Importance of glycemic index in diabetes.
To date there are 11 medium to long-term studies that have specifically used the glycemic index (GI) approach to determine the clinical gains in diabetes or lipid management. All but one study produced positive findings. On average; low-GI diets reduced glycosylated hemoglobin by 9%; fructosamine by 8%; urinary C-peptide by 20%; and day-long blood glucose by 16%. Cholesterol was reduced by an average of 6% and triglycerides by 9%. These are modest improvements but so too were the changes to the diet. Unlike high-fiber diets; low-GI diets are "user friendly." As part of studies on the GI of foods; we determined the glycemic and insulin responses to 44 foods containing simple sugars. Their mean (+/- SE) GI was 62 +/- 14; which compares favorably with bread (GI = 73; glucose = 100). There was often no difference in the GI between the sweetened and unsweetened product. The time has come to reassess the value of GI in planning meals for diabetics.
Magnesium intake and risk of type 2 diabetes: a meta-analysis
OBJECTIVE: To assess the association between magnesium intake and risk of type 2 diabetes. DESIGN: Meta-analysis of prospective cohort studies. DATA SOURCES: We retrieved studies published in any language by systematically searching MEDLINE from 1966 to February 2007 and by manually examining the references of the original articles. STUDY SELECTION: We included prospective cohort studies reporting relative risks with 95% confidence intervals for the association between magnesium intake and incidence of type 2 diabetes. RESULTS: The seven identified cohort studies of magnesium intake [from foods only (n = 4) or from foods and supplements combined (n = 3)] and incidence of type 2 diabetes included 286;668 participants and 10;912 cases. All but one study found an inverse relation between magnesium intake and risk of type 2 diabetes; and in four studies the association was statistically significant. The overall relative risk for a 100 mg day(-1) increase in magnesium intake was 0.85 (95% CI; 0.79-0.92). Results were similar for intake of dietary magnesium (RR; 0.86; 95% CI; 0.77-0.95) and total magnesium (RR; 0.83; 95% CI; 0.77-0.89). There was no evidence of publication bias (P = 0.99). CONCLUSIONS: Magnesium intake was inversely associated with incidence of type 2 diabetes. This finding suggests that increased consumption of magnesium-rich foods such as whole grains; beans; nuts; and green leafy vegetables may reduce the risk of type 2 diabetes.
Magnesium intake and risk of type 2 diabetes in men and women
OBJECTIVE: To examine the association between magnesium intake and risk of type 2 diabetes. RESEARCH DESIGN AND METHODS: We followed 85;060 women and 42;872 men who had no history of diabetes; cardiovascular disease; or cancer at baseline. Magnesium intake was evaluated using a validated food frequency questionnaire every 2-4 years. After 18 years of follow-up in women and 12 years in men; we documented 4;085 and 1;333 incident cases of type 2 diabetes; respectively. RESULTS: After adjusting for age; BMI; physical activity; family history of diabetes; smoking; alcohol consumption; and history of hypertension and hypercholesterolemia at baseline; the relative risk (RR) of type 2 diabetes was 0.66 (95% CI 0.60-0.73; P for trend <0.001) in women and 0.67 (0.56-0.80; P for trend <0.001) in men; comparing the highest with the lowest quintile of total magnesium intake. The RRs remained significant after additional adjustment for dietary variables; including glycemic load; polyunsaturated fat; trans fat; cereal fiber; and processed meat in the multivariate models. The inverse association persisted in subgroup analyses according to BMI; physical activity; and family history of diabetes. CONCLUSIONS: Our findings suggest a significant inverse association between magnesium intake and diabetes risk. This study supports the dietary recommendation to increase consumption of major food sources of magnesium; such as whole grains; nuts; and green leafy vegetables.
Effect of diets enriched in almonds on insulin action and serum lipids in adults with normal glucose tolerance or type 2 diabetes.
BACKGROUND: Nuts appear to have cardiovascular benefits but their effect in diabetic patients is unclear. OBJECTIVE: The objective was to assess effects of almond-enriched diets on insulin sensitivity and lipids in patients with normoglycemia or type 2 diabetes. DESIGN: Study 1 assessed the effect of almonds on insulin sensitivity in 20 free-living healthy volunteers who received 100 g almonds/d for 4 wk. Study 2 was a randomized crossover study that compared 4 diets in 30 volunteers with type 2 diabetes: 1) high-fat; high-almond (HFA; 37% total fat; 10% from almonds); 2) low-fat; high-almond (LFA; 25% total fat; 10% from almonds); 3) high-fat control (HFC; 37% total fat; 10% from olive or canola oil); and 4) low-fat control (LFC; 25% total fat; 10% from olive or canola oil). After each 4-wk diet; serum lipids and oral glucose tolerance were measured. RESULTS: In study 1; almond consumption did not change insulin sensitivity significantly; although body weight increased and total and LDL cholesterol decreased by 21% and 29%; respectively (P < 0.05). In study 2; total cholesterol was lowest with the HFA diet (4.46 +/- 0.14; 4.52 +/- 0.14; 4.63 +/- 0.14; and 4.63 +/- 0.14 mmol/L with the HFA; HFC; LFA; and LFC diets; respectively; P = 0.0004 for fat level). HDL cholesterol was significantly lower with the almond diets (P = 0.002); however; no significant effect of fat source on LDL:HDL was observed. Glycemia was unaffected. CONCLUSIONS: Almond-enriched diets do not alter insulin sensitivity in healthy adults or glycemia in patients with diabetes. Almonds had beneficial effects on serum lipids in healthy adults and produced changes similar to high monounsaturated fat oils in diabetic patients.
Glycemic index of foods: a physiological basis for carbohydrate exchange.
The determine the effect of different foods on the blood glucose; 62 commonly eaten foods and sugars were fed individually to groups of 5 to 10 healthy fasting volunteers. Blood glucose levels were measured over 2 h; and expressed as a percentage of the area under the glucose response curve when the same amount of carbohydrate was taken as glucose. The largest rises were seen with vegetables (70 +/- 5%); followed by breakfast cereals (65 +/- 5%); cereals and biscuits (60 +/- 3%); fruit (50 +/- 5%); dairy products (35 +/- 1%); and dried legumes (31 +/- 3%). A significant negative relationship was seen between fat (p less than 0.01) and protein (p less than 0.001) and postprandial glucose rise but not with fiber or sugar content.
Nut and peanut butter consumption and risk of type 2 diabetes in women.
CONTEXT: Nuts are high in unsaturated (polyunsaturated and monounsaturated) fat and other nutrients that may improve glucose and insulin homeostasis. OBJECTIVE: To examine prospectively the relationship between nut consumption and risk of type 2 diabetes. DESIGN; SETTING; AND PARTICIPANTS: Prospective cohort study of 83 818 women from 11 states in the Nurses' Health Study. The women were aged 34 to 59 years; had no history of diabetes; cardiovascular disease; or cancer; completed a validated dietary questionnaire at baseline in 1980; and were followed up for 16 years. MAIN OUTCOME MEASURE: Incident cases of type 2 diabetes. RESULTS: We documented 3206 new cases of type 2 diabetes. Nut consumption was inversely associated with risk of type 2 diabetes after adjustment for age; body mass index (BMI); family history of diabetes; physical activity; smoking; alcohol use; and total energy intake. The multivariate relative risks (RRs) across categories of nut consumption (never/almost never;
Low-glycemic-index starchy foods in the diabetic diet.
Eight patients with noninsulin-dependent diabetes underwent two 2-wk study periods in random order during which they were provided with carbohydrate foods with either a high or low glycemic index (GI). Over both high-GI and low-GI periods there were significant reductions in body weight; serum fructosamine; and cholesterol. Reductions in fasting blood glucose; HbA1c; and urinary c-peptide-to-creatinine ratio were significant only over the low-GI period despite a smaller mean weight loss. Reductions in triglyceride were significant only over the high-GI diet. Inclusion of low-GI foods into diets of patients with diabetes may be an additional measure that favorably influences carbohydrate metabolism without increasing insulin demand.
High monounsaturated fat diets for patients with diabetes mellitus: a meta-analysis.
The most recent position statement on nutrition from the American Diabetes Association recommends an individualized approach to nutrition that is based on the nutritional assessment and desired outcomes of each patient and that takes into consideration patient preferences and control of hyperglycemia and dyslipidemia. To achieve these nutritional goals; either low-saturated-fat; high-carbohydrate diets or high-monounsaturated-fat diets can be advised. A meta-analysis of various studies comparing these two approaches to diet therapy in patients with type 2 diabetes revealed that high-monounsaturated-fat diets improve lipoprotein profiles as well as glycemic control. High-monounsaturated-fat diets reduce fasting plasma triacylglycerol and VLDL-cholesterol concentrations by 19% and 22%; respectively; and cause a modest increase in HDL-cholesterol concentrations without adversely affecting LDL-cholesterol concentrations. Furthermore; there is no evidence that high-monounsaturated-fat diets induce weight gain in patients with diabetes mellitus provided that energy intake is controlled. Therefore; a diet rich in cis-monounsaturated fat can be advantageous for both patients with type 1 or type 2 diabetes who are trying to maintain or lose weight.
Structured Dietary Advice Incorporating Walnuts Achieves Optimal Fat and Energy Balance in Patients with Type 2 Diabetes Mellitus.
OBJECTIVE: A cardioprotective dietary fat profile is recommended for the treatment of type 2 diabetes. The clinical feasibility of advice strategies targeting specific fatty acid intakes and the extent to which they can be achieved by free-living populations needs to be tested. Walnuts; with high n-3 polyunsaturated fatty acid (PUFA) content; may help optimize fatty acid intakes; but regular consumption might increase total fat and energy intakes. This study examined whether advice that refers to a total dietary pattern inclusive of walnuts would result in low-fat energy-controlled diets with optimal dietary fat proportions for patients with type 2 diabetes mellitus. RESEARCH DESIGN AND METHODS: A parallel-design; controlled trial was completed by 55 free-living men and women with established type 2 diabetes mellitus. Participants were randomly assigned to one of three groups: low-fat (general advice); modified low-fat (total diet advice using exchange lists to differentiate PUFA-rich foods); walnut-specific (modified low fat including 30 g walnuts/day). Dietary intakes and clinical outcomes were measured at baseline; and at 3 and 6 months. Dietary goals were: less than 10% of energy from saturated fat; 7% to 10% of energy from PUFA; adequate n-3 PUFA (>or=2.22 g alpha-linolenic acid; >or=0.65 g eicosapentaenoic acid [EPA]+docosahexaenoic acid [DHA]) and n-6 to n-3 ratio less than 10. The proportion of subjects achieving dietary goals and major food sources of fat were determined. RESULTS: At baseline; dietary intakes were not significantly different between groups. No group and few individuals (10%) were consuming adequate PUFA; with meat the main source of dietary fat (22% total dietary fat). At 3 and 6 months; energy and macronutrient intakes were similar among groups. The walnut group; however; was the only group to achieve all fatty acid intake targets (P <.01); and had the greatest proportion of subjects achieving targets ( P <.05). Walnuts were the main source of dietary fat (31%) and n-3 PUFA (50%); while 350 g oily fish/day provided a further 17% n-3 PUFA consumed by this group. CONCLUSIONS: Specific advice for the regular inclusion of walnuts in the context of the total diet helps achieve optimal fat intake proportions without adverse effects on total fat or energy intakes in patients with type 2 diabetes mellitus.
Diet composition and the metabolic syndrome: what is the optimal fat intake?
Two cholesterol-raising fatty acids in the diet; saturated fatty acids and trans fatty acids; increase the serum low-density lipoprotein cholesterol concentration. This fact justifies the recommendation of a reduced intake of cholesterol-raising fatty acids. Emerging data suggest that diets higher in unsaturated fatty acids; particularly monounsaturated fatty acids; have several advantages over high-carbohydrate intakes. This advantage appears to hold; particularly for populations having a high prevalence of insulin resistance; such as the US population. If the US public were to modify its eating habits in the direction of better weight control and more exercise; higher intakes of carbohydrate might be better tolerated. At the same time; the experience with the Mediterranean population reveals that in healthier populations; diets relatively high in unsaturated fatty acids are well tolerated and are associated with a low prevalence of both coronary heart disease and type 2 diabetes.