Walter Feldheim

Digestibility of energy, protein, fat and non-starch polysaccharides in mixed diets: Comparative studies between man and the rat

The apparent digestibility of energy, protein, fat and non-starch polysaccharides (NSP) of low and high dietary fibre (DF) mixed diets were studied in three series of experiments with man and the rat. Low DF diets were used as control diets in each experimental series and the DF level was increased by adding fruits and vegetables (Study 1), citrus fibre concentrate (Study 2) and insoluble barley fibre (Study 3). In Study 3 the high DF diet was fed at two protein levels. There was in most cases good agreement between the digestibility of energy between man and the rat, with the digestibility of energy of the low DF control diets of 0.941-0.950 in man compared with 0.933-0.952 in the rat and of the high DF diets of 0.897-0.931 in man and 0.865-0.920 in the rat. The biggest difference in digestible energy between the two species was found for the diet enriched with fruits and vegetables (0.032 absolute units) and citrus fibre concentrate (0.025 absolute units). Apparent digestibility of protein was slightly lower in man than in the rat for all diets in Studies 1 and 2. In Study 3, however, apparent digestibility of protein was consistently lower in man than in the rat with differences in absolute digestibilities between the two species varying from 0.023 (high DF/high protein) to 0.071 (high DF/low protein). The digestibility of fat was the same in man and in the rat in all but the high DF diet of Study 2. The rat appears to have a lower capacity to digest fibre polysaccharides than man and the digestibility of NSP was consistently lower in the rat than in man. The biggest difference between the two species was found for the diets in Study 2 where the digestibility of NSP in man was measured to be 0.774-0.885 compared with only 0.501-0.517 in the rat. For the other diets the differences in NSP digestibility were 0.077-0.137 absolute units. In spite of some differences between man and the rat in their ability to digest nutrients the various diets are ranked in the same order by the two species.

Fermentation of non-starch polysaccharides in mixed diets and single fibre sources: comparative studies in human subjects and in vitro.

The present study investigated whether the extent of fermentation of NSP in human subjects could be predicted by an in vitro batch system. Fibre sources studied were five mixed diets containing different amounts and types of fibre and three single fibre sources (citrus fibre concentrate, coarse and fine wholemeal rye bread). Fermentation in human subjects was determined in balance experiments in women who were also donors of the faecal inocula. In vitro fermentations were performed with fibre residues prepared from duplicates of the fibre-containing foods consumed during the balance trials. Fermentation of total NSP in vivo was between 65.8 and 88.6% for the mixed diets and 54.4, 58.0 and 96.9% for the coarse and fine wholemeal rye breads and the citrus fibre concentrate respectively. For the mixed diets and the citrus fibre concentrate, mean differences between the extent of NSP degradation after 24 h in vitro incubation and that in vivo were between -0.7 and 5.0%. Differences were significant for one diet (P < 0.05). For the wholemeal rye breads, the fermentation in vitro exceeded that in vivo significantly, but the magnitude of the difference in each case was small and without physiological importance. Particle size of breads had no influence on the extent of NSP degradation. These results indicate that the in vitro batch system used could provide quantitative data on the fermentation in vivo of NSP in mixed diets and some single fibre sources. An in vitro incubation time of 24 h was sufficient to mimic the NSP degradation in vivo.

The influence of lecithin on plasma choline concentrations in triathletes and adolescent runners during exercise

SummaryAn investigation was carried out on the effect of lecithin (phosphatidylcholine, 90%) on the plasma choline concentrations during continuous strain in 10 top level triathletes (4 women and 6 men), trial I, and 13 excellent adolescent runners (3 girls and 10 boys), trial II. Venous blood, collected before and immediately after the race, was separated and plasma was assayed by an improved high performance liquid chromatography method for choline. Each study comprised three experiments. In trial I the triathletes performed two periods of bicycle exercise each lasting 2 h at an average speed of 35 km · h−1, and in the second study (trial II) the subjects were subjected to severe physical stress on two occasions during cross-country races of durations between 30–60 min according to their ages. The participants received either a placebo or 0.2 g lecithin · kg body mass−1, 1 h before each exercise. As a control the same dose of lecithin was administered without any exercise (both trials I and II). Bicycle exercise without lecithin supply decreased plasma choline concentrations in all the triathletes, on average by 16.9% (P≤0.01). When lecithin was given before exercise, average plasma choline concentrations remained at the same level as the initial values. The supply of lecithin without exercise led to a significant increase of the plasma choline concentrations, on average by 26.9% (P≤0.01). In trial II, when running without a supply of lecithin, the mean plasma choline concentrations in the adolescent runners remained stable which may have been due to the duration of the physical stress. When lecithin was given before exercise, plasma choline concentrations increased, on average by 18.9% (P≤0.01). The administration of lecithin without exercise led in these participants to an increase in plasma choline concentrations, on average by 54% (P≤0.001).It was found from the present study that a combination of both lecithin intake and hard physical stress prevented in most subjects a decrease in plasma choline and this could affect performance.

FIBRE-MEDIATED PHYSIOLOGICAL EFFECTS OF RAW AND PROCESSED CARROTS IN HUMANS

Fibre-mediated physiological effects of raw and processed carrots were investigated in twenty-four young women under strict dietary control in two randomized crossover studies. For 3 weeks between 405 and 688 g of either raw frozen, blanched or canned carrots (first study), or raw or raw frozen carrots (second study) were consumed in addition to a low-fibre basal diet. Carrots provided 15 g dietary fibre (DF)/d. Total DF intake was 16.0 to 19.0 g (control periods) and 31 to 34 g (experimental periods). Faecal bulking effects of raw and processed carrots were similar (between 2.4 and 3.7 g additional stool/g carrot fibre in the diet). Faecal excretion of dry matter, fibre, and protein also increased significantly during carrot consumption. Fermentability of carrot fibre constituents was high (91-94%) and independent of processing, in spite of differences in the distribution of soluble and insoluble fibre and in the texture of raw and processed carrots. There was no effect of either type of carrot on serum total and high-density-lipoprotein-cholesterol or on faecal bile acid excretion.

Particle size of whole meal rye bread does not affect the digestibility of macro-nutrients and non-starch polysaccharides and the energy value of dietary fibre in humans

The effect of particle size of whole meal rye bread on the apparent digestibility of macro-nutrients, non-starch polysaccharides (NSP) and energy, the energy value of rye NSP and on faecal weight was studied in balance experiments in seven young women. The whole meal breads were prepared from one single batch of rye milled to two different particle sizes (coarse bread: 50% of particles > 2 mm, 90% > 1 mm; fine bread: 86% of particles < 0.5 mm, 58% < 0.2 mm). Two diets containing either coarse (350 g day-1) or fine (377 g day-1) whole meal bread and a low fibre control diet were consumed for 3 weeks each in a 3 X 3 cross-over design. Relative to the low fibre control diet, digestibility of protein, NSP and energy was significantly lower for the diets containing the whole meal breads. Digestibility of fat was the same for all diets. Partial digestible energy value for each g of NSP from coarse and fine whole meal rye bread was calculated to be -3 +/- 7 and 1 +/- 5 kJ, respectively. There were no differences between coarse and fine whole meal rye bread in the effects on the parameters measured with the exception on faecal wet weight, which was higher for the coarse bread diet.

Contribution of barley fiber to the metabolizable energy of human diets

Abstract The metabolizable energy (ME) of a low fiber diet and of a high fiber diet supplemented with 15 g dietary fiber (DF) from a barley fiber concentrate was determined in balance experiments in 12 young women. The ME of the diets was also calculated by energy assessment procedures. Total daily intake of DF was 22.5 g with the low fiber diet and 38.6 g with the high fiber diet. The addition of barley fiber decreased the digestibility of dietary energy (95.0 vs. 92.7 %) and NSP (83.2 vs. 65.4 %) significantly, whereas the digestibility of nitrogen and fat was not affected. The partial digestible energy value of the barley fiber was calculated to be 3 kJ (0.8 kcal)/g. This value is above the energy value calculated for whole grain fiber, but lower than that for fiber from mixed diets. The ME of the experimental diets could best be estimated by the equations of Southgate and of Livesey and by a modification of the British energy assessment procedure.

Effects of a fiber concentrate from citrus fruits in humans

Abstract Ten female subjects consumed a fiber concentrate made from citrus fruits under strict dietary control in a randomized cross over study comprising 2 experimental periods each of 4 wk duration. The citrus fiber concentrate contained 68.6 g total dietary fiber per 100 g, half of which was soluble. The fiber preparation was incorporated into various fiber free or low fiber foods in an amount providing 24 g total dietary fiber daily. The control diet contained these foods but without added fiber. Total dietary fiber intake was 21.2 and 45.1 g/d during the control and the high fiber diet periods, respectively. When the control diet was fed, mean total serum cholesterol levels remained stable, whereas high density lipoprotein (HDL)-cholesterol was reduced by 6.5% after 4 wk. When the citrus fiber was consumed for 4 wk, both serum total and HDL-cholesterol levels were decreased significantly by 10.6 and 14.5%, respectively. The addition of citrus fiber to the diet increased fecal wet and dry weight by 1.5 and 0.2 g, respectively, per gram of additional fiber. Fecal excretions of both energy and nitrogen were increased due to the intake of citrus fiber, whereas fecal fat was not affected. The additional fiber source was fermented completely. The partial digestible energy value of the citrus fiber was calculated to be 12 kJ (2.9 kcal)/g.

Quantitative Bestimmung von Vitamin A in Leber und Leberwurst unter Anwendung von Hochdruck-Flüssigchromatographie (HPLC)

SummarySamples of liver sausage and liver tissue from slaughtered animals were analysed for preformed vitamin A. A sensitive reversed phase HPLC method with fluorescence detection was used to determine the amount of free and esterified retinol in extracts of these samples. Under our chromatographic conditions retinyl myristate and linoleate run together as do retinyl palmitate and oleate. The contents of all forms of vitamin A were expressed in milligrams of all-trans retinol per 100 g wet weight. The average concentrations of total vitamin A for turkey, pig, calf, beef, and chicken liver were 42.31, 38.15, 22.74, 14.98, and 13.22, respectively. In addition to these differences, the fatty acid composition of liver retinyl esters, as well as the amount of retinol, also varied considerably among species. Approximately 95% of the hepatic vitamin A was present as retinyl ester with retinyl palmitate/oleate as the main ester fraction. The second most abundant fatty acid in the retinyl ester fraction of calf, beef, and chicken liver was stearic acid followed by myristic/linoleic acid. An increment of retinol, however, was also found in these tissue samples. By contrast, in turkey liver the retinol fraction was increased and therefore both retinyl stearate and retinol were present in nearly equal amounts, whereas the retinyl ester fatty acids from pig liver contained relatively more myristate/linoleate and less stearate than those from liver of the other domestic animals (apparently a hallmark of pig liver). The retinol and retinyl ester pattern present in liver sausage was similar to, but not identical with, that of pig liver. The mean vitamin A concentration of liver sausage was 6.97. On the basis of these findings, it is concluded that the values for the vitamin A content of food obtained from food-composition tables leads to a significant underestimation of the vitamin A activity in turkey, pig and calf liver as well as in liver sausage.ZusammenfassungUnter Anwendung von Hochdruck-Flüssigchromatographie wurde sowohl Lebergewebe von verschiedenen Schlachttieren als auch Leberwurst auf den Vitamin-A-Gehalt hin untersucht. Vitamin A wurde als freies und verestertes Retinol nach Trennung an einer C-18-Umkehrsäule mit Hilfe eines Fluorescenzdetektors bestimmt. Im Rahmen dieser Untersuchungen wurde in Puten-, Schweine-, Kalbs-, Rinder- und Hühnerleber ein mittlerer Vitamin-A-Gehalt von 42,31, 38,15, 22,74, 14,98 bzw. 13,22 mg Retinol-Äquivalent/100 g Frischgewicht gefunden. Tierartspezifische Unterschiede wurden darüber hinaus in der Zusammensetzung der in der Leber vorhandenen Vitamin-A-Speicher beobachtet. Die Leber von Kalb, Rind und Huhn enthielt in der Reihenfolge ihrer Konzentrationen Retinylpalmitat bzw.-oleat, Retinylstearat, Retinylmyristat bzw. -linoleat und Retinol. Bei einer ansonsten unveränderten Sequenz entsprach in der Putenleber die Retinol-Konzentration der von Retinylstearat, während für die Schweineleber charakteristisch war, daß these weniger Retinylstearat als Retinylmyristat bzw. -linoleat enthielt. Erwartungsgemäß entsprach das in der Leberwurst nachweisbare Vitamin-A-Muster annähernd dem in der Schweineleber. Die von uns untersuchten Leberwurstproben wiesen einen durchschnittlichen Vitamin-A-Gehalt von 6,97 mg Retinol-Äquivalent/100 g auf. Diesem und den übrigen Ergebnissen zufolge ist davon auszugehen, daß sowohl die in Puten-, Schweine- und Kalbsleber als auch die in entsprechenden Fleischerzeugnissen vorliegende Vitamin-A-Konzentration größer ist als bisher angenommen.

Untersuchungen zur Bestimmung des Tocopherolgehalts im unverseifbaren Anteil von Lupinenöl (L. mutabilis)

Der Gehalt der einzelnen Tocopherole im Lupinenol (L. mutabilis) wird durch Gaschromatographie und Hochdruckflussigkeits-Chromatographie bestimmt. Neben einem vorherrschendem Anteil an γ-Tocopherol (420–690 ppm) werden α- und erstmalig auch °-Tocopherol jeweils nur im Spurenbereich nachgewiesen (1–7 ppm). Es kann gezeigt werden, das durch die fur GC-Messung notwendige Verseifung und Derivatisierung der Proben Tocopherolverluste im Mittel um 30% verursacht werden. Die Tocopherole des Lupinenols liegen uberwiegend in unveresterter Form vor.SummaryThe content of individual tocopherols was determined in 11 samples of lupine oil (L. mutabilis) from Peru by GC- and HPLC-procedures. The main component is γ-tocopherol (42–69 mg/100 g oil); α-and δ-tocopherol were found in traces (0.1–0.7 mg/100 g oil). The pretreatment of samples, necessary for the GC-methods leads to tocopherol losses of 30% on average, this loss is mainly caused by the saponification of the samples. The tocopherols are predominantly present in an unesterifed state.ZusammenfassungDer Gehalt der einzelnen Tocopherole im Lupinenöl (L. mutabilis) wird durch Gaschromatographie und Hochdruckflüssigkeits-Chromatographie bestimmt. Neben einem vorherrschendem Anteil an γ-Tocopherol (420–690 ppm) werden α- und erstmalig auch °-Tocopherol jeweils nur im Spurenbereich nachgewiesen (1–7 ppm). Es kann gezeigt werden, daß durch die für GC-Messung notwendige Verseifung und Derivatisierung der Proben Tocopherolverluste im Mittel um 30% verursacht werden. Die Tocopherole des Lupinenöls liegen überwiegend in unveresterter Form vor.

Einbeziehung der Ballaststoffe in die Berechnung des Brennwertes von Lebensmitteln

The metabolizable energy (ME) of 16 diets containing various amounts and sources of dietary fibre was calculated by different energy assessment procedures and determined experimentally in balance studies in humans. ME was calculated by the German procedure (§35 LMBG; 4/9/4) and by the British procedure (4/9/3.75). In addition, both calculation procedures were modified to take into account the energy value of dietary fibre. Dietary fibre was multiplied by an energy conversion factor of 1 or 2 kcal/g, respectively. The best agreement between measured and calculated ME was obtained when a conversion factor of 1 kcal/g fibre (German procedure) or of 2 kcal/g (British procedure) was used.ZusammenfassungDer nach verschiedenen Verfahren berechnete physiologische Brennwert von 16 Kostformen mit unterschiedlichen Ballaststoffgehalten und -trägern wurde mit den Werten verglichen, die in Bilanzuntersuchungen am Menschen experimentell bestimmt wurden. Der Brennwert wurde nach dem deutschen Verfahren nach § 35 LMBG (4/9/4) und nach dem britischen Verfahren (4/9/3.75) berechnet. Beide Methoden wurden zusätzlich modifiziert, um die Energie der Ballaststoffe zu berücksichtigen. Ballaststoffe wurden mit 1 bzw. 2 kcal/g berechnet. Die beste Übereinstimmung von berechnetem und experimentell bestimmtem physiologischen Brennwert wurde erreicht, wenn Ballaststoffe mit 1 kcal/g (deutsches Verfahren) bzw. mit 2 kcal/g (britisches Verfahren) bewertet wurden.The metabolizable energy (ME) of 16 diets containing various amounts and sources of dietary fibre was calculated by different energy assessment procedures and determined experimentally in balance studies in humans. ME was calculated by the German procedure (section 35 LMBG; 4/9/4) and by the British procedure (4/9/3.75). In addition, both calculation procedures were modified to take into account the energy value of dietary fibre. Dietary fibre was multiplied by an energy conversion factor of 1 or 2 kcal/g, respectively. The best agreement between measured and calculated ME was obtained when a conversion factor of 1 kcal/g fibre (German procedure) or of 2 kcal/g (British procedure) was used.