Chemistry Reference
In-Depth Information
promising studies have been conducted with probiotics (Kalliomaki
et al., 2003;
Ishida
et al., 2005; Weston
et al., 2005; Ishida
et al., 2006), but the potential effects
of prebiotics in children on atopic eczema, either therapeutic or preventive, are little
known (AFSSA, 2003). Similarly, no studies are available demonstrating a signifi-
cant effect of a prebiotic on allergic conditions in adults (AFSSA, 2005). However,
in patients with atopic eczema a correlation was shown between the amount of bifi-
dobacteria and the severity of atopic eczema (Bunselmeyer, 2006) and recent stud-
ies proved the efficiency of consumption of synbiotics, such as
Lactobacillus casei
subsp.
casei
with dextran (Ogawa
et al., 2006), on the prevention and treatment of
allergic reactions in adults (pollen allergy) or children (atopic dermatitis) (Passeron
et al., 2006). On the contrary, two studies reported allergic reactions after consump-
tion of foods containing inulin (Salminen
et al., 1998; Gay-Crosier
et al., 2000).
3.2.3 The barrier Effect
Resident bacteria are a crucial line of resistance to colonization by exogenous
microbes and, therefore, are highly relevant in protecting the internal medium of the
host against pathogenic organisms and toxic substances (Cherbut, 2003). It is prob-
ably through their effects on the colonic flora that prebiotics are able to reinforce the
intestinal barrier as it has been demonstrated that inulin and FOS modify the profile of
bacterial biofilms associated with the intestinal mucosa (Cummings and Macfarlane,
2002). Studies in animal models implanted or not with human flora suggested favor-
able effects of inulin and FOS on intestinal mucosa, e.g., increase of the thickness of
the mucin layer and of the number of mucus-containing cells (Hoebler
et al., 2002;
Kleessen
et al., 2003), and modification of the distribution between neutral, acidic,
and sulfated mucins in favor of sulfated mucins, possibly more protective (Fontaine
et al., 1996). A clinical study conducted in humans failed to show a change in mucin
expression (Meijer
et al., 2000). Gaudier et al. (2004) suggested that the effects of
fructans on mucins could be mediated by the production of butyrate because this
SCFA increases the production of certain mucin genes (MUC3) (Gaudier
et al., 2004).
As mentioned by Fowler et al. (2003), mucins are highly heterogeneous among indi-
viduals, so that the effect of fructans could be different depending on the subject.
However, prebiotics also could have deleterious effects on the intestinal barrier. A
study found that inulin and FOS increased the hepato-splenic translocation of salmo-
nella
in vivo
in rats (Ten Bruggencate
et al., 2004). In healthy humans, a recent pla-
cebo-controlled cross-over study found that FOS consumption (20 g/day over a 2-week
period) doubled fecal mucin excretion indicating mucosal irritation (Ten Bruggencate
et al., 2006). These results have to be balanced by the fact that overall observed effects
were more moderate than those in rats and that the dose ingested was relatively high,
especially as it was added in a liquid food (lemonade), leading to increased flatulence
and intestinal bloating. Overall, the effect of fructans on the intestinal barrier should
be further studied in well-designed clinical trials in humans.
