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

Carbohydrate nutrition is associated with the 5-year incidence of chronic kidney disease

It has been shown that dietary glycemic index (GI) and fiber could have a role in the development of chronic diseases; however, the link between carbohydrate nutrition and development of chronic kidney disease (CKD) is unclear. We aimed to determine whether cross-sectional and longitudinal associations exist between carbohydrate nutrition (mean dietary GI, dietary intakes of carbohydrate, sugar, starch, and fiber) and CKD. Data included 2600 Blue Mountains Eye Study (1997-1999) participants aged ≥50 y. Baseline biochemistry including serum creatinine was measured. Moderate CKD was defined as estimated glomerular filtration rate (eGFR) < 60 mL·min(-1)·1.73 m(-2). Dietary data were collected in a semiquantitative FFQ. Cross-sectionally, participants in the 4th quartile of mean dietary GI intake compared with those in the first quartile (reference) had a 55% increased likelihood of having eGFR < 60 mL·min(-1)·1.73 m(-2) [multivariable-adjusted OR = 1.55 (95% CI = 1.07-2.26); P-trend = 0.01]. After multivariable adjustment, participants in the 4th quartile of dietary cereal fiber intake compared with those in the first quartile (reference) had a 50% reduced risk of incident moderate CKD (P-trend = 0.03). Higher baseline consumption of energy-dense, nutrient-poor sources of carbohydrate (e.g. cookies) yielded a 3-fold higher risk of incident CKD (P-trend = 0.01). In summary, we observed a novel link between high cereal fiber intake and reduced incidence of moderate CKD and this was supported by the cross-sectional association with dietary GI. Conversely, our data suggest that higher intake of energy-dense, nutrient-poor sources of carbohydrate, potentially through acute hyperglycemia, could impair renal function.

Dietary glycemic load is a predictor of age-related hearing loss in older adults

Age-related hearing loss is a frequent disability in older adults and nutrition could play a role in the development of this condition. Carbohydrate nutrition [including dietary glycemic index (GI) and load (GL)] may be linked to hearing loss. We aimed to determine the association between carbohydrate nutrition (including mean dietary GI and GL, and the dietary intakes of carbohydrate and sugar), starch, cereal and total fiber, and age-related hearing loss. The Blue Mountains Hearing Study is a population-based survey of age-related hearing loss (1997-1999 to 2002-2004). Hearing loss was measured in 2956 participants (aged ≥50 y) and was defined as the pure-tone average of frequencies 0.5, 1.0, 2.0, and 4.0 kHz > 25 dB hearing level. Dietary data were collected in a semiquantitative FFQ. A purpose-built database based on Australian GI values was used to calculate the mean GI. A higher mean dietary GI was associated with an increased prevalence of any hearing loss, comparing quintiles 1 (lowest) and 5 (highest), [multivariable-adjusted odds ratio = 1.41 (95% CI = 1.01-1.97)]. Participants in the highest quartile of mean dietary GL intake compared with those in the lowest quartile had a 76% greater risk of developing incident hearing loss (P-trend = 0.04). Higher carbohydrate and sugar intakes were associated with incident hearing loss (P-trend = 0.03 and P-trend = 0.05, respectively). In summary, a high-GL diet was a predictor of incident hearing loss, as was higher intake of total carbohydrate. Hence, high postprandial glycemia might be a potential underlying biological mechanism in the development of age-related hearing loss.

Development and validation of a comprehensive semi-quantitative food frequency questionnaire that includes FODMAP intake and glycemic index

BACKGROUND

Fermentable, short chain carbohydrates (FODMAPs) have been identified as triggers for functional gastrointestinal symptoms. In addition, excess FODMAP consumption has been implicated in the onset of Crohn's disease, and animal studies suggest that a low glycemic index diet can impair absorption of fructose, a major dietary FODMAP. Such hypotheses cannot be tested without the ability to quantify FODMAP ingestion with a validated dietary assessment tool.

OBJECTIVE

To assess the validity and reproducibility of a 297-item comprehensive, semi-quantitative food frequency questionnaire (FFQ) in estimating intake of macro- and micronutrients, FODMAPs, and glycemic index/load.

SUBJECTS/SETTING

One hundred healthy participants were recruited to complete the FFQ on two occasions, plus four 1-week food diaries kept during a 12-month period. Participants exhibiting major dietary change during the study period or low energy reporting on the FFQ were excluded.

MAIN OUTCOME MEASURES

Validation and reproducibility of the semi-quantitative FFQ by comparison with the mean of four 1-week food diaries.

STATISTICAL ANALYSES PERFORMED

Validation was assessed using Wilcoxon signed rank test, Spearman's correlation, Bland-Altman, and weighted κ statistics. Reproducibility was examined using Shrout-Fleiss intraclass correlation coefficient.

RESULTS

Seventy-two participants fulfilled inclusion and exclusion criteria. Demographics of the participants were comparable with 2006 Australian Census data. Consistent with other reported FFQs, the FFQ overestimated nutrient intake by a mean 140% (range=95% to 249%). However, based on the other analyses performed, it demonstrated validity for intake of sugars, fiber, alcohol, glycemic index, glucose, FODMAPs, calcium, folate, phosphate, potassium, iron, and magnesium; moderate validation for energy, total fat, saturated fat, carbohydrates, sodium, thiamin, sucrose, and retinol; poor validation for protein, mono/polyunsaturated fat, starch, glycemic load, niacin, and zinc. Riboflavin intake was not validated. Intraclass correlation coefficients for reproducibility ranged from 0.352 to 0.928.

CONCLUSIONS

The FFQ was validated for assessment of a wide range of nutrients, including the new class of carbohydrates, FODMAPs, and glycemic index. This provides a useful tool for dietary research, particularly in the area of gastroenterological disorders.

Carbohydrate nutrition and inflammatory disease mortality in older adults

BACKGROUND

Several studies suggest that carbohydrate nutrition is related to oxidative stress and inflammatory markers.

OBJECTIVE

We examined whether dietary glycemic index (GI), dietary fiber, and carbohydrate-containing food groups were associated with the mortality attributable to noncardiovascular, noncancer inflammatory disease in an older Australian cohort.

DESIGN

Analysis included 1490 postmenopausal women and 1245 men aged ge 49 y at baseline (1992-1994) from a population-based cohort who completed a validated food-frequency questionnaire. Cox proportional hazards ratios were calculated both for death from diseases in which inflammation or oxidative stress was a predominant contributor and for cardiovascular mortality.

RESULTS

Over a 13-y period, 84 women and 86 men died of inflammatory diseases. Women in the highest GI tertile had a 2.9-fold increased risk of inflammatory death compared with women in the lowest GI tertile [multivariate hazard ratio in energy-adjusted tertile 3 (tertile 1 as reference): 2.89; 95% CI: 1.52, 5.51; P for trend: 0.0006, adjusted for age, smoking, diabetes, and alcohol and fiber consumption]. Increasing intakes of foods high in refined sugars or refined starches (P = 0.04) and decreasing intakes of bread and cereals (P = 0.008) or vegetables other than potatoes (P = 0.007) also independently predicted a greater risk, with subjects' GI partly explaining these associations. In men, only an increased consumption of fruit fiber (P = 0.005) and fruit (P = 0.04) conferred an independent decrease in risk of inflammatory death. No associations were observed with cardiovascular mortality.

CONCLUSION

These data provide new epidemiologic evidence of a potentially important link between GI and inflammatory disease mortality among older women.

Glycemic index, glycemic load, and the risk of pancreatic cancer among postmenopausal women in the women's health initiative observational study and clinical trial

BACKGROUND

Several reports have suggested that conditions associated with hyperinsulinemia and insulin resistance, such as diets high in carbohydrates, may influence the risk of pancreatic cancer, although results from prior studies have been mixed.

METHODS

We utilized data from the population-based women's health initiative (WHI) cohort to determine whether dietary factors that are associated with increased postprandial blood glucose levels are also associated with an increased risk of pancreatic cancer. The WHI included 161,809 postmenopausal women of ages 50-79, in which 332 cases of pancreatic cancer were identified over a median of 8 years of follow-up; 287 of these cases met the criteria for analysis. A validated 122-item food frequency questionnaire was used to estimate dietary glycemic load (GL), glycemic index (GI), total and available carbohydrates, fructose and sucrose. Baseline questionnaires and physical exams provided information on demographic, medical, lifestyle, and anthropometric characteristics. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between the exposures of interest and pancreatic cancer risk, with adjustment for potential confounders.

RESULTS

Dietary GL, GI, carbohydrates, fructose, and sucrose were not associated with increased risk of pancreatic cancer. The multivariable adjusted HR for the highest vs. the lowest quartile of GL was 0.80 (95% CI = 0.55-1.15, trend p = 0.31) and 1.13 (95% CI = 0.78-1.63, trend p = 0.94) for GI. The results remained negative when individuals with a history of diabetes were excluded.

CONCLUSIONS

Our results do not support the hypothesis that dietary intake of carbohydrates is associated with increased risk of pancreatic cancer.

Reproducibility and relative validity of dietary glycaemic index and glycaemic load assessed by the food-frequency questionnaire used in the Dutch cohorts of the European Prospective Investigation into Cancer and Nutrition

Limited information is available on the reproducibility and validity of dietary glycaemic index (GI) and glycaemic load (GL) estimated by habitual diet assessment methods such as FFQ, including the FFQ used in the Dutch cohorts of the European Prospective Investigation into Cancer and Nutrition study. To examine the reproducibility and relative validity of GI and GL, we used data from 121 Dutch men and women aged 23-72 years. They completed the FFQ three times at intervals of 6 months and twelve 24-h dietary recalls (24HDR) monthly during 1991-2. GI and GL were calculated using published values. Intra-class correlation coefficients of the three repeated FFQ were 0.78 for GI and 0.74 for GL. Pearson correlation coefficients between the first FFQ and the weighted average of the 24HDR were 0.63 for both GI and GL. Weighted kappa values between the first FFQ and the average of the 24HDR (in quintiles) were 0.40 for GI and 0.41 for GL. Bland-Altman plots showed a proportional bias in GI (beta = 0.46), but not in GL (beta = 0.06). In conclusion, this FFQ can be used in epidemiological studies to investigate the relationship of GI and GL with disease risks, but the proportional bias should be taken into account when using this FFQ to assess the absolute GI values.

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

Associations between the glycemic index (GI) or glycemic load (GL) and diseases are heterogeneous in epidemiological studies. Differences in assigning GI values to food items may contribute to this inconsistency. Our objective was to address methodological issues related to the use of current GI and GL values in epidemiological studies. We performed ecological comparison and correlation studies by calculating dietary GI and GL from country-specific dietary questionnaires (DQ) from 422,837 participants from 9 countries participating in the European Prospective Investigation into Cancer and Nutrition study and single standardized 24-h dietary recalls (24-HDR) obtained from a representative sample (n = 33,404) using mainly Foster Powell's international table as a reference source. Further, 2 inter-rater and 1 inter-method comparison were conducted, comparing DQ GI values assigned by independent groups with values linked by us. The ecological correlation between DQ and 24-HDR was good for GL (overall r = 0.76; P < 0.005) and moderate for GI (r = 0.57; P < 0.05). Mean GI/GL differences between DQ and 24-HDR were significant for most centers. GL but not GI from DQ was highly correlated with total carbohydrate (r = 0.98 and 0.15, respectively; P < 0.0001) and this was higher for starch (r = 0.72; P < 0.0001) than for sugars (r = 0.36; P < 0.0001). The inter-rater and inter-method variations were considerable for GI (weighted kappa coefficients of 0.49 and 0.65 for inter-rater and 0.25 for inter-method variation, respectively) but only mild for GL (weighted kappa coefficients > 0.80). A more consistent methodology to attribute GI values to foods and validated DQ is needed to derive meaningful GI/GL estimates for nutritional epidemiology.

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 glycemic index and the risk of age-related macular degeneration

BACKGROUND

Dietary factors are known risk factors for age-related macular degeneration (AMD) -- the leading cause of visual loss among persons aged > or =65 y. High-glycemic-index diets have been hypothesized as a risk factor for AMD, but prospective data are unavailable.

OBJECTIVE

The objective was to examine the association between dietary glycemic index and the 10-y incidence of AMD in the Blue Mountain Eye Study population.

DESIGN

This was a population-based cohort study with 3,654 participants (> or =49 y) examined at baseline (1992-1994); 2,335 patients were reexamined after 5 y and 1952 after 10 y. The Wisconsin System was used to grade 10-y incident early and late AMD from retinal photographs. A food-frequency questionnaire was used to collect dietary information at baseline, and an Australian database was used to calculate the mean glycemic index.

RESULTS

Over 10 y, 208 of 1,810 persons (cumulative incidence: 14.1%) developed early AMD. After age, smoking, other risk factors, and dietary constituents were adjusted for, a higher mean dietary glycemic index was associated with an increased 10-y risk of early AMD in a comparison of quartiles 1 and 4 [relative risk (RR): 1.77; 95% CI: 1.13, 2.78; P for trend = 0.03]. Conversely, a greater consumption of cereal fiber (RR: 0.68; 95% CI: 0.44, 1.04; P for trend = 0.05) and breads and cereals (predominantly lower glycemic index foods such as oatmeal) (RR: 0.67; 95% CI: 0.44, 1.02; P for trend = 0.03) was associated with a reduced risk of incident early AMD. No relation was observed with late AMD.

CONCLUSIONS

A high-glycemic-index diet is a risk factor for early AMD -- the recognized precursor of sight-threatening late AMD. Low-glycemic-index foods such as oatmeal may protect against early AMD.

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.

The glycemic index and cardiovascular disease risk

Postprandial hyperglycemia is increasingly recognized as an independent risk factor for cardiovascular disease. Glycemic "spikes" may adversely affect vascular structure and function via multiple mechanisms, including (acutely and/or chronically) oxidative stress, inflammation, low-density lipoprotein oxidation, protein glycation, and procoagulant activity. Postprandial glycemia can be reliably predicted by considering both the amount and type of carbohydrate. In particular, the glycemic index (GI), a measure of postprandial glycemic potency weight for weight of carbohydrate, has provided insights that knowledge of the sugar or starch content has not. In prospective observational studies, dietary GI and/or glycemic load independently predict cardiovascular disease, with relative risk ratios of 1.2 to 1.7 comparing highest and lowest quintiles. In randomized controlled trials in overweight subjects, diets based on low-GI carbohydrates have produced better cardiovascular-related outcomes than conventional low-fat diets. Taken together, the findings suggest that health professionals may be able to improve cardiovascular outcomes by recommending the judicious use of low- GI/glycemic load foods.