Correlation between dietary glycemic index and cardiovascular disease risk factors among Japanese women

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSION

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

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

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

Overall Glycemic Index and Glycemic Load of Vegan Diets in Relation to Plasma Lipoproteins and Triacylglycerols

BACKGROUND

To investigate the overall glycemic index (GI), glycemic load (GL), and intake of dietary fiber, and to examine the associations between these factors and plasma lipoproteins and triacylglycerols in adult vegans in the German Vegan Study (GVS).

METHODS

Cross-sectional study, Germany. Healthy men (n = 67) and women (n = 87), who fulfilled the study criteria (vegan diet for >or=1 year prior to study start; minimum age of 18 years; no pregnancy/childbirth during the last 12 months) and who participated in all study segments.

RESULTS

The average dietary GL of the GVS population was 144, and the average GI was 51.4. The adjusted geometric mean total, HDL, and LDL cholesterol concentrations decreased across the increasing quartiles of GL, carbohydrate and dietary fiber intake. The associations between total cholesterol, HDL cholesterol, LDL cholesterol and GL density and GI were inconsistent. Also, associations between GI, GL, the intake of carbohydrates, and triacylglycerol concentration were not observed.

CONCLUSIONS

Fiber-rich vegan diets are characterized by a low GI and a low to moderate GL. The data do not support the hypothesis that a carbohydrate-rich diet per se is associated with unfavorable effects on triaclyglycerols that would be predicted to increase the risk of coronary heart disease.

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

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

Dietary fiber intake, dietary glycemic index and load, and body mass index: a cross-sectional study of 3931 Japanese women aged 18–20 years

OBJECTIVE

Few observational studies have investigated dietary fiber intake and dietary glycemic index (GI) and glycemic load (GL) simultaneously in relation to obesity, particularly in non-Western populations. We examined the associations between dietary fiber intake and dietary GI and GL, and body mass index (BMI) in young Japanese women.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 3931 female Japanese dietetic students aged 18-20 years from 53 institutions in Japan.

METHODS

Dietary fiber intake and dietary GI and GL (GI for glucose=100) were assessed by a validated, self-administered, diet history questionnaire. BMI was calculated from self-reported body weight and height.

RESULTS

Mean values of BMI, dietary fiber intake, dietary GI and dietary GL were 21.0 kg/m(2), 6.5 g/4186 kJ, 65.1 and 82.1/4186 kJ, respectively. White rice (GI=77) was the major contributor to dietary GI and GL (45.8%). After controlling for potential dietary and nondietary confounding factors, dietary fiber intake was negatively correlated with BMI (adjusted mean=21.1 kg/m(2) in the lowest and 20.7 kg/m(2) in the highest quintiles; P for trend=0.0007). Conversely, dietary GI and GL were independently positively correlated with BMI (20.8 and 21.2 kg/m(2); P for trend=0.03, and 20.5 and 21.5 kg/m(2); P for trend=0.0005, respectively).

CONCLUSIONS

Dietary fiber intake showed an independent negative association with BMI, and dietary GI and GL showed an independent positive association with BMI among relatively lean young Japanese women.

Soy foods have low glycemic and insulin response indices in normal weight subjects

BACKGROUND

Foods with a low glycemic index (GI) may provide a variety of health benefits. The objective of the present study was to measure the GI and insulin index (II) of select soy foods.

METHODS

The study was conducted in two parts with low-carbohydrate products being tested separately. In Experiment 1, subjects averaged 23.2 years of age with BMI = 22.0 kg/m2, while subjects in Experiment 2 averaged 23.9 years of age with BMI = 21.6 kg/m2. The reference (glucose) and test foods were served in portions containing 10 g of carbohydrates in Experiment 1 (two test foods) and 25 g of carbohydrates in Experiment 2 (four test foods). Subjects consumed the reference food twice and each test food once. For each test, subjects were instructed to consume a fixed portion of the reference food or test food together with 250 g of water within 12 min. Blood samples were collected before each test and at 15, 30, 45, 60, 90, and 120 min after consumption of reference or test foods to quantify glucose and insulin. Two-hour blood glucose and plasma insulin curves were constructed and areas under the curves were calculated. GI and II values for each subject and test food were calculated.

RESULTS

In Experiment 1, both low-carbohydrate soy foods were shown to have significantly (P < 0.05) lower GI and II values than the reference food. In Experiment 2, three of the four test foods had significantly (P < 0.05) lower GI and II values than the reference food.

CONCLUSION

All but one of the soy foods tested had a low GI, suggesting that soy foods may be an appropriate part of diets intended to improve control of blood glucose and insulin levels.

Glycemic index and glycemic load in relation to changes in body weight, body fat distribution, and body composition in adult Danes

BACKGROUND

A diet with a high glycemic index (GI) and glycemic load (GL) may promote overconsumption of energy and increase the risk of weight gain.

OBJECTIVE

The objective of the study was to investigate the relation between GI and GL of habitual diets and subsequent 6-y changes in body weight, body fat distribution, and body composition in a random group of adult Danes.

DESIGN

A prospective cohort study was conducted in a subsample of men and women from the Danish arm of the Monitoring Trends and Determinants in Cardiovascular Disease study. The subsample comprised 185 men and 191 women born in 1922, 1932, 1942, or 1952. A baseline health examination and a dietary history interview were carried out in 1987 and 1988; a follow-up health examination was performed in 1993 and 1994.

RESULTS

Positive associations between GI and changes in body weight (DeltaBW), percentage body fat (Delta%BF), and waist circumference (DeltaWC) were observed in women after adjustment for covariates. Significant GI x sex x physical activity interactions for DeltaBW, Delta%BF, and DeltaWC were observed, and the associations in the sedentary women were particularly positive. No significant associations with GI were observed in men, and no significant associations with GL were observed in either sex.

CONCLUSIONS

High-GI diets may lead to increases in BW, body fat mass, and WC in women, especially in sedentary women, which suggests that physical activity may protect against diet-induced weight gain. No associations with GI were observed in men, which suggests sex differences in the association between GI and obesity development.

Cereal grains and legumes in the prevention of coronary heart disease and stroke: a review of the literature

A number of reviewers have examined studies investigating the relationship between coronary heart disease and stroke prior to 2000. Since then, several key studies have been published. Five studies have examined the relationship between wholegrain consumption, coronary heart disease (CHD) and cardiovascular (CVD) disease and found protection for either or both diseases. The researchers concluded that a relationship between wholegrain intake and CHD is seen with at least a 20% and perhaps a 40% reduction in risk for those who eat wholegrain food habitually vs those who eat them rarely. Notwithstanding the fact that fibre is an important component of wholegrains, many studies have not shown an independent effect of fibre alone on CHD events. Thus in terms of CHD prevention, fibre is best obtained from wholegrain sources. Wholegrain products have strong antioxidant activity and contain phytoestrogens, but there is insufficient evidence to determine whether this is beneficial in CHD prevention. Soluble fibre clearly lowers cholesterol to a small but significant degree and one would expect that this would reduce CHD events. There have been a small number of epidemiological studies showing soy consumption is associated with lower rates of heart disease. Countering the positive evidence for wholegrain and legume intake has been the Nurses Health Study in 2000 that showed women who were overweight or obese consuming a high glycaemic load (GL) diet doubled their relative risk of CHD compared with those consuming a low GL diet. Although the literature relating GL with CHD events is somewhat mixed, the relationship with risk factors such as HDL cholesterol, triglyceride and C reactive protein is relatively clear. Thus, carbohydrate-rich foods should be wholegrain and, if they are not, then the lowest glycaemic index (GI) product should be used. Promotion of carbohydrate foods should be focused on wholegrain cereals because these have proven to be associated with health benefits. There is insufficient evidence about whether the addition of other components of wholegrains such as polyphenolics or minerals (such as magnesium or zinc) would improve the health benefits of refined grain foods and this needs investigation. Whether adding bran to refined carbohydrate foods can improve the situation is also not clear, and it was found that added bran lowered heart disease risk in men by 30%. This persisted after full adjustment (including GL) suggesting, at least in men, that fibre may be more important than GI. Thus there are two messages: The intake of wholegrain foods clearly protects against heart disease and stroke but the exact mechanism is not clear. Fibre, magnesium, folate and vitamins B6 and vitamin E may be important. The intake of high GI carbohydrates (from both grain and non-grain sources) in large amounts is associated with an increased risk of heart disease in overweight and obese women even when fibre intake is high but this requires further confirmation in normal-weight women.

RECOMMENDATION

Carbohydrate-rich foods should be wholegrain and if they are not, then the lowest GI product available should be consumed. Glycemic index is largely irrelevant for foods that contain small amounts of carbohydrate per serve (such as most vegetables).

Dietary glycemic index and load in relation to metabolic risk factors in Japanese female farmers with traditional dietary habits

BACKGROUND

Little is known about the relation of dietary glycemic index (GI) and glycemic load (GL) to metabolic risk factors, particularly in non-Western populations.

OBJECTIVE

We examined the cross-sectional associations between dietary GI and GL and several metabolic risk factors in healthy Japanese women with traditional dietary habits.

DESIGN

The subjects were 1354 Japanese female farmers aged 20-78 y from 5 regions of Japan. Dietary GI and GL were assessed with a self-administered diet-history questionnaire. Body mass index (BMI) was calculated as weight (kg) divided by the square of height (m). Fasting blood samples were collected for biochemical measurements.

RESULTS

The mean dietary GI was 67, and the mean dietary GL (/1000 kcal) was 88 (GI for glucose = 100). White rice (GI = 77) was the major contributor to dietary GI and GL (58.5%). After adjustment for potential dietary and nondietary confounding factors, dietary GI was positively correlated with BMI (n = 1354; P for trend = 0.017), fasting triacylglycerol (n = 1349; P for trend = 0.001), fasting glucose (n = 764; P for trend = 0.022), and glycated hemoglobin (n = 845; P for trend = 0.038). Dietary GL was independently negatively correlated with HDL cholesterol (n = 1354; P for trend = 0.004) and positively correlated with fasting triacylglycerol (P for trend = 0.047) and fasting glucose (P for trend = 0.012).

CONCLUSIONS

Both dietary GI and GL are independently correlated with several metabolic risk factors in subjects whose dietary GI and GL were primarily determined on the basis of the GI of white rice.

Dietary patterns and risk of nonfatal acute myocardial infarction in Costa Rican adults

OBJECTIVE

To investigate the association between dietary patterns and risk of a first nonfatal acute myocardial infarction (MI) in Costa Rican adults.

DESIGN

Population-based case-control study.

SUBJECTS

A total of 496 incident MI cases and 518 population-based randomly selected controls matched to the cases by age (+/-5 years), gender, and county of residence. Subjects were interviewed with a validated food frequency questionnaire. Dietary patterns were identified by factor analysis. Odds ratios (OR) and 95% confidence intervals (CI) were obtained using multivariate conditional logistic regression adjusted for several recognized risk factors for MI.

RESULTS

Two diet patterns were identified, 'vegetable' characterized by increased intake of vegetables and fruits, and 'staple', characterized by an increased use of palm oil for cooking, and intake of refined grains (mostly white rice and white bread), legumes, coffee, added sugar, and red meat. Compared to the lowest quintile of the staple diet pattern, the highest quintile was associated with an increased risk of MI (OR: 3.70, 95% CI: 2.30-5.97). Adjusting for potential confounders did not change the results (OR: 3.53, 95% CI: 1.98-6.31). Consistently, an increasing staple pattern score was associated with lower HDL cholesterol (P for trend <0.02) and alpha-linolenic acid in adipose tissue (P for trend <0.0001). The vegetable pattern was not associated with MI.

CONCLUSIONS

The staple dietary pattern of Costa Rican adults is associated with low plasma HDL cholesterol, low alpha-linolenic acid in adipose tissue, and increased risk of MI.

Dietary glycaemic index and glycaemic load in Danish children in relation to body fatness

The aim of this study was to describe dietary glycaemic index (GI) and glycaemic load (GL) values in the diets of Danish children, and to examine the associations between dietary GI, GL and body fatness. Data were collected during 1997-8 as part of the European Youth Heart Study. The study population comprised 485 children aged 10 years and 364 children aged 16 years from Odense County, Denmark. Dietary GI and GL were estimated using international food tables, and the associations between energy-adjusted dietary GI, GL and body fatness were analysed by multiple linear regression. The mean daily dietary GI value was 85 (SD 6.9) with a range of 62-111. No significant differences were found between age groups and gender. The daily dietary GL was higher among boys aged 16, with a GL of 330 (sd 95) (P<0.05), compared with girls or younger boys. Dietary GL was higher among 10-year-old boys than girls (250 (sd 81) v. 230 (sd 66) P<0.05), whereas dietary GL among 16-year-old girls was 230 (sd 56). Neither dietary GI nor GL was associated with the sum of four skinfolds (SigmaSF) among girls or among 10-year-old boys. Among 16-year-old boys, significant associations were observed between dietary GI and SigmaSF (beta=0.60, SE=0.21, P=0.006), and between dietary GL and SigmaSF (beta=0.15, SE=0.06, P=0.009). In conclusion, dietary GI and GL were positively associated with body fatness among Danish boys aged 16 years, whereas no associations were found among girls or younger boys.

Postprandial blood glucose and insulin responses to pre-germinated brown rice in healthy subjects

Effects of pre-germinated brown rice (PGBR) on postprandial blood glucose and insulin concentrations were compared with brown rice (BR) and white rice (WR) in two studies. In the first study, we investigated the time course of postprandial blood glucose and insulin concentrations after ingesting 25% (W/V) glucose solution, PGBR, BR or WR in 19 healthy young subjects. In the second study, dose-dependent effect of PGBR on the time course of postprandial blood glucose concentrations was compared among 4 different mixtures of PGBR and WR in 13 healthy young subjects. They were solely PGBR, 2/3 PGBR (PGBR: WR = 2 : 1), 1/3 PGBR (PGBR : WR = 1 : 2) and solely WR. Each sample was studied on a different day. The samples were selected randomly by the subjects. All the rice samples contained 50 g of available carbohydrates. The previous day the subjects ate the assigned dinner by 9:00 pm and then were allowed only water until the examination. The next morning, they ingested each test rice sample with 150 ml of water in 5-10 min. Blood was collected into capillary tubes from finger at 0, 30, 60, 90 and 120 min after the ingestion. The incremental areas under the curve (IAUC) of blood glucose concentrations (IAUC-Glc) for 120 min after the administration of PGBR and BR were lower than those after WR. In contrast the IAUC-Glc of BR and PGBR were not different (Study 1). The higher the ratio of PGBR/WR, the lower the glycemic index became (Study 2). These results suggest that intake of PGBR instead of WR is effective for the control of postprandial blood glucose concentration without increasing the insulin secretion.