The effect of low-glycemic carbohydrate on insulin and glucose response in vivo and in vitro in patients with coronary heart disease

A head-to-head comparison review of biological and toxicological studies of isomaltulose, d-tagatose, and trehalose on glycemic control

Diabetes mellitus is the most common metabolic disorder contributing to significant morbidity and mortality in humans. Different preventive and therapeutic agents, as well as various pharmacological strategies or non-pharmacological tools, improve the glycemic profile of diabetic patients. Isomaltulose, d-tagatose, and trehalose are naturally occurring, low glycemic sugars that are not synthesized by humans but widely used in food industries. Various studies have shown that these carbohydrates can regulate glucose metabolism and provide support in maintaining glucose homeostasis in patients with diabetes, but also can improve insulin response, subsequently leading to better control of hyperglycemia. In this review, we discussed the anti-hyperglycemic effects of isomaltulose, D-tagatose, and trehalose, comparing their properties with other known sweeteners, and highlighting their importance for the development of the pharmaceutical and food industries.

Glenn A, M. S. Wolever T, G. Josse R, L. O’Connor D, Thompson A, D. Noseworthy R, Seider M, Sobie M, Bhatti G, Cavanagh J, Jones E, B. Darling P. Evaluation of Glycemic Index Education in People Living with Type 2 Diabetes: Participant Satisfaction, Knowledge Uptake, and Application

The glycemic index (GI) has been included in the Canadian clinical practice guidelines for type 2 diabetes (T2D) management since 2003, and even longer in other parts of the world (e.g., Australia). Despite this, dietitians have reported that GI is "too difficult for patients to understand and apply." They have called for diverse GI-utility data and evidence-informed education materials. To address these concerns, we developed and evaluated a GI education workshop and supporting materials, using the Kirkpatrick Model, for a T2D population. Participants (n = 29) with T2D attended a dietitian-facilitated workshop and received education materials. A mixed-form questionnaire (GIQ) and 3-day-diet-record were used to capture patient demographics, satisfaction, knowledge, and application, prior to and immediately after the workshop, 1-week, and 4-weeks post-education. Dietary GI was significantly lower at 1 and 4 weeks post-education (mean ± SEM; both 54 ± 1), compared to pre-education (58 ± 1; p ≤ 0.001). Participants (28/29) were satisfied with the intervention. The GI knowledge score was significantly higher post-education at baseline (83.5 ± 3.4%; p ≤ 0.001), week one (87.5 ± 2.6%; p = 0.035), and week four (87.6 ± 3.8%; p = 0.011) when compared to pre-education (53.6 ± 5.1%). A significant reduction in dietary GI was achieved by participants living with T2D, after completing the workshop, and they were able to acquire and apply GI knowledge in a relatively short period.

Reduced Feed Intake, Rather than Increased Energy Losses, Explains Variation in Growth Rates of Normal-Birth-Weight Piglets

Background

Substantial variation in growth rates exists in normal-birth-weight piglets, possibly due to differences in energy efficiency. Within this population, slow growth rates are associated with reduced insulin sensitivity. Slowly digestible starch (SDS) may improve growth efficiency in slowly growing pigs, because it reduces postprandial blood glucose.

Objective

The aim of this study was to investigate maintenance energy requirements and efficiency of energy used for growth (incremental energy efficiency) of slow-growing or fast-growing piglets (SG-pigs and FG-pigs, respectively) with equal birth weight that were fed either an SDS or a rapidly digestible-starch (RDS) diet.

Methods

Sixteen groups of either five 10-wk-old SG-pigs (mean ± SD: 11.3 ± 1.4 kg) or FG-pigs (15.1 ± 1.7 kg) were housed in climate respiration chambers and fed diets containing 40% RDS or SDS for 2 wk. In week 1, feed was available ad libitum. In week 2, feed supply was restricted to 65% of the observed weekly averaged feed intake [kJ · kg body weight (BW)-0.6 · d-1] in week 1. After week 2, pigs were feed deprived for 24 h, after which heat production was determined. Energy balances, apparent total tract digestibility (ATTD), and incremental energy efficiencies were calculated and analyzed using a general linear model.

Results

Gross energy intake (kJ · kg BW-0.6 · d-1) was 4% greater (P = 0.047) for FG-pigs than for SG-pigs. ATTD of fat was 6%-units greater (P = 0.003) for RDS-fed than for SDS-fed pigs. Fasting heat production and incremental energy efficiencies did not differ between pig types or diets. Incremental use of metabolizable energy for fat retention was 2% units (P = 0.054) greater for RDS-fed than SDS-fed pigs.

Conclusions

A lower energy intake rather than greater maintenance requirements or lower energy efficiency explains the slow growth of SG-pigs. Incremental RDS intake increased fat deposition more than SDS, whereas energy efficiency was not affected. Thus, feeding SDS instead of RDS does not improve growth efficiency but may result in slightly leaner pigs.

Low glycaemic index diets for the prevention of cardiovascular disease

BACKGROUND

The glycaemic index (GI) is a physiological measure of the ability of a carbohydrate to affect blood glucose. Interest is growing in this area for the clinical management of people at risk of, or with, established cardiovascular disease. There is a need to review the current evidence from randomised controlled trials (RCTs) in this area. This is an update of the original review published in 2008.

OBJECTIVES

To assess the effect of the dietary GI on total mortality, cardiovascular events, and cardiovascular risk factors (blood lipids, blood pressure) in healthy people or people who have established cardiovascular disease or related risk factors, using all eligible randomised controlled trials.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and CINAHL in July 2016. We also checked reference lists of relevant articles. No language restrictions were applied.

SELECTION CRITERIA

We selected RCTs that assessed the effects of low GI diets compared to diets with a similar composition but a higher GI on cardiovascular disease and related risk factors. Minimum trial duration was 12 weeks. Participants included were healthy adults or those at increased risk of cardiovascular disease, or previously diagnosed with cardiovascular disease. Studies in people with diabetes mellitus were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened and selected studies. Two review authors independently assessed risk of bias, evaluated the overall quality of the evidence using GRADE, and extracted data following the Cochrane Handbook for Systematic Reviews of Interventions. We contacted trial authors for additional information. Analyses were checked by a second reviewer. Continuous outcomes were synthesized using mean differences and adverse events were synthesized narratively.

MAIN RESULTS

Twenty-one RCTs were included, with a total of 2538 participants randomised to low GI intervention (1288) or high GI (1250). All 21 included studies reported the effect of low GI diets on risk factors for cardiovascular disease, including blood lipids and blood pressure.Twenty RCTs (18 of which were newly included in this version of the review) included primary prevention populations (healthy individuals or those at high risk of CVD, with mean age range from 19 to 69 years) and one RCT was in those diagnosed with pre-existing CVD (a secondary prevention population, with mean age 26.9 years). Most of the studies did not have an intervention duration of longer than six months. Difference in GI intake between comparison groups varied widely from 0.6 to 42.None of the included studies reported the effect of low GI dietary intake on cardiovascular mortality and cardiovascular events such as fatal and nonfatal myocardial infarction, unstable angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, and stroke. The unclear risk of bias of most of the included studies makes overall interpretation of the data difficult. Only two of the included studies (38 participants) reported on adverse effects and did not observe any harms (low-quality evidence).

AUTHORS' CONCLUSIONS

There is currently no evidence available regarding the effect of low GI diets on cardiovascular disease events. Moreover, there is currently no convincing evidence that low GI diets have a clear beneficial effect on blood lipids or blood pressure parameters.

The effect of maternal and post-weaning low and high glycaemic index diets on glucose tolerance, fat deposition and hepatic function in rat offspring

Clinical studies have reported beneficial effects of a maternal low glycaemic index (GI) diet on pregnancy and neonatal outcomes, but the impact of the diet on the offspring in later life, and the mechanisms underlying these effects, remain unclear. In this study, Albino Wistar rats were fed either a low GI (n=14) or high GI (n=14) diet during pregnancy and lactation and their offspring weaned onto either the low or high GI diet. Low GI dams had better glucose tolerance (AUC[glucose], 1322±55 v. 1523±72 mmol min/l, P<0.05) and a lower proportion of visceral fat (19.0±2.9 v. 21.7±3.8% of total body fat, P<0.05) compared to high GI dams. Female offspring of low GI dams had lower visceral adiposity (0.45±0.03 v. 0.53±0.03% body weight, P<0.05) and higher glucose tolerance (AUC[glucose], 1243±29 v. 1351±39 mmol min/l, P<0.05) at weaning, as well as lower hepatic PI3K-p85 mRNA at 12 weeks of age. No differences in glucose tolerance or hepatic gene expression were observed in male offspring, but the male low GI offspring did have reduced hepatic lipid content at weaning. These findings suggest that consuming a low GI diet during pregnancy and lactation can improve glucose tolerance and reduce visceral adiposity in the female offspring at weaning, and may potentially produce long-term reductions in the hepatic lipogenic capacity of these offspring.

Sweet potato [Ipomoea batatas (L.) Lam. "Tainong 57"] starch improves insulin sensitivity in high-fructose diet-fed rats by ameliorating adipocytokine levels, pro-inflammatory status, and insulin signaling

The aim of this study was to investigate the effects of low-glycemic index (GI) sweet potato starch on adipocytokines, pro-inflammatory status, and insulin signaling in the high-fructose diet-induced insulin-resistant rat. We randomly divided 24 insulin-resistant rats and 16 normal rats into two groups fed a diet containing 575 g/kg of starch: a low-GI sweet potato starch (S) or a high-GI potato starch (P). The four experimental groups were labeled as follows: insulin-resistant P (IR-P), insulin-resistant S (IR-S), normal P (N-P) and normal S (N-S). After 4 wk on the experimental diets, an intraperitoneal glucose tolerance test (IPGTT) was conducted, and the homeostasis model assessment (HOMA), adipocytokines, pro-inflammatory cytokines levels, and insulin signaling-related protein expression were measured. The homeostasis model assessment values were significantly lower in the IR-S than in the IR-P group, suggesting that insulin sensitivity was improved among sweet potato starch-fed rats. Levels of tumor necrosis factor-α, interleukin-6, resistin, and retinol binding protein-4 were significantly lower in the IR-S versus the IR-P group, indicating an improvement of pro-inflammatory status in sweet potato starch-fed rats. The sweet potato starch diet also significantly enhanced the protein expression of phospho-Tyr-insulin receptor substrate-1 and improved the translocation of glucose transporter 4 in the skeletal muscle. Our results illustrated that sweet potato starch feeding for 4 wk can improve insulin sensitivity in insulin-resistant rats, possibly by improving the adipocytokine levels, pro-inflammatory status, and insulin signaling.

Effect of flaxseed gum on reduction of blood glucose and cholesterol in type 2 diabetic patients

The effects of ingestion of flaxseed gum on blood glucose and cholesterol, particularly low-density lipoprotein cholesterol, in type 2 diabetes were evaluated. Flaxseed gum was incorporated in wheat flour chapattis. Sixty patients of type 2 diabetes were fed a daily diet for 3 months, along with six wheat flour chapattis containing flaxseed gum (5 g), as per the recommendations of the American Diabetic Association. The control group (60 individuals) consumed an identical diet but the chapattis were without gum. The blood biochemistry profiles monitored before starting the study and at monthly intervals showed fasting blood sugar in the experimental group decreased from 154 ± 8 mg/dl to 136 ± 7 mg/dl (P=0.03) while the total cholesterol reduced from 182 ± 11 mg/dl to 163 ± 9 mg/dl (P=0.03). Results showed a decrease in low-density lipoprotein cholesterol from 110 ± 8 mg/dl to 92 ± 9 mg/dl (P=0.02). The study demonstrated the efficacy of flax gum in the blood biochemistry profiles of type 2 diabetes.

Low glycaemic index diets and blood lipids: a systematic review and meta-analysis of randomised controlled trials

AIMS

Low glycaemic index (GI) diets are beneficial in the management of hyperglycemia. Cardiovascular diseases are the major cause of mortality in diabetes therefore it is important to understand the effects of GI on blood lipids. The aim was to systematically review randomised controlled trials (RCTs) of low GI diets on blood lipids.

DATA SYNTHESIS

We searched OVID Medline, Embase and Cochrane library to March 2012. Random effects meta-analyses were performed on twenty-eight RCTs comparing low- with high GI diets over at least 4 weeks (1272 participants; studies ranged from 6 to 155 participants); one was powered on blood lipids, 3 had adequate allocation concealment. Low GI diets significantly reduced total (-0.13 mmol/l, 95%CI -0.22 to -0.04, P = 0.004, 27 trials, 1441 participants, I(2) = 0%) and LDL-cholesterol (-0.16 mmol/l, 95%CI -0.24 to -0.08, P < 0.0001, 23 trials, 1281 participants, I(2) = 0%) compared with high GI diets and independently of weight loss. Subgroup analyses suggest that reductions in LDL-C are greatest in studies of shortest duration and greatest magnitude of GI reduction. Furthermore, lipid improvements appear greatest and most reliable when the low GI intervention is accompanied by an increase in dietary fibre. Sensitivity analyses, removing studies without adequate allocation concealment, lost statistical significance but retained suggested mean falls of ~0.10 mmol/l in both. There were no effects on HDL-cholesterol (MD -0.03 mmol/l, 95%CI -0.06 to 0.00, I(2) = 0%), or triglycerides (MD 0.01 mmol/l, 95%CI -0.06 to 0.08, I(2) = 0%).

CONCLUSIONS

This meta-analysis provides consistent evidence that low GI diets reduce total and LDL-cholesterol and have no effect on HDL-cholesterol or triglycerides.

Food-based ingredients to modulate blood glucose

Maintenance of normal blood glucose levels is important for avoiding chronic diseases such as type 2 diabetes, cardiovascular problems, and obesity. Type 2 diabetes is one of the major health problems affecting the world population and this condition can be exacerbated by poor diet, low physical activity, and genetic abnormalities. Food plays an important role in the management of blood glucose and associated complications in diabetes. This is attributed to the ability of food-based ingredients to modulate blood glucose without causing any adverse health consequences. This chapter focuses on four important food groups such as cereals, legumes, fruits, and spices that have active ingredients such as soluble dietary fiber, polyphenols, and antinutrients with the ability to reduce glycemic and insulin response in humans. Other food ingredients such as simple sugars, sugar alcohols, and some proteins are also discussed in moderation.

Impact of glycaemic index and dietary fibre on insulin sensitivity during the refeeding phase of a weight cycle in young healthy men

Previous studies suggest that a low-glycaemic index (LGI) diet may improve insulin sensitivity (IS). As IS has been shown to decrease during refeeding, we hypothesised that an LGI- v. high-GI (HGI) diet might have favourable effects during this phase. In a controlled nutritional intervention study, sixteen healthy men (aged 26·8 (SD 4·1) years, BMI 23·0 (SD 1·7) kg/m2) followed 1 week of overfeeding, 3 weeks of energy restriction and of 2 weeks refeeding at ^50% energy requirement (50% carbohydrates, 35% fat and 15% protein). During refeeding, subjects were divided into two matched groups receiving either high-fibre LGI or lower-fibre HGI foods (GI 40 v. 74, fibre intake 65 (SD 6) v. 27 (SD 4) g/d). Body weight was equally regained in both groups with refeeding (mean regain 70·5 (SD 28·0)% of loss). IS was improved by energy restriction and decreased with refeeding. The decreases in IS were greater in the HGI than in the LGIgroup (group £ time interactions for insulin, homeostasis model assessment of insulin resistance (HOMAIR), Matsuda IS index (MatsudaISI);all P,0·05). Mean interstitial glucose profiles during the day were also higher in the HGI group (DAUCHGI-LGI of continuous interstitial glucose monitoring: 6·6 mmol/l per 14 h, P¼0·04). At the end of refeeding, parameters of IS did not differ from baseline values in either diet group (adiponectin, insulin, HOMAIR, Matsuda ISI, M-value; all P.0·05). In conclusion, nutritional stress imposed by dietary restriction and refeeding reveals a GI/fibre effect in healthy non-obese subjects. LGI foods rich in fibre may improve glucose metabolism during the vulnerable refeeding phase of a weight cycle.

Weight loss and improvements in fatigue in systemic lupus erythematosus: a controlled trial of a low glycaemic index diet versus a calorie restricted diet in patients treated with corticosteroids

Background: Patients with systemic lupus erythematosus (SLE) may require prolonged periods of corticosteroid therapy which lead to excessive weight gain and increased cardiovascular risk. Objective: To assess the utility of a low glycaemic index diet in patients with corticosteroid dependent SLE in achieving weight loss and improving glycaemic control. Design: A total of 23 women were enrolled in a 6 week study. All had mild, stable SLE, were receiving corticosteroids and had a body mass index > 25 kg/m2. Subjects were randomly assigned to a low glycaemic index (Low GI) diet or a calorie restricted (Low Cal) diet. The primary end point was weight loss. Secondary end points included tolerability of diet, bio-markers of cardiovascular risk, disease activity, fatigue and sleep quality. Results: Weight loss in both treatment groups was significant (mean ± SD: Low GI diet 3.9 ± 0.9 kg; Low Cal diet 2.4 ± 2.2 kg, p < 0.01 from baseline in each group). There were also significant improvements in waist and hip measurements. However, the difference in weight loss and waist and hip measurements between the two diet groups was not statistically significant. There was a statistically significant reduction in Fatigue Severity Scale in both diet groups, ( p < 0.03). Both Low GI and Low Cal diets were well tolerated, resulting in no serious adverse effects or increase in disease activity. Conclusion: Significant weight loss is achievable over 6 weeks in a diet-specific trial in subjects with stable SLE, who are on low dose prednisolone. Both diets were equally tolerable, and did not cause flares in disease activity. Our results suggest that dietary manipulation may significantly improve fatigue in subjects with SLE.

Foods for the prevention of diabetes: how do they work?

With the diabetes epidemic reaching menacing proportions worldwide, there is an urgent need for the development of cost-efficient prevention strategies to be effective at the population level. Great potential in this direction lies in properly designed, large-scale dietary interventions. The macronutrient composition and the caloric content of our diet are major determinants of glucose homeostasis and there is a continuously growing list of foods, nutrients or individual compounds that have been associated with an increased or reduced incidence of diabetes mellitus. These include fat, carbohydrates, fibre, alcohol, polyphenols and other micronutrients or individual dietary compounds, which have been shown to either promote or prevent a progression towards a (pre-)diabetic state. This review aims to briefly summarize relevant epidemiological data linking foods to diabetes and to provide insights into the mechanisms through which these effects are mediated. These include improvement of insulin sensitivity or promotion of insulin resistance, regulation of inflammatory pathways, regulation of glucose transport and tissue glucose uptake, aggravation or attenuation of postprandial glycaemia/insulinaemia, interactions with hormonal responses and β-cell-dependent mechanisms.

Glycemic index and glycemic load of carbohydrates in the diabetes diet

Medical nutrition therapy is the first line of treatment for the prevention and management of type 2 diabetes and plays an essential part in the management of type 1 diabetes. Although traditionally advice was focused on carbohydrate quantification, it is now clear that both the amount and type of carbohydrate are important in predicting an individual's glycemic response to a meal. Diets based on carbohydrate foods that are more slowly digested, absorbed, and metabolized (i.e., low glycemic index [GI] diets) have been associated with a reduced risk of type 2 diabetes and cardiovascular disease, whereas intervention studies have shown improvements in insulin sensitivity and glycated hemoglobin concentrations in people with diabetes following a low GI diet. Research also suggests that low GI diets may assist with weight management through effects on satiety and fuel partitioning. These findings, together with the fact that there are no demonstrated negative effects of a low GI diet, suggest that the GI should be an important consideration in the dietary management and prevention of diabetes.

Perceived barriers to application of glycaemic index: valid concerns or lost in translation?

The term glycaemic-index (GI) originally appeared in the literature in the early 1980s. GI categorizes carbohydrate according to glycaemic effect postprandially. Since its inception, GI has obtained and maintained interest of academics and clinicians globally. Upon review of GI literature, it becomes clear that the clinical utility of GI is a source of controversy. Can and should GI be applied clinically? There are academics and clinicians on both sides of the argument. Certainly, this controversy has been a stimulus for the evolution of GI methodology and application research, but may also negatively impact clinicians' perception of GI if misunderstood. This article reviews two assessments of GI that are often listed as barriers to application; the GI concept is (1) too complex and (2) too difficult for clients to apply. The literature reviewed does not support the majority of purported barriers, but does indicate that there is a call from clinicians for more and improved GI education tools and clinician GI education. The literature indicates that the Registered Dietitian (RD) can play a key role in GI knowledge translation; from research to application. Research is warranted to assess GI education tool and knowledge needs of clinicians and the clients they serve.

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

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

Dietary hyperglycemia, glycemic index and metabolic retinal diseases

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

Glycaemic index, appetite and body weight

Much interest has been focused on the relationship between glycaemic index and body-weight loss, some of which is fueled by popular media. However, there is a number of potential mechanisms that could be triggered by reducing the glycaemic index of the carbohydrate consumed in the diet. For example, the effect of foods on the gastrointestinal tract and the effect on blood glucose both could lead to potential appetite effects. Acute meal studies seem to point to an effect of glycaemic index on appetite regulation. However, the results of longer-term studies of weight loss are not as clear. In the present review a possible reason for this variation in outcome from the weight-loss studies will be discussed. The present review focuses on the possibility that the fermentable fibre content of the low-glycaemic-index diet may be important in weight-loss efficacy. A novel receptor that binds SCFA, the products of carbohydrate fermentation, has recently been described on the enteroendocrine L-cell in the colon. This cell releases a number of anorectic hormones and could offer an explanation of the appetite suppressant effects of fermentable carbohydrates. It could also explain the variability in the results of glycaemic-index weight-loss studies.

Consumption of a high glycemic index diet increases abdominal adiposity but does not influence adipose tissue pro-oxidant and antioxidant gene expression in C57BL/6 mice

The hypothesis of this study is that consumption of a high glycemic index (GI) starch will increase adiposity, increase expression of the pro-oxidant enzyme (nicotinamide adenine dinucleotide phosphate [NADPH] oxidase), and decrease expression of the antioxidant enzymes (catalase, glutathione peroxidase [GPx], and superoxide dismutase [SOD]) in adipose tissue of mice. C57BL/6 mice (n = 5-8/group) were fed a diet containing either high-GI starch (100% amylopectin) or low-GI starch (60% amylose/40% amylopectin) under low-fat (LF) or high-fat (HF) conditions for 16 weeks. Meal tolerance tests (MTTs) indicated that the postprandial blood glucose response over 120 minutes for the high-GI mice under LF and HF conditions was significantly greater than for mice fed low-GI diets. This result was not due to increased food consumption by the high-GI mice during the MTT. Although there was no difference in body weight between mice fed high-GI or low-GI starch, LF high-GI mice had significantly greater adiposity compared to LF low-GI mice. High-fat mice had a significant increase in NADPH oxidase expression compared to LF mice, but there was no significant effect of starch on NADPH oxidase expression. High-fat diet significantly decreased the expression of GPx and catalase, but there was no significant effect of starch on GPx and catalase expression. There was no difference in SOD expression among any of the diet groups. In conclusion, high GI diets increase adiposity under LF conditions but do not influence pro-oxidant or antioxidant enzyme gene expression in adipose tissue of C57BL/6 mice.

Glycaemic index of some commercially available rice and rice products in Great Britain

The glycaemic response to nine types of rice (white basmati, brown basmati, white and brown basmati, easy-cook basmati, basmati and wild rice, long-grain rice, easy-cook long-grain rice, Thai red rice, Thai glutinous rice) and two types of rice vermicelli (Guilin rice vermicelli, Jiangxi rice vermicelli) commercially available in the United Kingdom were compared against a glucose standard in a non-blind, randomized, repeated-measure, crossover design trial. Fourteen healthy subjects (six males, eight females), mean age 38 (standard deviation 16) years and mean body mass index 21.3 (standard deviation 2.3) kg/m(2), were recruited for the study. Subjects were served portions of the test foods and a standard food (glucose), on separate occasions, each containing 50 g available carbohydrates. Capillary blood glucose was measured from finger-prick samples in fasted subjects (-5 and 0 min) and at 15, 30, 45, 60, 90 and 120 min after the consumption of each test food. For each type of food, its glycaemic index (GI) was calculated geometrically by expressing the incremental area under the blood glucose curve as a percentage of each subject's average incremental area under the blood glucose curve for the standard food. The 10 foods exhibited a range of GI values from 37 to 92. The study indicated that rice noodles, long-grain rice, easy-cook long-grain rice and white basmati rice were low-GI foods, whilst all of the other foods were medium-GI and high-GI foods. The information presented in this paper may be useful in helping people select low-GI foods from the customary foods consumed by the British and Asian populations.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSION

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

Preventing and managing cardiometabolic risk: the logic for intervention

Cardiometabolic risk (CMR), also known as metabolic syndrome or insulin resistance syndrome, comprises obesity (particularly central or abdominal obesity), high triglycerides, low HDL, elevated blood pressure, and elevated plasma glucose. Leading to death from diabetes, heart disease, and stroke, the root cause of CMR is inadequate physical activity, a Western diet identified primarily by low intake of fruits, vegetables, and whole grains, and high in saturated fat, as well as a number of yet-to-be-identified genetic factors. While the pathophysiological pathways related to CMR are complex, the universal need for adequate physical activity and a diet that emphasizes fruits and vegetables and whole grains, while minimizing food high in added sugars and saturated fat suggests that these behaviors are the appropriate focus of intervention.

Dietary carbohydrates and cardiovascular disease risk factors in the Framingham offspring cohort

OBJECTIVE

Evidence from observational studies has suggested that carbohydrate quality rather than absolute intake is associated with greater risk of chronic diseases. The aim of this study was to examine the relationship between carbohydrate intake and dietary glycemic index and several cardiovascular disease risk factors.

METHODS

We examined cross-sectional associations between total carbohydrate and dietary glycemic index (GI) intakes and several cardiovascular disease risk factors (CVD) in a sample of 2,941 Framingham Offspring Participants. CVD risk factors included waist, blood pressure, lipids, fasting insulin, fasting glucose, and the insulin sensitivity index (ISI(0,120)). Dietary intake was assessed by a food frequency questionnaire (FFQ) and categorized by quintiles of dietary intake.

RESULTS

After adjustment for potential confounding factors, dietary GI was positively associated with fasting triglycerides (mean: 115mg/dL in the lowest and 127 mg/dL in the highest quintile of intake; P for trend < 0.001), fasting insulin (26.8 and 28.9 microu/mL, respectively, P for trend < 0.0001), and inversely associated with HDL cholesterol (49 and 47 mg/dL, respectively, P for trend 0.003) and ISI(0,120) (26.8 and 25.1, P for trend < 0.001). There was no significant relationship between dietary GI and waist circumference, total cholesterol, LDL cholesterol and fasting glucose. Intakes of total carbohydrate were inversely associated with waist circumference and HDL cholesterol, and positively associated with fasting triglycerides.

CONCLUSION

These cross-sectional findings support the hypothesis that a high GI diet unfavorably affects CVD risk factors and therefore, substitution of high with low GI dietary carbohydrates may have reduce the risk of CVD.

Low-carbohydrate-diet score and risk of type 2 diabetes in women

BACKGROUND

Low-carbohydrate weight-loss diets remain popular; however, the long-term effects of these diets are not known.

OBJECTIVE

The objective was to examine the association between low-carbohydrate-diet score and risk of type 2 diabetes

DESIGN

We prospectively examined the association between low-carbohydrate-diet score (based on percentage of energy as carbohydrate, fat, and protein) and risk of diabetes among 85 059 women in the Nurses' Health Study.

RESULTS

During 20 y of follow-up, we documented 4670 cases of type 2 diabetes. The multivariate relative risk (RR) of diabetes, after adjustment for body mass index and other covariates, in a comparison of the highest decile of low-carbohydrate-diet score with the lowest was 0.90 (95% CI: 0.78, 1.04; P for trend = 0.26). The multivariate RR for the comparison of extreme deciles of low-carbohydrate-diet score based on total carbohydrate, animal protein, and animal fat was 0.99 (95% CI: 0.85, 1.16; P for trend = 1.0), whereas the RR for a low-carbohydrate-diet score based on total carbohydrate, vegetable protein, and vegetable fat was 0.82 (95% CI: 0.71, 0.94; P for trend = 0.001). A higher dietary glycemic load was strongly associated with an increased risk of diabetes in a comparison of extreme deciles (RR: 2.47; 95% CI: 1.75, 3.47; P for trend < 0.0001)). A higher carbohydrate consumption was also associated with an increased risk of diabetes in a comparison of extreme deciles (RR: 1.26; 95% CI: 1.07, 1.49; P for trend = 0.003).

CONCLUSION

These data suggest that diets lower in carbohydrate and higher in fat and protein do not increase the risk of type 2 diabetes in women. In fact, diets rich in vegetable sources of fat and protein may modestly reduce the risk of diabetes.

State of the Art Reviews: Glycemic Index, Obesity, and Chronic Disease

There is increasing evidence that both the amount and type of carbohydrate play an important role in weight management and risk of chronic disease. Classifying carbohydrates according to their post-prandial glycemic effect (ie, the glycemic index of foods) has yielded more useful insights than the historical distinctions of simple versus complex chemical structure. Diets based on carbohydrate foods that are more slowly digested and absorbed (ie, low glycemic index diets) have been independently linked to reduced risk of type 2 diabetes, cardiovascular disease, and some types of cancer. In individuals with diabetes, intervention studies have shown improvements in insulin sensitivity and glycated hemoglobin concentration with low glycemic index diets. Research also suggests that low glycemic index diets may assist with weight management through effects on satiety and fuel partitioning. Although ongoing research is needed, the current findings, together with the fact that there are no demonstrated negative effects of a low glycemic index diet, suggest that the glycemic index should be an important consideration in the dietary management and prevention of obesity and chronic disease.

Glycemic response and health--a systematic review and meta-analysis: the database, study characteristics, and macronutrient intakes

BACKGROUND

Reduction of dietary glycemic response has been proposed as a means of reducing the risk of diabetes and coronary heart disease. Its role in health maintenance and management, alongside unavailable carbohydrate (eg, fiber), is incompletely understood.

OBJECTIVE

We aimed to assess the evidence relating the glycemic impact of foods to a role in health maintenance and management of disease.

DESIGN

We searched the literature for relevant controlled dietary intervention trials on glycemic index (GI) according to inclusion and exclusion criteria, extracted the data to a database, and synthesized the evidence via meta-analyses and meta-regression models.

RESULTS

Among literature to January 2005, 45 relevant publications were identified involving 972 subjects with good health or metabolic disease. With small reductions in GI (<10 units), increases in available carbohydrate, energy, and protein intakes were found in all studies combined. Falling trends in energy, available carbohydrate, and protein intakes then occurred with progressive reductions in GI. Fat intake was essentially unchanged. Unavailable carbohydrate intake was generally higher for intervention diets but showed no trend with GI (falling or rising). Among studies reporting on GI, variation in glycemic load was approximately equally explained by variation in GI and variation in available carbohydrate intake. An exchange of available and unavailable carbohydrate (approximately 1 g/g) was evident in these studies.

CONCLUSIONS

Among GI studies, observed reductions in glycemic load are most often not solely due to substitution of high for low glycemic carbohydrate foods. Available carbohydrate intake is a confounding factor. The role of unavailable carbohydrate remains to be accounted for.

Determining the relationship between dietary carbohydrate intake and insulin resistance

Insulin resistance underlies type 2 diabetes, CVD and the metabolic syndrome, driven by changes in diet, lifestyle, energy over–consumption and obesity. Nutritional recommendations for insulin resistance remain an area of controversy, particularly the quantity and types of dietary carbohydrate. The present review gives an overview of insulin resistance, its relationship to impaired insulin secretion and the metabolic syndrome, research methodologies used to measure insulin action and the epidemiological and intervention studies on the relationship between dietary carbohydrate and insulin resistance. Epidemiological studies provide little evidence to suggest that total dietary carbohydrate predicts risk of type 2 diabetes, and high–carbohydrate, high–fibre diets with low–glycaemic index (GI) may even contribute to diabetes prevention. Despite inherent limitations associated with techniques used to measure insulin resistance and dietary assessment, most intervention studies reveal an increase in glucose tolerance or insulin sensitivity with high–carbohydrate, low–fat diets in non–diabetic and diabetic individuals. When energy is restricted the source or reduced content of carbohydrate does not appear to be as important as fat for body weight. Thus, low energy intake is key to weight loss and augmentation of insulin sensitivity. Given this, widespread adoption of popular low–carbohydrate high–fat diets highlights the necessity to evaluate dietary interventions regarding safety and metabolic effects. While current evidence supports FAO/WHO recommendations to maintain a high–carbohydrate diet with low–GI foods, the relationships between carbohydrate and insulin sensitivity remains an important research area. Emerging technologies should further enhance understanding of gene–diet interactions in insulin resistance, providing useful information for future nutrition policy decisions.

Impact of resistant starch on body fat patterning and central appetite regulation

Background

Adipose tissue patterning has a major influence on the risk of developing chronic disease. Environmental influences on both body fat patterning and appetite regulation are not fully understood. This study was performed to investigate the impact of resistant starch (RS) on adipose tissue deposition and central regulation of appetite in mice.

Methodology and Principle Findings

Forty mice were randomised to a diet supplemented with either the high resistant starch (HRS), or the readily digestible starch (LRS). Using ¹H magnetic resonance (MR) methods, whole body adiposity, intrahepatocellular lipids (IHCL) and intramyocellular lipids (IMCL) were measured. Manganese-enhanced MRI (MEMRI) was used to investigate neuronal activity in hypothalamic regions involved in appetite control when fed ad libitum. At the end of the interventional period, adipocytes were isolated from epididymal adipose tissue and fasting plasma collected for hormonal and adipokine measurement. Mice on the HRS and LRS diet had similar body weights although total body adiposity, subcutaneous and visceral fat, IHCL, plasma leptin, plasma adiponectin plasma insulin/glucose ratios was significantly greater in the latter group. Adipocytes isolated from the LRS group were significantly larger and had lower insulin-stimulated glucose uptake. MEMRI data obtained from the ventromedial and paraventricular hypothalamic nuclei suggests a satiating effect of the HRS diet despite a lower energy intake.

Conclusion and Significance

Dietary RS significantly impacts on adipose tissue patterning, adipocyte morphology and metabolism, glucose and insulin metabolism, as well as affecting appetite regulation, supported by changes in neuronal activity in hypothalamic appetite regulation centres which are suggestive of satiation.

The effect of a high-protein, low glycemic–load diet versus a conventional, high glycemic–load diet on biochemical parameters associated with acne vulgaris: A randomized, investigator-masked, controlled trial

BACKGROUND

No previous study has sought to examine the influence of dietary composition on acne vulgaris.

OBJECTIVE

We sought to compare the effect of an experimental low glycemic-load diet with a conventional high glycemic-load diet on clinical and endocrine aspects of acne vulgaris.

METHODS

A total of 43 male patients with acne completed a 12-week, parallel, dietary intervention study with investigator-masked dermatology assessments. Primary outcomes measures were changes in lesion counts, sex hormone binding globulin, free androgen index, insulin-like growth factor-I, and insulin-like growth factor binding proteins.

RESULTS

At 12 weeks, total lesion counts had decreased more in the experimental group (-21.9 [95% confidence interval, -26.8 to -19.0]) compared with the control group (-13.8 [-19.1 to -8.5], P = .01). The experimental diet also reduced weight (P = .001), reduced the free androgen index (P = .04), and increased insulin-like growth factor binding protein-1 (P = .001) when compared with a high glycemic-load diet.

LIMITATIONS

We could not preclude the role of weight loss in the overall treatment effect.

CONCLUSION

This suggests nutrition-related lifestyle factors play a role in acne pathogenesis. However, these preliminary findings should be confirmed by similar studies.

A low-glycemic-load diet improves symptoms in acne vulgaris patients: a randomized controlled trial

BACKGROUND

Although the pathogenesis of acne is currently unknown, recent epidemiologic studies of non-Westernized populations suggest that dietary factors, including the glycemic load, may be involved.

OBJECTIVE

The objective was to determine whether a low-glycemic-load diet improves acne lesion counts in young males.

DESIGN

Forty-three male acne patients aged 15-25 y were recruited for a 12-wk, parallel design, dietary intervention incorporating investigator-blinded dermatology assessments. The experimental treatment was a low-glycemic-load diet composed of 25% energy from protein and 45% from low-glycemic-index carbohydrates. In contrast, the control situation emphasized carbohydrate-dense foods without reference to the glycemic index. Acne lesion counts and severity were assessed during monthly visits, and insulin sensitivity (using the homeostasis model assessment) was measured at baseline and 12 wk.

RESULTS

At 12 wk, mean (+/-SEM) total lesion counts had decreased more (P=0.03) in the low-glycemic-load group (-23.5 +/- 3.9) than in the control group (-12.0 +/- 3.5). The experimental diet also resulted in a greater reduction in weight (-2.9 +/- 0.8 compared with 0.5 +/- 0.3 kg; P<0.001) and body mass index (in kg/m(2); -0.92 +/- 0.25 compared with 0.01 +/- 0.11; P=0.001) and a greater improvement in insulin sensitivity (-0.22 +/- 0.12 compared with 0.47 +/- 0.31; P=0.026) than did the control diet.

CONCLUSION

The improvement in acne and insulin sensitivity after a low-glycemic-load diet suggests that nutrition-related lifestyle factors may play a role in the pathogenesis of acne. However, further studies are needed to isolate the independent effects of weight loss and dietary intervention and to further elucidate the underlying pathophysiologic mechanisms.

Motivational effects of 12-week moderately restrictive diets with or without special attention to the Glycaemic Index of foods

Low glycaemic index (GI) diets may facilitate weight loss via behavioural and/or endocrine mechanisms. This study investigated whether the outcomes of the Weight Watchers POINTS Weight-Loss System could be improved by encouraging dieters to select low GI, high-carbohydrate foods. Ninety-six women (age 20-72 years; BMI 25-40 kg/m2) were recruited as they started the Weight Watchers POINTS programme for 12 weeks. Weekly classes were randomized so that seven (forty-five women) followed the regular programme while seven others (fifty-one women) followed a revised programme encouraging the selection of low GI foods. Anthropometric and biochemical parameters were measured before and after the 12-week diets. Participants rated hunger and desire to eat using visual analogue scales on 1 d per week, several times per d. Attrition was the same in both groups (32 v. 30 %), as well as many benefits (5 % weight loss, decreases in insulinaemia and blood lipids, waist and hip circumferences, blood pressure). Hunger and desire to eat were rated consistently lower in the low GI group over the 12-week diet. Group differences in subjective sensations were especially large in the afternoon. The 12-week weight management yielded many significant anthropometric and biochemical benefits that were not improved by encouraging dieters to select low GI foods. The subjective benefits (lower hunger and desire to eat) of the low GI diet may be a worthwhile contribution to the motivation of dieters that might affect adherence to the diet over the long term.

Muesli with 4 g oat β-glucans lowers glucose and insulin responses after a bread meal in healthy subjects

OBJECTIVE

To evaluate the impact of an extruded muesli product based on beta-glucan-rich oat bran on postprandial glycaemia and insulinaemia.

SUBJECT/DESIGN

The study is divided in two series. Blood glucose and serum insulin responses were studied after subjects consuming test meals including a serving of muesli with 3 g (series 1) and 4 g (series 2) of beta-glucans, respectively. The muesli was a component in a single serving packet with muesli and yoghurt. This was served together with white wheat bread in the morning after an overnight fast. The compositions were standardized to contain 50 g available carbohydrates. As a reference meal a serving packet without beta-glucans was included. The study was performed at Applied Nutrition and Food Chemistry, Lund University, Sweden. Nineteen and thirteen healthy volunteers with normal body mass index were recruited for series 1 and 2, respectively.

RESULTS

Muesli with 3 g of beta-glucans, included in a mixed bread meal, gave no significant differences in glycaemic response compared to a reference meal without muesli and beta-glucans. In contrast, muesli with 4 g of beta-glucans significantly (P<0.05) lowered the glucose and insulin responses compared to the reference meal.

CONCLUSIONS

Muesli enriched with 4 g of beta-glucans reduces postprandial glucose and insulin levels to a breakfast based on high glycaemic index products. A total of 4 g of beta-glucans from oats seems to be a critical level for a significant decrease in glucose and insulin responses in healthy people.

Glycaemic index and metabolic disease risk

There is growing evidence that the type of carbohydrate consumed is important in relation to metabolic disease risk, and there is currently particular interest in the role of low-glycaemic-index (GI) foods. Observational studies have associated low-GI diets with decreased risk of type 2 diabetes and CHD, and improvements in various metabolic risk factors have been seen in some intervention studies. However, findings have been mixed and inconsistent. There are a number of plausible mechanisms for the effects of these foods on disease risk, which arise from the differing metabolic responses to low- and high-GI foods, with low-GI foods resulting in reductions in hyperglycaemia, hyperinsulinaemia and late postprandial circulating NEFA levels. Low-GI foods may also increase satiety and delay the return of hunger compared with high-GI foods, which could translate into reduced energy intake at later time points. However, the impact of a low-GI diet on body weight is controversial, with many studies confounded by dietary manipulations that differ in aspects other than GI. There is currently much interest in GI from scientists, health professionals and the public, but more research is needed before clear conclusions can be drawn about relationships with metabolic disease risk.

Glucagon-like peptide-1 (7-36) amide response to low versus high glycaemic index preloads in overweight subjects with and without type II diabetes mellitus

BACKGROUND AND OBJECTIVE

Glucagon-like-peptide-1 (7-36) amide (GLP-1) is an insulin secretagogue and potential treatment for type II diabetes mellitus. An alternative to GLP-1 administration is endogenous dietary stimulation. We described a greater GLP-1 release following ingestion of liquids versus solids. We add to this work studying the effect of fluid preloads with differing glycaemic indices (GI) on the metabolic response to a meal.

SUBJECTS AND DESIGN

GLP-1, insulin and glucose responses were measured in six overweight individuals and six subjects with type II diabetes on three occasions, after preload (milk, low GI; Ovaltine Light, high GI; or water, non-nutritive control) and meal ingestion.

RESULTS

In people with and without diabetes, the high GI preload produced the greatest glucose incremental area under the curve (IAUC)(0-20), followed by the low GI preload, and water (P<0.001). In both groups, insulin IAUC(0-20) was higher following high and low GI preloads compared with water (NS). In people without diabetes, the GLP-1 response was higher when high and low GI preloads were consumed compared with water (P=0.041), with no significant difference between nutritive preloads. GLP-1 response did not differ between preloads in people with diabetes. Despite initial differences, total IAUCs(0-200) for biochemical variables did not differ by preload.

CONCLUSION

We confirm that nutritive liquids stimulate GLP-1 to a greater extent than water in subjects without diabetes; however, this does not influence subsequent meal-induced response. The GI of preloads does not influence the degree of GLP-1 stimulation.

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.

BRIEF REPORT: nutrition and weight loss information in a popular diet book: is it fact, fiction, or something in between?

BACKGROUND/OBJECTIVE

Diet books dominate the New York Times Advice Best Seller list and consumers cite such books as an important source of nutrition information. However, the scientific support for nutrition claims presented as fact (nutrition facts) in diet books is not known.

DESIGN/MEASUREMENTS

We assessed the quality of nutrition facts in the best-selling South Beach Diet using support in peer-reviewed literature as a measure of quality. We performed structured literature searches on nutrition facts located in the books' text, and then assigned each fact to 1 of 4 categories (1) fact supported, (2) fact not supported, (3) fact both supported and not supported, and (4) no related papers. A panel of expert reviewers adjudicated the findings.

RESULTS

Forty-two nutrition facts were included. Fourteen (33%) facts were supported, 7 (17%) were not supported, 18 (43%) were both supported and not supported, and 3 (7%) had no related papers, including the fact that the diet had been "scientifically studied and proven effective."

CONCLUSIONS

Consumers obtain nutrition information from diet books. We found that over 67% of nutrition facts in a best-seller diet book may not be supported in the peer-reviewed literature. These findings have important implications for educating consumers about nutrition information sources.

Effects of GI and content of indigestible carbohydrates of cereal-based evening meals on glucose tolerance at a subsequent standardised breakfast

OBJECTIVE

To evaluate the impact of four low-glycaemic index (GI) and one high-GI cereal-based evening meals on glucose tolerance at a subsequent standardised breakfast.

DESIGN

Wheat kernels, barley kernels, spaghetti, spaghetti with added wheat bran and white wheat bread (WWB) were consumed in the evening in a random order at five different occasions. At the subsequent breakfast, blood glucose, serum insulin, plasma short chain fatty acid, plasma free fatty acid (FFA) and breath hydrogen were measured.

SETTING

The study was performed at Applied Nutrition and Food Chemistry, Lund University, Sweden.

SUBJECTS

Fifteen healthy volunteers were recruited. One subject was later excluded owing to abnormal blood glucose values.

RESULTS

The blood glucose response (0-120 min) to the standardised breakfast was significantly lower after consuming barley kernels in the evening compared with evening meals with WWB (P=0.019) or spaghetti+wheat bran (P=0.046). There were no significant differences in insulin concentrations at breakfast. Breath hydrogen excretion at breakfast was significantly higher after an evening meal with barley kernels compared with WWB, wheat kernels or spaghetti (P=0.026, 0.026 and 0.015, respectively), and the concentration of plasma propionate at breakfast was significantly higher following an evening meal with barley kernels compared with an evening meal with WWB (P=0.041). In parallel, FFA concentrations were significantly lower after barley kernels compared with WWB (P=0.042) or spaghetti evening meals (P=0.019).

CONCLUSIONS

The improved glucose tolerance at breakfast, following an evening meal with barley kernels appeared to emanate from suppression of FFA levels, mediated by colonic fermentation of the specific indigestible carbohydrates present in this product, or, to the combination of the low-GI features and colonic fermentation.

Potato and french fry consumption and risk of type 2 diabetes in women

BACKGROUND

Potatoes, a high glycemic form of carbohydrate, are hypothesized to increase insulin resistance and risk of type 2 diabetes.

OBJECTIVE

The objective was to examine prospectively the relation between potato consumption and the risk of type 2 diabetes.

DESIGN

We conducted a prospective study of 84,555 women in the Nurses' Health Study. At baseline, the women were aged 34-59 y, had no history of chronic disease, and completed a validated food-frequency questionnaire. The participants were followed for 20 y with repeated assessment of diet.

RESULTS

We documented 4496 new cases of type 2 diabetes. Potato and french fry consumption were both positively associated with risk of type 2 diabetes after adjustment for age and dietary and nondietary factors. The multivariate relative risk (RR) in a comparison between the highest and the lowest quintile of potato intake was 1.14 (95% CI: 1.02, 1.26; P for trend = 0.009). The multivariate RR in a comparison between the highest and the lowest quintile of french fry intake was 1.21 (95% CI: 1.09, 1.33; P for trend < 0.0001). The RR of type 2 diabetes was 1.18 (95% CI: 1.03, 1.35) for 1 daily serving of potatoes and 1.16 (95% CI: 1.05, 1.29) for 2 weekly servings of french fries. The RR of type 2 diabetes for substituting 1 serving potatoes/d for 1 serving whole grains/d was 1.30 (95% CI: 1.08, 1.57). The association between potato consumption and risk of type 2 diabetes was more pronounced in obese women.

CONCLUSIONS

Our findings suggest a modest positive association between the consumption of potatoes and the risk of type 2 diabetes in women. This association was more pronounced when potatoes were substituted for whole grains.

Hyperglycemia, lipoprotein glycation, and vascular disease

Hyperlipidemia and its treatment are currently recognized as important modulators of cardio-vascular mortality in the presence of disordered glucose control. On the other hand, the effects of hyperglycemia and its treatment on hyperlipidemia are not widely appreciated. Hyperglycemia is commonly associated with an increase in intestinal lipoproteins and a reduction in high-density lipoprotein (HDL). This could be a consequence of hyperglycemia-induced glycation of lipoproteins, which reduces the uptake and catabolism of the lipoproteins via the classical low-density lipoprotein (LDL) receptor. A high dietary carbohydrate load increases the glycation of intestinal lipoproteins, prolongs their circulation, and increases their plasma concentration. Hyperglycemia also leads to inhibition of lipoprotein lipase, further aggravating hyperlipidemia. Circulating advanced glycation end-products (AGEs) also bind lipoproteins and delay their clearance, a mechanism that has particularly been implicated in the dyslipidemia of diabetic nephropathy. As uptake via scavenger receptors is not inhibited, glycation increases the proportion of lipoproteins that are taken up via inflammatory cells and decreases the proportion taken up by hepatocytes via classical LDL receptors. This promotes the formation of atheromatous plaques and stimulates inflammation. Hyperglycemia increases the formation of oxidized LDL and glycated LDL, which are important modulators of atherosclerosis and cardiovascular death. The risk of cardiovascular death is increased by even short-term derangement of blood sugar control, owing perhaps to the glycation of lipoproteins and other critical proteins. Glycated LDL could prove very useful in measuring the effect of hyperglycemia on cardiovascular disease, its risk factors, and its complications. Comparing different glucose-lowering and lipid-lowering drugs in respect to their influence on glycated LDL could increase knowledge of the mechanism by which they alter cardiovascular risk.

Veganism and its relationship with insulin resistance and intramyocellular lipid

OBJECTIVE

To test the hypothesis that dietary factors in the vegan diet lead to improved insulin sensitivity and lower intramyocellular lipid (IMCL) storage.

DESIGN

Case-control study.

SETTING

Imperial College School of Medicine, Hammersmith Hospital Campus, London, UK.

SUBJECTS

A total of 24 vegans and 25 omnivores participated in this study; three vegan subjects could not be matched therefore the matched results are shown for 21 vegans and 25 omnivores. The subjects were matched for gender, age and body mass index (BMI).

INTERVENTIONS

Full anthropometry, 7-day dietary assessment and physical activity levels were obtained. Insulin sensitivity (%S) and beta-cell function (%B) were determined using the homeostatic model assessment (HOMA). IMCL levels were determined using in vivo proton magnetic resonance spectroscopy; total body fat content was assessed by bioelectrical impedance.

RESULTS

There was no difference between the groups in sex, age, BMI, waist measurement, percentage body fat, activity levels and energy intake. Vegans had a significantly lower systolic blood pressure (-11.0 mmHg, CI -20.6 to -1.3, P=0.027) and higher dietary intake of carbohydrate (10.7%, CI 6.8-14.5, P<0.001), nonstarch polysaccharides (20.7 g, CI 15.8-25.6, P<0.001) and polyunsaturated fat (2.8%, CI 1.0-4.6, P=0.003), with a significantly lower glycaemic index (-3.7, CI -6.7 to -0.7, P=0.01). Also, vegans had lower fasting plasma triacylglycerol (-0.7 mmol/l, CI -0.9 to -0.4, P<0.001) and glucose (-0.4 mmol/l, CI -0.7 to -0.09, P=0.05) concentrations. There was no significant difference in HOMA %S but there was with HOMA %B (32.1%, CI 10.3-53.9, P=0.005), while IMCL levels were significantly lower in the soleus muscle (-9.7, CI -16.2 to -3.3, P=0.01).

CONCLUSION

Vegans have a food intake and a biochemical profile that will be expected to be cardioprotective, with lower IMCL accumulation and beta-cell protective.