Chemistry Reference
In-Depth Information
while high amounts may inhibit it (Lupton, 2004). In the study performed by Rafter et
al. (2007), the synbiotic intervention resulted in significant
alterations in the composi-
tion of the colonic bacterial ecosystem,
which presumably have consequences for the
metabolic activity
of this organ. These results also provide indirect evidence that
some
of the consequences of the synbiotic intervention might
be decreased exposure of the
epithelium to cytotoxic and genotoxic
agents, decreased colonic cell proliferation, and
improved mucosa
structure. These exciting results suggest that synbiotics
may repre-
sent a feasible
means of chemoprevention of colon cancer in humans.
3.4 EFFECTs oF FruCTANs oN METAbolIsM
oF MINErAls AND vITAMINs
Demonstrating an effect of a given food factor on mineral bioavailability in
humans is difficult for methodological reasons (Guéguen and Pointillart, 2000;
Scholz-Ahrens
et al., 2001). The choice of relevant biological markers is essential.
Abrams et al. (1994) showed that calcium absorption can be correctly measured
using either the chemical balance or the dual-stable-isotope methods. But the site
(serum or urines samples) as well as the timing (e.g., urine collected less or more
than 24 hours after tracer administration) for markers measurement chosen can also
induce various interpretations of results as observed on trials dealing with nondigest-
ible oligosaccharides (Coudray and Fairweather-Tait, 1998).
3.4.1 Fructans and Calcium Absorption
A review on calcium (Ca) consumption in France revealed that a large part of the
population consumes less than two-thirds of the recommended dietary allowance
(RDA), the critical threshold for defining groups at risk (Guéguen, 1996). Therefore,
there is real public health interest in studying the impact of prebiotics, such as fruc-
tans, on Ca absorption, especially for prevention of osteoporosis.
In adolescents, van den Heuvel et al.
(1998) found that 15 g/day inulin, FOS, or
GOS had no effect on the intestinal absorption using the dual-stable-isotope method.
Griffin et al. (2003) showed that the main determinant of the effect of fructans in
preadolescents was “Ca absorption during the placebo period.” In fact, individuals
with lower Ca absorption during the placebo period had the greatest increase in
Ca absorption. Regarding the nature of the prebiotic tested, a study in adolescent
girls demonstrated that 8 g/day of a mixture of inulin and oligofructose significantly
increased Ca absorption while 8 g/day of oligofructose alone had no effect (Griffin
et al., 2002), confirming previous findings in animals (Coudray
et al., 2003; Kruger
et al., 2003).
In young men, Coudray et al. showed that 40 g inulin per day increased Ca
absorption using the chemical balance (Coudray
et al., 1997). In postmenopausal
women, Holloway et al. (2003) tested a mixture of inulin and oligofructose for 6
weeks (Holloway
et al., 2003), showing no effect of prebiotics on Ca absorption, but
a great variation in individual responses to the treatment. Interestingly, the efficacy
