Chemistry Reference
In-Depth Information
and fructo-oligosaccharides (FOS) in elderly subjects has been demonstrated in
clinical trials.
29,44,45
Prebiotics may have adverse side effects, such as abdominal
discomfort, bloating, and increased frequency of flatulence, when consumed in
high doses, and therefore it is important to determine the appropriate daily doses
in order to avoid the undesired side effects. For FOS the bifidogenic effectiveness
could not be demonstrated with a daily dose of approximately 4 g or less,
6
but an
8 g-dose per day yielded increased fecal counts of bifidobacteria and was well
tolerated although increased frequency of flatus and bloating with mild symp-
toms occurred.
29
Feeding of 8 or 15 g per day of galacto-oligosaccharide (GOS)
did not show any bifidogenic effect in adults,
46-48
but a constipation-relieving
effect was observed with 9 g daily intake of GOS in the elderly individuals.
49
The constipation-relieving effect in elderly subjects was also demonstrated for
inulin.
45
Potentially adverse effects of prebiotics have been revealed in experimentation
with animals. Ten Bruggencate et al.
50,51
revealed that inulin and FOS disturbed the
intestinal barrier in rats and increased the translocation of
Salmonella
. In humans,
however, the daily consumption of 20 g FOS did not affect the intestinal permeabil-
ity, although increased flatulence and intestinal bloating were observed indicating
for excessive dosage.
52
Changes in the microbial metabolism including decreased concentrations of
fecal SCFA have been reported for elderly people.
14
It has been considered that
prebiotics could redirect the microbial metabolism to a favorable course. However,
clinical studies with adults did not detect any effect of FOS or GOS on the fecal
concentration of SCFA.
48,53
Likewise, Kleessen et al.
45
did not detect any change in
the concentration fecal SCFA in response to inulin or lactose in elderly subjects, but
a slight trend toward higher molar ratios of acetate to butyrate was observed.
Other
interesting findings from prebiotic trials include the possible change in cholesterol
metabolism, which could possibly be related to decreased cholesterol bacterial trans-
formation.
29
The potentially beneficial change in cholesterol metabolism requires
further studies.
Few studies with prebiotics have focused on the possibility of improving the low
noise inflammatory process frequently observed in elderly subjects.
6
The rationale
behind the assumption is that intestinal microbes may contribute to the inflamma-
tory status in elderly people and that prebiotics could affect at the level of the compo-
sition of the gut microbiota including the mucosa-associated microbiota. Previously
it was shown that prebiotic carbohydrates can change the composition of the mucosa-
associated microbiota by increasing the bifidobacteria, lactobacilli, and eubacteria
populations.
54
In a prebiotic trial with FOS, a decreased level of proinflammatory
gene activation—tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6)
mRNA—and decreased serum levels of sCD14, a product shed by activated mac-
rophages, were measured.
6
Guigoz et al.
44
reported similar decrease in IL-6 mRNA
in blood leucocytes and decreased phagocytic activity of granulocytes and mono-
cytes in response to FOS. Thus, specific prebiotics may influence the inflammatory
condition of elderly individuals. It should be emphasized that the obtained results are
preliminary, but this interesting area of research certainly warrants further research.
