Faecal SIgA secretion in infants fed on pre- or probiotic infant formula.

Secretory immunoglobulin A (SIgA) plays an important role in the defence of the gastrointestinal tract. The level of faecal SIgA antibody is associated with increased neutralization and clearance of viruses. Formula-fed infants who lack the transfer of protective maternal SIgA from breast milk may benefit from strategies to support maturation of humoral immunity and endogenous production of SIgA. We aimed at studying the effects of standard, prebiotic and probiotic infant formulas on the faecal SIgA levels. At birth, infants of whom the mother had decided not to breastfeed were allocated to one of three formula groups in a randomized, double-blind fashion. Nineteen infants received standard infant formula; 19 received prebiotic formula containing a specific mixture of 0.6 g galacto-oligosaccharides (GOS)/fructo-oligosaccharides (FOS)/100 ml formula and 19 received probiotic formula containing 6.0 x 10(9) cfu Bifidobacterium animalis/100 ml formula. Faecal samples were taken on postnatal day 5, day 10, wk 4 and every 4 wk thereafter until wk 32. SIgA in faeces was determined by an enzyme-linked immunosorbent assay. During the intervention, infants fed on prebiotic formula showed a trend towards higher faecal SIgA levels compared with the standard formula-fed infants reaching statistical significance at the age of 16 wk. In contrast, infants fed on the probiotic formula showed a highly variable faecal SIgA concentration with no statistically significant differences compared with the standard formula group. Formula-fed infants may benefit from infant formulas containing a prebiotic mixture of GOS and FOS because of the observed clear tendency to increase faecal SIgA secretion. Adding viable B. animalis strain Bb-12 to infant formula did not reveal any sign for such a trend.

The bovine protein alpha-lactalbumin increases the plasma ratio of tryptophan to the other large neutral amino acids, and in vulnerable subjects raises brain serotonin activity, reduces cortisol concentration, and improves mood under stress.

BACKGROUND: Increased brain serotonin may improve the ability to cope with stress, whereas a decline in serotonin activity is involved in depressive mood. The uptake of the serotonin precursor, tryptophan, into the brain is dependent on nutrients that influence the cerebral availability of tryptophan via a change in the ratio of plasma tryptophan to the sum of the other large neutral amino acids (Trp-LNAA ratio). Therefore, a diet-induced increase in tryptophan availability may increase brain serotonin synthesis and improve coping and mood, particularly in stress-vulnerable subjects. OBJECTIVE: We tested whether alpha-lactalbumin, a whey protein with a high tryptophan content, may increase the plasma Trp-LNAA ratio and reduce depressive mood and cortisol concentrations in stress-vulnerable subjects under acute stress. DESIGN: Twenty-nine highly stress-vulnerable subjects and 29 relatively stress-invulnerable subjects participated in a double-blind, placebo-controlled study. Subjects were exposed to experimental stress after the intake of a diet enriched with either alpha-lactalbumin or sodium-caseinate. Diet-induced changes in the plasma Trp-LNAA ratio and prolactin were measured. Changes in mood, pulse rate, skin conductance, and cortisol concentrations were assessed before and after the stressor. RESULTS: The plasma Trp-LNAA ratio was 48% higher after the alpha-lactalbumin diet than after the casein diet (P = 0.0001). In stress-vulnerable subjects this was accompanied by higher prolactin concentrations (P = 0.001), a decrease in cortisol (P = 0.036), and reduced depressive feelings (P = 0.007) under stress. CONCLUSIONS: Consumption of a dietary protein enriched in tryptophan increased the plasma Trp-LNAA ratio and, in stress-vulnerable subjects, improved coping ability, probably through alterations in brain serotonin.

Effect of transgalactooligosaccharides on the composition of the human intestinal microflora and on putative risk markers for colon cancer.

BACKGROUND: Nondigestible oligosaccharides have been claimed to benefit the health of the colon by selectively stimulating the growth of bifidobacteria and by decreasing the toxicity of the colon contents. OBJECTIVE: We compared the effect of 2 doses of transgalactooligosaccharides and a placebo on the composition and activity of the intestinal microflora in 18 women and 22 men. DESIGN: Strictly controlled experimental diets were supplied to 3 intervention groups in a parallel design. The study was divided into 2 consecutive 3-wk periods during which each participant consumed a run-in diet followed by an intervention diet that differed only in the amount of transgalactooligosaccharides: 0 (placebo), 7.5, and 15 g/d. Breath samples and fecal samples were collected at the end of both the run-in and intervention periods. RESULTS: Apparent fermentability of transgalactooligosaccharides was 100%. The highest dose of transgalactooligosaccharides significantly increased the concentration of breath hydrogen by 130% (P < 0.01) and the nitrogen density of the feces by 8.5% (P < 0.05). The number of bifidobacteria increased after both placebo and transgalactooligosaccharides ingestion, but the differences between these increases were not significantly different. Transgalactooligosaccharides did not significantly affect bowel habits; stool composition; the concentration of short-chain fatty acids or bile acids in fecal water; the concentration of ammonia, indoles, or skatoles in feces; fecal pH; or the composition of the intestinal microflora. CONCLUSION: We conclude that transgalactooligosaccharides are completely fermented in the human colon, but do not beneficially change the composition of the intestinal microflora, the amount of protein fermentation products in feces, or the profile of bile acids in fecal water.

Consumption of fructooligosaccharides does not favorably affect blood glucose and serum lipid concentrations in patients with type 2 diabetes.

BACKGROUND: Fructooligosaccharides have been claimed to lower fasting glycemia and serum total cholesterol concentrations, possibly via effects of short-chain fatty acids produced during fermentation. OBJECTIVE: We studied the effects of fructooligosaccharides on blood glucose, serum lipids, and serum acetate in 20 patients with type 2 diabetes. DESIGN: In a randomized, single-blind, crossover design, patients consumed either glucose as a placebo (4 g/d) or fructooligosaccharides (15 g/d) for 20 d each. Average daily intakes of energy, macronutrients, and dietary fiber were similar with both treatments. RESULTS: Compliance, expressed as the proportion of supplements not returned, was near 100% during both treatments. Fructooligosaccharides did not significantly affect fasting concentrations (mmol/L) of serum total cholesterol (95% CI: -0.07, 0.48), HDL cholesterol (-0.04, 0.04), LDL cholesterol (-0.06, 0.34), serum triacylglycerols (-0.21, 0.44), serum free fatty acids (-0.08, 0.04), serum acetate (-0.01, 0.01), or blood glucose (-0.37, 0.40). CONCLUSIONS: We conclude that 20 d of dietary supplementation with fructooligosaccharides had no major effect on blood glucose, serum lipids, or serum acetate in patients with type 2 diabetes. This lack of effect was not due to changes in dietary intake, insufficient statistical power, or noncompliance of the patients.

Bacterial fermentation of fructooligosaccharides and resistant starch in patients with an ileal pouch-anal anastomosis.

Patients with large bowel disease may undergo ileal pouch-anal anastomosis, in which the colon is removed and part of the distal ileum is used to construct a pelvic reservoir. Competence of the ileal pouch to ferment carbohydrates is associated with the absence of pouchitis. However, the extent to which bacterial fermentation takes place and whether it is affected by diet are unclear. We investigated fermentation of two nondigestible carbohydrates, fructooligosaccharides and resistant starch, in 15 healthy patients with an ileal pouch by using a placebo-controlled crossover design (with glucose as the placebo). Apparent fermentability of fructooligosaccharides was 83%; that of resistant starch was 46%. Resistant starch increased fecal excretion of butyrate by 69% whereas fructooligosaccharides reduced excretion of amino acid-derived isobutyrate by 94% and of isovalerate by 77%. Fructooligosaccharides also significantly increased fecal weight (651 compared with 541 g/d) and breath-hydrogen excretion (286 compared with 85 ppm x h). Bacterial fermentation of nondigestible carbohydrates in pouches takes place to an appreciable extent and in a substrate-specific manner. The relation between such fermentation and inflammation of the pouch (pouchitis) deserves study.

Fate of fructo-oligosaccharides in the human intestine.

There is a need for studies on colonic fermentation in order to learn more about health and diseases of the colon. The aim of the present study was to evaluate the fate of two different doses of fructo-oligosaccharides (5 and 15 g/d) v. glucose in the intestine of healthy men. Twenty-four volunteers participated in a 5-week study. The study was a completely balanced multiple crossover trial using an orthogonal Latin-square design for three periods, with supplement periods of 7 d and two 7 d wash-out periods. Breath samples and faecal samples were collected. There was a clear gaseous response to the consumption of fructo-oligosaccharides. The highest dose significantly increased 24 h integrated excretion of breath H2 (P < 0.05). Breath H2 excretion after ingestion of 5 g fructo-oligosaccharides was higher than control, but did not reach significance. No effects on the total concentration of short-chain fatty acids in faeces were observed, no modification of the molar proportions of the various short-chain fatty acids was observed. The faecal pH did not change. No changes in faecal weight were observed. No fructo-oligosaccharides were recovered in faeces. We conclude that fructo-oligosaccharides added to the diet of young Western subjects are fully metabolized in the large intestine. The level of fermentation seem to be dose-dependent.

Fatness in relation to substrate oxidation during exercise.

The aim of this study was to test the hypothesis that differences in fuel utilisation during exercise, determined by muscle fibre-type profile, are an aetiological factor for obesity as proposed by Wade et al. (Lancet 1990, 335, 805-8). An investigation was carried out of relationships between body fatness (assessed by skinfolds, densitometry and dual X-ray absorptiometry) and fuel utilisation represented by the respiratory exchange ratio (RER, assessed by indirect calorimetry) during three cycle ergometer exercises. Exercise 1 was an exact replication of the Wade protocol (fixed 100 Watt load and unstandardised with respect to antecedent diet and activity). Exercises 2 (fasted) and 3 (fed) were highly standardised and adjusted to represent the same relative workload for each subject (45% VO2max). The subjects were 37 randomly-selected untrained men. None of the exercises yielded significant correlations between fatness and RER. The results refute the initial hypothesis linking substrate oxidation and body fatness. Inspection of the body composition data for Wade's subjects reveals that they were abnormally lean. This suggests that their findings may have been confounded by coincident correlations between fitness and fatness, and may not represent a true causal relationship.