Title: Alternative Sweeteners

Tagatose 111
IV. USE OF D-TAGATOSE BASED ON BIOLOGICAL
PROPERTIES
d-Tagatose is a sweet-tasting monosaccharide with interesting nutritional and
physiological properties. It is only partly absorbed in the small intestine, and the
major part is fermented in the colon, where it is converted into biomass, SCFAs,
CO 2, and H 2. d-Tagatose can be considered as a prebiotic on the basis of the
promotion of beneficial bacteria and an increase in the generation of SCFAs,
specifically an increased level of butyrate. Furthermore, the reduced absorption
and special fermentation mean that the caloric value of d-tagatose is a maximum
of 1.5 kcal/g. d-Tagatose consumption does not induce an increase of blood glucose
or insulin levels and even blunts the glucose level when d-tagatose is taken
before glucose or sucrose. This makes d-tagatose a desirable sugar substitute for
people with diabetes. d-Tagatose is so slowly converted to organic acids by tooth
plaque bacteria that it does not cause dental caries. It has satisfied the Swiss
regulation as safe for teeth. The aforementioned properties suggest several dietary
applications as products for people with diabetes, prebiotic foods, noncariogenic
confections and low-calorie foods.
A. Caloric Value of D-Tagatose
Ingested d-tagatose is incompletely absorbed from the small intestine of animals
and man. The fractional absorption is about 20% in rats and 25% in pigs. In
humans, the fractional absorption is estimated at not more than 20% on the basis
of data of a structurally related carbohydrate (l-rhamnose). The absorbed fraction
of d-tagatose is readily metabolized through the glycolytic pathway yielding 3.75
kcal/g. The unabsorbed fraction of d-tagatose reaches the large intestine, where
it is completely fermented by the intestinal microflora. The formed SCFAs are
absorbed almost completely and are metabolized. The metabolic fate of d-tagatose
resembles, therefore, that of other incompletely digested carbohydrates (e.g.,
polyols).
The energy value of d-tagatose was evaluated in two studies in rats and
one study in pigs. A net metabolizable energy value of 0.12 kcal/g was obtained
for d-tagatose in one of the rat studies (14). This may be explained by an inhibition
of absorption of sucrose that was present in the basal diet in a very high
concentration and/or by the relatively low amount of fermentable fiber in the
basal diet. The second rat study suggested a metabolizable energy value of about
1.2 kcal/g (15). Most relevance was attached to the pig study because the digestive
tracts of pigs and humans show many similarities. The pig study resulted in
a net metabolizable energy value of 1.4 kcal/g for d-tagatose (16).
Estimation of the net metabolizable energy value of d-tagatose by the factorial
method gave a range of 1.1–1.4 kcal/g. In this method, the energy contributed