This review featured an overview of
GI's implications in health and disease,
including discussions relative to type 2
diabetes, obesity and heart disease. In
conclusion, a critique argued that insuf-
ficient data exists on which to base
dietary advice for the achievement of
disease-risk reduction.
From this review, it is apparent that
great effort has been applied to under-
standing the role of dietary carbohy-
drates in human health and disease risk.
While there is no definitive proof that
reducing glycemic impact will prevent
disease on an individual basis, epidemi-
ological data, together with prospective
and intervention studies, suggest that
reducing the glycemic effect of the diet
may reduce disease risk. There are no
contraindications, other than that con-
sumers may have difficulty in under-
standing what action they need to take
in order to reduce glycemic challenge.
Recent meta-analyses
During the last year, several meta-
analyses have been published linking
glycemic response to biomarkers of dis-
ease risk. One reviewed 14 randomized
controlled studies, which considered the
role of low-glycemic diets in the man-
agement of diabetes. The studies
involved a total of 356 subjects and last-
ed from 12 days to 12 months. The low-
GI diets reduced glycated hemoglobin
(HbA1C) by 0.43 percentage points
compared to high-GI diets. HbA1C is a
well recognized biomarker of glucose
tolerance. The authors' overall conclu-
sion is that low-GI foods have a small
but clinically useful effect, equivalent to
pharmacological agents.
Another meta-analysis reviewed
international nutrition recommenda-
tions with special emphasis on carbohy-
drate and fiber. The authors also con-
cluded that there is a role for reducing
the glycemic response of the diet and
recommended that GI information
should be incorporated into exchanges
and teaching material for individuals
with diabetes.
In a review of 16 randomized con-
trolled trials published between 1981
and 2003, researchers found that low-GI
diets significantly reduced fructosamine
by 0.1 mmole per liter, HbA1C by
0.27%, total cholesterol by 0.33 mmole
per liter, and tended to reduce LDL cho-
lesterol in people with type 2 diabetes
by 0.15 mmole per liter compared with
high-GI diets. No changes were seen in
HDL cholesterol and triacylglycerols.
Their findings support the use of GI as a
scientifically based tool to enable selec-
tion of carbohydrate-containing foods
to reduce total cholesterol and improve
metabolic control of people with dia-
betes. There was only limited data on
healthy individuals.
One review of the evidence for low-
GI diets in relation to coronary heart
disease identified 15 studies meeting
strict inclusion criteria. There was some
(limited) evidence showing a relation-
ship between low-GI diets and lower
total cholesterol (compared to high-GI
diets). A small reduction in HbA1C was
seen after 12 weeks, but not after five
weeks. The researchers concluded that
more studies of at least 12 weeks dura-
tion are needed.
Whole grains, which have a lower GI than
refined grains--among other health bene-
fits--recently helped boost sales of baked
goods like bread, and would make good
additions to foods formulated for reduced
glycemic response.
