0.2170.2 g (P ¼ 0.015) and 0.2470.4 g (not signifi- 31.1 0.11 48.3 0.06

a a b a a cant)), whereas linoleic acid increased almost exclusively in 7 0.20.0 3.8 0.30 0.30.0 0.02 0.6 0.01 0.0 0.3 0.33.6 0.02 1.3 1.6 0.4 esterified form (0.14 0.2 g (not significant)). Figure 1 pre- g 7 7 7 7 7 7 7 7 7 sents the major fatty acids in the free and esterified fractions. The fatty acid profiles of the additional fecal fat after Salatrim differed clearly between the free and esterified % fractions. Stearic and palmitic acids dominated in the free fatty acids, covering nearly 60% and nearly 30% of the 0.20.1 8.0 0.22 1.3 0.02 0.0 0.1 0.04 0.0 1.1 0.09 0.1 0.1 0.33 2.3 5.87 0.8 33.50.9 1.82 35.40.3 2.84 12.3 0.52 increase, respectively. Among the esterified fatty acids, the 7 7 7 7 7 7 7 7 7 g distribution was more even. Stearic acid (38.1% of the s.d.). 2.58

7 additional esterified fatty acids) was still the major com- 0.01. % 1.3 0.03 pound, but also unsaturated oleic (30.5%) and linoleic acids 27.0 0.86 42.3 0.91 14.1 0.32 X

P (19.1%) increased substantially. a a b a a 4 0.01. 1.6 0.9 0.60.1 9.0 0.21 0.50.0 0.03 0.5 0.00 1.3 0.0 0.3 0.34.1 0.22 o g P 7 7 7 7 7 7 7 7 7 Apparent absorption of stearic acid The addition of 30 g of structured triacylglycerol with 16.7 g

% of stearic acid increased the test meal stearic acid content Total fatty acids Free fatty acids Esterified fatty acidsover five-fold Change after Salatrim and more than doubled the stearic acid intake 0.9 28.70.5 3.12 17.6 1.04 0.5 15.10.1 0.67 1.4 0.04 0.0 0.3 0.04 0.8 28.9 2.00 0.0 1.0 0.09 0.2 0.2 0.39 2.8 7.38 during the 48-h test period (the test day and the preceding Control Salatrim Control Salatrim Control Salatrim Total fatty acids Free fatty acids Esterified fatty acids 7 7 7 7 7 7 7 7 7 g day). After the Salatrim meal, ca. 2 g more stearic acid was

Fecal fatty acid content and composition after the control and Salatrim meals during the collection period (varying between 24 and 96 h) found in the feces and the apparent absorption of the stearic acid from Salatrim was 87.2%. Compared with the control, the subjects did not report more gastrointestinal events after Significantly different from control: 0.05 Significantly different from control: 18:018:1(n-9) 0.59 0.97 18:2(n-6) 0.51 18:3(n-3) 0.05 22:0 0.01 16:0 0.98 20:0Other 0.03 Total 0.24 3.38 Table 4 Values are presenteda as a mean ofb eight subjects ( the Salatrim meal.

European Journal of Clinical Nutrition Stearic acid absorption from Salatrim S Tuomasjukka et al 1356 Discussion concentration and its energy value (Treadwell et al., 2002), possibly owing to fat crystallization at high stearic acid Absorption of Salatrim concentration. Consumption of Salatrim fat with conven- It has been claimed that only 2/3 of the stearic acid of tional fats (as in our study) could thus result with enhanced Salatrim is absorbed owing to formation of insoluble calcium absorption of stearic acid. and magnesium stearate after the triacylglycerol hydrolysis (Hayes et al., 1994). It has also been proposed that the reduced availability from Salatrim may result from the high Fecal lipid content and composition stearic acid density in the triacylglycerol molecule (Livesey, With healthy young subjects on a typical Western diet the 2000). We investigated the absorption of stearic acid by gastrointestinal transit time has generally been o3 days measuring the fecal fat content after ingestion of a single (Wyman et al., 1976; Stasse-Wolthuis et al., 1980; Eastwood 30 g dose of Salatrim with a high-fat meal. We found that the et al., 1986; Haack et al., 1998) or o2 days (Muir et al., 2004). stearic acid content increased significantly by 2.15 g, in- In the present study, the detected transit times were very dicating an apparent absorption of stearic acid from Salatrim short (38714 h) and the defecation frequency high (1.070.4 of 87.2%. Only 10.4% of the fecal stearic acid was esterified, times per day). Whenever there was no detectable color, the disproving the hypothesis of reduced lipolysis of Salatrim. feces were analyzed for at least 72 h. We are confident that The design of our study, in which Salatrim was added to the collection time was sufficient for unabsorbed stearic acid the control meal resulting in differing fat contents in the defecation. control and the Salatrim test meals, may have had some Little systematic work has been conducted on the effect on the absorption process. We chose not to replace a composition of fecal lipids. In some early studies, fatty acids portion of the fat of the control meal with Salatrim because (free or esterified) were thought to comprise the whole of the of the impossibility of defining an equivalent portion of lipid extract, resulting in gross overestimation of fecal fatty conventional and Salatrim fats. In principle, the substituted acid losses. Carey et al. (1983) report that fatty acids and their portions could be similar in either total lipophilic matter, soaps account for 80% of the fecal lipids, but in 1991 Denke long-chain fatty acids or energy (kJ); all these are different and Grundy (1991) noted that the fatty acids can be in terms of weight, and the use of any of them would have overestimated by 100% if they are quantified without made the interpretation of the results more complicated. internal standard. Therefore, we opted for the simple design, in which the Crude fat excretion of healthy men on various experi- control was supplemented with Salatrim. As no reports can mental diets (based mostly on natural triacylglycerols or be found describing a clear and significant effect of fat dose their transesterified products) has generally varied between 4 on fat absorption, we do not believe that the difference in fat and 12 g/day (Carey et al., 1983; Mitchell et al., 1989; content has had a significant effect on the results. Shahkhalili et al., 2000). The proportion of fatty acids (free, To our knowledge, only one human study on the fecal soaps or derived from acylglycerols) of the total lipids has excretion of stearic acid after consumption of Salatrim fat rarely been reported, but the fatty acid concentration in feces has been published. As a part of the original introduction of has been between 0.2 and 6 g/day (Bonanome and Grundy, Salatrim, Finley et al. (1994) reported the fecal excretion of 1988; Denke et al., 1993), typically 2–4 g/day (see e.g. Denke fat after Salatrim exposure. These results are in stark contrast and Grundy, 1991; Dougherty et al., 1995; Snook et al., to ours: the earlier study reported that over a third of 1999). In the present study, crude fat excretion was at the Salatrim was excreted, whereas we found only 13% of the expected level. The amount of fatty acids in the feces (g/day) ingested stearic acid in the feces. was in line with earlier investigations, but their proportion It is clear that the single-dose methodology does not in the total lipid extract was lower. This is most likely a result achieve the accuracy of longer exposure to test fat, but it is of the extraction method, which is efficient for both also evident that differences in study protocols do not suffice nonpolar and polar lipids. Preliminary analysis of the for explaining the conflicting results. One source for esterified fatty acids suggests that they are mostly present variation could be the Salatrim compositions used; the in acylglycerols. earlier study used Salatrim 23CA, where acetic and propionic The differences in the fatty acid profiles in the free and the acid accounted for 22.5 and 3.2 wt% of the total fatty acids, esterified fractions after Salatrim are interesting (Figure 1). respectively. In the present study, acetic acid was the only the increase in fecal free fatty acids resembles the profile of short-chain fatty acid present. Stearic acid content was ca Salatrim fat, whereas the increase in esterified fatty acids 57% in both Salatrim fats. With our current limited knowl- bears a similarity with that of the whole Salatrim test meal. edge of the metabolism of Salatrim fats in humans, it is not The dominating role of palmitic and stearic acids among the possible to estimate whether the differences in short-chain free fatty acids supports the view that once hydrolyzed, fatty acids could be responsible for the differences in saturated long-chain fatty acids more easily remain unab- absorption. Another difference might lie in the stearic acid sorbed. A substantial portion of the esterified fatty acids in concentration of the test meals. In a rat study, an inverse feces is probably derived from the poorly absorbed trisatu- relation was found between the test fat stearic acid rated triacylglycerols of the Salatrim fat (Livesey, 2000).

European Journal of Clinical Nutrition Stearic acid absorption from Salatrim S Tuomasjukka et al 1357 Calculated from the manufacturer’s information, the theo- other stearic acid-rich fats. The atypical structure of Salatrim retical proportion of triacylglycerols with three saturated fats with short- and long-chain fatty acids esterified in the long-chain fatty acids is 3.3% (ca.1.0g per Salatrim test same glycerol backbone does not influence the degree of meal). absorption of the long-chain fatty acids. In its 59th meeting, the JECFA stated that no conclusions can be drawn about the caloric value of Salatrim from the Absorption of stearic acid data presented to the committee (Anonymous, 2002b). In There are a number of studies in which different types of contrast, based on the opinion of the Scientific Committee stearic acid-rich fats have resulted in poor absorption. on Food, the European Union has recently approved However, in well-controlled dietary intervention studies, Salatrim as a reduced calorie fat with a caloric value of the absorption has been just marginally lower than that of 5–6 kcal/g (Anonymous, 2003, 2002c). The conflicting results the other fatty acids. Three factors are probably responsible from the few available human absorption studies with for the variation. Salatrim, together with the fact that stearic acid from First, in the early studies, tristearin was used as the stearic conventional fats is well absorbed, call for a serious re- acid source (e.g. Arnschink, 1890; Mattson, 1959; Mattson evaluation of the caloric value of Salatrim. et al., 1979). With a melting point of 731C (Small, 1991), tristearin is poorly emulsified and digested. It has been shown that concurrent melting, emulsification and mixing with low melting point fats dramatically increases tristearin Acknowledgements absorption (Hashim and Babayan, 1978; Emken, 1994). The study was fully sponsored by the University of Turku. Further support for the importance of melting point can be found from postprandial lipemia studies, where the transesterified fats with similar fatty acid composition but higher melting points than their natural counterparts, showed References significantly lower plasma lipid concentration (Sanders et al., 2003; Berry and Sanders, 2005), which is an indication Anonymous N (2002a). Compendium of food additive specifications, addendum 10. FAO Food and Nutrition Paper 52, Add. 10. of lower or slower absorption. Anonymous N (2002b). Evaluation of certain food additives. Fifty- Secondly, many earlier studies used an animal model, most ninth report of the Joint FAO/WHO Expert Committee on Food often rat. Later, it has been stated that ‘the rat is not a good Additives. World Health Organ Tech Rep 913: i, viii, 1–153, back cover. model for humans with respect to stearic acid absorption’ Anonymous N (2002c). Opinion of the Scientific Committee on Food (Benford et al., 2002), simply because the results in rats differ on a request for the safety assessment of Salatrims for use as a from those in humans. There are several reasons for this, but reduced calorie fats alternative as novel food ingredients. a good point was made by Shahkhalili et al. (2000) when they Anonymous N (2003). Commission decision of 1 December 2003 authorising the placing on the market of salatrims as novel food compared the calcium:fat ratios in typical rodent and human ingredients under Regulation (EC) No 258/97 of the European diets: the ratio is 4–18 times higher in the rodent diet. If Parliament and of the Council. Offici J European Union L326, calcium soaps do have a role in the excretion of free stearic 32–33. acids, this must be of much greater importance in the rat. Arnschink L (1890). Versuche u¨ber die resorption vershiedener Fette aus dem Darmkanale. Aeitschrift Biologie 26, 434–451. Also in the study by Finley et al. (1994) there was a clear Baer DJ, Judd JT, Kris-etherton PM, Zhao G, Emken EA (2003). Stearic discrepancy between the measured absorption of stearic acid acid absorption and its metabolizable energy value are minimally in rats (29–32% and humans (64–72%)). Thirdly, if the lower than those of other fatty acids in healthy men fed mixed concentration of stearic acid within the dietary fat does diets. J Nutr 133, 4129–4134. Benford D, Grieg JB, Lupton JR, Leclercq C (2002). WHO Food Additive influence stearic acid absorption, as suggested (Treadwell Series: 50Salatrim (Short- and long-chain acyltriglyceride molecules). et al., 2002), a plausible explanation would be the higher WHO Food Additive Series. WHO: Geneva. stearic acid concentration used in the rat studies, which is Berry SEE, Sanders TAB (2005). Influence of triacylglycerol structure simply unfeasible in human trials (and in human diet in of stearic acid-rich fats on postprandial lipaemia. Proc Nutr Soc 64, 205–212. general). Bonanome A, Grundy SM (1988). Effect of dietary stearic acid Salatrim is a synthetic, randomized triacylglycerol consist- on plasma cholesterol and lipoprotein levels. N Engl J Med 318, ing mostly of mono- and diacetostearines, and with a minor 1244–1248. proportion of poorly digested tristearate. It has been Carey MC, Small DM, Bliss CM (1983). Lipid digestion and absorption. Annu Rev Physiol 45, 651–677. suggested that in the mono- and diacetostearines, short- Christie WW (1982). A simple procedure for rapid transmethylation chain acetic acid is favorably hydrolyzed (Finley et al., 1994), of glycerolipids and cholesteryl esters. J Lipid Res 23, 1072–1076. producing a high melting point and poorly digestible di- and Denke MA, Fox MM, Schulte MC (1993). Short-term dietary calcium monostearoylglycerols (Livesey, 2000). In the present study, fortification increases fecal saturated fat content and reduces serum lipids in men. JNutr123, 1047–1053. this hypothesis was shown to be untenable. We also showed Denke MA, Grundy SM (1991). Effects of fats high in stearic acid on that the total (free and esterified) fecal stearic acid loss from lipid and lipoprotein concentrations in men. Am J Clin Nutr 54, Salatrim is not significantly different from that reported for 1036–1040.

European Journal of Clinical Nutrition Stearic acid absorption from Salatrim S Tuomasjukka et al 1358 Dougherty RM, Allman MA, Iacono JM (1995). Effects of diets Mitchell DC, McMahon KE, Shively CA, Apgar JL, Kris-Etherton PM containing high or low amounts of stearic acid on plasma (1989). Digestibility of cocoa butter and corn oil in human lipoprotein fractions and fecal fatty acid excretion of men. Am J subjects: a preliminary study. Am J Clin Nutr 50, 983–986. Clin Nutr 61, 1120–1128. Morrison WR, Smith LM (1964). Preparation of fatty acid methyl Eastwood MA, Elton RA, Smith JH (1986). Long-term effect of esters and dimethylacetals from lipids with boron fluoride– wholemeal bread on stool weight, transit time, fecal bile acids, methanol. J Lipid Res 5, 600–608. fats, and neutral sterols. Am J Clin Nutr 43, 343–349. Muir JG, Yeow EGW, Keogh J, Pizzey C, Bird AR, Sharpe K et al. Emken EA (1994). Metabolism of dietary stearic acid relative to other (2004). Combining wheat bran with resistant starch has more fatty acids in human subjects. Am J Clin Nutr 60, 1023S–1028S. beneficial effects on fecal indexes than does wheat bran alone. Am Finley JW, Klemann LP, Leveille GA, Otterburn MS, Walchak CG J Clin Nutr 79, 1020–1028. (1994). Caloric availability of SALATRIM in rats and humans. Sanders TAB, Berry SEE, Miller GJ (2003). Influence of triacylglycerol J Agric Food Chem 42, 495–499. structure on the postprandial response of factor VII to stearic acid- Finley JW, Leveille GA, Dixon RM, Walchak CG, Sourby JC, Smith RE rich fats. Am J Clin Nutr 77, 777–782. et al. (1994). Clinical assessment of salatrim a reduced-calorie Shahkhalili Y, Duruz E, Acheson K (2000). Digestibility of cocoa triacylglycerol. J Agric Food Chem 42, 2982. butter from chocolate in humans: a comparison with corn oil. Haack VS, Chesters JG, Vollendorf NW, Story JA, Marlett JA (1998). Eur J Clin Nutr 54, 120–125. Increasing amounts of dietary fiber provided by foods normalizes Small DM (1991). The effects of glyceride structure on absorption physiologic response of the large bowel without altering and metabolism. Annu Rev Nutr 11, 413–434. calcium balance or fecal steroid excretion. Am J Clin Nutr 68, Snook JT, Park S, Williams G, Tsai Y, Lee N (1999). Effect of synthetic 615–622. triglycerides of myristic, palmitic, and stearic acid on serum Hashim SA, Babayan VK (1978). Studies in man of partially absorbed lipoprotein metabolism. Eur J Clin Nutr 53, 597–605. dietary fats. Am J Clin Nutr 31, S273–S276. Stasse-Wolthuis M, Albers HFF, Van Jeveren JGC, Wil de Jong J, Hayes JR, Pence DH, Scheinbach S, D’Amelia RP, Klemann LP, Wilson Hautvast JGAJ, Hermus RJ et al. (1980). Influence of dietary fiber NH et al. (1994). Review of triacylglycerol digestion, absorption, from vegetables and fruits, bran or citrus pectin on serum lipids, and metabolism with respect to Salatrim triacylglycerols. J Agric fecal lipids, and colonic function. Am J Clin Nutr 33, 1745–1756. Food Chem 42, 474–483. Treadwell RM, Pronczuk A, Hayes KC (2002). Glyceride stearic acid Livesey G (2000). The absorption of stearic acid from triacylglycerols: content and structure affect the energy available to growing rats. an inquiry and analysis. Nutrit Res Rev 13, 185–214. JNutr132, 3356–3362. Mattson FH (1959). Absorbability of stearic acid when fed as a simple Weast RC (ed). (1993). CRC Handbook of Chemistry and Physics, 73rd or mixed triglyceride. J Nutr 69, 338–342. edn. CRC Press: Boca Raton, FL, USA, 1992–1993. Mattson FH, Nolen GA, Webb MR (1979). The absorbability by rats of Wyman JB, Heaton KW, Manning AP, Wicks AC (1976). The effect on various triglycerides of stearic and oleic acid and the effect of intestinal transit and the feces of raw and cooked bran in different dietary calcium and magnesium. J Nutr 109, 1682–1687. doses. Am J Clin Nutr 29, 1474–1479.

European Journal of Clinical Nutrition