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

Dietary fiber does not displace energy but is associated with decreased serum cholesterol concentrations in healthy children

BACKGROUND

Dietary fiber has health benefits, but fiber recommendations for children are controversial because fiber may displace energy.

OBJECTIVE

The objective was to longitudinally evaluate dietary fiber intake in children and to study associations between growth variables, serum cholesterol concentrations, and intakes of fiber, energy, and nutrients.

DESIGN

Altogether, 543 children from a prospective randomized atherosclerosis prevention trial (the Special Turku Coronary Risk factor Intervention Project; STRIP) participated in this study between the ages of 8 mo and 9 y. The intervention children (n = 264) were counseled to replace part of saturated fat with unsaturated fat. Nutrient intakes, weight, height, and serum total, HDL-, and LDL-cholesterol and triglyceride concentrations were analyzed. Children were divided into 3 groups according to mean dietary fiber intake in foods: low (lowest 10%), high (highest 10%), and average (middle 80%) fiber intakes.

RESULTS

Fiber intake associated positively with energy intake and inversely with fat intake. Children with a high fiber intake received more vitamins and minerals than did children in other groups. In longitudinal growth analyses, weights and heights were similar in all 3 fiber intake groups, and fiber intake (g/d) associated positively with weight gain between 8 mo and 2 y. Serum cholesterol concentrations decreased with increasing fiber intakes. Children in the intervention group had a higher fiber intake than did the control children during the entire follow-up period.

CONCLUSION

Fiber intake did not displace energy or disturb growth between 13 mo and 9 y of age. Serum cholesterol values correlated inversely with fiber intake, which indicated that part of the cholesterol-lowering intervention effect in the STRIP project may have been explained by dietary fiber.

Association of glycemic load with cardiovascular disease risk factors: the Women's Health Initiative Observational Study

OBJECTIVE

Associations between dietary glycemic load (GL) and cardiovascular disease risk factors, including plasma lipoprotein/lipid levels, blood pressure, and glucose metabolism factors, in the Women's Health Initiative Observational Study were examined.

METHODS

A random sample of 878 Observational Study participants (postmenopausal women 50-79 y of age) with baseline blood measurements (647 white, 104 black, 127 Hispanic) was included. Dietary GL was estimated from baseline food-frequency questionnaires, which assessed dietary intake over the previous 3 mo. At the baseline visit, participants completed demographic and health habit questionnaires, fasting blood samples were collected, anthropometric measurements were completed, and blood pressure was assessed.

RESULTS

In all participants combined, GL was inversely associated with high-density lipoprotein cholesterol (P for trend = 0.004) and positively associated with log(10)-transformed triacylglycerols (P = 0.008). Although there were no statistically significant interactions of race/ethnicity with associations between GL and cardiovascular disease risk factors, stratified results were suggestive, showing that GL was positively associated with total cholesterol (P = 0.018) and low-density lipoprotein cholesterol (P = 0.038) in Hispanics. In white subjects, there was a trend of reduced high-density lipoprotein cholesterol with higher GL (P = 0.003), whereas GL was positively associated with log(10)-transformed triacylglycerols (P = 0.015). Associations between GL and high-density lipoprotein cholesterol and between GL and triacylglycerols also differed by body mass index, although the interactions were not statistically significant.

CONCLUSION

Among these generally healthy postmenopausal women, GL was associated with high-density lipoprotein cholesterol and triacylglycerols. Suggestive effects of race/ethnicity and body mass index on these associations need to be confirmed in larger studies.

Design and methods for testing a simple dietary message to improve weight loss and dietary quality

BACKGROUND

The current food pyramid guidelines have been criticized because of their complexity and the knowledge required for users to understand the recommendations. Simplification of a dietary message to focus on a single key aspect of dietary quality, e.g., fiber intake, may make the message much easier to comprehend and adhere, such that respondents can achieve greater weight loss, better dietary quality and overall metabolic health.

METHODS AND DESIGN

This is a randomized controlled clinical trial with two equal sized arms. In total, 240 obese adults who meet diagnostic criteria for the metabolic syndrome will be randomized to one of the two conditions: 1) a high fiber diet and 2) the American Heart Association (AHA) diet. In the high fiber diet condition, patients will be given instruction only on achieving daily dietary fiber intake of 30 g or more. In the AHA diet condition, patients will be instructed to make the several dietary changes recommended by the AHA 2006 guidelines. The trial examines participant weight loss and dietary quality as well as changes in components of the metabolic syndrome, inflammatory biomarkers, low-density lipoprotein cholesterol levels, insulin levels, and glycosolated hemoglobin. Potential mediators, i.e., diet adherence and perceived ease of the diet, and the intervention effect on weight change will also be examined.

DISCUSSIONS

The purpose of this paper is to outline the study design and methods for testing the simple message of increasing dietary fiber. If the simple dietary approach is found efficacious for weight loss; and, improves dietary quality, metabolic health, and adherence, it might then be used to develop a simple public health message.

TRIAL REGISTRATION

NCT00911885.

Dietary patterns are associated with metabolic syndrome in adult Samoans

The prevalence of metabolic syndrome has reached epidemic levels in the Samoan Islands. In this cross-sectional study conducted in 2002-2003, dietary patterns were described among American Samoan (n = 723) and Samoan (n = 785) adults (> or =18 y) to identify neo-traditional and modern eating patterns and to relate these patterns to the presence of metabolic syndrome using Adult Treatment Panel III criteria. The neo-traditional dietary pattern, similar across both polities, was characterized by high intake of local foods, including crab/lobster, coconut products, and taro, and low intake of processed foods, including potato chips and soda. The modern pattern, also similar across both polities, was characterized by high intake of processed foods such as rice, potato chips, cake, and pancakes and low intake of local foods. The neo-traditional dietary pattern was associated with significantly higher serum HDL-cholesterol in American Samoa (P-trend = 0.05) and a decrease in abdominal circumference in American Samoa and Samoa (P-trend = 0.004 and 0.01, respectively). An inverse association was found with metabolic syndrome, although it did not reach significance (P = 0.23 in American Samoa; P = 0.13 in Samoa). The modern pattern was significantly positively associated with metabolic syndrome in Samoa (prevalence ratio = 1.21 for the fifth compared with first quintile; 95% CI: 0.93.1.57; P-trend = 0.05) and with increased serum triglyceride levels in both polities (P < 0.05). Reduced intake of processed foods high in refined grains and adherence to a neo-traditional eating pattern characterized by plant-based fiber, seafood, and coconut products may help to prevent growth in the prevalence of metabolic syndrome in the Samoan islands.

Effects of a fibre-enriched milk drink on insulin and glucose levels in healthy subjects

Background

The glycaemic response to foods is dependent on the quality and content of carbohydrates. Carbohydrates in the form of dietary fibre have favourable effects on insulin and glucose metabolism and may help to control energy intake. Dairy products have a relatively low carbohydrate content, and most of the carbohydrate is in the form of lactose which causes gastrointestinal symptoms in part of the population. In order to avoid these symptoms, dairy products can be replaced with lactose-free dairy products which are on the market in many parts of the world. However, the effects of lactose-free products on insulin and glucose metabolism have not been studied.

Methods

In the present study, we investigated the effects of 1) a lactose-free milk drink, 2) a novel fibre-enriched, fat- and lactose-free milk drink and 3) normal fat-free milk on serum glucose and insulin levels and satiety using a randomized block design. Following an overnight fast, 26 healthy volunteers ingested 200 ml of one of these drinks on three non-consecutive days. Insulin and glucose levels and subjective satiety ratings were measured before the ingestion of the milk product and 20, 40, 60, 120 and 180 minutes after ingestion. The responses were calculated as the area under the curve subtracted by the baseline value (AUC minus baseline).

Results

The insulin response was significantly lower for the fibre-enriched milk drink than it was for the other milk products (AUC, P = 0.007). There were no differences in the response for glucose or in the AUC for the subjective satiety ratings between the studied milk products.

Conclusion

The present results suggest that this novel milk drink could have positive effects on insulin response.

Glycaemic index and glycaemic load values of a selection of popular foods consumed in Hong Kong

The objective of the present paper is to provide glycaemic index (GI) and glycaemic load (GL) values for a variety of foods that are commonly consumed in Hong Kong and expand on the international GI table of Chinese foods. Fasted healthy subjects were given 50 g of available carbohydrate servings of a glucose reference, which was tested twice, and test foods of various brands of noodles (n5), instant cereals (n3) and breads (n2), which were tested once, on separate occasions. For each test food, tests were repeated in ten healthy subjects. Capillary blood glucose was measured via finger-prick samples in fasting subjects ( − 5, 0 min) and at 15, 30, 45, 60, 90 and 120 min after the consumption of each test food. The GI of each test food was calculated geometrically by expressing the incremental area under the blood glucose response curve (IAUC) of each test food as a percentage of each subject's average IAUC for the reference food. GL was calculated as the product of the test food's GI and the amount of available carbohydrate in a reference serving size. The majority of GI values of foods tested were medium (a GI value of 56–69) to high (a GI value of 70 or more) and compared well with previously published values. More importantly, our dataset provides GI values of ten foods previously untested and presents values for foods commonly consumed in Hong Kong.

Glycaemic load is associated with insulin resistance in older Australian women

BACKGROUND/OBJECTIVES

Diets with a high postprandial glycaemic response may contribute to the long-term development of insulin resistance and diabetes; however, earlier epidemiological studies are conflicting on whether glycaemic index (GI) or glycaemic load (GL) are dietary factors associated with the progression. Our objectives were to estimate GI and GL in a group of older women, and evaluate cross-sectional associations with insulin resistance.

SUBJECTS/METHODS

The subjects were 329 Australian women aged 42-81 years participating in year 3 of the Longitudinal Assessment of Ageing in Women study. Dietary intakes were assessed by diet history interviews and analysed using a customized GI database. Insulin resistance was defined as a homeostasis model assessment value of >3.99, based on fasting blood glucose and insulin concentrations.

RESULTS

GL was significantly higher in the 26 subjects who were classified as insulin resistant compared with subjects who were not (134+/-33 versus 114+/-24, P<0.001). In a logistic regression model, an increment of 15 GL units increased the odds of insulin resistance by 2.09 (95% confidence interval (1.55, 2.80), P<0.001) independently of potential confounding variables. No significant associations were found when insulin resistance was assessed as a continuous variable.

CONCLUSIONS

The results of this cross-sectional study support the concept that diets with a higher GL are associated with an increased risk of insulin resistance. Further studies are required to determine whether reducing the glycaemic intake, either by consuming lower GI foods or through smaller serves of carbohydrate, can contribute to a reduction in development of insulin resistance and long-term risk of type II diabetes.

Acute effects of dietary glycemic index on antioxidant capacity in a nutrient-controlled feeding study

Oxidative stress, caused by an imbalance between antioxidant capacity and reactive oxygen species, may be an early event in a metabolic cascade elicited by a high glycemic index (GI) diet, ultimately increasing the risk for cardiovascular disease and diabetes. We conducted a feeding study to evaluate the acute effects of low-GI compared with high-GI diets on oxidative stress and cardiovascular disease risk factors. The crossover study comprised two 10-day in-patient admissions to a clinical research center. For the admissions, 12 overweight or obese (BMI: 27-45 kg/m(2)) male subjects aged 18-35 years consumed low-GI or high-GI diets controlled for potentially confounding nutrients. On day 7, after an overnight fast and then during a 5-h postprandial period, we assessed total antioxidant capacity (total and perchloric acid (PCA) protein-precipitated plasma oxygen radical absorbance capacity (ORAC) assay) and oxidative stress status (urinary F(2alpha)-isoprostanes (F(2)IP)). On day 10, we measured cardiovascular disease risk factors. Under fasting conditions, total antioxidant capacity was significantly higher during the low-GI vs. high-GI diet based on total ORAC (11,736 +/- 668 vs. 10,381 +/- 612 micromol Trolox equivalents/l, P = 0.002) and PCA-ORAC (1,276 +/- 96 vs. 1,210 +/- 96 micromol Trolox equivalents/l, P = 0.02). Area under the postprandial response curve also differed significantly between the two diets for total ORAC and PCA-ORAC. No diet effects were observed for the other variables. Enhancement in plasma total antioxidant capacity occurs within 1 week on a low-GI diet, before changes in other risk factors, raising the possibility that this phenomenon may mediate, at least in part, the previously reported effects of GI on health.

Cross-sectional association of dietary patterns with insulin-resistant phenotypes among adults without diabetes in the Framingham Offspring Study

Cluster analysis is a valuable tool for exploring the health consequences of consuming different dietary patterns. We used this approach to examine the cross-sectional relationship between dietary patterns and insulin-resistant phenotypes, including waist circumference, BMI, fasting insulin, 2 h post-challenge insulin, insulin sensitivity index (ISI0,120), HDL-cholesterol, TAG and blood pressure, using data from the fifth examination cycle of the Framingham Offspring Study. Among 2875 participants without diabetes, we identified four dietary patterns based on the predominant sources of energy: 'Fruits, Reduced Fat Dairy and Whole Grains', 'Refined Grains and Sweets', 'Beer' and 'Soda'. After adjusting for multiple comparisons and potential confounders, compared with the 'Fruits, Reduced Fat Dairy and Whole Grains' pattern, the 'Refined Grains and Sweets' pattern had significantly higher mean waist circumference (92.4 v. 90.5 cm; P = 0.008) and BMI (27.3 v. 26.6 kg/m2; P = 0.02); the 'Soda' pattern had significantly higher mean fasting insulin concentration (31.3 v. 28.0 microU/ml; P < or = 0.001); the 'Beer' pattern had significantly higher mean HDL-cholesterol concentration (1.46 v. 1.31 mmol/l; P < 0.001). No associations were observed between dietary patterns and ISI0,120, TAG, and systolic or diastolic blood pressure. Our findings suggest that consumption of a diet rich in fruits, vegetables, whole grains and reduced-fat dairy protects against insulin-resistant phenotypes and displacing these healthy choices with refined grains, high-fat dairy, sweet baked foods, candy and sugar-sweetened soda may promote insulin-resistant phenotypes.

Randomized control trial to improve adiposity and insulin resistance in overweight Latino adolescents

Few randomized trials attempt to improve insulin sensitivity and associated metabolic risks in overweight Latino youth. The purpose of this study is to examine the effects of a modified carbohydrate nutrition program combined with strength training on insulin sensitivity, adiposity, and other type 2 diabetes risk factors in overweight Latino adolescents. In a 16-week randomized trial, 54 overweight Latino adolescents (15.5 +/- 1.0 years) were randomly assigned to: (i) Control (C; n = 16), (ii) Nutrition (N; n = 21), or (iii) Nutrition + Strength training (N+ST; n = 17). The N group received modified carbohydrate nutrition classes (once per week), while the N+ST received the same nutrition classes plus strength training (twice per week). The following were measured at pre- and postintervention: strength by 1-repetition maximum, dietary intake by 3-day records, body composition by dual-energy X-ray absorptiometry, glucose/insulin indices by oral glucose tolerance test (OGTT) and intravenous glucose tolerance test with minimal modeling. Across intervention group effects were tested using analysis of covariance with post hoc pairwise comparisons. A significant overall intervention effect was found for improvement in bench press (P < 0.001) and reductions in energy (P = 0.05), carbohydrate (P = 0.04) and fat intake (P = 0.03). There were no significant intervention effects on insulin sensitivity, body composition, or most glucose/insulin indices with the exception of glucose incremental area under the curve (IAUC) (P = 0.05), which decreased in the N and N+ST group by 18 and 6.3% compared to a 32% increase in the C group. In conclusion, this intense, culturally tailored intervention resulted in no significant intervention effects on measured risk factors with the exception of a beneficial effect on glycemic response to oral glucose.

Increased interleukin-10 but unchanged insulin sensitivity after 4 weeks of (1, 3)(1, 6)-beta-glycan consumption in overweight humans

Obesity-induced insulin resistance has been suggested to be a systemic inflammatory condition with activation of the innate immune system. Animal studies indicate that certain dietary fibers such as (1,3)(1,6)-beta-D-glycans (BDG) have potent effects on immune activity such as increasing the antiinflammatory cytokine interleukin-10 (IL-10) and reducing the secretion of inflammatory factors. Therefore, we hypothesized that BDG consumption improves inflammatory markers and insulin sensitivity in overweight and obese subjects with moderately increased levels of C-reactive protein, indicating subclinical inflammation. We screened 180 overweight and obese subjects for moderately increased C-reactive protein levels on 2 or more occasions, in the absence of any signs of acute infection. Twelve of the subjects met all inclusion criteria and were investigated in a randomized, double-blind, placebo-controlled, crossover design for 2 x 4 weeks (washout > or =4 weeks). Subjects ingested capsules containing 3 x 0.5 g of highly purified BDG or 3 x 0.5 g of placebo (waxy maize starch) daily. Maintenance of the normal diet of the participants and the correct intake of the capsules were monitored, using 6 x 3-day food recording and counting of the provided capsules. Predefined outcome measures were BDG-induced changes in pro and antiinflammatory markers in circulating blood and gene expression in adipose tissue and peripheral insulin sensitivity expressed as M value. The BDG consumption for 4 weeks significantly increased both circulating levels and adipose tissue messenger RNA (mRNA) expression of the antiinflammatory cytokine IL-10 in overweight and obese humans. Insulin sensitivity as well as circulating levels and mRNA expression of proinflammatory cytokines were unaffected by BDG treatment. Increased IL-10 after BDG consumption might be a contributing factor to the known beneficial effects of dietary fiber intake.

Fructose consumption: considerations for future research on its effects on adipose distribution, lipid metabolism, and insulin sensitivity in humans

Results from a recent study investigating the metabolic effects of consuming fructose-sweetened beverages at 25% of energy requirements for 10 wk demonstrate that a high-fructose diet induces dyslipidemia, decreases insulin sensitivity, and increases visceral adiposity. The purpose of this review is to present aspects of the study design which may be critical for assessment of the metabolic effects of sugar consumption. Collection of postprandial blood samples is required to document the full effects of fructose on lipid metabolism. Fasting triglyceride (TG) concentrations are an unreliable index of fructose-induced dyslipidemia. Differences in the short-term (24-h) and long-term (>2 wk) effects of fructose consumption on TG and apolipoprotein-B demonstrate that acute effects can differ substantially from those occurring after sustained fructose exposure. Investigating the effects of fructose when consumed ad libitum compared with energy-balanced diets suggest that additive effects of fructose-induced de novo lipogenesis and positive energy balance may contribute to dyslipidemia and decreased insulin sensitivity. Increases of intra-abdominal fat observed in subjects consuming fructose, but not glucose, for 10 wk indicate that the 2 sugars have differential effects on regional adipose deposition. However, the increase of fasting glucose, insulin, and homeostasis model assessment-insulin resistance at 2 wk and the lack of increase of 24-h systemic FFA concentrations suggest that fructose decreases insulin sensitivity independently of visceral adiposity and FFA. The lower postprandial glucose and insulin excursions in subjects consuming fructose and increased excursions in those consuming glucose do not support a relationship between dietary glycemic index and the development of dyslipidemia, decreased insulin sensitivity, or increased visceral adiposity.

Dietary glycemic load, glycemic index, and refined grains intake are associated with reduced β-cell function in prediabetic Japanese migrants

OBJECTIVE: To investigate the association between carbohydrate intakes and β-cell function (HOMA-β) in Japanese-Brazilians with impaired glucose tolerance (IGT). METHODS: Dietary intakes were assessed by a validated food frequency questionnaire in a cross-sectional survey carried out in 2000. The associations between diet and HOMA-β were verified in 270 newly diagnosed IGT in multiple linear regression models. RESULTS: The mean (SD) age was 58 (11) years and the mean HOMA-β was 65 (47). The glycemic load was inversely associated with HOMA-β, β1 -0.140 (95%CI = -1.044; -0.078), p = 0.023. The inverse association was also observed for refined grains intakes: -0.186 (95%CI = -0.4862; -0.058), p = 0.012. After adjustments for body mass index, the glycemic index was inversely associated with HOMA-β: -0.1246 (95%CI = -2.2482, -0.0257), p < 0.001. CONCLUSIONS: These data suggested that dietary glycemic load, glycemic index, and refined grains intakes are associated with reduced β-cell function, and the quality of dietary carbohydrates may be relevant for maintaining β-cell function among individuals with IGT.

Dietary carbohydrates and cardiovascular disease risk factors in the Framingham offspring cohort

OBJECTIVE

Evidence from observational studies has suggested that carbohydrate quality rather than absolute intake is associated with greater risk of chronic diseases. The aim of this study was to examine the relationship between carbohydrate intake and dietary glycemic index and several cardiovascular disease risk factors.

METHODS

We examined cross-sectional associations between total carbohydrate and dietary glycemic index (GI) intakes and several cardiovascular disease risk factors (CVD) in a sample of 2,941 Framingham Offspring Participants. CVD risk factors included waist, blood pressure, lipids, fasting insulin, fasting glucose, and the insulin sensitivity index (ISI(0,120)). Dietary intake was assessed by a food frequency questionnaire (FFQ) and categorized by quintiles of dietary intake.

RESULTS

After adjustment for potential confounding factors, dietary GI was positively associated with fasting triglycerides (mean: 115mg/dL in the lowest and 127 mg/dL in the highest quintile of intake; P for trend < 0.001), fasting insulin (26.8 and 28.9 microu/mL, respectively, P for trend < 0.0001), and inversely associated with HDL cholesterol (49 and 47 mg/dL, respectively, P for trend 0.003) and ISI(0,120) (26.8 and 25.1, P for trend < 0.001). There was no significant relationship between dietary GI and waist circumference, total cholesterol, LDL cholesterol and fasting glucose. Intakes of total carbohydrate were inversely associated with waist circumference and HDL cholesterol, and positively associated with fasting triglycerides.

CONCLUSION

These cross-sectional findings support the hypothesis that a high GI diet unfavorably affects CVD risk factors and therefore, substitution of high with low GI dietary carbohydrates may have reduce the risk of CVD.

Should glycemic index and glycemic load be considered in dietary recommendations?

High glycemic index (GI) and glycemic load (GL) have been proposed to be associated with increased risk of lifestyle diseases. Since protein intake varies little in humans, adherence to the common recommendation to reduce fat intake probably leads to increases in carbohydrate intake, which emphasizes the need to investigate the effects of carbohydrate on diet-related conditions and diseases. This review examines the epidemiological literature linking GI and GL to heart disease, insulin sensitivity, type 2 diabetes, dyslipidemia, and obesity among initially healthy people. The evidence for associations between GI and particularly GL and health among free-living populations is mixed. Only the positive association between GI and development of type 2 diabetes was consistent across cross-sectional and longitudinal studies for both sexes. Low GI/GL may protect against heart disease in women, and cross-sectional studies indicate low GI/GL may reduce high-density-lipoprotein cholesterol and triacylglycerol levels in both sexes. Based on the evidence found in this review, it seems premature to include GI/GL in dietary recommendations.

Is there a role for the glycemic index in coronary heart disease prevention or treatment?

The clinical application of the glycemic index (GI) to the prevention and treatment of chronic diseases is controversial. No evidence exists for the implementation of low-GI diets for a reduction in coronary heart disease (CHD) mortality, events, or morbidity. Observational studies report conflicting evidence on the role of low-GI diets in CHD and risk factors for CHD. Randomized clinical trials report a small reduction in total cholesterol (-6.6 mg/dL) from low-GI diets compared with high-GI diets, but no reduction in other risk factors, such as low-density lipoprotein or high-density lipoprotein cholesterol, triglycerides, fasting glucose, insulin, or body weight. Currently, the research suggests a minimal role for the implementation of low-GI diets in the prevention or treatment of CHD.

Glycemic load, glycemic index, and body mass index in Spanish adults

BACKGROUND

Studies on obesity and glycemic index (GI) or glycemic load (GL) have had inconsistent results, perhaps in part because of underreporting or to heterogeneous dietary patterns across food cultures.

OBJECTIVES

We examined associations between body mass index (BMI) and GI or GL in a Mediterranean population, accounting for underreporting. We also constructed dietary factors related to GI and GL to better understand food patterns related to these measures.

DESIGN

Cross-sectional data on 8195 Spanish adults aged 35-74 y were analyzed. A validated food-frequency questionnaire was used to estimate GI and GL, with glucose as the reference value. Reduced-rank regression was used to construct dietary patterns that explained variation in GI and GL. Multivariate linear regression was used to estimate associations between BMI and GI, GL, and their respective diet factors with and without adjusting for energy, which may lie on the causal pathway between glycemic quality and obesity. Effects of excluding underreporters (ratio of energy intake:basal metabolic rate < 1.20) were examined.

RESULTS

Food patterns underlying high GI differed substantially from those of high GL, with fruits, vegetables, and legumes related positively to GL but negatively to GI. After excluding underreporters, GL was negatively associated with BMI, adjusting for energy. GI was not associated with BMI in any model.

CONCLUSIONS

After adjusting for energy, GL was associated with reduced BMI in this Mediterranean population. Underreporting did not explain this inverse relation, which was observed among subjects with plausible intakes.

Macronutrients and insulin resistance in cholesterol gallstone disease

Cholelithiasis is a major source of digestive morbidity worldwide. Cholesterol stones account for the majority of gallstones in the United States and other Western countries. The pathogenesis of cholesterol gallstone disease is multifactorial with key factors including cholesterol supersaturation of bile, altered biliary motility, and nucleation and growth of cholesterol crystals. Increasing evidence suggests that many, but not all, causative factors of cholesterol gallstones are related to insulin resistance which, in association with obesity, has reached an epidemic level worldwide. Experimental studies show that hyperinsulinemia, a key feature of insulin resistance, may cause increased hepatic cholesterol secretion and cholesterol supersaturation of bile and gallbladder dysmotility, and thereby may enhance gallstone formation. Insulin resistance syndrome can be modified by environmental factors, including dietary factors. The impact of diet on insulin sensitivity is mediated by both dietary composition and its energy content. The contribution of specific dietary elements to the prevalence and incidence of cholesterol gallstone disease has been explored in animal and human studies. There is considerable evidence to suggest that different types of fatty acids, independent of the total amount of fat consumption, affect insulin sensitivity and cholesterol gallstone disease differently. The effects of salt intake, consumption of protein and carbohydrates, and alcohol drinking on insulin resistance are controversial. Additional intervention trials and controlled experimental feeding studies are needed to further clarify these relationships and to provide useful prophylactic and therapeutic strategies.

Dietary glycemic index, development of islet autoimmunity, and subsequent progression to type 1 diabetes in young children

CONTEXT

Dietary factors may trigger or exacerbate the autoimmune disease process.

OBJECTIVE

Our objective was to examine dietary glycemic index (GI) and glycemic load (GL) for association with islet autoimmunity (IA) development, and progression from IA to type 1 diabetes.

DESIGN

The Diabetes Autoimmunity Study in the Young follows children at increased genetic type 1 diabetes risk. Diet is collected prospectively via a parent-reported food frequency questionnaire.

SETTING

This was an observational study of children in the Denver area.

PATIENTS

A total of 1776 Diabetes Autoimmunity Study in the Young children younger than 11.5 yr was included in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

IA, defined as the presence of autoantibodies to insulin, glutamic acid decarboxylase, or protein tyrosine phosphatase at two consecutive visits, or the presence of autoantibodies at one visit and diabetic on the next consecutive visit was determined. Type 1 diabetes was diagnosed by a physician. A total of 89 subjects developed IA, and 17 subsequently developed type 1 diabetes during follow-up. Our hypothesis was formulated after data collection.

RESULTS

GI and GL were not associated with IA development. More rapid progression to type 1 diabetes in children with IA was associated with higher dietary GI (hazard ratio: 2.20; 95% confidence interval: 1.17-4.15) and marginally associated with GL (hazard ratio: 1.59; 95% confidence interval: 0.96-2.64) at the first IA-positive visit.

CONCLUSIONS

Higher dietary GI and GL are not associated with IA development, but higher GI is associated with more rapid progression to type 1 diabetes in children with IA, perhaps due to increased demand on the beta-cell to release insulin. Further study is needed to confirm this finding and identify the underlying biological mechanism.

Dietary energy density but not glycemic load is associated with gestational weight gain

BACKGROUND

Most pregnant women gain more weight than the ranges recommended. Excessive weight gain is linked to pregnancy complications and to long-term maternal and child health outcomes.

OBJECTIVE

The objective was to examine the impact of dietary glycemic load and energy density on total gestational weight gain and the weight gain ratio (observed weight gain/expected weight gain).

DESIGN

Data are from 1231 women with singleton pregnancies who participated in the Pregnancy, Infection, and Nutrition Cohort Study. Dietary information was collected at 26-29 wk of gestation with the use of a semiquantified food-frequency questionnaire. Linear regression models were used to estimate the associations between quartiles of glycemic load and energy density with total gestational weight gain and weight gain ratio.

RESULTS

Dietary patterns of pregnant women significantly differed across many sociodemographic and behavioral characteristics, with the greatest contrasts seen for glycemic load. After adjustment for covariates, compared with women in the first quartile consuming a mean dietary energy density of 0.71 kcal/g (reference), women in the third quartile consuming a mean energy density of 0.98 kcal/g gained an excess of 1.13 kg (95% CI: 0.24, 2.01), and women in the fourth quartile consuming a mean energy density of 1.21 kcal/g gained an excess of 1.08 kg (95% CI: 0.20, 1.97) and had an increase of 0.13 (95% CI: 0.006, 0.24) units in the weight gain ratio. All other comparisons of energy intakes were not statistically significant. Glycemic load was not associated with total gestational weight gain or weight gain ratio.

CONCLUSION

Dietary energy density is a modifiable factor that may assist pregnant women in managing gestational weight gains.

Optimizing management of metabolic syndrome to reduce risk: focus on life-style

The prevalence of metabolic syndrome (MS) is increasing all over the world and its incidence is expected to rise in the next years. Although genetic predisposition appears to play an important role in the regulation of metabolic parameters and in particular of body weight, the rapid increase in the prevalence of obesity and MS suggests that ecological factors (social, economic, cultural and physical environment) are promoting those conditions in susceptible individuals. People with MS are at increased risk of type 2 diabetes and cardiovascular disease and therefore they represent a priority target for preventive strategies. Life-style modifications based on healthy diet and increased physical activity are an effective preventing and therapeutic approach. Unfortunately, implementation of life-style modification and maintenance of effects is a difficult task both at personal and social level, thus drug therapy can be taken into account.

Validity of carbohydrate, glycaemic index and glycaemic load data obtained using a semi-quantitative food-frequency questionnaire

Objective

To assess the ability of a food-frequency questionnaire (FFQ) to rank Australians according to their intake of total carbohydrate, sugar, starch, fibre, glycaemic index (GI) and glycaemic load (GL).

Design

Cross-sectional sample from a population cohort.

Setting

Two postcode areas west of Sydney, Australia.

Subjects

From 1992 to 1994, a total of 2868 older Australians provided dietary data using a 145-item Willett-derived FFQ. A representative sub-sample of 78 subjects completed three 4-day weighed food records (WFRs). Pearson and Spearman correlations, Bland–Altman plots and weighted kappa values were calculated.

Results

Compared with the WFR, the FFQ provided higher mean estimates of all nutrients except starch and GI. All Pearson and/or Spearman correlations were greater than 0.5, except for GL. For GI, sugar, starch and fibre, the regression lines from the Bland–Altman analysis indicated a non-significant linear trend (P = 0.07, P = 0.36, P = 0.28 and P = 0.10, respectively). For GL and total carbohydrate, however, there was a significant linear trend (P = 0.006 and P < 0.0001, respectively), indicating that as the GL and carbohydrate intake of individuals increased, so did the magnitude of the error between the FFQ and WFR. Weighted kappa values all indicated moderate to good agreement, with the exception of GL which was only fair. The proportions of subjects correctly classified within one quintile for all of the nutrients were over 50% and gross misclassification was low (<10%).

Conclusion

This FFQ was able to rank individuals according to their intakes of total carbohydrate, sugar, starch, fibre and GI, but not as well for GL.

High dose flaxseed oil supplementation may affect fasting blood serum glucose management in human type 2 diabetics

Type 2 diabetes is characterized partially by elevated fasting blood serum glucose and insulin concentrations and the percentage of hemoglobin as HbA1c. It was hypothesized that each of blood glucose and its co-factors insulin and HbA1c and would show a more favorable profile as the result of flaxseed oil supplementation. Patients were recruited at random from a population pool responding to a recruitment advertisement in the local newspaper and 2 area physicians. Completing the trial were 10 flaxseed oil males, 8 flaxseed oil females, 8 safflower (placebo) oil males and 6 safflower oil females. Patients visited on two pre-treatment occasions each three months apart (visits 1 and 2). At visit 2 subjects were randomly assigned in double blind fashion and in equal gender numbers to take flaxseed oil or safflower oil for three further months until visit 3. Oil consumption in both groups was approximately 10 g/d. ALA intake in the intervention group was approximately 5.5 g/d. Power was 0.80 to see a difference of 1 mmol of glucose /L using 12 subjects per group with a p < 0.05. Flaxseed oil had no impact on fasting blood serum glucose, insulin or HbA1c levels. It is concluded that high doses of flaxseed oil have no effect on glycemic control in type 2 diabetics.

Raisins and additional walking have distinct effects on plasma lipids and inflammatory cytokines

Background

Raisins are a significant source of dietary fiber and polyphenols, which may reduce cardiovascular disease (CVD) risk by affecting lipoprotein metabolism and inflammation. Walking represents a low intensity exercise intervention that may also reduce CVD risk. The purpose of this study was to determine the effects of consuming raisins, increasing steps walked, or a combination of these interventions on blood pressure, plasma lipids, glucose, insulin and inflammatory cytokines.

Results

Thirty-four men and postmenopausal women were matched for weight and gender and randomly assigned to consume 1 cup raisins/d (RAISIN), increase the amount of steps walked/d (WALK) or a combination of both interventions (RAISINS + WALK). The subjects completed a 2 wk run-in period, followed by a 6 wk intervention. Systolic blood pressure was reduced for all subjects (P = 0.008). Plasma total cholesterol was decreased by 9.4% for all subjects (P < 0.005), which was explained by a 13.7% reduction in plasma LDL cholesterol (LDL-C) (P < 0.001). Plasma triglycerides (TG) concentrations were decreased by 19.5% for WALK (P < 0.05 for group effect). Plasma TNF-α was decreased from 3.5 ng/L to 2.1 ng/L for RAISIN (P < 0.025 for time and group × time effect). All subjects had a reduction in plasma sICAM-1 (P < 0.01).

Conclusion

This research shows that simple lifestyle modifications such as adding raisins to the diet or increasing steps walked have distinct beneficial effects on CVD risk.

Glycemic index and glycemic load in relation to food and nutrient intake and metabolic risk factors in a Dutch population

BACKGROUND

Previous studies on the glycemic index (GI) and glycemic load (GL) reported inconsistent findings on their association with metabolic risk factors. This may partly have been due to differences in underlying dietary patterns.

OBJECTIVE

We aimed to examine the association of GI and GL with food and nutrient intake and with metabolic risk factors including blood glucose, insulin, lipids, and high-sensitivity C-reactive protein (CRP).

DESIGN

The study entailed cross-sectional analyses of data from 2 joint observational studies, the CoDAM Study and the Hoorn Study.

RESULTS

In total, 974 subjects aged 42-87 y were included in the study. The mean (+/-SD) GI was 57 +/- 4 and the mean GL was 130 +/- 39. Dairy products, potatoes and other tubers, cereal products, and fruit were the main predictive food groups for GI. GL was closely correlated with intake of total carbohydrates (r(s) = 0.97), which explained >95% of the variation in GL. After adjustment for potential confounders, GI was significantly inversely associated with HDL cholesterol and positively associated with fasting insulin, the homeostasis model assessment index of insulin resistance, the ratio of total to HDL cholesterol, and CRP. No association was observed between GL and any of the metabolic risk factors, except for a borderline significant positive association with CRP.

CONCLUSIONS

In this population, a low-GI diet, which is high in dairy and fruit but low in potatoes and cereals, is associated with improved insulin sensitivity and lipid metabolism and reduced chronic inflammation. GL is highly correlated with carbohydrate intake and is not clearly associated with the investigated metabolic risk factors.

Childhood Obesity: Adrift in the “Limbic Triangle”

The prevalence and severity of childhood obesity have increased steadily over the past three decades. The human species evolved to rigorously defend its lower limit for weight and adiposity but is tolerant of the upper limit, which, until recent times, was rarely approached. Neuroendocrine mechanisms within the limbic core of the brain prevent starvation (ventromedial hypothalamus), heighten reward (ventral tegmental area and nucleus accumbens), and attenuate stress (amygdala), in order to promote food-seeking and ingestive behavior and to conserve energy output. In a stressful modern environment with ready access to calorie-dense, highly palatable foods and limited venues for activity, normal, reflexive responsiveness to these three drives makes weight gain all but inevitable. The obesity that ensues often engenders insulin resistance, which undermines the ability of normal hunger and satiety signals to accurately modulate energy intake versus expenditure. Obesity interventions that rely on cognitive information alone cannot free children from this "limbic triangle." Integrated multidisciplinary family- and community-based education, effective stress reduction, and a societal commitment to alter the food and built environments are all necessary components to battle the global obesity epidemic.

Prevalence and independent predictors of insulin resistance in children from Crete, Greece: the Children Study

BACKGROUND

It has been proposed that insulin resistance (IR) is associated with the development of Type 2 diabetes mellitus and cardiovascular disease. The aim of this study is to determine the prevalence of IR in Greek schoolchildren and to investigate factors associated with IR.

METHODS

Between October 2005 and March 2006, 522 children were recruited from Crete. Physical activity and dietary habits, anthropometric and biochemical characteristics, as well as medical history of pupils' parents were recorded. IR was estimated using the homeostasis model assessment (HOMA-IR), fasting glucose-to-insulin ratio (FGIR) and quantitative insulin sensitivity check index (QUICKI). Multiple linear regression was used to determine independent predictors for IR.

RESULTS

Fasting insulin levels and HOMA-IR scores were higher in obese children and girls compared with their normal-weight peers (P < 0.001). Moreover, the former had lower values in FGIR and QUICKI indices compared with the latter, indicating that obese children and girls are more insulin resistant compared with their counterparts (P < 0.001). The prevalence of IR was 9.2% (2.9% in normal-weight, 10.5% in overweight and 31.0% in obese children), using as a threshold HOMA-IR > 2.10 97.5th percentile of normal-weight participants). Multiple linear regression revealed that central adiposity, female gender and intake of simple carbohydrates is associated positively with HOMA-IR values, even after controlling for many other factors.

CONCLUSION

These findings demonstrate that girls and obese children, particularly those with central adiposity, are at high risk of developing IR. Therefore, these groups should be targets of Type 2 diabetes mellitus and cardiovascular disease preventive interventions.

Dietary glycemic index and glycemic load and the risk of type 2 diabetes in older adults

BACKGROUND

It is unclear whether immediate dietary effects on blood glucose influence the risk of developing type 2 diabetes.

OBJECTIVE

The objective of this study was to examine whether the dietary glycemic index (GI) and glycemic load (GL) were associated with the risk of type 2 diabetes in older adults.

DESIGN

The Health, Aging, and Body Composition Study is a prospective cohort study of 3075 adults who were 70-79 y old at baseline (n=1898 for this analysis). The intakes of specific nutrients and food groups and the risk of type 2 diabetes over a 4-y period were examined according to dietary GI and GL.

RESULTS

Dietary GI was positively associated with dietary carbohydrate and negatively associated with the intakes of protein, total fat, saturated fat, alcohol, vegetables, and fruit. Dietary GL was positively associated with dietary carbohydrate, fruit, and fiber and negatively associated with the intakes of protein, total fat, saturated fat, and alcohol. Persons in the higher quintiles of dietary GI or GL did not have a significantly greater incidence of type 2 diabetes.

CONCLUSIONS

These findings do not support a relation between dietary GI or GL and the risk of type 2 diabetes in older adults. Because dietary GI and GL show strong nutritional correlates, the overall dietary pattern should be considered.

Role of glycemic index and glycemic load in the healthy state, in prediabetes, and in diabetes

The choice of carbohydrate-rich foods in the habitual diet should take into account not only their chemical composition but also their ability to influence postprandial glycemia (glycemic index). Fiber-rich foods generally have a low glycemic index (GI), although not all foods with a low GI necessarily have high fiber content. Several beneficial effects of low-GI, high-fiber diets have been shown, including lower postprandial glucose and insulin responses, an improved lipid profile, and, possibly, reduced insulin resistance. In nondiabetic persons, suggestive evidence is available from epidemiologic studies that a diet based on carbohydrate-rich foods with a low-GI, high-fiber content may protect against diabetes or cardiovascular disease. However, no intervention studies have so far evaluated the potential of low-GI, high-fiber diets to reduce the risk of diabetes, although in studies aimed at diabetes prevention by lifestyle modifications, an increase in fiber consumption was often part of the intervention. In relation to prevention of cardiovascular disease, intervention studies evaluating the effect of a low-GI diet on clinical events are not available; moreover, the results of the few available intervention studies evaluating the effects of GI on the cardiovascular disease risk factor profile are not always concordant. The best evidence of the clinical usefulness of GI is available in diabetic patients in whom low-GI foods have consistently shown beneficial effects on blood glucose control in both the short-term and the long-term. In these patients, low-GI foods are suitable as carbohydrate-rich choices, provided other attributes of the foods are appropriate.

The metabolic syndrome in relation with the glycemic index and the glycemic load

The metabolic syndrome (MS) is a clustering of metabolic abnormalities that increases the risk to develop chronic diseases such as cardiovascular disease and type 2 diabetes mellitus. Although its precise aetiology is unknown, dietary habits play a major role. Nowadays, more and more attention is paid to the glycemic index (GI) and the glycemic load (GL) of a diet. The GI of a food is a value based on the average increase in blood glucose levels occurring when a 50 g carbohydrate portion of that food is consumed. The GL accounts for the amount of carbohydrate per serving. From reviewing the current literature, we conclude that for healthy and/or overweight subjects the importance of low GI or GL diets in relation to the metabolic syndrome has not been established. One of the reasons is that the diets used in the intervention studies frequently not only differed in GI or GL, but also in fibre, protein and/or fat content. In some of the prospective cohort studies, effects of GI or GL attenuated or even disappeared after correcting for fibre intake. This makes it impossible to ascribe the possible beneficial metabolic effects of low GI or GL diets unequivocally to the GI or GL. The question, therefore, remains open on to what components of the metabolic syndrome are specifically affected by the GI per se. To answer this question, controlled longer-term intervention studies are needed to monitor the effects of the GI on the various components of the metabolic syndrome.

Dietary fiber intake and retinal vascular caliber in the Atherosclerosis Risk in Communities Study

BACKGROUND

Dietary fiber appears to decrease the risk of cardiovascular morbidity and mortality. Microvascular abnormalities can be observed by retinal examination and contribute to the pathogenesis of various cardiovascular diseases. The impact of dietary fiber on the retinal microvasculature is not known.

OBJECTIVE

We aimed to examine the association between dietary fiber intake and retinal vascular caliber.

DESIGN

At the third visit (1993-1995) of the Atherosclerosis Risk in Communities (ARIC) Study, a population-based cohort of adults in 4 US communities, the retinal vascular caliber of 10,659 participants was measured and summarized from digital retinal photographs. Usual dietary intake during the same period was assessed with a 66-item food-frequency questionnaire.

RESULTS

After control for potential confounders including hypertension, diabetes, lipids, demographic factors, cigarette smoking, total energy intake, micronutrients intake, and other cardiovascular disease risk factors, higher intake of fiber from all sources and from cereal were significantly associated with wider retinal arteriolar caliber and narrower venular caliber. Participants in the highest quintile of fiber intake from all sources had a 1.05-microm larger arteriolar caliber (P for trend = 0.012) and a 1.11-microm smaller venular caliber (P for trend = 0.029).

CONCLUSIONS

Dietary fiber was related to wider retinal arteriolar caliber and narrower venular caliber, which are associated with a lower risk of cardiovascular disease. These data add to the growing evidence of the benefits of fiber intake on various aspects of cardiovascular pathogenesis.

Carbohydrate quantity and quality in relation to body mass index

The increased prevalence of overweight and obesity in the United States since approximately 1980 is temporally associated with an increase in carbohydrate intake, with no appreciable change in absolute intake of fat. Despite speculation that both carbohydrate quantity and quality have contributed significantly to excess weight gain, the relationship between carbohydrate intake and body mass index (BMI) is controversial. A review of relevant literature indicates that most epidemiologic studies show an inverse relationship between carbohydrate intake and BMI, even when controlling for potential confounders. These observational studies are supported by results from a number of dietary intervention studies wherein modest reductions in body weight were observed with an ad libitum, low-fat, high-carbohydrate diet without emphasis on energy restriction or weight loss. With few exceptions, high glycemic load is associated with lower BMI, even when adjusted for total energy intake. Data on the association between glycemic index and BMI are not as consistent, with more studies showing either no association or an inverse relationship, rather than a positive relationship. Whole-grain intake is generally inversely associated with BMI; refined grain intake is not. Because overall dietary quality tends to be higher for high-carbohydrate diets, a low-fat dietary strategy with emphasis on fiber-rich carbohydrates, particularly cereal fiber, may be beneficial for health and weight control.

Associations of dietary sugar and glycemic index with adiposity and insulin dynamics in overweight Latino youth

BACKGROUND

Few studies have examined the relation between dietary carbohydrate quality, adiposity, and insulin dynamics in children.

OBJECTIVE

The objective of the study was to determine which aspects of dietary carbohydrate, specifically dietary sugar, fiber, glycemic index, or glycemic load, are associated with adiposity and insulin dynamics in overweight Latino children.

DESIGN

We examined 120 overweight Latino children (10-17 y old) with a family history of type 2 diabetes. Dietary intake was determined by repeated 24-h diet recalls. Adiposity was assessed by using total-body dual-energy X-ray absorptiometry. Insulin dynamics [insulin sensitivity (SI), acute insulin response, and disposition index (an index of beta-cell function)] were measured by using a frequently sampled intravenous-glucose-tolerance test.

RESULTS

After adjustment for covariates, total sugar (g/d) was positively correlated with body mass index (BMI; in kg/m(2)), BMI z scores, and total fat mass (r = 0.20, r = 0.22, and r = 21, respectively; P < 0.05) and negatively correlated with SI and disposition index (r = -0.29 and r = -0.24, respectively; P < 0.05). Dietary fiber, glycemic index, and glycemic load were not significantly correlated with adiposity or insulin dynamics before or after control for covariates. Regression analyses showed that total sugar intake explained an additional 3.4%, 4.6%, and 2.4% of the variance in BMI, BMI z scores, and total fat mass, respectively, and an additional 5.6% and 4.8% of the variance in SI and disposition index (P < 0.05), respectively, after control for covariates.

CONCLUSION

In this cohort, total sugar intake, rather than glycemic index or glycemic load, was associated with higher adiposity measures, lower SI, and lower measures of insulin secretion.

Relationship of glycaemic index with cardiovascular risk factors: analysis of the National Diet and Nutrition Survey for people aged 65 and older

Objective

To identify associations between dietary glycaemic index (GI) and weight, body mass index and other risk factors for cardiovascular disease (CVD) – waist-to-hip ratio (WHR), lipoprotein fractions, triacylglycerols (TAG) and blood pressure (BP) – in an older British population.

Design

Cross-sectional dietary, anthropometric and biochemical data from the National Diet and Nutritional Survey for adults aged over 65 years were reanalysed using a hierarchical regression model. Associations between body weight, CVD risk factors, and dietary factors including GI and fibre intakes were explored among 1152 healthy older people living in the UK between 1994 and 1995.

Results

In the unadjusted model, GI was significantly and directly associated with TAG (β = 0.008 ± 0.003) and diastolic BP (β = 0.325 ± 0.164) in males. These relationships were attenuated and non-significant after adjustment for potential confounding factors. WHR (β = 0.003 ± 0.001) and TAG (β = 0.005 ± 0.002) were significantly predicted by GI in males and females combined. The association with WHR was attenuated by adjustment for sex, age, region and social class; the relationship with TAG was non-significant after adjustment for other potential dietary confounders.

Conclusion

After controlling for potential confounders, no clear links were detected between GI and body weight or other CVD risk factors. This study provides little evidence for advising the consumption of a low-GI diet in the elderly to prevent weight gain or improve other CVD risk factors.

Improvement of insulin resistance after diet with a whole-grain based dietary product: results of a randomized, controlled cross-over study in obese subjects with elevated fasting blood glucose

Subjects with obesity and elevated fasting blood glucose are at high risk of developing type 2 diabetes which may be reduced by a dietary intervention leading to an improvement of insulin resistance. We investigated the potential of a whole-grain based dietary product (WG) with reduced starch content derived from double-fermented wheat during a hypo-energetic diet to positively influence body weight, fasting blood glucose, insulin resistance and lipids in comparison to a nutrient-dense meal replacement product (MR) in a randomized two-way cross-over study with two 4-week treatment periods separated by a 2-week wash-out. Subjects replaced at least two daily meals with WG and MR, respectively, targeting for a consumption of 200 g of either product per day. Total daily energy intake was limited to 7120 kJ. Thirty-one subjects (BMI 33·9 (sd 2·7) kg/m2, fasting blood glucose 6·3 (sd 0·8) mmol/l) completed the study. In both treatment groups body weight ( − 2·5 (sd 2·0) v. − 3·2 (sd 1·6) kg for WG v. MR), fasting blood glucose ( − 0·4 (sd 0·3) v. − 0·5 (sd 0·5) mmol/l), total cholesterol ( − 0·5 (sd 0·5) v. − 0·6 (sd 0·5) mmol/l), TAG ( − 0·3 (sd 0·9) v. − 0·3 (sd 1·2) mmol/l) and homeostasis model assessment (HOMA) insulin resistance score ( − 0·7 (sd 0·8) v. − 1·1 (sd 1·7) μU/ml ×  mmol/l) improved (P < 0·05) with no significant differences between the treatments. After statistical adjustment for the amount of body weight lost, however, the comparison between both groups revealed that fasting serum insulin (P = 0·031) and HOMA insulin resistance score (P = 0·049) improved better with WG than with MR. We conclude that WG favourably influences metabolic risk factors for type 2 diabetes independent from the amount of body weight lost during a hypo-energetic diet.

Dietary glycemic index and glycemic load are associated with high-density-lipoprotein cholesterol at baseline but not with increased risk of diabetes in the Whitehall II study

BACKGROUND

Findings of the effect of dietary glycemic index (GI) and glycemic load (GL) on the risk of incident diabetes are inconsistent.

OBJECTIVE

We examined the associations of dietary GI and GL with clinical variables at baseline and the incidence of diabetes.

DESIGN

The 7321 white Whitehall II participants (71% men) attending screening in 1991-1993, free of diabetes at baseline, and with food-frequency questionnaire data were followed for 13 y.

RESULTS

At baseline, dietary GI and GL were associated inversely with HDL cholesterol, and GI was associated directly with triacylglycerols. Dietary GI and GL were related inversely to fasting glucose and directly to 2-h postload glucose, but only the association between GI and 2-h postload glucose was robust to statistical adjustments for employment grade, physical activity, smoking status, and intakes of alcohol, fiber, and carbohydrates. High-dietary GI was not associated with increased risk of incident diabetes. Hazard ratios (HRs) across sex-specific tertiles of dietary GI were 1.00, 0.95 (95% CI: 0.73, 1.24), and 0.94 (95% CI: 0.72, 1.22) (adjusted for sex, age, and energy misreporting; P for trend = 0.64). Corresponding HRs across tertiles of dietary GL were 1.00, 0.92 (95% CI: 0.71, 1.19), and 0.70 (95% CI: 0.54, 0.92) (P for trend = 0.01). The protective effect on diabetes risk remained significant after adjustment for employment grade, smoking, and alcohol intake but not after further adjustment for carbohydrate and fiber intakes.

CONCLUSION

The proposed protective effect of low-dietary GI and GL diets on diabetes risk could not be confirmed in this study.

A prospective study of dietary carbohydrate quantity and quality in relation to risk of ovulatory infertility

OBJECTIVE

To evaluate whether the amount or quality of carbohydrate in diet is associated with ovulatory infertility.

SUBJECTS AND METHODS

In total, 18,555 married, premenopausal women without a history of infertility were followed as they attempted a pregnancy or became pregnant during an 8-year period. Diet was assessed two times during follow-up using a validated food-frequency questionnaire and prospectively related to the incidence of infertility due ovulatory disorder.

RESULTS

During follow-up, 438 women reported ovulatory infertility. Total carbohydrate intake and dietary glycemic load were positively related to ovulatory infertility in analyses adjusted for age, body mass index, smoking, parity, physical activity, recency of contraception, total energy intake, protein intake and other dietary variables. The multivariable-adjusted risk ratio (RR) (95% confidence interval (CI)) of ovulatory infertility comparing the highest-to-lowest quintile of total carbohydrate intake was 1.91 (1.27-3.02). The corresponding RR (95% CI) for dietary glycemic load was 1.92 (1.26-2.92). Dietary glycemic index was positively related to ovulatory infertility only among nulliparous women. Intakes of fiber from different sources were unrelated to ovulatory infertility risk.

CONCLUSIONS

The amount and quality of carbohydrate in diet may be important determinants of ovulation and fertility in healthy women.

Is the fructose index more relevant with regards to cardiovascular disease than the glycemic index?

The glycemic index (G.I.) is a means for categorizing carbohydrates based on their ability to raise blood glucose, subsequently this index has been popularized as a way for selecting foods to reduce the risk for obesity, diabetes, and cardiovascular disease. We suggest that the G.I. is better aimed at identifying foods that stimulate insulin secretion rather than foods that stimulate insulin resistance. In this regard, fructose has a low G.I. but may be causally linked with the obesity and cardiovascular disease epidemic. The reported association of high G.I. with cardiovascular disease may be due to the association of sugar intake which contains fructose, but which has a high G.I. due to its glucose content. We propose the use of a fructose index to categorize foods and propose studies to determine the effect of low fructose diets as a means to prevent obesity, diabetes, and cardiovascular disease in the population.

Hepatic steatosis and increased adiposity in mice consuming rapidly vs. slowly absorbed carbohydrate

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is fast becoming a major public health concern, coincident with the increasing prevalence of obesity. Although lifestyle greatly influences development of NAFLD, the specific dietary causes remain largely unknown. The purpose of this study was to determine whether a diet high in rapidly absorbed carbohydrate (RAC) vs. slowly absorbed carbohydrate (SAC), controlled for confounding dietary factors, causes NAFLD in mice with similar body weight. An animal model was chosen because of logistical and ethical challenges to conducting this study in humans.

RESEARCH METHODS AND PROCEDURES

Male 129SvPas mice were fed diets high in either RAC (amylopectin; high glycemic index) or SAC (amylose; low glycemic index) for 25 weeks. Diets were controlled for macronutrient and micronutrient content, differing only in starch type. Body weight and composition were measured throughout the study. Hepatic and plasma triacylglycerol concentrations were quantified at the end of the study.

RESULTS

Body weight was not significantly different between the two groups. However, total body adiposity increased twice as much, in absolute terms, in the mice fed RAC vs. SAC (12.2 +/- 2.9% vs. 6.1 +/- 4.2%, p < 0.0001). Hepatic triacylglycerol content was 2-fold greater in the RAC group (20.7 +/- 9.4 vs. 9.6 +/- 4.9 mg/g, p = 0.01). In addition, plasma insulin and triacylglycerol concentrations were higher in the RAC group.

DISCUSSION

A diet high in RAC causes accumulation of fat in liver, adipose tissue, and plasma in mice. Therefore, a low glycemic index diet may help prevent or treat NAFLD in humans.

Effect of short-term Pritikin diet therapy on the metabolic syndrome

The Pritikin Program (Aventura, FL) involves the use of a very-low-fat, low-sodium, high-fiber diet and exercise to decrease the risk of coronary heart disease (CHD). This study evaluated the effect of short-term Pritikin therapy on the metabolic risk factors for CHD in patients with the metabolic syndrome. Sixty-seven subjects who had the metabolic syndrome and attended the Pritikin Longevity Center & Spa for 12-15 days were studied. Short-term Pritikin therapy improved most CHD risk factors: body mass index decreased by 3% (P<.001); systolic and diastolic blood pressure, and serum glucose and low-density lipoprotein cholesterol concentrations decreased by 10%-15% (P<.001); serum triglyceride concentration decreased by 36% (P<.001); and 37% of subjects no longer met National Cholesterol Education Program criteria for the metabolic syndrome. Serum high-density lipoprotein cholesterol, however, decreased by 3% (P<.05). These data demonstrate that brief treatment with a very-low-fat, low-sodium, high-fiber diet and regular exercise simultaneously improves multiple CHD risk factors in patients with the metabolic syndrome.