Biology Reference
In-Depth Information
35,988 postmenopausal women from the Iowa Women's Health Study, no
relationship was found between GI and diabetes risks (
Meyer et al., 2000
)
.
These inconsistent results may be due to the use of food-frequency question-
naires that were not designed to measure GI and thereby resulted in incor-
rect assessment of GI.
Several studies have investigated the effects of a low-GI diet on insulin
sensitivity. In 30 patients with advanced Coronary Heart Disease (CHD), a
10-unit reduction in dietary GI from 86 to 76 resulted in improved insulin
sensitivity in 4 weeks in subjects in the low-GI group compared with the
high-GI group (
Frost, Keogh, Smith, Akinsanya, & Leeds, 1996
)
.
In another study, when GI was reduced by 24 units from 91 to 67 in the
diet of 16 women at increased risk of CHD, insulin sensitivity was improved
in those under a low-GI diet for 3 weeks, compared with the high-GI group
(
Frost, Leeds, Trew, Margara, & Dornhorst, 1998
)
. An interesting result
from this study was that the effects of lowering GI were not seen in control
subjects with no parental history of CHD, suggesting that those subjects who
already have some extent of insulin resistance might get the most benefits of a
low-GI diet. This was supported by another study in which no effects of a
low-GI diet on insulin sensitivity was observed in seven lean insulin-
sensitive men following nutrient-matched high- and low-GI diets (mean
GI difference 24) for 30 days (
Kiens & Richter, 1996
)
. Further,
Sloth
in a 10-week parallel study of 45 overweight women who consumed low-
or high-GI foods incorporated into ad libitum habitual diets.
Low-GI diets were found to improve insulin secretion in some studies.
Insulin secretion from pancreatic
b
-cells was found to be improved by a
low-GI diet in subjects with impaired glucose tolerance after 4 months
although the difference in mean GI from a high-GI diet was only 4 units
(
Wolever & Mehling, 2002
)
. Although the authors remarked that this effect
could be partly due to the high fiber intake with the low-GI diet, it must
not be forgotten that presence of fiber in itself could lower GI of foods.
A similar situation is evident in an 8-week crossover study in 20 post-
menopausal women who consumed high-fiber rye bread and white wheat
The rye bread, which was high in fiber, phytates, and tannins, had a lower
GI than wheat bread thereby resulting in enhanced insulin secretion
suggesting an improvement in
b
-cell function. Low-GI foods produce an
attenuated glucose response, which regulates the responses of other hor-
mones such as insulin and glucagon. A high-insulin response generated by
high-GI foods results in the glucose uptake and glycogen synthesis in skeletal
