Glycemic index and load-dynamic dietary guidelines in the context of diseases

Review: efficacy of alginate supplementation in relation to appetite regulation and metabolic risk factors: evidence from animal and human studies

This review provides a critical update on human and animal studies investigating the effect of alginate supplementation on appetite regulation, glycaemic and insulinemic responses, and lipid metabolism with discussion of the evidence on potential mechanisms, efficacy and tolerability. Dependent on vehicle applied for alginate supplementation, the majority of animal and human studies suggest that alginate consumption does suppress satiety and to some extent energy intake. Only one long-term intervention trial found effects on weight loss. In addition, alginates seem to exhibit beneficial influence on postprandial glucose absorption and insulin response in animals and humans. However, alginate supplementation was only found to have cholesterol-lowering properties in animals. Several mechanisms have been suggested for the positive effect observed, which involve delayed gastric emptying, increased viscosity of digesta and slowed nutrient absorption in the small intestine upon alginate gel formation. Despite reasonable efficacy and tolerability from the acute or short-term studies, we still realize there is a critical need for development of optimal alginate types and vehicles as well as studies on further long-term investigation on alginate supplementation in humans before inferring that it could be useful in the management of obesity and the metabolic syndrome.

Papel do índice glicêmico e da carga glicêmica na prevenção e no controle metabólico de pacientes com diabetes melito tipo 2

O controle glicêmico intensificado pode prevenir e/ou retardar o aparecimento das complicações crônicas do diabetes melito (DM). O carboidrato da dieta é o principal determinante da glicemia pós-prandial, sendo o índice glicêmico (IG) e a carga glicêmica úteis para prever a resposta glicêmica aos alimentos. O objetivo deste manuscrito foi revisar criticamente o papel das dietas de baixo IG na prevenção e controle metabólico do diabetes melito tipo 2 (DMT2). O risco para desenvolvimento de DMT2 com dietas de alto IG variou de 1,21 a 1,59. A redução de 12 a 32 unidades no IG da dieta diminuiu em 0,39 a 0,50 pontos percentuais a HbA1c. Os efeitos dessas dietas no perfil lipídico e peso corporal no DMT2 permanecem controversos. Em conclusão, as evidências atuais indicam que a incorporação do IG no planejamento dietético de pacientes com DMT2 contribui para a melhora do controle glicêmico.

Dietary glycemic index, glycemic load, and risk of cancer: a prospective cohort study

Previous studies have provided limited evidence for a harmful effect of high glycemic index and dietary glycemic load on cancer. The authors analyzed associations among glycemic index, glycemic load, and risk of cancer in women and men in the National Institutes of Health-AARP Diet and Health Study. Published glycemic index values were assigned to 225 foods/food groups. Glycemic load was calculated by multiplying the glycemic index, carbohydrate content, and intake frequency of individual foods reported on a food frequency questionnaire. From 1995 through 2003, the authors identified 15,215 and 33,203 cancer cases in women and men, respectively. Cox proportional hazards models were used to estimate multivariate relative risks and 95% confidence intervals. For women and men, respectively, the relative risks for total cancer for high versus low glycemic index were 1.03 (P(trend)=0.217) and 1.04 (P(trend)=0.012) and, for glycemic load, were 0.90 (P(trend)=0.024) and 0.93 (P(trend)=0.01). Associations with total cancer held only among the overweight for glycemic index and among those of healthy weight for glycemic load. These findings suggest that glycemic index and glycemic load are not strong predictors of cancer incidence. The direction and small magnitude of associations might be explained by the manner in which high glycemic index and glycemic load track with overall diet and lifestyle patterns.

Dietary glycaemic index, glycaemic load and endometrial and ovarian cancer risk: a systematic review and meta-analysis

Long-term consumption of a high glycaemic index (GI) or glycaemic load (GL) diet may lead to chronic hyperinsulinaemia, which is a potential risk factor for cancer. To date, many studies have examined the association between GI, GL and cancer risk, although results have been inconsistent, therefore our objective was to conduct a systematic review of the literature. Medline and Embase were systematically searched using terms for GI, GL and cancer to identify studies published before December 2007. Random effects meta-analyses were performed for endometrial cancer, combining maximally adjusted results that compared risk for those in the highest versus the lowest category of intake. Separate analysis examined risk by body mass index categories. Five studies examining GI and/or GL intake and endometrial cancer risk were identified. Pooled effect estimates for endometrial cancer showed an increased risk for high GL consumers (RR 1.20; 95% CI: 1.06–1.37), further elevated in obese women (RR 1.54; 95% CI: 1.18–2.03). No significant associations were observed for GI. Only two studies examined ovarian cancer and therefore no meta-analysis was performed, but results indicate positive associations for GL also. A high GL, but not a high GI, diet is positively associated with the risk of endometrial cancer, particularly among obese women.

Effect of glycemic index on satiety and body weight

Despite extensive study, the practical significance of the glycemic index of food is still debatable. The purpose of this review paper was to evaluate the effect of glycemic index on food intake and body weight based on the analysis of published studies about this topic. According to some authors, ingestion of high glycemic index diets tends to enhance appetite and promote positive energy balance. The increase of appetite associated with the ingestion of these diets is attributed to an especially sharp early post-prandial rise of blood glucose followed by a marked release of insulin and subsequent rebound relative hypoglycemia and low levels of blood fatty acids, suggesting the difficulty that the body has to access its stored metabolic fuels. Short-term investigations have generally demonstrated that ingestion of low glycemic index foods results in greater satiety and lower energy intake than high glycemic index foods. However, less is known about the importance of glycemic index to energy balance and weight control associated with chronic ingestion of foods differing in glycemic index. Carefully designed long-term studies are required to assess the efficacy of glycemic index in the treatment and prevention of obesity in humans.

Methods for nutrigenomics and longevity studies in Drosophila: effects of diets high in sucrose, palmitic acid, soy, or beef

Nutrigenomics is the study of gene-nutrient interactions and how they affect the health and metabolism of an organism. Combining nutrigenomics with longevity studies is a natural extension and promises to help identify mechanisms whereby nutrients affect the aging process, life span, and, with the incorporation of age-dependent functional measures, health span. The topics we discuss in this chapter are genetic techniques, dietary manipulations, metabolic studies, and microarray analysis methods to investigate how nutrition affects gene expression, life span, triglyceride levels, total protein levels, and live weight in Drosophila. To better illustrate nutrigenomic techniques, we analyzed Drosophila larvae or adults fed control diets (high sucrose) and compared these with larvae or adults fed diets high in the saturated fat palmitic acid, soy, or 95% lean ground beef. The main results of these studies are, surprisingly, that triglyceride and total protein levels are significantly decreased by the beef diet in all adults, and total protein levels are significantly increased in male flies fed the soy diet. Furthermore, and less surprisingly, we found that all three experimental diets significantly decreased longevity and increased the length of time to develop from egg to adult. We also describe preliminary microarray results with adult flies fed the different diets, which suggest that only about 2-3% of the approx 18,000 genes have significantly altered mRNA expression levels compared with flies fed a control sucrose diet. The significance of these results and other types of nutrigenomics and longevity analyses is discussed.

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.

The effect of beta-glucan on the glycemic and insulin index

OBJECTIVE

To determine the effects of oat products with increasing beta-glucan content on the glycemic (GI) and insulin indexes (II) of oat products, and to establish the effect of physical properties of beta-glucan on these physiological responses.

DESIGN

Test group (n=10) randomly attended to three glucose tolerance tests and glycemic response tests for four oat bran products.

SETTINGS

Functional Foods Forum and the Department of Food Chemistry, University of Turku, and the Department of Food Technology, University of Helsinki.

SUBJECTS

One male and nine female volunteers were recruited from university students and staff, and all completed the study.

INTERVENTIONS

GI and II of different products were calculated for each subject using the average of parallel glucose tolerance tests and the subsequent glycemic/insulinemic responses for each product. Average indexes for products were calculated according to the individual data.

RESULTS

The glycemic responses to oat products with increasing amounts of beta-glucan had lower peak values than the reference glucose load. The amount of extractable beta-glucan had a high correlation between the glycemic and insulinemic response.

CONCLUSION

In addition to the total amount of beta-glucan in oat products, the amount of extractable beta-glucan in oat products explains the magnitude of the decrease in glycemic responses to carbohydrate products.

Challenges and strategies: weight management in type 2 diabetes

This article examines the link between obesity and type 2 diabetes and discusses some of the challenges health-care professionals face in helping people with diabetes achieve and maintain a healthy weight. Increasing numbers of people in both developed and developing countries are being classified as overweight or obese, which is resulting in growing numbers of people being diagnosed with type 2 diabetes. Worryingly this includes large numbers of children developing type 2 diabetes as the younger age groups are becoming overweight or obese. The health-care practitioner's role is explored and strategies to promote and achieve a healthy lifestyle for people with type 2 diabetes are offered. Such strategies are linked to obesity management through, diet, exercise and behavioural therapy.

Acceptability of lower glycemic index foods in the diabetes camp setting

OBJECTIVE

To determine the acceptability of lower glycemic index (GI) foods served at diabetes camp.

DESIGN

Crossover design of standard and lower GI menus.

SETTING

Three consecutive 5-day diabetes camp sessions.

PARTICIPANTS

140 youth, age 7-16, with type 1 or 2 diabetes.

INTERVENTION

A standard camp cycle menu was reformulated to include 2 1/2 days of standard foods and 2 1/2 days of lower GI foods.

MAIN OUTCOME MEASURES

Youth provided satisfaction ratings after meals and snacks using measures designed for this study. Observations of food consumption were conducted on a random sample of youth for each meal.

ANALYSIS

Descriptive analyses and t-tests were conducted to assess differences in satisfaction with and consumption of standard and lower GI foods.

RESULTS

Lower GI foods served at dinner and for snacks received satisfaction ratings equal to standard foods (dinner: 3.68 lower GI versus 3.79 standard, P = .30; snacks: 3.74 lower GI versus 3.79 standard, P = .60). Lower GI foods served at breakfast and lunch received lower, though very acceptable, ratings (breakfast: 3.76 lower GI versus 4.04 standard, P < .01; lunch: 3.64 lower GI versus 3.88 standard, P = .01). Consumption of all meals was acceptable. No differences occurred in the frequency of high or low blood sugars between standard and lower GI days.

CONCLUSIONS AND IMPLICATIONS

Higher quality carbohydrates may be provided to youth in institutional settings while maintaining sufficient levels of acceptability; specific findings are instructive for designing efforts to increase their consumption.

Glycemic load, glycemic index, and carbohydrate intake in relation to risk of cholecystectomy in women

BACKGROUND & AIMS

High-carbohydrate diets with a high glycemic response may exacerbate the metabolic consequences of the insulin-resistance syndrome. The effect on the incidence of gallstone disease is not clear.

METHODS

We examined the associations between high-carbohydrate diets with a high glycemic response and the risk of cholecystectomy in a cohort of women who were aged from 35 to 61 years in 1984 and had no history of gallstone disease. As part of the Nurses' Health Study, the women reported on questionnaires mailed to them every 2 years both their carbohydrate intake and whether they had undergone cholecystectomy.

RESULTS

During 16 years of follow-up, we ascertained 5771 new cases of cholecystectomy. After adjusting for age and other known or suspected risk factors in a multivariate model, the relative risk for the highest compared with the lowest quintile of dietary carbohydrate was 1.35 (95% CI: 1.17-1.55, P for trend < .0001). The relative risks for the highest compared with the lowest quintile were 1.50 for glycemic load (95% CI: 1.32-1.71, P for trend < .0001) and 1.32 for glycemic index (95% CI: 1.20-1.45, P for trend < .0001). Independent positive associations were also seen for intakes of starch and sucrose.

CONCLUSIONS

Our findings suggest that a higher intake of carbohydrate, dietary glycemic load, and glycemic index may enhance risk of cholecystectomy in women.