Agriculture Reference
In-Depth Information
Health benefits of fructans
Since fructans largely escape digestion in the upper intestine, they are an
important source of energy for bacteria that produce
fructosidases in the
caeco-colon. This leads to a proliferation of beneficial bacteria like
Bifidobacteria
and
Lactobacilli
to the detriment of harmful bacteria. These health-beneficial
bacteria have been termed 'probiotic' bacteria, and products containing them
are widely sold as dietary supplements. The proliferation of probiotic bacteria
favoured by fructans has been termed the 'prebiotic effect' of fructans
(Delzenne, 2003). These effects result in a colonic microbiota that produces
short-chain fatty acids there (e.g. lactate and butyrate). This results in a lower
pH that in turn favours increased absorption of mineral cations from the gut
into the bloodstream. The short-chain fatty acids produced can be absorbed
and reach the liver and modify lipid metabolism, with consequences for lipids
circulating in the blood that include reductions in total and LDL cholesterol.
The changes in colonic bacteria may reduce carcinogen activation in the
colon and stimulate the immune system, leading to improved resistance to
infection and cancer resistance - in particular, but not exclusively, to colonic
cancer. Benefits for glucose metabolism - including increased insulin secretion
and changes in hormone metabolism - have also been reported in animal
studies on fructans. So, the benefits for health of ingestion of non-digestible
oligosaccharides like fructans are multifaceted and are systemic; they are not
confined solely to effects in the digestive tract (Delzenne, 2003). The
mechanisms for these effects are far from fully understood, but they are yet
another aspect of the health-promoting benefits of edible alliums that are
earning them a reputation as 'functional foods' of particular importance in
counteracting the diet-related diseases of affluent societies.
Selenium and alliums
The mineral element selenium (Se) is known to be involved in the prevention of
cardiovascular disease, the stimulation of immune responses, the suppression
of inflammatory conditions, brain function, reproductive physiology and the
prevention of cancer, particularly prostrate cancer in men. The mean dietary
intake of Se in much of Europe is only about 60% of the recommended daily
amount (RDA) in the USA. Current research indicates that an intake of about
200
g/day gives maximal benefits to health, about three times the current
RDA in the USA. Hence, there is interest in supplementing dietary Se intake in
some countries.
Selenium is chemically similar to sulfur, being adjacent to it in Group 6 of
the periodic table. It is absorbed and incorporated into flavour compounds by
onions in a parallel fashion to sulfur. It is quite feasible to supply the Se RDA in
a single daily serving of onions grown in Se-enriched soil. Moreover, onions are
