Low Glycemic Index Diets vs. High Cereal Fibre Diets in Type 2 Diabetes
Condition: Type 2 Diabetes; Cardiovascular Disease
MeSH terms: Cardiovascular Diseases; Diabetes Mellitus, Type 2
Study type: Interventional

Summary: 
      Large observational studies have shown cereal fiber to protect from diabetes and heart
      disease. Despite the success of acarbose, an α-glucosidase hydrolase inhibitor, which lowers
      the glycemic index of foods containing starch, sucrose and maltodextrins, the use of diets
      containing low glycemic index foods still remains to be established. We will therefore
      provide otherwise healthy individuals with type 2 diabetes intensive counseling on food
      selection either to improve glucose control using high cereal fiber dietary strategies or low
      glycemic index foods. Studies will last 6 months with bloods taken for HbA1c, glucose and
      blood lipids. If the study shows a benefit for either or both diets then use of high fiber
      and/or low glycemic index foods in the diet may provide another potential way to improve
      glucose control and lower cholesterol levels in non-insulin dependent diabetes.
    

Detailed description: 
      Recruitment: Subjects will be recruited by placing advertisements in local newspapers and by
      distributing similar advertisements to the diabetes clinic and diabetes education programs.

      Information Sessions: Approximately 1000 volunteers in groups of 10-30 with or without
      spouses will attend one of a number of evening information sessions run from the Risk Factor
      Modification Center at St. Michael's Hospital. During the sessions the exact nature of the
      study will be described and volunteers will have the opportunity to ask specific questions
      about the study and taste the high fiber and low glycemic index foods.

      Screening: Potential subjects will then fill in and return to the investigators a detailed
      questionnaire concerning their medical history, medications (including vitamin, mineral and
      nutritional supplements) smoking habits, alcohol intake and exercise pattern and whether they
      are currently on a specific diet. Details will also be obtained concerning planned vacations.
      Those subjects deemed potentially eligible will be asked to give a fasting blood sample at
      the Risk Factor Modification Center. Individuals who meet the study criteria, are invited to
      return again to the Center. The principles of the diabetic diet which they are already
      expected to be following will be reinforced, which incorporate the key elements of an NCEP
      Step 2 diet (total calories from fat <30%, saturated fat <7%, polyunsaturated fat <10%,
      dietary cholesterol <200 mg/day).

      All subjects will then be randomized to one 24-week treatment in a two-treatment parallel
      design.

      Treatments: 1) low glycemic index dietary advice (e.g. to eat intact grain cereals,
      pumpernickel bread, parboiled rice, cracked wheat, pasta, peas, beans and lentils) 2) high
      cereal fiber diet. Background diets will be the subjects' diabetic diets, modified as above,
      which will conform to CDA and NCEP Step 2 guidelines. Diet histories will be recorded at
      weeks 0, 2, 4, 8, 12, 16 and 24. These diets will be assessed for consistency by the
      dietitian in the subject's presence. Where necessary, modifications in diet will be made to
      ensure weight maintenance. Compliance will be assessed by 7 day food records.

      Duration: the study will consist of four months recruitment and patient selection, during
      which time estimation of individual caloric requirements will be performed, and 6 months
      treatment period

      Study Details: Fasting blood samples are obtained at day zero and weeks 2, 4, 8, 12, 16 and
      24 of each study period. Twenty-four hour urine for urinary C-peptide analyses will be
      obtained immediately prior to the beginning of the study and at the end of each 24-week
      treatment phase.

      Palatability and satiety: subjects will record their ratings using a 9-point bipolar semantic
      scale at weekly intervals during each study phase.

      Anthropometric measures: height at recruitment, waist and hip circumference, and body
      composition will be taken immediately prior to and at the end of each study phase. Body
      weight and blood pressure will be measured at clinic visits.

      This study will help to indicate whether dietary advice can make a significant difference to
      glycemic control as has been the case with drug therapy to reduce postprandial glycemia.
    

Intervention name(s): Low Glycemic Index diet; High Cereal Fibre Diets
Intervention type(s): Other; Other
Intervention description(s): Diet to emphasize carbohydrate foods low in glycemic index; Diet to emphasize whole wheat carbohydrate cgoices
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Nutrition; Type 2 Diabetes