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Jennifer Humphries
Persons with type 2 diabetes who had a diet high in low-glycemic
foods such as nuts, beans and lentils had greater improvement in
glycemic control and risk factors for coronary heart disease than
persons on a diet with an emphasis on high-cereal fiber, according to a
study in the December 17 issue of JAMA.
One dietary
strategy aimed at improving both diabetes control and cardiovascular
risk factors is the use of low–glycemic index diets, but there is
disagreement over their effectiveness, according to background
information in the article.
David J. A. Jenkins, M.D., of
St. Michael's Hospital and the University of Toronto, and colleagues
assessed the effects of a low–glycemic index diet vs. a high–cereal
fiber diet on glycemic control and cardiovascular risk factors for 210
patients with type 2 diabetes. The participants, who were treated with
antihyperglycemic medications, were randomly assigned to receive 1 of
the 2 diet treatments for 6 months.
In the low–glycemic
index diet, the following foods were emphasized: beans, peas, lentils,
nuts, pasta, rice boiled briefly and low–glycemic index breads
(including pumpernickel, rye pita, and quinoa and flaxseed) and
breakfast cereals (including large flake oatmeal and oat bran). In the
high–cereal fiber diet, participants were advised to take the "brown"
option (whole grain breads; whole grain breakfast cereals; brown rice;
potatoes with skins; and whole wheat bread, crackers, and breakfast
cereals). Three servings of fruit and five servings of vegetables were
encouraged on both treatments.
The researchers found that
hemoglobin A1c (HbA1c; a substance of red blood cells tested to measure
the blood glucose level) decreased by -0.50 percent absolute HbA1c
units in the low–glycemic index diet compared with -0.18 percent
absolute HbA1c units in the high–cereal fiber diet. Significant
treatment effects were observed for high-density lipoprotein
cholesterol (HDL-C) and the low-density lipoprotein cholesterol
(LDL-C):HDL-C ratio. HDL-C increased in the low–glycemic index diet
group by 1.7 mg/dL and decreased by -0.2 mg/dL in the high–cereal fiber
diet group. The LDL-C:HDL-C ratio showed a greater reduction in the
low–glycemic index diet group compared with the high–cereal fiber diet
group.
"Lowering the glycemic index of the diet improved
glycemic control and risk factors for coronary heart disease (CHD).
These data have important implications for the treatment of diabetes
where the goal has been tight glycemic control to avoid complications.
The reduction in HbA1c was modest, but we think it has clinical
relevance," the authors write. "Low–glycemic index diets may be useful
as part of the strategy to improve glycemic control in patients with
type 2 diabetes taking antihyperglycemic medications."
"Pharmacological
interventions to improve glycemic control in type 2 diabetes have often
failed to show a significant reduction in cardiovascular events. In
view of the 2- to 4-fold increase in CHD risk in participants with type
2 diabetes, the ability of a low–glycemic index diet to address both
glycemic control and CHD risk factors increases the clinical relevance
of this approach for patients with type 2 diabetes, such as those in
this study, who are overweight and also taking statins for CHD risk
reduction."
Source: JAMA Archives and Journals.
Original article: David J. A. Jenkins et al. Effect of a Low–Glycemic Index or a High–Cereal Fiber Diet on Type 2 Diabetes. JAMA. 2008;300(23):2742-2753.
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