Glycemische Index | mei 2007
Wetenschappelijke publicaties over glycemische index
Hieronder een overzicht van wetenschappelijke artikelen in relatie tot glycemische index die in het laatste half jaar zijn gepubliceerd.Diet compounds, glycemic index and obesity-related cardiac effects.
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Novelli EL. Int J Cardiol. 2007 Mar 23. Epub ahead of print.
BACKGROUND: Diet compounds may influence obesity-related cardiac oxidative stress and metabolic sifting. Carbohydrate-rich diet may be disadvantageous from fat-rich diet to cardiac tissue and glycemic index rather than lipid profile may predict the obesity-related cardiac effects.
MATERIALS AND METHODS: Male Wistar rats were divided into three groups (n=8/group): (C) receiving standard chow (3.0 kcal/g); (CRD) receiving carbohydrate-rich diet (4.0 kcal/g), and (FRD) receiving fat-rich diet (4.0 kcal/g). Rats were sacrificed after the oral glucose tolerance test (OGTT) at 60 days of dietary treatments. Lipid profile and oxidative stress parameters were determined in serum. Myocardial samples were used to determine oxidative stress, metabolic enzymes, glycogen and triacylglycerol.
RESULTS: FRD rats showed higher final body weight and body mass index than CRD and C. Serum cholesterol and low-density lipoprotein were higher in FRD than in CRD, while triacylglycerol and oxidized low-density lipoprotein cholesterol were higher in CRD than in FRD. CRD rats had the highest myocardial lipid hydroperoxide and diminished superoxide dismutase and catalase activities. Myocardial glycogen was lower and triacylglycerol was higher in CRD than in C and FRD rats. Although FRD rats had depressed myocardial-reducing power, no significant changes were observed in myocardial energy metabolism. Myocardial beta-hydroxyacyl coenzyme-A dehydrogenase and citrate synthase, as well as the enhanced lactate dehydrogenase/citrate synthase ratio indicated that fatty acid degradation was decreased in CRD rats. Glycemic index was positively correlated with obesity-related cardiac effects.
CONCLUSIONS: Isoenergetic carbohydrate-rich and fat-rich diets induced different degree of obesity and differently affected lipid profile. Carbohydrate-rich diet was deleterious relative to fat-rich diet in the heart enhancing lipoperoxidation and shifting the metabolic pathway for energy production. Glycemic index rather than dyslipidemic profile may predict the obesity effects on cardiac tissue.
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Clinical update: the low-glycaemic-index diet.
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For most of the past half century, the US Government and many official health agencies have advocated a low-fat diet for the prevention and treatment of obesity, diabetes, and heart disease. The rationale seemed obvious: fat is energy dense and tasty, making this nutrient easily overconsumed and saturated fat adversely affects LDL-cholesterol and insulin resistance. In the article, the clinical relevance of GI is being discussed: are the data consistent, how does glycaemic response change when several foods are eaten in combination and is a low GI practical? Although the data are variable, most published studies report beneficial effects of lowering GI and virtually no study suggests potential for harm (by contrast with low-fat and very-low-carbohydrate diets that can adversely affect some risk factors for cardiovascular disease). Additional well-controlled and adequately powered studies are needed to examine the long-term effects of a low-GI diet on human health. (www.thelancet.com)
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Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults
A Randomized Trial
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CONTEXT: The results of clinical trials involving diet in the treatment of obesity have been inconsistent, possibly due to inherent physiological differences among study participants.
OBJECTIVE: To determine whether insulin secretion affects weight loss with 2 popular diets.
DESIGN, SETTING AND PARTICIPANTS: Randomized trial of obese young adults (aged 18-35 years; n=73) conducted from September 2004 to December 2006 in Boston, Mass, and consisting of a 6-month intensive intervention period and a 12-month follow-up period. Serum insulin concentration at 30 minutes after a 75-g dose of oral glucose was determined at baseline as a measure of insulin secretion. Outcomes were assessed at 6, 12, and 18 months. Missing data were imputed conservatively. Interventions A low–glycemic load (40% carbohydrate and 35% fat) vs low-fat (55% carbohydrate and 20% fat) diet. Main Outcome Measures Body weight, body fat percentage determined by dualenergy x-ray absorptiometry, and cardiovascular disease risk factors.
RESULTS: Change in body weight and body fat percentage did not differ between the diet groups overall. However, insulin concentration at 30 minutes after a dose of oral glucose was an effect modifier (group_time_insulin concentration at 30 minutes: P=.02 for body weight and P=.01 for body fat percentage). For those with insulin concentration at 30 minutes above the median (57.5 μIU/mL; n=28), the low–glycemic load diet produced a greater decrease in weight (–5.8 vs –1.2 kg; P=.004) and body fat percentage (–2.6% vs –0.9%; P=.03) than the low-fat diet at 18 months. There were no significant differences in these end points between diet groups for those with insulin concentration at 30 minutes below the median level (n=28). Insulin concentration at 30 minutes after a dose of oral glucose was not a significant effect modifier for cardiovascular disease risk factors. In the full cohort, plasma high-density lipoprotein cholesterol and triglyceride concentrations improved more on the low–glycemic load diet, whereas lowdensity lipoprotein cholesterol concentration improved more on the low-fat diet.
CONCLUSIONS: Variability in dietary weight loss trials may be partially attributable to
differences in hormonal response. Reducing glycemic load may be especially important to achieve weight loss among individuals with high insulin secretion. Regardless of insulin secretion, a low–glycemic load diet has beneficial effects on high-density lipoprotein cholesterol and triglyceride concentrations but not on low-density lipoprotein cholesterol concentration.
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Effects of the glycemic index of breakfast on metabolic responses to brisk walking in females.
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OBJECTIVE: The aim of this study was to examine the metabolic responses during 1 h of brisk walking, 3 h after ingesting high glycemic index (HGI) and moderate glycemic index (MGI) breakfasts.
DESIGN AND SUBJECTS: Six females completed three treadmill walking trials ( 50% O2 max), separated by at least 1 month. Three hours before walking, they ingested either water or a HGI or MGI breakfast. The MGI breakfast consisted of a mixture of an HGI breakfast cereal and low GI carbohydrate (CHO) foods. The GI values of the HGI and MGI meals were 77 and 51, respectively.
SETTING: The study took place in the School of Sport and Exercise Sciences at Loughborough University, Loughborough, UK. RESULTS: In the HGI and MGI trials, plasma glucose and serum insulin concentrations peaked 15 min into the postprandial period. At the onset of exercise, plasma insulin concentrations were twofold higher in the HGI (31.5 7.7 l U l-1) than in the MGI trial (15.2 1.9 l U l-1) (P<0.05). However, there were no differences in substrate utilization between the two CHO trials.
CONCLUSION: These results suggest that although the addition of LGI CHO foods to an HGI breakfast cereal reduces the overall GI of the meal, the metabolic response to exercise is similar to that following a breakfast comprised entirely of HGI foods.
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Influence of the glyceamic index of an evening meal on substrate oxidation following breakfast and during exercise the next day in healthy women.
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OBJECTIVE:To investigate whether the 'overnight second-meal effect' results in altered substrate oxidation during the postprandial period following breakfast and subsequent sub-maximal exercise in women.
SUBJECTS/METHODS:Seven recreationally active women were recruited for the study. In each trial, participants were provided with their evening meal on day 1, which was composed of either high glycaemic index (HGI) or low glycaemic index (LGI) carbohydrates (CHO). On day 2, participants were provided with a standard HGI breakfast and then performed a 60 min run at 65% \[Vdot]O(2 max) 3 h later.
RESULTS: The incremental area under the curve (IAUC) for plasma glucose concentrations during the postprandial period following breakfast was greater in the HGI trial compared to the LGI trial (P<0.01). Similarly, the IAUC for serum insulin concentrations was greater in the HGI trial than the LGI trial (P<0.05). No differences in plasma free-fatty acids (FFA) or plasma glycerol concentrations were found between trials during the postprandial period. During subsequent exercise, there were no significant differences in substrate metabolism.
CONCLUSION: The glycaemic index of an evening meal does not alter substrate oxidation at rest following breakfast or during subsequent submaximal exercise in women. This study provides further evidence for the overnight second-meal effect on glycaemic responses following a LGI mixed evening meal.
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Determination of the glyceamic index of various staple carbohydrate-rich foods in the UK diet.
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OBJECTIVE: To determine the glycaemic index (GI) of various staple carbohydrate-rich foods in the UK diet, and to consider the factors influencing the GI of foods.
DESIGN: Subjects were served with 25 or 50 g portions of glucose on three occasions, followed by a selection of test foods providing an equal amount of available carbohydrate, in random order. Each test food was consumed by 10 subjects. Capillary blood glucose levels were measured in the fasted state and over the 120 min following commencement of consumption of the foods.
SETTING: The study was carried out in a research institute (MRC Human Nutrition Research, Cambridge, UK). SUBJECTS: Forty-two healthy adult volunteers were studied.
METHODS: The GI values of 33 foods were measured according to the WHO/FAO recommended methodology. These foods included various breads, breakfast cereals, pasta, rice and potatoes, all of which were commercially available in the UK.
CONCLUSIONS: The results illustrate a number of factors which are important in influencing the GI of a food, highlighting the importance of measuring the GI of a food, rather than assuming a previously published value for a similar food. This is useful both to researchers analysing dietary surveys or planning intervention studies, and also to health professionals advising individuals on their diets.
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Metabolic fate of intravenously administered N-acetylneuraminic acid-6-14C in newborn piglets.
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BACKGROUND: Sialic acid (N-acetylneuraminic acid), a component of gangliosides and sialylglycoproteins, may be a conditional nutrient in early life because endogenous synthesis is limited. The aim of this study was to investigate the metabolic fate of intravenously administrated N-acetylneuraminic acid 614C (sialic acid) in piglets.
METHOD: Three-day-old male domestic piglets (Sus scrofa) were injected via the jugular vein with 5 μCi (11-12x106 cpm) of N-acetylneuraminic acid-614C (specific activity of 55 mCi/mmol). Blood samples were collected at regular intervals over the next 120 min. The organs were then removed and the urine collected for determination of residual radioactivity.
RESULTS: Within 2 min of injection, 80% of the activity was removed from the blood and by 120 min the remaining activity approached 8%. At 120 min, the brain contained significantly more radioactivity (cpm/g tissue) than the liver, pancreas, heart and spleen, but less than the kidneys. Within the brain, the percentage of total injected activity was highest in the cerebrum (0.175 ± 0.008) followed by the cerebellum (0.0295 ± 0.006, p = 0.00006) and the thalamus (0.029 ± 0.006, p = 0.00003).
CONCLUSIONS: An exogenous source of sialic acid is capable of crossing the blood-brain barrier and being taken up into various tissues. The findings suggest that dietary sources of sialic acid may contribute to early brain development in newborn mammals.
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Effects of a reduced-glycemic-load diet on body weight, body composition and cardiovascular disease risk markers in overweight and obese adults.
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BACKGROUND: Lowering the dietary glycemic load and increasing protein intake may be advantageous for weight management.
OBJECTIVE: This randomized controlled trial was designed to evaluate the effects of an ad libitum reduced-glycemic-load (RGL) diet on body weight, body composition, and cardiovascular disease (CVD) risk markers in overweight and obese adults during an initial weight-loss phase (12 wk) and a weight-loss maintenance phase (weeks 24-36).
DESIGN: Subjects were assigned to RGL (n = 43) or low-fat, portion-controlled (control; n = 43) diet groups. The RGL group was instructed to eat until satisfied, maintaining a low carbohydrate intake during weeks 0-2 and adding low-glycemic-index carbohydrate thereafter. Control subjects were instructed to reduce fat intake and decrease portion sizes, with a targeted energy deficit of 500 to 800 kcal/d.
RESULTS: The RGL group had lost significantly more weight than did the control group at week 12 (-4.9 and -2.5 kg, respectively; P = 0.002), but the 2 groups did not differ significantly at week 36 (-4.5 and -2.6 kg, respectively; P = 0.085). Changes in fat mass differed between the groups at week 12 (-1.9 and -0.9 kg, respectively; P = 0.016) but not at week 36 (-2.0 and -1.3 kg, respectively; P = 0.333). At the end of the study, no differences were found in responses for CVD risk markers except a larger mean change in HDL cholesterol in the RGL group than in the control group (3.8 and 1.9 mg/dL, respectively; P = 0.037).
CONCLUSION: These findings provide evidence that an ad libitum RGL diet is a reasonable alternative to a low-fat, portion-controlled eating plan for weight management.
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The effect of a 12-week low glyceamic index diet on heart disease risk factors and 24 h glyceamic response in healthy middle-aged volunteers at risk of heart disease: a pilot study.
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OBJECTIVE: To compare the effects of two energy-restricted healthy diets, one with a low GI and one with a high GI, on heart disease risk factors and weight loss in subjects at risk of heart disease.
DESIGN: A 12-week randomized parallel study of low and high GI, healthy eating diets was carried out.
SETTING: The study was carried out at the Hammersmith Hospital.
SUBJECTS: Eighteen subjects were recruited by advertisement and randomized to one of the two diets. Fourteen completed the study but one was excluded from the final analysis.
METHODS: At randomization, subjects were advised to follow the intervention diet for 12 weeks. Before randomization and on completion of the study, anthropometrics, fasting cholesterol and glucose blood tests and 24-h glucose measurements were taken using a continuous glucose monitoring system (CGMS). Statistical analysis was carried out using non-parametric tests. Median (IQR) are presented.Results:A significantly different dietary GI was achieved in the low GI (median: 51.3 (IQR: 51.0-52.0) compared to the high GI (59.3 (59.2-64.0) (P=0.032) group. By week 12, both groups reduced their energy intake by: low GI group: (-)167 ((-)312-(-123) kcal/day (P=0018) vs high GI group: (-)596 ((-)625-(-)516) (P=0.018) kcal/day, the difference between the groups being significant (P=0.010). However, only the low GI group lost weight ((-)4.0 ((-)4.4-(-)2.4) kg (P=0.018) whereas the high GI group did not significantly change in weight ((-)1.5 ((-)3.6-0.8) kg (P=0.463). By week 12, the low GI group also had a significantly lower 24-h area under the curve (AUC) (7556 (7315-8434) vs 8841 (8424-8846) mmol-h/l (P=0.045) and overnight AUC (2429 (2423-2714) vs 3000 (2805-3072) mmol-h/l (P=0.006) glucose as measured by CGMS. There were no differences in the other heart disease risk factors ssessed.
CONCLUSIONS: This pilot study provides some evidence that consuming a low GI diet in addition to weight loss and healthy eating may reduce cardiovascular risk. Other potential benefits of GI might have been masked by weight loss in the low GI group. Larger-scale studies need to follow. Sponsorship:The study was funded by the British Heart Foundation.
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A low glyceamic index breakfast cereal preferentially prevents children’s cognitive performance from declining throughout the morning.
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This study investigated whether the glycaemic index (GI) of breakfast cereal differentially affects children's attention and memory. Using a balanced cross-over design, on two consecutive mornings 64 children aged 6-11 years were given a high GI cereal and a low GI cereal in a counterbalanced order. They performed a series of computerised tests of attention and memory, once prior to breakfast and three times following breakfast at hourly intervals. The results indicate that children's performance declines throughout the morning and that this decline can be significantly reduced following the intake of a low GI cereal as compared with a high GI cereal on measures of accuracy of attention (M=-6.742 and -13.510, respectively, p<0.05) and secondary memory (M=-30.675 and -47.183, respectively, p<0.05).
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Low-Carbohydrate Diets: Assessing the Science and Knowledge Gaps, Summary of an ILSI North America Workshop
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Given their growing popularity, the committee reviewed the science on the health impacts related to low carbohydrate diets. Toward this effort, the committee hosted a workshop for experts to explore diet trends; health effects of low-carbohydrate diets; definitions of "low carb" diets and foods; and immediate research needs.
"Low-Carbohydrate Diets: Assessing the Science and Knowledge Gaps; Summary of an ILSI North America Workshop," appears in the December 2006 issue of the Journal of the American Dietetic Association. Contact Richard Carson (rcarson@ilsi.org) for your free copy.
Richard Carson
Senior Project Manager
ILSI North America
One Thomas Circle, NW
Ninth Floor
Washington, DC 20005
Tel: +1.202.659.0074
Fax: +1.202.659.3859
rcarson@ilsi.org
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The effects of the dietary glycemic load on type 2 diabetes risk factors during weight loss.
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OBJECTIVE: To compare the effects of two calorie-restricted diets that differ in glycemic load (GL) on glucose tolerance and inflammation.
RESEARCH METHODS AND PROCEDURES: Thirty-four healthy overweight adults, ages 24 to 42 years, were randomized to 30% provided calorie-restricted diets with high (HG) or low (LG) glycemic load for 6 months. Outcomes were changes in glucose-insulin dynamics and C-reactive protein (CRP) levels.
RESULTS: Compared with baseline, levels of fasting insulin, homeostasis model assessment of insulin resistance, post-load insulin at 30 minutes, and incremental area-under-the-curve-insulin during the oral glucose tolerance test were significantly lower in both groups at 6 months (p range, 0.01 to 0.05), but after adjustment for baseline values and weight change, there were no differences between the two groups with regard to changes over time in any parameter. The mean percentage change in insulin sensitivity by a frequently sampled intravenous glucose tolerance test was +26% in the HG group and +24% in the LG group (p = 0.83); first-phase acute insulin release was -20% in the HG group and -21% in the LG group (p = 0.77). More participants on the LG diet (14 of 16 subjects) had a decline in serum CRP, compared with those on the HG diet (7 of 16 subjects) (p < 0.05).
DISCUSSION: In healthy overweight adults provided with food for 6 months, the dietary GL did not seem to influence chronic adaptations in glucose-insulin dynamics above that associated with weight loss. This finding highlights the importance of absolute weight loss over the dietary macronutrient composition used to achieve weight loss. The finding of greater declines in CRP concentration after consumption of a low-GL diet warrants further investigation.
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Glycemic and insulinemic responses as determinants of appetite in humans.
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BACKGROUND: The importance of the postprandial glycemic and insulinemic responses for appetite and energy intake (EI) is controversial.
OBJECTIVE: The aim of the study was to test the hypothesis that postprandial appetite sensations and subsequent EI are determined by postprandial glycemic and insulinemic responses after the intake of a range of breakfast meals.
DESIGN: The study was a randomized, crossover meal test including 28 healthy young men, each of whom tested 10 of 14 breakfast meals. Each meal contained 50 g carbohydrate with various glycemic index and energy and macronutrient contents. Blood samples were taken, and appetite sensations were measured 3 h after the meals. Subsequently, EI at lunch (EI(lunch)) was recorded. RESULTS: The glycemic response was unrelated to appetite sensations, whereas the insulinemic response was positively associated with postprandial fullness (R2 = 0.33, P < 0.05). In contrast, the insulinemic response was unrelated to the subsequent EI(lunch), whereas the glycemic response was positively associated with EI(lunch) (R2 = 0.33, P < 0.05). Although no significant difference in EI(lunch) was observed between different breakfast conditions, a low breakfast EI was associated with a high EI(lunch) (R2 = 0.60, P < 0.001).
CONCLUSIONS: The current study does not support the contention that the postprandial glycemic response has an important effect on short-term appetite sensations, but a low-glycemic index meal may reduce subsequent EI. In contrast, postprandial insulin seems to affect short-term appetite sensations.
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Carbohydrate nutrition, glycaemic load, and plasma lipids: the Insulin Resistance Atherosclerosis Study.
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AIMS: We evaluated the relationship of carbohydrate nutrition and selected food groups with lipids using data from the Insulin Resistance Atherosclerosis Study (IRAS Exam I, 1992-1994).
METHODS AND RESULTS: A total of 1026 middle-aged adults with normal or impaired glucose tolerance had complete data on fasting lipids and usual dietary intake from an interviewer-administered, validated food frequency questionnaire. Published glycaemic index (GI) values were assigned to food items and average dietary GI and glycaemic load (GL) were calculated per participant. Intake of carbohydrates differed by gender, men consuming more absolute digestible carbohydrates with higher GI and GL than women. In multivariate models adjusting for energy intake, in men, GL and carbohydrates were associated positively with total and LDL cholesterol, and inversely with HDL. In women, associations were limited to triglycerides. We estimated that a 100 g higher intake in GL or carbohydrates was associated with a 7-8 mg/dL higher total or LDL cholesterol level in men, and a 13-17 mg/dL higher triglyceride level in women. In the combined sample, GL and carbohydrates were consistently associated with all lipid levels and GI was inversely associated with HDL cholesterol.
CONCLUSION: Our findings underscore the importance of carbohydrate nutrition for plasma lipids.
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Low-glycaemic index diets and body weight regulation.
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Low-fat diets produce spontaneous weight loss in the research setting, but as a public health strategy, they have been disappointing. Insulin resistance and impairments in insulin secretory function leading to postprandial hyperglycaemia are now common, making the current context greatly different to that of 25 years ago. There is increasing evidence that reducing the proportion of energy derived from carbohydrate or reducing the glycaemic index (GI) of the carbohydrate improves the rate of fat loss and cardiovascular risk factors. The proposed mechanisms include higher satiety, higher metabolic rate, reduced postprandial glycaemia and/or insulinaemia and higher fat oxidation. Although dietary glycaemic load can be reduced either by lowering the GI of the carbohydrate or by reducing carbohydrate energy, the metabolic and physiological consequences are not the same. Exchanging high for low-GI foods, without changing the macronutrient ratio, may be optimal because it is simple, cost-effective and often associated with higher intake of whole grains and greater food volume, and factors that maximize the chance of sustained weight loss. Healthy low-GI diets allow for moderate intakes of sugars, including sweetened dairy foods, fruits and confectionery items, and can be easily adapted for individuals of different ethnicities, vegetarians and low-income groups.
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Low glycemic index diets and body weight.
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In their review (low-glycaemic index diets and body weight regulation (2006)), McMillan-Price and Brand-Miller argue that the low glycemic index (GI) diet is a simple and more popular diet that will successfully improve cardiovascular risk factors and reduce body weight. We do not find that there is convincing evidence in the existing literature to suggest that a low GI diet is superior in achieving improvement in cardiovascular health and in reducing body weight in healthy overweight subjects, when compared to official dietary advice recommending a diet high in vegetables, fruit and fiber, and low in sugar and fat. This lack of evidence might partly be due to the lack of long-term, well-powered studies, with well-controlled diets differing only in GI. Data also suggest that subjects' insulin sensitivity might be an important predictor of the effects of a low GI diet, and therefore findings from studies in insulin-resistant and diabetic subjects should not be extrapolated to findings in healthy individuals. We agree with McMillan-Price and Brand-Miller when they state that 'in practice it is difficult to tease out the separate effects of GI, palatability, volume, fiber and other factors that influence satiety responses to realistic meals'. Predicting GI of realistic meals has also proven difficult. We therefore find that future studies should focus on individual food factors, such as the effect of whole grain, including intact grains, fiber, including resistant starch, energy density and preparation methods. This approach would allow for more tightly controlled trials, with less confounding factors, and also lead to simpler dietary advice with assured efficacy.
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Dietary glycaemic index from an epidemiological point of view.
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The concept of glycaemic index (GI) was developed 25 years ago by Jenkins and co-workers in 1981 and first studied to help diabetic patients with blood glucose control. In 1997 two epidemiological studies were published showing that high GI food consumption is associated with an increased risk of type 2 diabetes. At the same time the concept of the glycaemic load (GL) was introduced, based on GI and total carbohydrate intake. Since then, many studies have been conducted to investigate the role of dietary GI and GL in the prevention and management of type 2 diabetes, cardiovascular disease, obesity and other chronic diseases such as cancer. The current review will focus on the epidemiological evidence obtained so far. In addition, several key methodological issues will be addressed, such as the dietary assessment method used, the application of the international GI and GL table, and the correlated dietary patterns.
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Physiological mechanisms and observed health impacts related to the glycaemic index: some observations.
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This paper discusses common misconceptions about the glycaemic index (GI). The rate of carbohydrate digestion is only one of the many determinants of GI and, hence, in vitro methods cannot reliably predict the GI of a food. GI has been criticized as being extremely variable between subjects and not applying in mixed meals. In fact, however, GI controls for differences in glycaemic response between individuals and apparent differences are due to within-individual, variation which does not detract from the ability of GI to predict average glycaemic responses. The conclusion that GI does not apply in mixed meals is based on flawed methodology; recent studies show that nearly 90% of the variation in glycaemic response of realistic mixed meals can be explained by differences in carbohydrate content and GI. The health benefits of low GI foods tend to be ascribed to their slow rate of digestion and reduced post-prandial insulin responses. While the former is important, it is not the only mechanism involved, since low GI sugars may have some of the same effects as slowly absorbed starch. The role of insulin is questioned because, unlike GI, the insulinaemic index (II) of foods may vary in different subjects and, hence, may not be a valid measure. It is not clear that high insulin exacerbates obesity; indeed, there is good evidence that hyperinsulinaemia is associated with reduced weight gain. The public health message about GI is usually to avoid refined foods, eat more fruits and vegetables instead of concentrated juice, and have more pasta and less potato. However, with respect to GI, all of these recommendations are wrong and will ultimately cause confusion and rejection of the concept. An alternative, more scientifically accurate message is suggested.
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Glycaemic instability is an underestimated problem in Type II diabetes.
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The aim of the present study was to assess the level of glycaemic control by the measurement of 24 h blood glucose profiles and standard blood analyses under identical nutritional and physical activity conditions in patients with Type II diabetes and healthy normoglycaemic controls. A total of 11 male patients with Type II diabetes and 11 healthy matched controls participated in a 24 h CGMS (continuous subcutaneous glucose-monitoring system) assessment trial under strictly standardized dietary and physical activity conditions. In addition, fasting plasma glucose, insulin and HbA1c (glycated haemoglobin) concentrations were measured, and an OGTT (oral glucose tolerance test) was performed to calculate indices of whole-body insulin sensitivity, oral glucose tolerance and/or glycaemic control. In the healthy control group, hyperglycaemia (blood glucose concentration >10 mmol/l) was hardly present (2+−1% or 0.4+−0.2/24 h). However, in the patients with Type II diabetes, hyperglycaemia was experienced for as much as 55+−7% of the time (13+−2 h over 24 h) while using the same standardized diet. Breakfast-related hyperglycaemia contributed most (46+−7%; P<0.01 as determined by ANOVA) to the total amount of hyperglycaemia and postprandial glycaemic instability. In the diabetes patients, blood HbA1c content correlated well with the duration of hyperglycaemia and the postprandial glucose responses (P<0.05). In conclusion, CGMS determinations show that standard measurements of glycaemic control underestimate the amount of hyperglycaemia prevalent during real-life conditions in Type II diabetes. Given the macro- and micro-vascular damage caused by postprandial hyperglycaemia, CGMS provides an excellent tool to evaluate alternative therapeutic strategies to reduce hyperglycaemic blood glucose excursions.
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Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial
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Das SK, Gilhooly CH, Golden JK, Pittas AG, Fuss PJ, Cheatham RA, Tyler S, Tsay M, McCrory MA, Lichtenstein AH, Dallal GE, Dutta C, Bhapkar MV, DeLany JP, Saltzman E, Roberts SB. Am J Clin Nutr; 85;4; 1023-1030
BACKGROUND: There remains no consensus about the optimal dietary composition for sustained weight loss.
OBJECTIVE: The objective was to examine the effects of 2 dietary macronutrient patterns with different glycemic loads on adherence to a prescribed regimen of calorie restriction (CR), weight and fat loss, and related variables.
DESIGN: A randomized controlled trial (RCT) of diets with a high glycemic load (HG) or a low glycemic load (LG) at 30% CR was conducted in 34 healthy overweight adults with a mean (±SD) age of 35 ± 6 y and body mass index (kg/m 2) of 27.6 ± 1.4. All food was provided for 6 mo in diets controlled for confounding variables, and subjects self-administered the plans for 6 additional months. Primary and secondary outcomes included energy intake measured by doubly labeled water, body weight and fatness, hunger, satiety, and resting metabolic rate.
RESULTS: All groups consumed significantly less energy during CR than at baseline (P < 0.01), but changes in energy intake, body weight, body fat, and resting metabolic rate did not differ significantly between groups. Both groups ate more energy than provided (eg, 21% and 28% CR at 3 mo and 16% and 17% CR at 6 mo with HG and LG, respectively). Percentage weight change at 12 mo was –8.04 ± 4.1% in the HG group and –7.81 ± 5.0% in the LG group. There was no effect of dietary composition on changes in hunger, satiety, or satisfaction with the amount and type of provided food during CR.
CONCLUSIONS: These findings provide more detailed evidence to suggest that diets differing substantially in glycemic load induce comparable long-term weight loss.
Bron en samenvattingen: www.pubmed.org
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