MEDICINSKI GLASNIK

20
Medicinski Glasnik, Volumen 9, Number 1, February 2012
effect of RS from corn or rice on blood glucose
and insuline levels, colonic events and hypolipidemic
actions and humoral immune responses in
Sprague-Dawley streptozotocin-induced diabetic
rats was investigated (37). The results showed no
significant effect of RS on blood glucose and insuline,
but intestinal transit time was significantly
shortened and plasma total lipid and both blood
and liver cholesterol concentrations were lowered.
RS consumption resulted in non-esterified
fatty acid and 3-hydroxybutyrate levels suppression
5 h after meal tolerance test (38).
Yamada et al.(2005) reported that bread containing
RS significantly inhibited postprandial increase in
glucose in adults with fasting blood glucose level
between 100 and 140 mg/dL in comparison with
bread without RS (39) and Sands et al. (2009) reported
that consumption of slowly digesting waxy
maize starch leads to blunted plasma glucose and
insulin response (40). Al-Tamimi et al. (2010)
reported that substitution of standard starch with
RS4 attenuated postprandial glucose and insulin
levels in normoglycemic humans, although available
carbohydrate amount in the food was not
changed (41). However, their study did not provide
information whether this was due to dietary
fibre and/or RS aspects of consumed food.
In addition, Robertson et al. (2003) reported that
replacement of “refined flour” with “high RS flour”
could improve postprandial insulin sensitivity
in normal healthy subjects due to increased rate
of colonic fermentation. However, they reported
that difference in insulin levels noted were likely
to be due to an increase in hepatic internalization
of insulin rather than to differences in insulin secretion.
They also observed lowering of plasma
glucose concentration despite the higher level of
insulin clearance and lower circulating insulin
levels. This phenomenon was partly attributed
to high portal concentration of propionate which
has insulin-like effects, stimulating glycolysis,
activating glycogen synthase in isolated hepatocytes
and reducing gluconeogenesis (38).
These researches indicate that RS could have beneficial
impact on prevention of type II diabetes
and cardiovascular diseases, where RS1 is most
effective of all RS types (42). In addition, ingesting
low-glycemic hydrothermally modified starch before
cycling exercise blunted the initial spike in serum
glucose and insulin and preserved a short burst
maximal performance measurement after prolonged
cycling bout in adult male cyclists (43).
RS stimulates growth of Bifidobacterium, Lactobacillus,
Eubacterium, Bacteroides, Enterobacter
and Streptococcus (6, 31, 27, 44-46) and inhibits
growth of Escherichia coli, Clostridium difficile
and sulphur- and sulphate-reducing bacteria, and
enhances mucosa regeneration. This is supported
by research on recovery time needed for children
with cholera induced diarrhoea and other types
of infectious diarrhoea. These children recovered
much easier when RS (as high-amylose starch)
was added to the usual therapy (6).
RS could have role in prevention of colon cancer,
since fermentation of RS in large intestine results
in large quantity of butyrate, which is even higher
than amount of butyrate produced by fermentation
of dietary fibre (47). Butiric acid inhibits
oxidative stress (48) and malignant transformation
of large intestinal epithelial cells (6, 49), and
stimulates apoptosis, differentiation of cancer cells
(47). It also regulates expression of proteins
involved in cellular dedifferentiation in various
tumor cells in culture (50). Beneficial effect of
butyric acid is supported by low incidence of colon
cancer in developing countries, where high
quantities of carbohydrate foods are consumed.
For instance, in Gambia, where incidence of colon
cancer is very low, mean daily intakes of starch
by adult men are 375 g. In Madras, India rice
is staple food and colon cancer incidence is very
low: 1.5/100 000 (47). Research conducted on
1,2-dimethylhydrazine treated Sprague-Dawley
rats showed that replacement of digestible starch
with resistant starch type 3 (RS3) prevent colon
carcinogenesis. This effect was indeed mediated
by enhanced apoptosis of damaged cells and
changes in parameters of dedifferentiation in colonic
mucosa (50).
This effect is even more pronounced when RS is
consumed in combination with insoluble dietary
fibres (e.g. wheat bran). Namely, RS is rapidly
fermented in proximal colon, and colon cancer,
as well as inflammatory bowel diseases, mainly
occurs in distal colon. Insoluble fibres shift fermentation
of RS to the distal bowel and enhance
positive effect of RS (51).
In conclusion, health properties of resistant starch
have been extensively researched. It is well
established that resistant starch has properties of