Dietary glycemic index, glycemic load, fiber, simple sugars, and insulin resistance: the Inter99 study

Use of intensified comprehensive cardiac rehabilitation to improve risk factor control in patients with type 2 diabetes mellitus or impaired glucose tolerance--the randomized DANish StUdy of impaired glucose metabolism in the settings of cardiac rehabilitation (DANSUK) study

BACKGROUND

The DANish StUdy of impaired glucose metabolism in the settings of cardiac rehabilitation (DANSUK) examined the effect of an intensified multifactorial intervention on risk factor profile in 104 patients with type 2 diabetes mellitus (T2DM) or impaired glucose tolerance (IGT) attending hospital-based outpatient comprehensive cardiac rehabilitation (CCR) compared to usual care (UC).

METHODS

Patients with ischemic heart disease (67%), congestive heart failure (7%), or at least 3 risk factors for ischemic heart disease (26%) discharged from 1 coronary care unit were referred to CCR. Of 473 eligible individuals, 201 agreed to participate in the study, and 52% had T2DM or IGT. Patients randomized to CCR received a stepwise implementation of behavioral modification and pharmacotherapy.

RESULTS

After 1 year, patients with T2DM in the CCR group experienced a mean change in HbA1c of -0.65% +/- 0.9% compared with a mean change of -0.08% +/- 0.7% in the UC group (P < .05). Mean change in systolic and diastolic blood pressures was -8 +/- 15 and -5 +/- 9 mm Hg in the CCR group compared with a mean change of -0.8 +/- 15 and -0.2 +/- 7 mm Hg in the UC group (P < .05). Patients with IGT attending CCR obtained a significantly higher exercise capacity compared with patients in the UC group (P < .05).

CONCLUSIONS

In a group of patients with impaired glucose metabolism attending CCR, an intensified multifactorial intervention with an integrated diabetes module was more efficient in improving risk factor control than UC. Besides the improvement in the exercise capacity of patients with IGT, in patients with T2DM, both HbA1c and blood pressure were lowered to a level that has been shown to reduce both cardiac and diabetic complications. These findings have important implications for patients with impaired glucose metabolism in the future settings of CCR.

[Association between dietary carbohydrates and type 2 diabetes mellitus: epidemiological evidence]

The prevalence of type 2 diabetes has been escalating throughout the world and usual food consumption is regarded as one of the most important environmental determinants for chronic diseases. Thus, the role of type and quality of carbohydrates on the etiology of type 2 diabetes is still poorly understood. The present review discusses the available epidemiological evidence regarding the effect of the type and source of carbohydrate of the usual diet and the risk of type 2 diabetes in adults. Although epidemiological investigations support the hypothesis for a potential risk effect of high glycemic index and low fiber content diets for diabetes, the results are controversial and the benefit may be related to the magnesium content of the structure of the grains, suggesting the relevance of taking into account the food sources instead of nutrients on investigations of diet and risk of chronic diseases. The available evidence suggests that eating a diet rich in whole grain cereals and vegetables and low in refined grains, sucrose and fructose contents is beneficial in the prevention of diabetes. Thus, more clinical trials are required to support the associations and establish biologically plausible pathways.

Glycaemic index and metabolic disease risk

There is growing evidence that the type of carbohydrate consumed is important in relation to metabolic disease risk, and there is currently particular interest in the role of low-glycaemic-index (GI) foods. Observational studies have associated low-GI diets with decreased risk of type 2 diabetes and CHD, and improvements in various metabolic risk factors have been seen in some intervention studies. However, findings have been mixed and inconsistent. There are a number of plausible mechanisms for the effects of these foods on disease risk, which arise from the differing metabolic responses to low- and high-GI foods, with low-GI foods resulting in reductions in hyperglycaemia, hyperinsulinaemia and late postprandial circulating NEFA levels. Low-GI foods may also increase satiety and delay the return of hunger compared with high-GI foods, which could translate into reduced energy intake at later time points. However, the impact of a low-GI diet on body weight is controversial, with many studies confounded by dietary manipulations that differ in aspects other than GI. There is currently much interest in GI from scientists, health professionals and the public, but more research is needed before clear conclusions can be drawn about relationships with metabolic disease risk.

Mediterranean diet and metabolic syndrome: a cross-sectional study in the Canary Islands

Objective

Assessment of relation between metabolic syndrome (MS) and Mediterranean diet (MD) adherence.

Design

Cross-sectional study. ATP III definition of MS was used. Adherence to MD was assessed with a Food Frequency Questionnaire. Intakes of cereal, fruit, legumes, vegetables, fish, nuts, monounsaturated to saturated ratio, alcohol from red wine, whole-fat dairy products and red meat were considered.

Setting

Representative sample of population from the Canary Islands (Spain) participating in the Canarian Nutrition Survey (ENCA).

Subjects

578 adults>18 years.

Results

Of the subjects, 24.4% presented MS. Once adjusted, MD adherence was not related to MS prevalence, but subjects in the third tertile of adherence presented 70% lower prevalence of the blood pressure criteria and 2.5 times more prevalence of the glycaemia criteria with respect to the first tertile. Red meat intake was associated with higher prevalence of blood pressure criteria. Moderate alcohol intake from red wine was associated with lower prevalence of these criteria in women and lower prevalence of HDL cholesterol criteria in men. Fruit intake showed a protective effect on triglyceride criteria, whereas vegetable intake was associated with higher prevalence of this criterion. Cereals' intake showed a protective effect over insulin resistance measured by high insulinaemia level. Fruit intake showed a significative protective effect over high Homeostasis Model Assessment index. Whole-fat dairy products showed a significant protective effect on the glycaemia criteria. High monounsaturated to saturated fatty acid intake showed a protective effect on insulin resistance.

Conclusions

Some components of the MD showed a protective effect on the MS and its components.

Dietary habits and nutrient intake in non-alcoholic steatohepatitis

OBJECTIVE

Non-alcoholic steatohepatitis (NASH) is one of the most important emerging health issues. Insulin resistance and metabolic syndrome play a central role in the pathogenesis of NASH. Intake of nutrients strongly affects insulin resistance, carbohydrate and lipid metabolism, and hepatic steatosis. However, there are few reports about the intake of various nutrients in non-alcoholic fatty liver disease. In this work, we identified the characteristics of dietary habits and nutrient intake in patients with NASH.

METHODS

Twenty-eight patients with NASH and 18 with simple steatosis (FL) were diagnosed from histologic findings, and their dietary habits and intake of nutrients were analyzed by detailed questioning by physicians and dieticians.

RESULTS

There was an excess intake of carbohydrates/energy in patients with NASH 20-59 y of age compared with patients with FL. Among carbohydrates, intake of simple carbohydrates was higher in those with NASH. There also was a low intake of protein/energy in patients with NASH 40-59 y of age and a low intake of zinc in those 20-59 y of age compared with patients with FL. Ratio of intake of polyunsaturated fatty acid to saturated fatty acid was lower in patients with NASH and those with FL compared with the general Japanese subjects.

CONCLUSION

These results suggest that imbalanced diets play important roles in development and progression of NASH and correction of these diets may be necessary in patients with NASH.

Association between dietary glycemic index, glycemic load, and body mass index in the Inter99 study: is underreporting a problem?

BACKGROUND

The few studies examining the potential associations between glycemic index (GI), glycemic load (GL), and body mass index (BMI) have provided no clear pictures. Underreporting of energy intake may be one explanation for this.

OBJECTIVE

We examined the associations between GI, GL, and BMI by focusing on the confounding factor of total energy intake and the effect of exclusion of low energy reporters (LERs).

DESIGN

This was a cross-sectional study of 6334 subjects aged 30-60 y. Dietary intake was estimated from a food-frequency questionnaire. GI and GL were estimated by using white bread as the reference food. Underreporting of energy intake was assessed as reported energy intake divided by basal metabolic rate (EI/BMR); LERs were defined as those having an EI/BMR < 1.14. Univariate and multiple linear regression models were used to test for associations between GI, GL, and BMI. The confounders were sex, age, smoking, physical activity, alcohol intake, and energy intake. All analyses were conducted on 1) the entire population and 2) a subsample excluding LERs.

RESULTS

In the univariate analyses of the entire population, GL was inversely associated with BMI. No association was observed for GI. After full adjustment (including energy intake), both GI and GL were positively associated with BMI. When LERs were excluded, GL was positively associated with BMI in all analyses, and GI was positively associated with BMI in the multiple analyses.

CONCLUSIONS

We showed a positive association between GI, GL, and BMI. Energy adjustment and the exclusion of LERs significantly affected the results of the analysis; thus, we stress the importance of energy adjustment.

Thematic review series: Patient-Oriented Research. Nutritional determinants of insulin resistance

Interpreting the literature relating to the nutritional determinants of insulin resistance is complicated by the wide range of methods used to determine insulin sensitivity. Excess adiposity is unquestionably the most important determinant of insulin resistance, although the effect may be tempered by a relatively high proportion of lean body mass. Weight loss is associated with improved insulin sensitivity. Thus, diet-related factors that promote excessive energy intake may be regarded as promoters of insulin resistance. In the context of energy balance, diets characterized by high intakes of saturated fat and low intakes of dietary fiber are associated with reduced insulin sensitivity. Total fat intakes greater than the usually consumed range appear to promote insulin resistance, although the relative proportions of total fat and carbohydrate within the usual range appear unimportant. Monounsaturated fatty acids with a cis configuration and fiber-rich carbohydrate foods appear to be appropriate substitutes for saturated fatty acids and rapidly digested glycemic carbohydrates. In animal studies, n-3 unsaturated fatty acids have been shown to enhance insulin sensitivity and fructose and sucrose to increase insulin resistance. However, human data are limited. Large prospective studies currently being conducted should confirm the most appropriate macronutrient composition of diets for preventing and treating insulin resistance as well as establishing whether a range of candidate genes explains the variation in response to dietary change.

Metabolic effects of fructose

PURPOSE OF REVIEW

Fructose is consumed in significant amounts in Western diets. An increase in fructose consumption over the past 10-20 years has been linked with a rise in obesity and metabolic disorders. Fructose/sucrose produces deleterious metabolic effects in animal models. This raises concern regarding the short-term and long-term effects of fructose and its risk in humans.

RECENT FINDINGS

In rodents, fructose stimulates lipogenesis and leads to hepatic and extrahepatic insulin resistance, dyslipidaemia and high blood pressure. Insulin resistance appears to be related to ectopic lipid deposition. In humans, short-term fructose feeding increases de-novo lipogenesis and blood triglycerides and causes hepatic insulin resistance. There is presently no evidence for fructose-induced muscle insulin resistance in humans. The cellular mechanisms underlying the metabolic effects of fructose involve production of reactive oxygen species, activation of cellular stress pathways and possibly an increase in uric acid synthesis.

SUMMARY

Consuming large amounts of fructose can lead to the development of a complete metabolic syndrome in rodents. In humans, fructose consumed in moderate to high quantities in the diet increases plasma triglycerides and alters hepatic glucose homeostasis, but does not appear to cause muscle insulin resistance or high blood pressure in the short term. Further human studies are required to delineate the effects of fructose in humans.

Urinary C-peptide excretion in free-living healthy children is related to dietary carbohydrate intake but not to the dietary glycemic index

This study first examined whether urinary C-peptide (UCP), stored at -20 degrees C, remains stable over the long term, and second, whether the dietary glycemic index (GI) and the glycemic load (GL: GI x g carbohydrates) are related to the 24-h UCP excretion of healthy children. Participants in the Dortmund Nutrition and Anthropometric Longitudinally Designed Study with 24-h urine collections and a simultaneously completed weighed dietary record were included. From these, 3 comparable groups of 7- to 8-y-old children (n = 40 each) from 1990, 1996, and 2002 were randomly selected (total n = 120). C-peptide was measured with a 1-site ELISA. A GI value was assigned to all recorded foods containing carbohydrates (CHO). Statistical equivalence tests corroborated that UCP excretion in the 3 sampling periods was equivalent when corrected for body weight and protein intake (P < 0.05). UCP excretion was associated with the GL after adjustment for body weight, protein, and fiber intake [mean UCP (95% CI) in GL tertiles 1-3: 6.19 (5.37, 7.14) vs. 7.82 (6.77, 9.02) vs. 7.76 (6.71, 8.97) nmol/d, P for difference 0.04]. GI was not significantly related to UCP excretion [adjusted means (95% CI): 7.27 (6.28, 8.41) vs. 6.51 (5.64, 7.51) vs. 7.94 (6.86, 9.18), P for difference 0.2]. In conclusion, UCP retrospectively measured with a 1-site ELISA remained stable for up to 12 y (from 1990 until 2002). The observed positive relation of UCP with GL appears to result largely from its association with the amount of CHO, whereas dietary GI may be relevant only at higher intake levels.

Perilipin gene variation determines higher susceptibility to insulin resistance in Asian women when consuming a high-saturated fat, low-carbohydrate diet

OBJECTIVE

To investigate the association between genetic variation in the adipocyte protein perilipin (PLIN) and insulin resistance in an Asian population as well as to examine their modulation by macronutrient intake.

RESEARCH DESIGN AND METHODS

A nationally representative sample (Chinese, Malays, and Indians) was selected in the Singapore National Health Survey following the World Health Organization-recommended model for field surveys of diabetes. A total of 1,909 men and 2,198 women (aged 18-69 years) were studied. Genetic (PLIN 11482G-->A and 14995A-->T), lifestyle, clinical, and biochemical data were obtained. Homeostasis model assessment of insulin resistance (HOMA-IR) was used to evaluate insulin resistance. Diet was measured by a validated food frequency questionnaire in one of every two subjects.

RESULTS

We did not find a significant between-genotype difference in insulin resistance measures. However, in women we found statistically significant gene-diet interactions (recessive model) between PLIN 11482G-->A/14995A-->T polymorphisms (in high linkage disequilibrium) and saturated fatty acids (SFAs; P = 0.003/0.005) and carbohydrate (P = 0.004/0.012) in determining HOMA-IR. These interactions were in opposite directions and were more significant for 11482G-->A, considered the tag polymorphism. Thus, women in the highest SFA tertile (11.8-19%) had higher HOMA-IR (48% increase; P trend = 0.006) than women in the lowest (3.1-9.4%) only if they were homozygotes for the PLIN minor allele. Conversely, HOMA-IR decreased (-24%; P trend = 0.046) as carbohydrate intake increased. These effects were stronger when SFAs and carbohydrate were combined as an SFA-to-carbohydrate ratio. Moreover, this gene-diet interaction was homogeneously found across the three ethnic groups.

CONCLUSIONS

PLIN 11482G-->A/14995A-->T polymorphisms modulate the association between SFAs/carbohydrate in diet and insulin resistance in Asian women.

High-fibre, low-fat diet predicts long-term weight loss and decreased type 2 diabetes risk: the Finnish Diabetes Prevention Study

AIMS/HYPOTHESIS

The aim of this study was to investigate the association of dietary macronutrient composition and energy density with the change in body weight and waist circumference and diabetes incidence in the Finnish Diabetes Prevention Study.

SUBJECTS AND METHODS

Overweight, middle-aged men (n=172) and women (n=350) with impaired glucose tolerance were randomised to receive either 'standard care' (control) or intensive dietary and exercise counselling. Baseline and annual examinations included assessment of dietary intake with 3-day food records and diabetes status by repeated 75-g OGTTs. For these analyses the treatment groups were combined and only subjects with follow-up data (n=500) were included.

RESULTS

Individuals with low fat (<median) and high fibre (>median) intakes lost more weight compared with those consuming a high-fat (>median), low-fibre (<median) diet (3.1 vs 0.7 kg after 3 years). In separate models, hazard ratios for diabetes incidence during a mean follow-up of 4.1 years were (highest compared with lowest quartile) 0.38 (95% CI 0.19-0.77) for fibre intake, 2.14 (95% CI 1.16-3.92) for fat intake, and 1.73 (95% CI 0.89-3.38) for saturated-fat intake, after adjustment for sex, intervention assignment, weight and weight change, physical activity, baseline 2-h plasma glucose and intake of the nutrient being investigated. Compared with the low-fat/high-fibre category, hazard ratios were 1.98 (95% CI 0.98-4.02), 2.68 (95% CI 1.40-5.10), and 1.89 (95% CI 1.09-3.30) for low-fat/low-fibre, high-fat/high-fibre, and high-fat/low-fibre, respectively.

CONCLUSIONS/INTERPRETATION

Dietary fat and fibre intake are significant predictors of sustained weight reduction and progression to type 2 diabetes in high-risk subjects, even after adjustment for other risk factors.

Dietary glycemic index and glycemic load, carbohydrate and fiber intake, and measures of insulin sensitivity, secretion, and adiposity in the Insulin Resistance Atherosclerosis Study

OBJECTIVE

We studied the association of digestible carbohydrates, fiber intake, glycemic index, and glycemic load with insulin sensitivity (S(I)), fasting insulin, acute insulin response (AIR), disposition index, BMI, and waist circumference.

RESEARCH DESIGN AND METHODS

Data on 979 adults with normal (67%) and impaired (33%) glucose tolerance from the Insulin Resistance Atherosclerosis Study (1992-1994) were analyzed. Usual dietary intake was assessed via a 114-item interviewer-administered food frequency questionnaire from which nutrient intakes were estimated. Published glycemic index values were assigned to food items and average dietary glycemic index and glycemic load calculated per subject. S(I) and AIR were determined by frequently sampled intravenous glucose tolerance test. Disposition index was calculated by multiplying S(I) with AIR. Multiple linear regression modeling was employed.

RESULTS

No association was observed between glycemic index and S(I), fasting insulin, AIR, disposition index, BMI, or waist circumference after adjustment for demographic characteristics or family history of diabetes, energy expenditure, and smoking. Associations observed for digestible carbohydrates and glycemic load, respectively, with S(I), insulin secretion, and adiposity (adjusted for demographics and main confounders) were entirely explained by energy intake. In contrast, fiber was associated positively with S(I) and disposition index and inversely with fasting insulin, BMI, and waist circumference but not with AIR.

CONCLUSION

Carbohydrates as reflected in glycemic index and glycemic load may not be related to measures of insulin sensitivity, insulin secretion, and adiposity. Fiber intake may not only have beneficial effects on insulin sensitivity and adiposity, but also on pancreatic functionality.

Independent association between triglycerides and coronary artery disease in Taiwanese type 2 diabetic patients

BACKGROUND

This study evaluated the association between triglycerides (TG) and coronary artery disease (CAD) in Taiwanese adults with type 2 diabetes mellitus (T2DM).

METHODS

A total of 1150 patients (542 men and 608 women) aged 62.5+/-11.6 years were studied. CAD was diagnosed by history or an abnormal electrocardiogram (coronary probable or possible by Minnesota codes). Age, body mass index (BMI), smoking, use of insulin, anti-hypertensive agents and lipid-lowering agents, fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), systolic blood pressure (SBP), diastolic blood pressure (DBP), serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c) were considered as potential confounders.

RESULTS

Patients with CAD were older, had higher prevalences of use of anti-hypertensive and lipid-lowering agents, and had higher BMI, SBP, DBP and TG. CAD increased significantly with increasing quartiles of TG (P-trend < 0.001). Ln(TG) was significantly correlated with BMI, FPG, HbA1c, DBP, TC, HDL-c (inversely) and LDL-c. Ln(TG) was associated with CAD with an unadjusted odds ratio of 1.411 (1.145-1.740). The odds ratio after adjustment for all confounders was slightly attenuated but still statistically significant: 1.380 (1.043-1.826). None of the other lipid parameters of TC, HDL-c and LDL-c were significantly associated with CAD in logistic models when they were entered for adjustment either separately or simultaneously. Sensitivity analyses by using history alone or history and coronary probable as diagnostic criteria for CAD did not change the association between TG and CAD.

CONCLUSIONS

TG is an independent risk factor for CAD in Taiwanese T2DM, independent of TC, HDL-c, LDL-c or other confounders.