Combining protein and carbohydrate increases postprandial insulin levels but does not improve glucose response in patients with type 2 diabetes

The Effect of Adding Protein to a Carbohydrate Meal on Postprandial Glucose and Insulin Responses: A Systematic Review and Meta-Analysis of Acute Controlled Feeding Trials

BACKGROUND

Protein influences acute postprandial glucose and insulin responses, but the effects of dose, protein type, and health status are unknown.

OBJECTIVES

We aimed to determine the acute effect of adding protein to carbohydrate on postprandial responses and identify effect modifiers.

METHODS

We searched MEDLINE, EMBASE, and Cochrane databases through 30 July, 2023 for acute, crossover trials comparing acute postprandial responses elicited by carbohydrate-containing test meals with and without added protein in adults without diabetes or with type 2 (T2DM) or type 1 (T1DM) diabetes mellitus. Group data were pooled separately using generic inverse variance with random-effects models and expressed as the ratio of means with 95% confidence interval. Risk of bias and certainty of evidence (Grading of Recommendations Assessment, Development, and Evaluation) were assessed.

RESULTS

In 154 trial comparisons of animal, dairy, and plant proteins (without diabetes, n = 22, 67, 32, respectively; T2DM, n = 14, 16, 3, respectively), each gram protein per gram available carbohydrate (g/g) reduced the glucose area under the curve (AUC) less in adults with T2DM than in those without diabetes (-10% compared with -50%, P < 0.05) but increased the insulin AUC similarly (+76% compared with +56%). In subjects without diabetes, each g/g of dairy and plant protein reduced glucose AUC by 52% and 55%, respectively, and increased the insulin AUC by 64% and 45%, respectively (all P < 0.05). Animal proteins significantly reduced the glucose AUC by 31% and increased the insulin AUC by 37% (pooled effects) but without a significant dose-response. In adults with T2DM, animal protein reduced the glucose AUC by 13% and increased the insulin AUC by 105%, with no significant dose-response. Dairy protein reduced the glucose AUC by 18% (no dose-response), but each g/g increased the insulin AUC by 34% (P < 0.05). In adults with T1DM, protein increased the glucose AUC by 40% (P < 0.05, n = 5). Data source (reported AUC compared with calculated AUC) and study methodology quality significantly modified some outcomes and contributed to high between-study heterogeneity.

CONCLUSIONS

In people without diabetes, adding dairy or plant protein to a carbohydrate-containing meal elicits physiologically significant reductions in glucose AUC and increases insulin AUC. Animal protein may slightly reduce the glucose AUC and may increase the insulin AUC. In people with T2DM, protein may not have such large and consistent effects. Further research is needed to determine if the effects of protein differ by health status and protein source. This study was registered at PROSPERO as CRD42022322090.

Dietary insulin index, dietary insulin load and dietary patterns and the risk of metabolic syndrome in Hoveyzeh Cohort Study

Postprandial insulin secretion has been associated with metabolic disorders such as hyperlipidemia and type 2 diabetes. Therefore, we aimed to explore the relationship between dietary insulin indices and dietary pattern with the risk of Metabolic Syndrome (MetS). The participants of the present cross-sectional study were included among the individuals who participated in the Hoveyzeh Cohort Study (HCS). A total of 3905 Iranian adults, aged 35-70 years, are included in the current analysis. The Food Frequency Questionnaire (FFQ) is used to calculate the dietary Insulin Index (DII), Insulin Load (DIL), and dietary pattern. Dietary pattern was derived using Reduced-Rank Regression (RRR) based on intake of protein (g/day), fiber (g/day), fat (g/day), magnesium (mg/day), and dietary insulin index were considered as response variables. The Generalized Linear Model was used to obtain the odds ratio (OR) and 95% confidence interval (CI) for MetS based on gender, while considering quartiles of DIL, DII scores, and dietary pattern, adjusted for potential confounders. The mean ± SD of age and BMI of the participants in the top quartile of DIL were 45.72 ± 8.05 years and 28.25 ± 5.02 kg/m2, respectively. The mean ± SD of DII was 40.53 ± 4.06 and the mean ± SD of DIL was 117,986.1 ± 30,714.06. A significant positive association was observed between DIL and MetS in women after adjusting for confounding factors (OR: 1.51; 95% CI 1.16; 1.96). No significant association was seen between DIL, DII, and MetS among men. A derived dietary pattern characterized by high intakes of fruits, sugar, sweet deserts, Whole Grains, and dairy was associated with an increased risk of MetS in adjusted model2 among women (OR: 1.41; 95% CI 1.13; 1.75) and men in the same model (OR: 2.09; 95% CI 1.35; 3.21).However, the final model was significant just for men (OR: 2.08; 95% CI 1.35; 3.21) and not for women (OR: 1.24; 95% CI 0.96; 1.60). Our findings showed that adherence to a diet with a high insulin load can increase the risk of MetS in women. In addition, a derived dietary pattern by RRR indicated that a diet rich in fruits, sugar, sweet deserts, whole Grains, and dairy is related to increased risk of MetS in both men and women.

Association of Dietary Insulin Index and Dietary Insulin Load With Metabolic Health Status in Iranian Overweight and Obese Adolescents

Background

Limited data are available on the association of dietary insulin load (DIL) and dietary insulin index (DII) with health status in pediatrics. We aimed to investigate the relationship of DIL and DII with metabolic health status in Iranian overweight/obese adolescents.

Methods

In this cross-sectional study, using a multistage cluster random-sampling method, 203 overweight/obese adolescents (aged 12 to <18 years) were included. A validated 147-item food frequency questionnaire (FFQ) was used for a dietary intake assessment. Glycemic and lipid profile, blood pressure (BP), and anthropometric indices were measured. Participants were categorized as metabolically healthy obese (MHO) or metabolically unhealthy obese (MUO) using the two methods of the International Diabetes Federation (IDF) and a combination of IDF with Homeostasis Model Assessment Insulin Resistance (HOMA-IR).

Results

According to IDF and IDF/HOMA-IR strategies, 38.9% (n = 79) and 33.0% (n = 67) of participants belonged to MUO category. After adjustments for potential confounders, subjects in the highest tertile of DIL in comparison with those in the lowest tertile had the odds ratio (OR) values of 8.44 (95% CI: 2.24-31.78) and 5.86 (95% CI: 1.39-24.58) for MUO based on IDF and IDF/HOMA-IR definitions, respectively. Moreover, after considering potential confounders, adolescents in the highest tertile of DII, compared to the lowest tertile, were, respectively, 6.93 (OR: 6.93; 95% CI: 2.59-18.57) and 5.26 (OR: 5.26; 95% CI: 1.85-14.97) times more likely to be MUO, based on IDF and IDF/HOMA-IR definitions. A significant decreasing trend was observed for OR of MUO in tertiles of DIL and DII. The stratified analysis revealed that these associations were stronger in obese participants; in overweight subjects, the association was not independent of confounders.

Conclusion

This population-based study revealed that higher DIL and DII were strongly related to increased OR of MUO in Iranian adolescents, especially in obese participants. Further investigations, especially with a prospective design, are needed to affirm these findings.

Dietary protein intake and obesity-associated cardiometabolic function

PURPOSE OF REVIEW

High-protein intake is commonly recommended to help people manage body weight. However, high-protein intake could have adverse health consequences. Here we review the latest findings concerning the effect of high-protein intake on cardiometabolic health.

RECENT FINDINGS

Calorie-reduced, high-protein, low-carbohydrate diets lower plasma glucose in people with type 2 diabetes (T2D). However, when carbohydrate intake is not markedly reduced, high-protein intake often does not alter plasma glucose and increases insulin and glucagon concentrations, which are risk factors for T2D and ischemic heart disease. High-protein intake does not alter plasma triglyceride and cholesterol concentrations but promotes atherogenesis in animal models. The effect of high-protein intake on liver fat remains unclear. In population studies, high-protein intake is associated with increased risk for T2D, nonalcoholic fatty liver disease, and possibly cardiovascular diseases.

SUMMARY

The relationship between protein intake and cardiometabolic health is complex and influenced by concomitant changes in body weight and overall diet composition. Although a high-protein, low-carbohydrate, reduced-energy diet can have beneficial effects on body weight and plasma glucose, habitual high-protein intake, without marked carbohydrate and energy restriction, is associated with increased cardiometabolic disease risk, presumably mediated by the changes in the hormonal milieu after high-protein intake.

A word of caution against excessive protein intake

Dietary protein is crucial for human health because it provides essential amino acids for protein synthesis. In addition, dietary protein is more satiating than carbohydrate and fat. Accordingly, many people consider the protein content when purchasing food and beverages and report 'trying to eat more protein'. The global market for protein ingredients is projected to reach approximately US$90 billion by 2021, largely driven by the growing demand for protein-fortified food products. This Perspective serves as a caution against the trend of protein-enriched diets and provides an evidence-based counterpoint that underscores the potential adverse public health consequences of high protein intake.

Comparison of Pro-Regenerative Effects of Carbohydrates and Protein Administrated by Shake and Non-Macro-Nutrient Matched Food Items on the Skeletal Muscle after Acute Endurance Exercise

Physical performance and regeneration after exercise is enhanced by the ingestion of proteins and carbohydrates. These nutrients are generally consumed by athletes via whey protein and glucose-based shakes. In this study, effects of protein and carbohydrate on skeletal muscle regeneration, given either by shake or by a meal, were compared. 35 subjects performed a 10 km run. After exercise, they ingested nothing (control), a protein/glucose shake (shake) or a combination of white bread and sour milk cheese (food) in a randomized cross over design. Serum glucose (n = 35), serum insulin (n = 35), serum creatine kinase (n = 15) and myoglobin (n = 15), hematologic parameters, cortisol (n = 35), inflammation markers (n = 27) and leg strength (n = 15) as a functional marker were measured. Insulin secretion was significantly stimulated by shake and food. In contrast, only shake resulted in an increase of blood glucose. Food resulted in a decrease of pro, and stimulation of anti-inflammatory serum markers. The exercise induced skeletal muscle damage, indicated by serum creatine kinase and myoglobin, and exercise induced loss of leg strength was decreased by shake and food. Our data indicate that uptake of protein and carbohydrate by shake or food reduces exercise induced skeletal muscle damage and has pro-regenerative effects.

The Effect of Added Peanut Butter on the Glycemic Response to a High-Glycemic Index Meal: A Pilot Study

OBJECTIVE

The purpose of this pilot study was to determine whether supplementation of a high-glycemic index breakfast meal with peanut butter attenuates the glycemic response.

METHODS

Sixteen healthy adults, aged 24.1 ± 3.5 years, reported in the morning to a nutrition assessment laboratory for two days of data collection, having fasted 8 to 12 hours. On day 1 (control), fasting blood glucose (BG) was measured using glucometers, then participants consumed two slices of white bread and 250 mL apple juice (60 g carbohydrate) within 15 minutes. BG was measured again at 15, 30, 60, 90, and 120 minutes after the first bite of the meal. On day 2, the protocol was repeated, except 32 g (2 tbsp) of peanut butter was added to the meal (treatment).

RESULTS

The spike in BG was significantly lower on the treatment versus control day (35.8 ± 16.4 vs. 51.0 ± 20.8 mg/dL, respectively; p < 0.01), and BG was significantly lower on the treatment day at 15, 30, and 60 minutes post-meal consumption (p < 0.05).

CONCLUSIONS

This study indicates that supplementation with 32 g (2 tbsp) peanut butter attenuates the magnitude of BG spike and overall glycemic response to high-glycemic index meal and may be a practical, beneficial strategy to prevent undesirable elevations in BG.

Fish oil-derived n-3 polyunsaturated fatty acids for the prevention and treatment of sarcopenia

PURPOSE OF REVIEW

Muscle mass and function decline progressively starting in middle age, which can result in sarcopenia and affect people's mobility and independence later in life. Exercise training and increased protein intake are typically recommended to counteract the age-associated decline in muscle mass and function. However, few people comply with exercise recommendations and the effectiveness of high-protein intake to halt the decline in muscle mass and function has not been proven. This review aims to explore recent developments in the potential for fish-oil derived n-3 polyunsaturated fatty acids (n-3 PUFA) to improve muscle mass and function in older people.

RECENT FINDINGS

The results from several recent studies demonstrate that dietary supplementation with fish oil-derived n-3 PUFA stimulates muscle protein synthesis and improves muscle mass and function in sedentary older adults and augments the resistance exercise training-induced increase in muscle strength in older adults. The exact mechanisms by which fish oil-derived n-3 PUFAs exert their beneficial effects on muscle mass and function remain to be elucidated.

SUMMARY

Fish-oil supplementation has antisarcopenic effects and should be considered in the clinical care of older adults.

Alterations in 3-Hydroxyisobutyrate and FGF21 Metabolism Are Associated With Protein Ingestion-Induced Insulin Resistance

Systemic hyperaminoacidemia, induced by either intravenous amino acid infusion or protein ingestion, reduces insulin-stimulated glucose disposal. Studies of mice suggest that the valine metabolite 3-hydroxyisobutyrate (3-HIB), fibroblast growth factor 21 (FGF21), adiponectin, and nonesterified fatty acids (NEFAs) may be involved in amino acid-mediated insulin resistance. We therefore measured in 30 women the rate of glucose disposal, and plasma 3-HIB, FGF21, adiponectin, and NEFA concentrations, under basal conditions and during a hyperinsulinemic-euglycemic clamp procedure (HECP), with and without concomitant ingestion of protein (n = 15) or an amount of leucine that matched the amount of protein (n = 15). We found that during the HECP without protein or leucine ingestion, the grand mean ± SEM plasma 3-HIB concentration decreased (from 35 ± 2 to 14 ± 1 µmol/L) and the grand median [quartiles] FGF21 concentration increased (from 178 [116, 217] to 509 [340, 648] pg/mL). Ingestion of protein, but not leucine, decreased insulin-stimulated glucose disposal (P < 0.05) and prevented both the HECP-mediated decrease in 3-HIB and increase in FGF21 concentration in plasma. Neither protein nor leucine ingestion altered plasma adiponectin or NEFA concentrations. These findings suggest that 3-HIB and FGF21 might be involved in protein-mediated insulin resistance in humans.

High-Protein Intake during Weight Loss Therapy Eliminates the Weight-Loss-Induced Improvement in Insulin Action in Obese Postmenopausal Women

High-protein (HP) intake during weight loss (WL) therapy is often recommended because it reduces the loss of lean tissue mass. However, HP intake could have adverse effects on metabolic function, because protein ingestion reduces postprandial insulin sensitivity. In this study, we compared the effects of ∼10% WL with a hypocaloric diet containing 0.8 g protein/kg/day and a hypocaloric diet containing 1.2 g protein/kg/day on muscle insulin action in postmenopausal women with obesity. We found that HP intake reduced the WL-induced decline in lean tissue mass by ∼45%. However, HP intake also prevented the WL-induced improvements in muscle insulin signaling and insulin-stimulated glucose uptake, as well as the WL-induced adaptations in oxidative stress and cell structural biology pathways. Our data demonstrate that the protein content of a WL diet can have profound effects on metabolic function and underscore the importance of considering dietary macronutrient composition during WL therapy for people with obesity.

Comparison of the effects of slowly and rapidly absorbed carbohydrates on postprandial glucose metabolism in type 2 diabetes mellitus patients: a randomized trial

BACKGROUND

Isomaltulose attenuates postprandial glucose and insulin concentrations compared with sucrose in patients with type 2 diabetes mellitus (T2DM). However, the mechanism by which isomaltulose limits postprandial hyperglycemia has not been clarified.

OBJECTIVE

The objective was therefore to assess the effects of bolus administration of isomaltulose on glucose metabolism compared with sucrose in T2DM.

DESIGN

In a randomized, double-blind, crossover design, 11 participants with T2DM initially underwent a 3-h euglycemic-hyperinsulinemic (0.8 mU · kg(-1) · min(-1)) clamp that was subsequently combined with 1 g/kg body wt of an oral (13)C-enriched isomaltulose or sucrose load. Hormonal responses and glucose kinetics were analyzed during a 4-h postprandial period.

RESULTS

Compared with sucrose, absorption of isomaltulose was prolonged by ∼50 min (P = 0.004). Mean plasma concentrations of insulin, C-peptide, glucagon, and glucose-dependent insulinotropic peptide were ∼10-23% lower (P < 0.05). In contrast, glucagon-like peptide 1 (GLP-1) was ∼64% higher (P < 0.001) after isomaltulose ingestion, which results in an increased insulin-to-glucagon ratio (P < 0.001) compared with sucrose. The cumulative amount of systemic glucose appearance was ∼35% lower after isomaltulose than after sucrose (P = 0.003) because of the reduction in orally derived and endogenously produced glucose and a higher first-pass splanchnic glucose uptake (SGU). Insulin action was enhanced after isomaltulose compared with sucrose (P = 0.013).

CONCLUSIONS

Ingestion of slowly absorbed isomaltulose attenuates postprandial hyperglycemia by reducing oral glucose appearance, inhibiting endogenous glucose production (EGP), and increasing SGU compared with ingestion of rapidly absorbed sucrose in patients with T2DM. In addition, GLP-1 secretion contributes to a beneficial shift in the insulin-to-glucagon ratio, suppression of EGP, and enhancement of SGU after isomaltulose consumption. This trial was registered at clinicaltrials.gov as NCT01070238.

Pre-exercise nutrition: the role of macronutrients, modified starches and supplements on metabolism and endurance performance

Endurance athletes rarely compete in the fasted state, as this may compromise fuel stores. Thus, the timing and composition of the pre-exercise meal is a significant consideration for optimizing metabolism and subsequent endurance performance. Carbohydrate feedings prior to endurance exercise are common and have generally been shown to enhance performance, despite increasing insulin levels and reducing fat oxidation. These metabolic effects may be attenuated by consuming low glycemic index carbohydrates and/or modified starches before exercise. High fat meals seem to have beneficial metabolic effects (e.g., increasing fat oxidation and possibly sparing muscle glycogen). However, these effects do not necessarily translate into enhanced performance. Relatively little research has examined the effects of a pre-exercise high protein meal on subsequent performance, but there is some evidence to suggest enhanced pre-exercise glycogen synthesis and benefits to metabolism during exercise. Finally, various supplements (i.e., caffeine and beetroot juice) also warrant possible inclusion into pre-race nutrition for endurance athletes. Ultimately, further research is needed to optimize pre-exercise nutritional strategies for endurance performance.

Nutrition of the critically ill &#8212; a 21st-century perspective

Health care-induced diseases constitute a fast-increasing problem. Just one type of these health care-associated infections (HCAI) constitutes the fourth leading cause of death in Western countries. About 25 million individuals worldwide are estimated each year to undergo major surgery, of which approximately 3 million will never return home from the hospital. Furthermore, the quality of life is reported to be significantly impaired for the rest of the lives of those who, during their hospital stay, suffered life-threatening infections/sepsis. Severe infections are strongly associated with a high degree of systemic inflammation in the body, and intimately associated with significantly reduced and malfunctioning GI microbiota, a condition called dysbiosis. Deranged composition and function of the gastrointestinal microbiota, occurring from the mouth to the anus, has been found to cause impaired ability to maintain intact mucosal membrane functions and prevent leakage of toxins - bacterial endotoxins, as well as whole bacteria or debris of bacteria, the DNA of which are commonly found in most cells of the body, often in adipocytes of obese individuals or in arteriosclerotic plaques. Foods rich in proteotoxins such as gluten, casein and zein, and proteins, have been observed to have endotoxin-like effects that can contribute to dysbiosis. About 75% of the food in the Western diet is of limited or no benefit to the microbiota in the lower gut. Most of it, comprised specifically of refined carbohydrates, is already absorbed in the upper part of the GI tract, and what eventually reaches the large intestine is of limited value, as it contains only small amounts of the minerals, vitamins and other nutrients necessary for maintenance of the microbiota. The consequence is that the microbiota of modern humans is greatly reduced, both in terms of numbers and diversity when compared to the diets of our paleolithic forebears and the individuals living a rural lifestyle today. It is the artificial treatment provided in modern medical care - unfortunately often the only alternative provided - which constitute the main contributors to a poor outcome. These treatments include artificial ventilation, artificial nutrition, hygienic measures, use of skin-penetrating devices, tubes and catheters, frequent use of pharmaceuticals; they are all known to severely impair the microbiomes in various locations of the body, which, to a large extent, are ultimately responsible for a poor outcome. Attempts to reconstitute a normal microbiome by supply of probiotics have often failed as they are almost always undertaken as a complement to - and not as an alternative to - existing treatment schemes, especially those based on antibiotics, but also other pharmaceuticals.

Role of proteins in insulin secretion and glycemic control

Dietary proteins are essential for the life of all animals and humans at all stages of the life cycle. They serve many structural and biochemical functions and have significant effects on health and wellbeing. Dietary protein consumption has shown an upward trend in developed countries in the past two decades primarily due to greater supply and affordability. Consumption is also on the rise in developing countries as affluence is increasing. Research shows that proteins have a notable impact on glucose homeostasis mechanisms, predominantly through their effects on insulin, incretins, gluconeogenesis, and gastric emptying. Since higher protein consumption and impaired glucose tolerance can be commonly seen in the same population demographics, a thorough understanding of the former's role in glucose homeostasis is crucial both toward the prevention and management of the latter. This chapter reviews the current state of the art on proteins, amino acids, and their effects on blood glucose and insulin secretion.

Nutrition of the critically ill - emphasis on liver and pancreas

About 25 million individuals undergo high risk surgery each year. Of these about 3 million will never return home from hospital, and the quality of life for many of those who return is often significantly impaired. Furthermore, many of those who manage to leave hospital have undergone severe life-threatening complications, mostly infections/sepsis. The development is strongly associated with the level of systemic inflammation in the body, which again is entirely a result of malfunctioning GI microbiota, a condition called dysbiosis, with deranged composition and function of the gastrointestinal microbiota from the mouth to the anus and impaired ability to maintain intact mucosal membrane functions and prevent leakage of toxins-bacterial endotoxins and whole or debris of bacteria, but also foods containing proteotoxins gluten, casein and zein and heat-induced molecules such as advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs). Markedly lower total anaerobic bacterial counts, particularly of the beneficial Bifidobacterium and Lactobacillus and higher counts of total facultative anaerobes such as Staphylococcus and Pseudomonas are often observed when analyzing the colonic microbiota. In addition Gram-negative facultative anaerobes are commonly identified microbial organisms in mesenteric lymph nodes and at serosal "scrapings" at laparotomy in patients suffering what is called "Systemic inflammation response system" (SIRS). Clearly the outcome is influenced by preexisting conditions in those undergoing surgery, but not to the extent as one could expect. Several studies have for example been unable to find significant influence of pre-existing obesity. The outcome seems much more to be related to the life-style of the individual and her/his "maintenance" of the microbiota e.g., size and diversity of microbiota, normal microbiota, eubiosis, being highly preventive. About 75% of the food Westerners consume does not benefit microbiota in the lower gut. Most of it, refined carbohydrates, is already absorbed in the upper part of the GI tract, and of what reaches the large intestine is of limited value containing less minerals, less vitamins and other nutrients important for maintenance of the microbiota. The consequence is that the microbiota of modern man has a much reduced size and diversity in comparison to what our Palelithic forefathers had, and individuals living a rural life have today. It is the artificial treatment provided by modern care, unfortunately often the only alternative, which belongs to the main contributor to poor outcome, among them; artificial ventilation, artificial nutrition, hygienic measures, use of skin penetrating devices, tubes and catheters, frequent use of pharmaceuticals, all known to significantly impair the total microbiome of the body and dramatically contribute to poor outcome. Attempts to reconstitute a normal microbiome have often failed as they have always been undertaken as a complement to and not an alternative to existing treatment schemes, especially treatments with antibiotics. Modern nutrition formulas are clearly too artificial as they are based on mixture of a variety of chemicals, which alone or together induce inflammation. Alternative formulas, based on regular food ingredients, especially rich in raw fresh greens, vegetables and fruits and with them healthy bacteria are suggested to be developed and tried.