Methodological challenges in the application of the glycemic index in epidemiological studies using data from the European Prospective Investigation into Cancer and Nutrition

Development of a national database for dietary glycemic index and load for nutritional epidemiologic studies in the United States

BACKGROUND

The quality of carbohydrate intake, as measured by the glycemic index (GI), has not been evaluated nationally over the past 2 decades in the United States.

OBJECTIVES

We aimed to develop a comprehensive and nationally representative dietary GI and glycemic load (GL) database from 1999 to 2018 National Health and Nutrition Examination Survey (NHANES) and to examine GI and GL time trends and subpopulation differences.

METHODS

We used an artificial intelligence (AI)-enabled model to match GI values from 2 GI databases to food codes from United States Department of Agriculture, which were manually validated. We examined nationally representative distributions of dietary GI and GL from 1999 to 2018 using the multistage, clustered sampling design of NHANES.

RESULTS

Assigned GI values covered 99.9% of total carbohydrate intake. The initial AI accuracy was 75.0%, with 31.3% retained after manual curation guided by substantive domain expertise. A total of 7976 unique food codes were matched to GI values, of which soft drinks and white bread were top contributors to dietary GI and GL. Of the 49,205 NHANES adult participants, the mean dietary GI was 55.7 (95% confidence interval [CI]: 55.5, 55.8) and energy-adjusted dietary GL was 133.0 (95% CI: 132.3, 133.8). From 1999 to 2018, dietary GI and GL decreased by 4.6% and 13.8%, respectively. Dietary GL was higher among females (134.6; 95% CI: 133.8, 135.5) than among males (131.3; 95% CI: 130.3, 132.3), those with ≤high school degree (137.7; 95% CI: 136.8, 138.7) than among those with ≥college degree (126.5; 95% CI: 125.3, 127.7), and those living under the poverty level (140.9; 95% CI: 139.6, 142.1) than among those above the poverty level. Differences in race were observed (Black adults, 139.4; 95% CI: 138.2, 140.7; White adults, 131.6; 95% CI: 130.5, 132.6).

CONCLUSIONS

The national GI and GL database facilitates large-scale and high-quality surveillance or cohort studies of diet and health outcomes in the United States.

Relative validity of a glycemic index extended food-frequency questionnaire

BACKGROUND AND AIMS

The dietary glycemic index (GI) and glycemic load (GL) are increasingly recognized as important for the prevention and management of diabetes mellitus. To extend the portfolio of assessment methods for large-scale epidemiological studies, we propose a GI-specific addition to an already established FFQ.

METHODS AND RESULTS

The German version of the EPIC-FFQ was extended by GI-specific questions for major carbohydrate sources varying notably in GI (breakfast cereals, bread, pasta, rice, potato etc.). We performed relative validation analyses comparing the GI-extended FFQ to three to four 3-day weighted dietary records (3-d WDR) in 100 middle-aged individuals with diabetes mellitus participating in the German Diabetes Study (GDS). Level of agreement between the two methods was assessed by correlation and cross-classification analyses as well as Bland-Altman-Plots, conducted separately for women and men. Spearman correlation analysis for female participants suggested good agreement between the GI-extended FFQ and 3-d WDRs for energy adjusted dietary GL (r = 0.52, p = 0.0004). For both women and men, agreement with the estimations of dietary GI, GL (for men) and carbohydrates from low and higher-GI food sources from the GI-extended FFQ was acceptable (r: 0.28-0.45). Classification of the dietary GI and GL in the opposite quartile was <10% comparing the GI-extended FFQ and 3-d WDR. Bland-Altman plots suggested a tendency for an overestimation of the dietary GI from the GI-extended FFQ in the lower GI-ranges, particularly for men.

CONCLUSION

Compared to the 3-d WDR, the GI-extended FFQ showed a moderate to good relative validity for parameters of carbohydrate quality.

Nutritional strategies to attenuate postprandial glycemic response

Maintaining good glycemic control to prevent complications is crucial in people with type 2 diabetes and in people with prediabetes and in the general population. Different strategies to improve glycemic control involve the prescription of blood glucose-lowering drugs and the modulation of physical activity and diet. Interestingly, lifestyle intervention may be more effective in lowering hyperglycemia than pharmaceutical intervention. Regulation of postprandial glycemia is complex, but specific nutritional strategies can be applied to attenuate postprandial hyperglycemia. These strategies include reducing total carbohydrate intake, consuming carbohydrates with a lower glycemic index, the addition of or substitution by sweeteners and fibers, using food compounds which delay or inhibit gastric emptying or carbohydrate digestion, and using food compounds which inhibit intestinal glucose absorption. Nevertheless, it must be noted that every individual may respond differently to certain nutritional interventions. Therefore, a personalized approach is of importance to choose the optimal nutritional strategy to improve postprandial glycemia for each individual, but this requires a better understanding of the mechanisms explaining the differential responses between individuals.

Glycaemic index, glycaemic load and cancer risk: results from the prospective NutriNet-Santé cohort

BACKGROUND

Evidence is accumulating that high dietary glycaemic index (GI) and glycaemic load (GL) are potential risk factors for several metabolic disorders (e.g. type-2 diabetes, cardiovascular diseases), but remains limited concerning cancer risk. Although, mechanistic data suggest that consuming high-GI foods may contribute to carcinogenesis through elevated blood glucose levels, insulin resistance or obesity-related mechanisms. Our objective was to study the associations between dietary GI/GL and cancer.

METHODS

In total, 103 020 French adults (median age = 40.2 years) from the NutriNet-Santé cohort (2009-2020) with no cancer or diabetes at baseline were included (705 137 person-years, median follow-up time = 7.7 years). Repeated 24-h dietary records linked with a detailed food-composition table (>3500 food/beverage items). We computed the average dietary GI and GL at the individual level. Associations between GI, GL, contribution of low- and medium/high-GI foods to energy and carbohydrate intake and cancer risk (overall, breast, prostate and colorectal) were assessed using multivariable Cox proportional-hazard models.

RESULTS

Higher dietary GL was associated with higher overall cancer risk [n = 3131 cases, hazard ratios (HRs) for sex-specific quintile 5 vs 1 = 1.25, 95% confidence interval (CI) = 1.03-1.52; Ptrend = 0.008] and specifically postmenopausal breast cancer (n = 924, HRQ5vs.Q1 = 1.64, 95% CI = 1.06-2.55; Ptrend = 0.03). A higher contribution of low-GI food/beverages to energy intake was associated with lower cancer risk whereas a higher contribution of medium/high-GI items to energy intake was positively associated with higher risk of overall, breast and postmenopausal breast cancers (Ptrend ≤ 0.02).

CONCLUSIONS

These results support a possible impact of GI/GL on cancer risk. If confirmed in other populations and settings, dietary GI/GL could be considered as modifiable risk factors for primary cancer prevention.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT03335644.

Perspective: Does Glycemic Index Matter for Weight Loss and Obesity Prevention? Examination of the Evidence on "Fast" Compared with "Slow" Carbs

High-glycemic index (high-GI) foods (so-called fast carbs) have been hypothesized to promote fat storage and increase risk of obesity. To clarify whether dietary GI impacts body weight, we searched PubMed and the Cochrane Database of Systematic Reviews for observational studies reporting associations between BMI and dietary GI, and for meta-analyses of randomized controlled trials (RCTs) comparing low-GI and high-GI diets for weight loss. Data on 43 cohorts from 34 publications, totaling 1,940,968 adults, revealed no consistent differences in BMI when comparing the highest with the lowest dietary GI groups. In the 27 cohort studies that reported results of statistical comparisons, 70% showed that BMI was either not different between the highest and lowest dietary GI groups (12 of 27 cohorts) or that BMI was lower in the highest dietary GI group (7 of 27 cohorts). Results of 30 meta-analyses of RCTs from 8 publications demonstrated that low-GI diets were generally no better than high-GI diets for reducing body weight or body fat. One notable exception is that low-GI diets with a dietary GI at least 20 units lower than the comparison diet resulted in greater weight loss in adults with normal glucose tolerance but not in adults with impaired glucose tolerance. While carbohydrate quality, including GI, impacts many health outcomes, GI as a measure of carbohydrate quality appears to be relatively unimportant as a determinant of BMI or diet-induced weight loss. Based on results from observational cohort studies and meta-analyses of RCTs, we conclude that there is scant scientific evidence that low-GI diets are superior to high-GI diets for weight loss and obesity prevention.

Validation of estimated glycaemic index and glycaemic load, stratified by race, in the Adventist Health Study-2 (AHS-2)

OBJECTIVE

Few studies have validated FFQ estimates of dietary glycaemic index (GI) and load (GL). We investigated how well our estimates of overall GI and GL from FFQs correlate with estimates from repeated 24 h recall data to validate overall GI and GL in the Adventist Health Study-2 (AHS-2).

DESIGN

The AHS-2 is a prospective population-based cohort of 95 873 Seventh-day Adventist adult church members enrolled from 2002 to 2007 to investigate diet, cancer and mortality.

SETTING

A 204-item FFQ was used to assess race- and gender-specific validity of GI and GL and 24 h recall data, from the calibration sub-study, were used as the reference.

PARTICIPANTS

The 734 calibration study participants were randomly selected by church and included approximately equal numbers of blacks and whites but were otherwise similar to the whole cohort with respect to gender, age, education and vegetarian status.

RESULTS

The deattenuated correlation coefficients for overall GI ranged from 0·19 (95 % CI -0·06, 0·53) in black men to 0·46 (95 % CI 0·40, 0·60) in black women, with both non-black men and women falling between those values (0·45 (95 % CI 0·35, 0·65) and 0·38 (95 % CI 0·27, 0·57), respectively). GL correlations were somewhat higher for all study participants. When looking at the entire cohort, the deattenuated validity correlation value for overall GI was (r 0·38, 95 % CI 0·36, 0·47) and GL was (r 0·39, 95 % CI 0·34, 0·49).

CONCLUSIONS

Our findings support the cautious use of our FFQ in epidemiological studies when assessing associations of overall GI and GL with disease risk. However, observed differences by race should be considered when interpreting results.

Management of Hypoglycemia in Adults with Type 1 Diabetes in Real-Life Condition

INTRODUCTION

Hypoglycemia is the most common acute complication in individuals with type 1 diabetes (T1D). Episodes of mild or moderate hypoglycemia should be treated in adults with a dose of around 15-20 g fast-acting carbohydrates. However, this self-treatment of hypoglycemia in real-life condition is not well documented.

OBJECTIVE

The aim of this study wasto determine the characteristics of hypoglycemia treatment in adults with T1D in a prospective study design.

METHODS

Individuals with T1D were advised to record information related to hypoglycemia episodes for a period of 14 days. Quantity and quality (including glycemic index [GI] and glycemic load) of carbohydrates consumed in every hypoglycemia episode and others factors related with hypoglycemia such as physical activity, fear of hypoglycemia, or hypoglycemia awareness were analyzed.

RESULTS

A total of 93 individuals (36.5 ± 16.2 years old, BMI of 24.9 ± 3.8 kg/m2, diabetes duration of 14.9 ± 10.4 years, and HbA1c levels of 7.3 ± 0.8%) were included in the study. A total of 483 episodes of mild or moderate hypoglycemia were reported, which supposed on average 2.7 ± 2.0 episodes a week. The quantity of carbohydrates consumed in all episodes of hypoglycemia was 25.9 ± 9.2 g. GI of food consumed in all episodes of hypoglycemia was classified as low (53.9 ± 8.3). Overtreatment of hypoglycemia, defined as ingestion of more than 20 g of carbohydrates, occurred in 50.3% of hypoglycemic episodes; even 22.3% of these episodes were treated with more than 30 g of carbohydrates. Fruit juice was the most popular option, chosen in almost 70% of the events. In addition, we observed other moderate or low GI foods such as milk, bread, cookies, and bakery products among the most consumed foods.

CONCLUSION

A majority of the studied individuals with T1D does not manage hypoglycemia according to current American Diabetes Association guidelines, in most cases by overtreating, choosing foods with low glycemic effect, and not varying the dose of carbohydrates, depending on the physical activity performed.

Dietary Glycemic Index and Glycemic Load Are Not Associated with the Metabolic Syndrome in Lebanese Healthy Adults: A Cross-Sectional Study

High dietary glycemic index (GI) and glycemic load (GL) were suggested to increase the risk of metabolic syndrome (MetS). This study aims to estimate dietary GI and GL in a sample of healthy Lebanese adults and examine their association with MetS and its individual abnormalities. The study uses data from a community-based survey of 501 Lebanese urban adults. Dietary intake was assessed using a food frequency questionnaire. Biochemical, anthropometric, and blood pressure measurements were obtained. Subjects with previous diagnosis of chronic disease, metabolic abnormalities, or with incomplete data or implausible energy intakes were excluded, yielding a sample of 283. Participants were grouped into quartiles of GI and GL. Multivariate logistic regression analyses were performed. Average dietary GI and GL were estimated at 59.9 ± 8 and 209.7 ± 100.3. Participants belonging to the highest GI quartile were at increased risk of having MetS (odds ratio (OR) = 2.251, 95% CI:1.120–4.525) but this association lost significance with further adjustments. Those belonging to the second quartile of GI had significantly lower odds of having hyperglycemia (OR: 0.380, 95% CI:0.174–0.833). No associations were detected between GL and MetS. The study contributes to the body of evidence discussing the relationship between GI, GL, and MetS, in a nutrition transition context.

The Role of Glycemic Index and Glycemic Load in the Development of Real-Time Postprandial Glycemic Response Prediction Models for Patients With Gestational Diabetes

The incorporation of glycemic index (GI) and glycemic load (GL) is a promising way to improve the accuracy of postprandial glycemic response (PPGR) prediction for personalized treatment of gestational diabetes (GDM). Our aim was to assess the prediction accuracy for PPGR prediction models with and without GI data in women with GDM and healthy pregnant women. The GI values were sourced from University of Sydney’s database and assigned to a food database used in the mobile app DiaCompanion. Weekly continuous glucose monitoring (CGM) data for 124 pregnant women (90 GDM and 34 control) were analyzed together with records of 1489 food intakes. Pearson correlation (R) was used to quantify the accuracy of predicted PPGRs from the model relative to those obtained from CGM. The final model for incremental area under glucose curve (iAUC120) prediction chosen by stepwise multiple linear regression had an R of 0.705 when GI/GL was included among input variables and an R of 0.700 when GI/GL was not included. In linear regression with coefficients acquired using regularization methods, which was tested on the data of new patients, R was 0.584 for both models (with and without inclusion of GI/GL). In conclusion, the incorporation of GI and GL only slightly improved the accuracy of PPGR prediction models when used in remote monitoring.

The Glycaemic Index-Food-Frequency Questionnaire: Development and Validation of a Food Frequency Questionnaire Designed to Estimate the Dietary Intake of Glycaemic Index and Glycaemic Load: An Effort by the PREVIEW Consortium

Dietary glycaemic index (GI) and glycaemic load (GL) are indices used to quantify the effect of carbohydrate quality and quantity on postprandial glycaemia. GI/GL-health associations are widely studied but data on the validity of integrated GI/GL measurements are scarce. We evaluated the performance of a food-frequency questionnaire (FFQ) specifically developed to assess GI/GL. In total, 263 Dutch men and 212 women (aged 55 ± 11 years) completed a 58-item GI-FFQ, an 183-item general-FFQ and a 2-day 24 h-recall and donated blood for glycated haemoglobin (HbA1c) determination. The level of agreement between these methods was evaluated by (1) cross-classification, (2) correlations and (3) Bland and Altman plots. The three dietary assessment methods provided comparable mean intake estimates for total carbohydrates (range: 214–237 g/day), mono/disaccharides (100–107 g/day), polysaccharides (114–132 g/day), as well as bread, breakfast cereals, potatoes, pasta, rice, fruit, dairy, cakes/cookies and sweets. Mean (±SD) GI estimates were also comparable between the GI-FFQ (54 ± 3), general-FFQ (53 ± 4) and 24 h-recalls (53 ± 5). Mean (±SD) GI-FFQ GL (117 ± 37) was slightly lower than the general-FFQ GL (126 ± 38) and 24 h-recalls GL (127 ± 37). Classification of GI in quartiles was identical for the GI-FFQ and general-FFQ for 43% of the population (r = 0.58) and with 24 h-recalls for 35% of the population (de-attenuated r = 0.64). For GL, this was 48% (r = 0.65) and 44% (de-attenuated r = 0.74). Correlations between GI and HbA1c were low (r = −0.09 for GI-FFQ, r = −0.04 for general-FFQ and r = 0.07 for 24 h-recalls). In conclusion, compared to a general-FFQ and 24 h-recalls, the GI-FFQ showed a moderate to good relative validity for carbohydrates, carbohydrate-rich foods and GI/GL. No metric predicted HbA1c.

Insufficient Fruit and Vegetable Intake in a Low- and Middle-Income Setting: A Population-Based Survey in Semi-Urban Tanzania

A daily intake of 5 portions of fruit and vegetables (FV) is recommended for protection against non-communicable diseases (NCDs). Inadequate FV intake is a global problem but resource-poor countries like Tanzania are most deprived and constitute settings where little is known for informing public health interventions. This study aimed to describe the prevalence of inadequate FV intake, frequency of FV intake, portions of FV intake and their associations with socio-demographic/lifestyle factors in South-Eastern Tanzania. Data on FV dietary indicators, socio-demographic factors, smoking, alcohol and healthcare use were collected from 7953 participants (≥15 years) of the population-based MZIMA open community cohort (2012–2013). Multivariable logistic regression was used to examine associations between FV intake outcomes and their socio-demographic/lifestyle determinants. Most (82%) of the participants did not meet the recommended daily FV intake While only a fraction consumed fruits daily (15.5%), almost half consumed vegetables daily (44.2%). However, the median (IQR) number of vegetable portions consumed was lower (2(1)/person/day) than that for fruits (2(2)/person/day) People with higher education were more likely to consume fruits daily. Independent correlates of inadequate FV intake included young age, being male, low education, low-income occupations, low alcohol, high tobacco and low healthcare use. Public health interventions should target the socio-economically deprived and culturally-rooted preferences while prioritizing promotion of vegetable for most immediate gain in overall FV intake.

A Japanese diet with low glycaemic index and glycaemic load is associated with both favourable and unfavourable aspects of dietary intake patterns in three generations of women

Objective

Western studies have suggested cultural differences in food and nutrient intake patterns associated with dietary glycaemic index (GI) and glycaemic load (GL). Here, we conducted a cross-sectional study to examine the GI and GL of Japanese diets in relation to food and nutrient intakes.

Design

Dietary intake was assessed using a validated, self-administered, diet history questionnaire.

Setting

A total of thirty-five of forty-seven prefectures in Japan.

Subjects

Young (age 18 years), middle-aged (mean age 48 years) and older (mean age 74 years) Japanese women (n 3961, 3800 and 2202, respectively).

Results

Irrespective of age, a positive association with dietary GI was seen for white rice only, which contributed most (37–42 %) to the variation in dietary GI. Conversely, all other food groups (such as fruit and vegetable juice, dairy products, noodles and fruit) were negative predictors of dietary GI. For dietary GL, 95–96 % of variation was explained by carbohydrate-rich food groups, all of which were positive predictors of GL. After adjustment for potential confounding factors, only carbohydrate intake was positively associated with dietary GI and GL, irrespective of age. Conversely, dietary GI and GL were inversely associated with intakes of all other nutrients examined (including SFA and Na).

Conclusions

A low-GI and -GL diet, which was characterized principally by a low intake of white rice, was associated with both favourable (higher intakes of dietary fibre and key vitamins and minerals) and unfavourable (higher intakes of SFA and Na) aspects of dietary intake patterns in three generations of Japanese women.

Short-term effects of a hypocaloric diet with low glycemic index and low glycemic load on body adiposity, metabolic variables, ghrelin, leptin, and pregnancy rate in overweight and obese infertile women: a randomized controlled trial

BACKGROUND

Obesity is related to hormonal disorders that affect the reproductive system. Low-glycemic index (LGI) diets seem to exert a positive effect on weight loss and on metabolic changes that result from obesity.

OBJECTIVE

We investigated the effects of a hypocaloric diet with an LGI and low glycemic load on anthropometric and metabolic variables, ghrelin and leptin concentrations, and the pregnancy rate in overweight and obese infertile women who were undergoing in vitro fertilization (IVF).

DESIGN

The study was a randomized block-design controlled trial in which we analyzed 26 overweight or obese infertile women. Patients were assigned to a hypocaloric LGI-diet group or a control group and followed the protocol for 12 wk. Body weight, body mass index (BMI), percentage of body fat, glucose, insulin, homeostasis model assessment of insulin resistance, serum lipids, reproductive hormones, leptin, acylated ghrelin, number of oocytes retrieved in the IVF cycle, and pregnancy rate were determined.

RESULTS

There were greater reductions in body mass, BMI, percentage of body fat, waist:hip ratio, and leptin in the LGI-diet group than in the control group (P < 0.05). Despite a change of 18% in mean values, there was no significant increase in acylated ghrelin concentrations in the LGI group compared with the control group (P = 0.215). The LGI-diet group had 85.4% more oocytes retrieved than did the control group (7.75 ± 1.44 and 4.18 ± 0.87, respectively; P = 0.039) in the IVF cycle. Three patients (21.4%) in the LGI group experienced a spontaneous pregnancy during the follow-up, which generated 3 live births.

CONCLUSIONS

The hypocaloric LGI diet promoted a decrease in BMI, percentage of body fat, and leptin concentrations, which improved oocyte development and pregnancy rate. These results support the clinical recommendation to advise overweight and obese women to lose weight through a balanced diet before being submitted for treatment with assisted reproduction technologies. A hypocaloric diet combined with LGI foods seems to be beneficial for these patients, but additional studies are required before this treatment is recommended. This trial was registered at clinicaltrials.gov as NCT02416960.

Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC)

BACKGROUND AND AIMS

The positive and negative health effects of dietary carbohydrates are of interest to both researchers and consumers.

METHODS

International experts on carbohydrate research held a scientific summit in Stresa, Italy, in June 2013 to discuss controversies surrounding the utility of the glycemic index (GI), glycemic load (GL) and glycemic response (GR).

RESULTS

The outcome was a scientific consensus statement which recognized the importance of postprandial glycemia in overall health, and the GI as a valid and reproducible method of classifying carbohydrate foods for this purpose. There was consensus that diets low in GI and GL were relevant to the prevention and management of diabetes and coronary heart disease, and probably obesity. Moderate to weak associations were observed for selected cancers. The group affirmed that diets low in GI and GL should always be considered in the context of diets otherwise understood as healthy, complementing additional ways of characterizing carbohydrate foods, such as fiber and whole grain content. Diets of low GI and GL were considered particularly important in individuals with insulin resistance.

CONCLUSIONS

Given the high prevalence of diabetes and pre-diabetes worldwide and the consistency of the scientific evidence reviewed, the expert panel confirmed an urgent need to communicate information on GI and GL to the general public and health professionals, through channels such as national dietary guidelines, food composition tables and food labels.

Dietary n-6 PUFA, carbohydrate:protein ratio and change in body weight and waist circumference: a follow-up study

OBJECTIVE

To investigate the association between the intake of n-6 PUFA and subsequent change in body weight and waist circumference at different levels of the carbohydrate:protein ratio.

DESIGN

Follow-up study with anthropometric measurements at recruitment and on average 5·3 years later. Dietary intake was determined at recruitment by using an FFQ that was designed for the study and validated. We applied linear regression models with 5-year change in weight or waist circumference as outcome and including a two-way interaction term between n-6 PUFA and carbohydrate intakes, lower-order terms, protein intake, long-chain n-3 PUFA intake and other potential confounders. Due to adjustment for intake of protein, levels of carbohydrate indirectly reflect levels of the carbohydrate:protein ratio.

SETTING

Diet, Cancer and Health follow-up study, Denmark.

SUBJECTS

Women and men (n 29 152) aged 55 years.

RESULTS

For a high intake of n-6 PUFA (6·9 % of energy) v. a low intake of n-6 PUFA (3·4 % of energy), the difference in 5-year weight change was -189·7 g (95 % CI -636·8, 257·4 g) at a low carbohydrate:protein ratio and -86·7 g (95 % CI -502·9, 329·6 g) at a high carbohydrate:protein ratio; the differences in 5-year waist circumference change were 0·26 cm (95 % CI -0·47, 0·98 cm) and -0·52 cm (95 % CI -1·19, 0·15 cm), respectively. Inclusion of the dietary glycaemic index did not change the results.

CONCLUSIONS

No consistent associations between the intake of n-6 PUFA and change in body weight or waist circumference at different levels of the carbohydrate:protein ratio were observed.

High dietary glycemic load is associated with increased risk of colon cancer

High dietary glycemic load (GL) has been inconsistently associated with risk of colon cancer. We analyzed data for 1093 incident cases and 1589 controls in a population-based case-control study of colon cancer to further clarify the GL-colon cancer relationship. GL was assessed using a self-administered food frequency questionnaire. Cases had a significantly higher GL intake (mean = 136.4, SD = 24.5) than controls (mean = 132.8, SD = 25.2) (P = 0.0003). In a multivariate unconditional logistic regression model, the odds ratios (ORs) for colon cancer increased significantly with increasing GL: compared to the bottom quartile of GL, the ORs (95% CI) for the 2nd through the upper quartiles were 1.38 (1.06, 1.80), 1.67 (1.30, 2.13), and 1.61 (1.25, 2.07), respectively (P trend < 0.0001). Stratified analyses showed that the association was more pronounced among older participants [ORs (95% CI) for the 2nd through the upper quartiles were 1.35 (0.91, 2.00), 1.87 (1.29, 2.71), 2.02 (1.39, 2.95), respectively] than among younger participants [ORs were 1.46 (1.02, 2.10), 1.53 (1.09, 2.15), and 1.35 (0.96, 1.91), respectively] (P int = 0.02). Our results provide support for the hypothesis that a diet with high GL increases the risk of colon cancer.

The Association Between Diet and Obesity in Specific European Cohorts: DiOGenes and EPIC-PANACEA

This review summarizes evidence from two projects embedded within the European Prospective Investigation into Cancer and Nutrition (EPIC) on the association between dietary factors and obesity risk, in particular change in weight and waist circumference. A total of 12 publications from DiOGenes and six from EPIC-PANACEA were reviewed. The results show that dietary fiber, especially cereal fiber, was inversely associated with weight or waist change, as well as fruit/vegetable intake and the Mediterranean dietary pattern. Energy density and meat consumption were positively associated with the anthropometric changes, as was glycemic index with waist change. Clear associations with macronutrient composition were not observed. In additional studies, interactions with genetic polymorphism were investigated and shown to be present for protein intake and GI, although effect estimates were small. These interactions require replication. These results show that in European populations dietary factors are independently associated with weight/waist change. The findings provide further clues for the prevention of obesity.

Associations of dietary glycaemic index and glycaemic load with food and nutrient intake and general and central obesity in British adults

Inconsistent associations between dietary glycaemic index (GI) and glycaemic load (GL) and body fatness may be partly due to differences in the underlying dietary patterns or energy under-reporting. In the present study, we examined the cross-sectional associations of dietary GI and GL with food and nutrient intake and general and central obesity, accounting for energy under-reporting. The subjects were 1487 British adults aged 19-64 years. Dietary intake was assessed using a 7 d weighed dietary record. Breads and potatoes were the positive predictive foods for dietary GI, while fruit, other cereals and dairy products were the negative predictors. These foods were similarly identified in the analysis of only acceptable reporters (AR; ratio of reported energy intake:estimated energy requirement within 0·665-1·335) and under-reporters (UR; ratio < 0·665). Dietary GL was closely correlated with carbohydrate intake. Multiple linear regression analyses showed that dietary GI was independently associated with a higher risk of general obesity (BMI ≥ 30 kg/m²) and central obesity (waist circumference ≥ 102 cm in men and ≥ 88 cm in women). Dietary GL was also associated with general (only women) and central obesity. Similarly, in the analysis of AR, the GI showed positive associations with general and central obesity, and, only in women, the GL showed positive associations with general and central obesity. Conversely, in the analysis of UR, the associations were generally weaker and many of them failed to reach statistical significance. In conclusion, we found independent positive associations of dietary GI and GL with general and central obesity in British adults.

Dietary glycemic index and glycemic load in relation to changes in body composition measures during adolescence: Northern Ireland Young Hearts Study

BACKGROUND

Epidemiologic evidence on the influence of dietary glycemic index (GI) and glycemic load (GL) on the development of obesity is limited.

OBJECTIVE

This prospective study examined the associations between dietary GI and GL and changes in body composition measures during adolescence.

DESIGN

In a representative sample of Northern Irish adolescents aged 12 years at baseline and 15 years at follow-up (n=426), dietary intake was assessed by a diet history interview. Body composition measures included body mass index (BMI; kg m(-2)), BMI z-score, sum of four skinfold thicknesses, percentage body fat, fat mass index (FMI; kg m(-2)) and fat-free mass index (kg m(-2)).

RESULTS

After adjustment for potential confounding factors, baseline GI was associated with increased change in FMI. Mean (95% confidence interval) values of changes in FMI according to tertiles of baseline GI were 0.41 (0.25, 0.57), 0.42 (0.26, 0.58) and 0.67 (0.51, 0.83) kg m(-2), respectively (P for trend=0.03). There was no significant association of baseline GI with changes in other body composition measures (P for trend≥0.054). Conversely, baseline GL showed no association with changes in any of the measures (P for trend≥0.41). Furthermore, changes in GI or GL were not associated with changes in any of the measures (P for trend≥0.16).

CONCLUSION

Dietary GI at age 12 years was independently associated with increased change in FMI between ages 12 and 15 years in a representative sample from Northern Ireland, whereas dietary GL showed no association with changes in any of the body composition measures examined.

Dietary glycaemic index and glycaemic load in relation to food and nutrient intake and indices of body fatness in British children and adolescents

The diversity of the associations of dietary glycaemic index (GI) and glycaemic load (GL) with dietary intake and body fatness observed in epidemiological studies may be partly due to the differences in underlying dietary intake patterns. We examined the cross-sectional associations of dietary GI and GL with food and nutrient intakes and indices of body fatness in 818 children aged 4–10 years and 818 adolescents aged 11–18 years in Britain, based on the data from the National Diet and Nutrition Survey. Dietary intake was assessed using a 7 d weighed dietary record. Overweight was defined as BMI ≥ 85th percentile of the age- and sex-specific British growth reference data. Central obesity was defined as waist:height ratio (WHtR) ≥ 0·5 (adolescents only). Breads, breakfast cereals and potatoes were the positive predictive food groups for dietary GI, while dairy products, fruit juice, other cereals and fruit were the negative predictors. Dietary GL was closely correlated with carbohydrate intake. Dietary GI showed no associations with overweight or central obesity. Conversely, dietary GL showed an independent association with a higher risk of overweight in children and a higher risk of central obesity (but not overweight) in adolescents. However, dietary GI and GL were not associated with BMI z-score in children and adolescents or WHtR in adolescents. In conclusion, the present study showed that dietary GL was independently associated with overweight in children and with central obesity in adolescents. Nevertheless, given no associations when body fatness measures were treated as continuous variables, the results must be interpreted cautiously.

Dietary fiber and the glycemic index: a background paper for the Nordic Nutrition Recommendations 2012

The aim of this study is to review recent data on dietary fiber (DF) and the glycemic index (GI), with special focus on studies from the Nordic countries regarding cardiometabolic risk factors, type 2 diabetes, cardiovascular disease, cancer, and total mortality. In this study, recent guidelines and scientific background papers or updates on older reports on DF and GI published between 2000 and 2011 from the US, EU, WHO, and the World Cancer Research Fund were reviewed, as well as prospective cohort and intervention studies carried out in the Nordic countries. All of the reports support the role for fiber-rich foods and DF as an important part of a healthy diet. All of the five identified Nordic papers found protective associations between high intake of DF and health outcomes; lower risk of cardiovascular disease, type 2 diabetes, colorectal and breast cancer. None of the reports and few of the Nordic papers found clear evidence for the GI in prevention of risk factors or diseases in healthy populations, although association was found in sub-groups, e.g. overweight and obese individuals and suggestive for prevention of type 2 diabetes. It was concluded that DF is associated with decreased risk of different chronic diseases and metabolic conditions. There is not enough evidence that choosing foods with low GI will decrease the risk of chronic diseases in the population overall. However, there is suggestive evidence that ranking food based on their GI might be of use for overweight and obese individuals. Issues regarding methodology, validity and practicality of the GI remain to be clarified.

Macronutrient composition of the diet and prospective weight change in participants of the EPIC-PANACEA study

BACKGROUND

The effect of the macronutrient composition of the usual diet on long term weight maintenance remains controversial.

METHODS

373,803 subjects aged 25-70 years were recruited in 10 European countries (1992-2000) in the PANACEA project of the EPIC cohort. Diet was assessed at baseline using country-specific validated questionnaires and weight and height were measured at baseline and self-reported at follow-up in most centers. The association between weight change after 5 years of follow-up and the iso-energetic replacement of 5% of energy from one macronutrient by 5% of energy from another macronutrient was assessed using multivariate linear mixed-models. The risk of becoming overweight or obese after 5 years was investigated using multivariate Poisson regressions stratified according to initial Body Mass Index.

RESULTS

A higher proportion of energy from fat at the expense of carbohydrates was not significantly associated with weight change after 5 years. However, a higher proportion of energy from protein at the expense of fat was positively associated with weight gain. A higher proportion of energy from protein at the expense of carbohydrates was also positively associated with weight gain, especially when carbohydrates were rich in fibre. The association between percentage of energy from protein and weight change was slightly stronger in overweight participants, former smokers, participants ≥60 years old, participants underreporting their energy intake and participants with a prudent dietary pattern. Compared to diets with no more than 14% of energy from protein, diets with more than 22% of energy from protein were associated with a 23-24% higher risk of becoming overweight or obese in normal weight and overweight subjects at baseline.

CONCLUSION

Our results show that participants consuming an amount of protein above the protein intake recommended by the American Diabetes Association may experience a higher risk of becoming overweight or obese during adult life.

Is glycaemic index (GI) a valid measure of carbohydrate quality?

Recent criticisms of the glycaemic index (GI) focus on its validity with assertions that GI methodology is not valid, GI values are inaccurate and imprecise, GI does not predict what foods are healthy and that whole grain and fibre are better markers of carbohydrate quality than GI. None of the critics provide sound reasons for rejecting GI because some of their arguments are based on flagrant errors in understanding and interpretation while others are not supported by current data or are inconsistent with other nutritional recommendations. This paper addresses current criticisms of GI and outlines reasons why GI is valid: (1) GI methodology is accurate and precise enough for practical use; (2) GI is a property of foods; and (3) GI is biologically meaningful and relevant to virtually everyone. Current dietary guidelines recommend increased consumption of whole grains and dietary fibre but do not mention GI. However, this is illogical because the evidence that GI affects health outcomes is at least as good or better than that for whole grains and fibre. GI is a novel concept from a regulatory point of view and a number of problems need to be addressed to successfully translate GI knowledge into practice. The problems are not insurmountable but no progress can be made until bias and misunderstanding about GI can be overcome and there is better agreement about what is the actual state of knowledge on GI so that the real issues can be identified and addressed.

Methodology for adding glycemic index to the National Health and Nutrition Examination Survey nutrient database

Generating valid estimates of dietary glycemic index (GI) and glycemic load (GL) has been a challenge in nutritional epidemiology. The methodologic issues may have contributed to the wide variation of GI/GL associations with health outcomes observed in existing literature. We describe a standardized methodology for assigning GI values to items in the National Health and Nutrition Examination Survey (NHANES) nutrient database using the new International Tables to develop research-driven, systematic procedures and strategies to estimate dietary GI/GL exposures of a nationally representative population sample. Nutrient databases for NHANES 2003-2006 contain information on 3,155 unique foods derived from the US Department of Agriculture National Nutrient Database for Standard Reference versions 18 and 20. Assignment of GI values were made to a subset of 2,078 carbohydrate-containing foods using systematic food item matching procedures applied to 2008 international GI tables and online data sources. Matching protocols indicated that 45.4% of foods had identical matches with existing data sources, 31.9% had similar matches, 2.5% derived GI values calculated with the formula for combination foods, 13.6% were assigned a default GI value based on low carbohydrate content, and 6.7% of GI values were based on data extrapolation. Most GI values were derived from international sources; 36.1% were from North American product information. To confirm data assignments, dietary GI and GL intakes of the NHANES 2003-2006 adult participants were estimated from two 24-hour recalls and compared with published studies. Among the 3,689 men and 4,112 women studied, mean dietary GI was 56.2 (men 56.9, women 55.5), mean dietary GL was 138.1 (men 162.1, women 116.4); the distribution of dietary GI was approximately normal. Estimates of population GI and GL compare favorably with other published literature. This methodology of adding GI values to an existing population nutrient database utilized systematic matching protocols and the latest comprehensive data sources on food composition. The database can be applied in clinical and survey research settings where there is interest in estimating individual and population dietary exposures and relating them to health outcomes.

Association between dietary meat consumption and incident type 2 diabetes: the EPIC-InterAct study

AIMS/HYPOTHESIS

A diet rich in meat has been reported to contribute to the risk of type 2 diabetes. The present study aims to investigate the association between meat consumption and incident type 2 diabetes in the EPIC-InterAct study, a large prospective case-cohort study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) study.

METHODS

During 11.7 years of follow-up, 12,403 incident cases of type 2 diabetes were identified among 340,234 adults from eight European countries. A centre-stratified random subsample of 16,835 individuals was selected in order to perform a case-cohort design. Prentice-weighted Cox regression analyses were used to estimate HR and 95% CI for incident diabetes according to meat consumption.

RESULTS

Overall, multivariate analyses showed significant positive associations with incident type 2 diabetes for increasing consumption of total meat (50 g increments: HR 1.08; 95% CI 1.05, 1.12), red meat (HR 1.08; 95% CI 1.03, 1.13) and processed meat (HR 1.12; 95% CI 1.05, 1.19), and a borderline positive association with meat iron intake. Effect modifications by sex and class of BMI were observed. In men, the results of the overall analyses were confirmed. In women, the association with total and red meat persisted, although attenuated, while an association with poultry consumption also emerged (HR 1.20; 95% CI 1.07, 1.34). These associations were not evident among obese participants.

CONCLUSIONS/INTERPRETATION

This prospective study confirms a positive association between high consumption of total and red meat and incident type 2 diabetes in a large cohort of European adults.

Dietary glycemic index, glycemic load, and digestible carbohydrate intake are not associated with risk of type 2 diabetes in eight European countries

The association of glycemic index (GI) and glycemic load (GL) with the risk of type 2 diabetes remains unclear. We investigated associations of dietary GI, GL, and digestible carbohydrate with incident type 2 diabetes. We performed a case-cohort study nested within the European Prospective Investigation into Cancer and Nutrition Study, including a random subcohort (n = 16,835) and incident type 2 diabetes cases (n = 12,403). The median follow-up time was 12 y. Baseline dietary intakes were assessed using country-specific dietary questionnaires. Country-specific HR were calculated and pooled using random effects meta-analysis. Dietary GI, GL, and digestible carbohydrate in the subcohort were (mean ± SD) 56 ± 4, 127 ± 23, and 226 ± 36 g/d, respectively. After adjustment for confounders, GI and GL were not associated with incident diabetes [HR highest vs. lowest quartile (HR(Q4)) for GI: 1.05 (95% CI = 0.96, 1.16); HR(Q4) for GL: 1.07 (95% CI = 0.95, 1.20)]. Digestible carbohydrate intake was not associated with incident diabetes [HR(Q4): 0.98 (95% CI = 0.86, 1.10)]. In additional analyses, we found that discrepancies in the GI value assignment to foods possibly explain differences in GI associations with diabetes within the same study population. In conclusion, an expansion of the GI tables and systematic GI value assignment to foods may be needed to improve the validity of GI values derived in such studies, after which GI associations may need reevaluation. Our study shows that digestible carbohydrate intake is not associated with diabetes risk and suggests that diabetes risk with high-GI and -GL diets may be more modest than initial studies suggested.

Dietary fiber, carbohydrate quality and quantity, and mortality risk of individuals with diabetes mellitus

BACKGROUND

Dietary fiber, carbohydrate quality and quantity are associated with mortality risk in the general population. Whether this is also the case among diabetes patients is unknown.

OBJECTIVE

To assess the associations of dietary fiber, glycemic load, glycemic index, carbohydrate, sugar, and starch intake with mortality risk in individuals with diabetes.

METHODS

This study was a prospective cohort study among 6,192 individuals with confirmed diabetes mellitus (mean age of 57.4 years, and median diabetes duration of 4.4 years at baseline) from the European Prospective Investigation into Cancer and Nutrition (EPIC). Dietary intake was assessed at baseline (1992-2000) with validated dietary questionnaires. Cox proportional hazards analysis was performed to estimate hazard ratios (HRs) for all-cause and cardiovascular mortality, while adjusting for CVD-related, diabetes-related, and nutritional factors.

RESULTS

During a median follow-up of 9.2 y, 791 deaths were recorded, 306 due to CVD. Dietary fiber was inversely associated with all-cause mortality risk (adjusted HR per SD increase, 0.83 [95% CI, 0.75-0.91]) and CVD mortality risk (0.76[0.64-0.89]). No significant associations were observed for glycemic load, glycemic index, carbohydrate, sugar, or starch. Glycemic load (1.42[1.07-1.88]), carbohydrate (1.67[1.18-2.37]) and sugar intake (1.53[1.12-2.09]) were associated with an increased total mortality risk among normal weight individuals (BMI≤25 kg/m(2); 22% of study population) but not among overweight individuals (P interaction≤0.04). These associations became stronger after exclusion of energy misreporters.

CONCLUSIONS

High fiber intake was associated with a decreased mortality risk. High glycemic load, carbohydrate and sugar intake were associated with an increased mortality risk in normal weight individuals with diabetes.

Association between FTO variant and change in body weight and its interaction with dietary factors: the DiOGenes study

Although FTO is an established obesity-susceptibility locus, it remains unknown whether it influences weight change in adult life and whether diet attenuates this association. Therefore, we investigated the association of FTO-rs9939609 with changes in weight and waist circumference (WC) during 6.8 years follow-up in a large-scale prospective study and examined whether these associations were modified by dietary energy percentage from fat, protein, carbohydrate, or glycemic index (GI). This study comprised data from five countries of European Prospective Investigation into Cancer and Nutrition (EPIC) and was designed as a case-cohort study for weight gain. Analyses included 11,091 individuals, of whom 5,584 were cases (age (SD), 47.6 (7.5) years), defined as those with the greatest unexplained annual weight gain during follow-up and 5,507 were noncases (48.0 (7.3) years), who were compared in our case-noncase (CNC) analyses. Furthermore, 6,566 individuals (47.9 (7.3) years) selected from the total sample (all noncases and 1,059 cases) formed the random subcohort (RSC), used for continuous trait analyses. Interactions were tested by including interaction terms in the models. In the RSC-analyses, FTO-rs9939609 was associated with BMI (β (SE), 0.17 (0.08) kg·m(-2)/allele; P = 0.034) and WC (0.47 (0.21) cm/allele; P = 0.026) at baseline, but not with weight change (5.55 (12.5) g·year(-1)/allele; P = 0.66) during follow up. In the CNC-analysis, FTO-rs9939609 was associated with increased risk of being a weight-gainer (OR: 1.1; P = 0.045). We observed no interaction between FTO-rs9939609 and dietary fat, protein and carbohydrate, and GI on BMI and WC at baseline or on change in weight and WC. FTO-rs9939609 is associated with BMI and WC at baseline, but association with weight gain is weak and only observed for extreme gain. Dietary factors did not influence the associations.

Glycemic index and glycemic load are associated with some cardiovascular risk factors among the PREMIER study participants

BACKGROUND

The clinical significance of glycemic index (GI) and glycemic load (GL) is inconclusive.

OBJECTIVE

This study was conducted to examine the association of GI and GL with clinical cardiovascular disease (CVD) risk factors including body weight, blood pressure (BP), serum lipids, fasting glucose, insulin and homocysteine over time among the PREMIER participants.

DESIGN

PREMIER was an 18-month randomized lifestyle intervention trial, conducted from 2000 to 2002, designed to help participants reduce BP by following the Dietary Approaches to Stop Hypertension (DASH) dietary pattern, losing weight, reducing sodium and increasing physical activity. GI and GL were estimated from 24 h diet recall data at baseline, 6 and 18 months after intervention. PROC MIXED model was used to examine the association of changes in GI or GL with changes in CVD risk factors.

RESULTS

A total of 756 randomized participants, 62% females and 34% African Americans and who averaged 50.0±0.3 years old and 95.3±0.7 kg, were included in this report. Neither GI nor GL changes was associated with changes in any risk factors at 6 months. At 18 months, however, the GI change was significantly and positively associated with total cholesterol (TC) change only (p<0.05, β=23.80±12.11 mg/dL or 0.62±0.31 mmol/L) with a significant age interaction. The GL change was significantly associated with TC (p=0.02, β=0.28±0.15 mg/dL or 0.01±0.00 mmol/L) positively and with low density lipoprotein cholesterol (LDL-C) changes negatively (p=0.03, β=-0.01±0.00 mg/dL or -0.00±0.00 mmol/L), and significant age interactions were observed for both.

CONCLUSIONS

GI and GL was associated with TC and LDL-C after controlling for energy, fat and fiber intake and other potential confounders and the associations were modified by age. Further investigation into this relationship is important because of its potential clinical impact.

Glycaemic, insulin and ghrelin responses to traditional South Asian flatbreads in diabetic and healthy subjects

In the South-East Asian subcontinent, flatbreads contribute the main portion of carbohydrate to a meal. There are no specific data on the effect of different flatbreads on satiety and recurrent hunger, as indicated by the duration of ghrelin suppression after a meal. The present study was designed to examine the glycaemic, insulin and ghrelin responses to traditional subcontinental breads in type 2 diabetic subjects and healthy volunteers. For this purpose, twelve normoglycaemic healthy volunteers and ten type 2 diabetic patients, in the fasting state, consumed one of five common flatbreads on consecutive days. Capillary blood glucose was examined in the fasting state and serially for 5 h after a meal. Serum insulin and ghrelin levels were determined at hourly intervals for 5 h after the consumption of bran and plain chapatti flatbreads. The incremental area under the curve (iAUC) was calculated for glycaemic and insulin responses, while the net AUC was used to assess the ghrelin response. The results showed that glycaemic and insulin iAUC were lowest for bran chapatti, and highest for plain chapatti. Furthermore, bran chapatti showed maximum ghrelin suppression in both normal and diabetic groups. In conclusion, the low-glycaemic index bran chapatti flatbread had a lower postprandial glycaemic excursion and insulin response, and a more prolonged suppression of ghrelin levels, compared with the plain chapatti flatbread, and in each case, the difference was greater for the diabetic subjects than for the normal subjects. The inclusion of these flatbreads in the diabetic/weight-reducing diet may help weight loss by promoting satiety and reducing hyperinsulinaemia.

Successful development of satiety enhancing food products: towards a multidisciplinary agenda of research challenges

In the context of increasing prevalence of overweight and obesity in societies worldwide, enhancing the satiating capacity of foods may help people control their energy intake and weight. This requires an integrated approach between various food-related disciplines. By structuring this approach around the new product development process, this paper aims to present the contours of such an integrative approach by going through the current state of the art around satiety enhancing foods. It portrays actual food choice as the end result of a complex interaction between internal satiety signals, other food benefits, and environmental cues. Three interrelated routes to satiating enhancement are to change the food composition to develop stronger physiological satiation and satiety signals, anticipate and build on smart external stimuli at the moment of purchase and consumption, and improve palatability and acceptance of satiety enhanced foods. Key research challenges in achieving these routes in the field of nutrition, food technology, consumer, marketing, and communication are outlined.

Informing food choices and health outcomes by use of the dietary glycemic index

Considerable epidemiologic evidence links consuming lower glycemic index (GI) diets with good health, particularly upon aging. The GI is a kinetic parameter that reflects the ability of carbohydrate (CHO) contained in consumed foods to raise blood glucose in vivo. Newer nutritional, clinical, and experimental data link intake of lower dietary GI foods to favorable outcomes of chronic diseases, and compel further examination of the record. Based upon the new information there are two specific questions: 1) should the GI concept be promoted as a way to prolong health, and 2) should food labels contain GI information? Further, what are the remaining concerns about methodological issues and consistency of epidemiological data and clinical trials that need to be resolved in order to exploit the benefits of consuming lower GI diets? These issues are addressed in this review.

Glycaemic index values in the Finnish food composition database: an approach to standardised value documentation

BACKGROUND/OBJECTIVES

The glycaemic index (GI) is used to describe the blood glucose-raising potential of carbohydrate-containing foods. Only a few descriptions of the addition of GI values to national food composition databases (FCDBs) exist. We tested whether the value documentation framework established within the European Food Information Resource (EuroFIR) Network could be used for GI values when adding them to the Finnish FCDB.

METHODS

The list of foods requiring GI values was based on the National FINDIET 2007 Survey data and extended with foods encoded in a food-frequency questionnaire used in other nationally representative studies. The minimum quality of GI measurements was verified when gathering values from various sources, using earlier defined criteria. If a measured GI value for a food was directly available, or could be imputed or estimated, the value was added to the Finnish FCDB and documented using core standard vocabularies of EuroFIR. The GI values of composite foods were calculated using recipe calculation software.

RESULTS

A total of 2210 foods required a GI value. GI values for 1322 foods were available and added to the FCDB. The remaining 888 foods were composite foods and received a GI value through recipe calculation. The standard vocabularies describing the origin of the GI values, the methods used in their derivation and their qualitative characteristics were suitable for GI values.

CONCLUSIONS

GI values can be added to FCDBs and documented using terms similar to those used for traditional food composition data. Standardised value documentation may provide transparency for GI database compilation processes.

Dietary hyperglycemia, glycemic index and metabolic retinal diseases

The glycemic index (GI) indicates how fast blood glucose is raised after consuming a carbohydrate-containing food. Human metabolic studies indicate that GI is related to patho-physiological responses after meals. Compared with a low-GI meal, a high-GI meal is characterized with hyperglycemia during the early postprandial stage (0-2h) and a compensatory hyperlipidemia associated with counter-regulatory hormone responses during late postprandial stage (4-6h). Over the past three decades, several human health disorders have been related to GI. The strongest relationship suggests that consuming low-GI foods prevents diabetic complications. Diabetic retinopathy (DR) is a complication of diabetes. In this aspect, GI appears to be useful as a practical guideline to help diabetic people choose foods. Abundant epidemiological evidence also indicates positive associations between GI and risk for type 2 diabetes, cardiovascular disease, and more recently, age-related macular degeneration (AMD) in people without diabetes. Although data from randomized controlled intervention trials are scanty, these observations are strongly supported by evolving molecular mechanisms which explain the pathogenesis of hyperglycemia. This wide range of evidence implies that dietary hyperglycemia is etiologically related to human aging and diseases, including DR and AMD. In this context, these diseases can be considered as metabolic retinal diseases. Molecular theories that explain hyperglycemic pathogenesis involve a mitochondria-associated pathway and four glycolysis-associated pathways, including advanced glycation end products formation, protein kinase C activation, polyol pathway, and hexosamine pathway. While the four glycolysis-associated pathways appear to be universal for both normoxic and hypoxic conditions, the mitochondria-associated mechanism appears to be most relevant to the hyperglycemic, normoxic pathogenesis. For diseases that affect tissues with highly active metabolism and that frequently face challenge from low oxygen tension, such as retina in which metabolism is determined by both glucose and oxygen homeostases, these theories appear to be insufficient. Several lines of evidence indicate that the retina is particularly vulnerable when hypoxia coincides with hyperglycemia. We propose a novel hyperglycemic, hypoxia-inducible factor (HIF) pathway, to complement the current theories regarding hyperglycemic pathogenesis. HIF is a transcription complex that responds to decrease oxygen in the cellular environment. In addition to playing a significant role in the regulation of glucose metabolism, under hyperglycemia HIF has been shown to increase the expression of HIF-inducible genes, such as vascular endothelial growth factor (VEGF) leading to angiogenesis. To this extent, we suggest that HIF can also be described as a hyperglycemia-inducible factor. In summary, while management of dietary GI appears to be an effective intervention for the prevention of metabolic diseases, specifically AMD and DR, more interventional data is needed to evaluate the efficacy of GI management. There is an urgent need to develop reliable biomarkers of exposure, surrogate endpoints, as well as susceptibility for GI. These insights would also be helpful in deciphering the detailed hyperglycemia-related biochemical mechanisms for the development of new therapeutic agents.

Dietary determinants of changes in waist circumference adjusted for body mass index - a proxy measure of visceral adiposity

Background

Given the recognized health effects of visceral fat, the understanding of how diet can modulate changes in the phenotype “waist circumference for a given body mass index (WC_BMI)”, a proxy measure of visceral adiposity, is deemed necessary. Hence, the objective of the present study was to assess the association between dietary factors and prospective changes in visceral adiposity as measured by changes in the phenotype WC_BMI.

Methods and Findings

We analyzed data from 48,631 men and women from 5 countries participating in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Anthropometric measurements were obtained at baseline and after a median follow-up time of 5.5 years. WC_BMI was defined as the residuals of waist circumference regressed on body mass index, and annual change in WC_BMI (ΔWC_BMI, cm/y) was defined as the difference between residuals at follow-up and baseline, divided by follow-up time. The association between energy, energy density (ED), macronutrients, alcohol, glycemic index (GI), glycemic load (GL), fibre and ΔWC_BMI was modelled using centre-specific adjusted linear regression, and random-effects meta-analyses to obtain pooled estimates. Men and women with higher ED and GI diets showed significant increases in their WC_BMI, compared to those with lower ED and GI [1 kcal/g greater ED predicted a ΔWC_BMI of 0.09 cm (95% CI 0.05 to 0.13) in men and 0.15 cm (95% CI 0.09 to 0.21) in women; 10 units greater GI predicted a ΔWC_BMI of 0.07 cm (95% CI 0.03 to 0.12) in men and 0.06 cm (95% CI 0.03 to 0.10) in women]. Among women, lower fibre intake, higher GL, and higher alcohol consumption also predicted a higher ΔWC_BMI.

Conclusions

Results of this study suggest that a diet with low GI and ED may prevent visceral adiposity, defined as the prospective changes in WC_BMI. Additional effects may be obtained among women of low alcohol, low GL, and high fibre intake.

Effect of a low glycemic index compared with a conventional healthy diet on polycystic ovary syndrome

BACKGROUND

Women with polycystic ovarian syndrome (PCOS) are intrinsically insulin resistant and have a high risk of cardiovascular disease and type 2 diabetes. Weight loss improves risk factors, but the optimal diet composition is unknown. Low-glycemic index (low-GI) diets are recommended without evidence of their clinical effectiveness.

OBJECTIVE

We compared changes in insulin sensitivity and clinical outcomes after similar weight losses after consumption of a low-GI diet compared with a conventional healthy diet in women with PCOS.

DESIGN

We assigned overweight and obese premenopausal women with PCOS (n = 96) to consume either an ad libitum low-GI diet or a macronutrient-matched healthy diet and followed the women for 12 mo or until they achieved a 7% weight loss. We compared changes in whole-body insulin sensitivity, which we assessed using the insulin sensitivity index derived from the oral-glucose-tolerance test (ISI(OGTT)); glucose tolerance; body composition; plasma lipids; reproductive hormones; health-related quality of life; and menstrual cycle regularity.

RESULTS

The attrition rate was high in both groups (49%). Among completers, ISI(OGTT) improved more with the low-GI diet than with the conventional healthy diet (mean +/- SEM: 2.2 +/- 0.7 compared with 0.7 +/- 0.6, respectively; P = 0.03). There was a significant diet-metformin interaction (P = 0.048), with greater improvement in ISI(OGTT) among women prescribed both metformin and the low-GI diet. Compared with women who consumed the conventional healthy diet, more women who consumed the low-GI diet showed improved menstrual cyclicity (95% compared with 63%, respectively; P = 0.03). Among the biochemical measures, only serum fibrinogen concentrations showed significant differences between diets (P < 0.05).

CONCLUSION

To the best of our knowledge, this study provides the first objective evidence to justify the use of low-GI diets in the management of PCOS.

Trends in dietary carbohydrate quality during puberty from 1988 to 2007: a cause for concern?

The extent to which the quality of dietary carbohydrates (CHO) changes throughout puberty is not known. We analysed trends in the quantity and quality of CHO intake among German adolescents by separately examining trends during puberty (pubertal trends) and trends in CHO intake from 1988 to 2007 (secular trends). Linear mixed-effects regression analyses were performed in 216 participants of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study who had provided weighed 3 d dietary records at the onset of the pubertal growth spurt (defined by age at take-off) and over the subsequent 4 years. Over the course of puberty, CHO quality changed little: added sugar intake from beverages increased in girls (0·25 (se 0·12) % energy (% E)/year, P = 0·04) and added sugar intake from sweets decreased in both sexes (boys: - 0·22 (se 0·11) % E/year, P = 0·049; girls: - 0·20 (se 0·10) % E/year, P = 0·04). For both sexes, significant upward secular trends were observed for CHO (% E), glycaemic load (g/MJ) and added sugar intakes from sources other than sweets and soft drinks (% E), while absolute fibre intake (g/d) decreased (P ≤ 0·04). Concomitant increases in total added sugar intake (% E) and decreases in fibre and whole-grain densities (g/MJ) (P = 0·001-0·02) were confined to boys only. The quality of dietary CHO consumed by healthy German adolescents shows notable secular declines, but does not change markedly during puberty. Public health initiatives should be tailored to improve the overall quality of CHO nutrition.

Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index

BACKGROUND

Studies have suggested that replacing saturated fatty acids (SFAs) with carbohydrates is modestly associated with a higher risk of ischemic heart disease, whereas replacing SFAs with polyunsaturated fatty acids is associated with a lower risk of ischemic heart disease. The effect of carbohydrates, however, may depend on the type consumed.

OBJECTIVES

By using substitution models, we aimed to investigate the risk of myocardial infarction (MI) associated with a higher energy intake from carbohydrates and a concomitant lower energy intake from SFAs. Carbohydrates with different glycemic index (GI) values were also investigated.

DESIGN

Our prospective cohort study included 53,644 women and men free of MI at baseline.

RESULTS

During a median of 12 y of follow-up, 1943 incident MI cases occurred. There was a nonsignificant inverse association between substitution of carbohydrates with low-GI values for SFAs and risk of MI [hazard ratio (HR) for MI per 5% increment of energy intake from carbohydrates: 0.88; 95% CI: 0.72, 1.07). In contrast, there was a statistically significant positive association between substitution of carbohydrates with high-GI values for SFAs and risk of MI (HR: 1.33; 95% CI: 1.08, 1.64). There was no association for carbohydrates with medium-GI values (HR: 0.98; 95% CI: 0.80, 1.21). No effect modification by sex was observed.

CONCLUSION

This study suggests that replacing SFAs with carbohydrates with low-GI values is associated with a lower risk of MI, whereas replacing SFAs with carbohydrates with high-GI values is associated with a higher risk of MI.

Soft drink and juice consumption and risk of pancreatic cancer: the Singapore Chinese Health Study

BACKGROUND

Sugar-sweetened carbonated beverages (called soft drinks) and juices, which have a high glycemic load relative to other foods and beverages, have been hypothesized as pancreatic cancer risk factors. However, data thus far are scarce, especially from non-European descent populations. We investigated whether higher consumption of soft drinks and juice increases the risk of pancreatic cancer in Chinese men and women.

METHODS

A prospective cohort analysis was done to examine the association between soft drink and juice consumption and the risk of pancreatic cancer in 60,524 participants of the Singapore Chinese Health Study with up to 14 years of follow-up. Information on consumption of soft drinks, juice, and other dietary items, as well as lifestyle and environmental exposures, was collected through in-person interviews at recruitment. Pancreatic cancer cases and deaths were ascertained by record linkage of the cohort database with records of population-based Singapore Cancer Registry and the Singapore Registry of Births and Deaths.

RESULTS

The first 14 years for the cohort resulted in cumulative 648,387 person-years and 140 incident pancreatic cancer cases. Individuals consuming > or = 2 soft drinks/wk experienced a statistically significant increased risk of pancreatic cancer (hazard ratio, 1.87; 95% confidence interval, 1.10-3.15) compared with individuals who did not consume soft drinks after adjustment for potential confounders. There was no statistically significant association between juice consumption and risk of pancreatic cancer.

CONCLUSION

Regular consumption of soft drinks may play an independent role in the development of pancreatic cancer.

Dietary fiber and subsequent changes in body weight and waist circumference in European men and women

BACKGROUND

Dietary fiber may play a role in obesity prevention. Until now, the role that fiber from different sources plays in weight change had rarely been studied.

OBJECTIVE

Our aim was to investigate the association of total dietary fiber, cereal fiber, and fruit and vegetable fiber with changes in weight and waist circumference.

DESIGN

We conducted a prospective cohort study with 89,432 European participants, aged 20-78 y, who were free of cancer, cardiovascular disease, and diabetes at baseline and who were followed for an average of 6.5 y. Dietary information was collected by using validated country-specific food-frequency questionnaires. Multiple linear regression analysis was performed in each center studied, and estimates were combined by using random-effects meta-analyses. Adjustments were made for follow-up duration, other dietary variables, and baseline anthropometric, demographic, and lifestyle factors.

RESULTS

Total fiber was inversely associated with subsequent weight and waist circumference change. For a 10-g/d higher total fiber intake, the pooled estimate was -39 g/y (95% CI: -71, -7 g/y) for weight change and -0.08 cm/y (95% CI: -0.11, -0.05 cm/y) for waist circumference change. A 10-g/d higher fiber intake from cereals was associated with -77 g/y (95% CI: -127, -26 g/y) weight change and -0.10 cm/y (95% CI: -0.18, -0.02 cm/y) waist circumference change. Fruit and vegetable fiber was not associated with weight change but had a similar association with waist circumference change when compared with intake of total dietary fiber and cereal fiber.

CONCLUSION

Our finding may support a beneficial role of higher intake of dietary fiber, especially cereal fiber, in prevention of body-weight and waist circumference gain.

Developing a methodology for assigning glycaemic index values to foods consumed across Europe

There is growing evidence that the glycaemic index (GI) of the diet is important with respect to body weight and metabolic disease risk. However, research is limited by the paucity of GI values for commonly consumed carbohydrate-rich foods in European countries. A new methodology has been developed for consistent assignment of GI values to foods across five European databases used in the Diogenes intervention study. GI values were assigned according to five decreasing levels of confidence (1) Measured values for specific foods; (2) Published values from published sources; (3) Equivalent values where published values for similar foods existed; (4) Estimated values assigned as one of three values representing low/medium/high GI ranges and (5) Nominal values assigned as 70, where no other value could be assigned with sufficient confidence. GI values were assigned to 5105 foods. In food records collected at baseline, the contribution to carbohydrate intake of foods assigned levels 1-2 ranged from 16% to 43% depending on country, and this increased to 53-81% including level 3 foods. The degree of confidence to assigned GI values differed across Europe. This standardized approach of assigning GI values will be made available to other researchers to facilitate further investigation into the effects of dietary GI on health.