Pet Nutrition
FOS in dog food
Dr A C Beynen
was professor of
veterinary nutrition
at the Faculty
of Veterinary
Medicine, Utrecht
University, The
Netherlands in the
period of 1993-2007.
40
FOS (fructo-oligosaccharides) refers to a group of
carbohydrates consisting of bonded fructose units. Labels of
dog foods with added FOS declare it as such, as inulin, or as
chicory root, extract or powder. Inulins present in or isolated
from chicory roots are FOS mixtures with longer fructose
chains. FOS blends comprising shorter chains are made from
inulin or table sugar. Admixed preparations in relevant dry dog
foods provide 0.025 to 1.0% FOS, while the amount of FOS
brought along by the base ingredients is unknown.
Foods with added FOS claim to balance the dog’s intestinal,
bacterial composition. FOS is purported to selectively feed
the good gut bacteria toward a healthier community. A
compilation of 11 and 9 dog experiments shows that 0.6%
supplemental FOS in dry food is required to produce a two-
and three-fold increase in the populations of the putative good
bacteria, bifidobacteria and lactobacilli.
Some promotional materials also assert that FOS aids in
canine digestion. Research data indicate that adding 0.6%
FOS to dry food increases net uptake of total, dietary dry
substances by the small intestine, but slightly decreases the
uptake along the total intestinal tract, or from mouth to anus.
Despite its latter effect, 0.6% added FOS in dry food does not
noticeably raise stool volume.
To sum up, 0.6% added FOS in dry food appreciably enhances
beneficial gut bacteria and small-intestinal digestion. That
inclusion level is higher than the amounts mixed into many dog
foods featuring FOS. Dog owners wishing to feed effective,
FOS-enhanced dry food, may consult product labels and/or
contact manufacturers to verify that the potential purchase
contains sufficient, added FOS. Noteworthily, there is no
evidence that dietary FOS maintains or improves visible health
and extends longevity in dogs.
Creature Companion | July 2019 • Vol. XII • Issue 7 • Noida