The acute impact of ingestion of sourdough and whole-grain breads on blood glucose, insulin, and incretins in overweight and obese men

Effects of whole grain intake on glucagon-like peptide 1 and glucose-dependent insulinotropic peptide: a systematic review and meta-analysis

CONTEXT

Whole grain intake may control help glycemia and reduce food intake by affecting the secretion of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP).

OBJECTIVE

This systematic review and meta-analysis aimed to assess the postprandial and long-term effects of whole grains on GLP-1 and GIP levels.

DATA SOURCES

PubMed, Web of Science, and Scopus online databases were searched systematically to identify relevant randomized clinical trials (RCTs) published up to April 2021.

STUDY SELECTION

RCTs that evaluated the effects of whole grains, compared with refined grains, on the postprandial area under the curve (AUC) value, the postprandial serum concentration of incretins from 0 to 180 minutes, or the fasting level of incretins after at least 14 days of intervention were included.

RESULTS

Nineteen studies were included in the meta-analysis. The results showed that acute intake of whole grains could not significantly change the AUC value of GLP-1 or GIP. However, the AUC value of GIP was reduced more significantly in (1) unhealthy participants (standard mean difference [SMD] -1.08; 95%CI, -2.07 to -0.10; I2 = 75.9%) compared with healthy participants, and (2) those with a baseline fasting blood glucose of ≥99 mg/dL (SMD -0.71; 95%CI, -1.30 to -0.11; I2 = 74.4%) compared with those with a baseline value of < 99 mg/dL. On the other hand, the results of time-response evaluation during 0 to 180 minutes after the intake of test meals showed that serum concentrations of GIP decreased significantly from 0 to 30 minutes (coefficient = -44.72; P = 0.005), but increased from 60 to 180 minutes (coefficient = 27.03; P = 0.005). However, long-term studies found no significant effects of whole grains on fasting concentrations of GLP-1 or GIP.

CONCLUSION

Whole grain intake did not affect postprandial levels of GLP-1 but enhanced postprandial levels of GIP from 60 to 180 minutes. Further high-quality trials are required to assess the long-term effects of whole grain intake on serum levels of incretins.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021256695.

Nutritional benefits of sourdoughs: A systematic review

Food fermentation using sourdough-i.e., consortia of lactic bacteria and yeasts-is increasingly considered among the public as a natural transformation yielding nutritional benefits; however, it is unclear whether its alleged properties are validated by science. The aim of this study was to systematically review the clinical evidence related to the effect of sourdough bread on health. Bibliographic searches were performed in 2 different databases (The Lens and PubMed) up to February 2022. Eligible studies were randomized controlled trials involving adults, healthy or not, given any type of sourdough bread compared with those given any type of yeast bread. A total of 573 articles were retrieved and investigated, of which 25 clinical trials met the inclusion criteria. The 25 clinical trials included a total of 542 individuals. The main outcomes investigated in the retrieved studies were glucose response (N = 15), appetite (N = 3), gastrointestinal markers (N = 5), and cardiovascular markers (N = 2). Overall, it is currently difficult to establish a clear consensus with regards to the beneficial effects of sourdough per se on health when compared with other types of bread because a variety of factors, such as the microbial composition of sourdough, fermentation parameters, cereals, and flour types potentially influence the nutritional properties of bread. Nonetheless, in studies using specific strains and fermentation conditions, significant improvements were observed in parameters related to glycemic response, satiety, or gastrointestinal comfort after bread ingestion. The reviewed data suggest that sourdough has great potential to produce a variety of functional foods; however, its complex and dynamic ecosystem requires further standardization to conclude its clinical health benefits.

Research of the influence of xanthan gum on rheological properties of dough and quality of bread made from sprouted wheat grain

The effect of microbial polysaccharide xanthan in the amount of 0.1-0.4% on the rheological characteristics of the dough from sprouted wheat grain and quality indicators of bread was studied. It was found that when xanthan gum is added, the dough's spreading and adhesion strength decreases, and the dough's resilience-elastic and plastic-viscous characteristics improve. Bread made from sprouted wheat grains with the addition of experimental dosages of xanthan has better structural-mechanical and physicochemical properties, as evidenced by higher indicators of crumb compressibility, specific volume, and moisture compared to the control sample. To obtain bread with the best quality indicators, it is recommended to use 0.3% xanthan.

Glycemic Index (GI) Values for Major Sources of Dietary Carbohydrates in Iran

BACKGROUND

The glycemic index (GI) values of staple foods are not available in a standardized method in Iran.

OBJECTIVES

The aim of this study was to measure the GI values of the major carbohydrate sources in a typical Iranian diet.

METHODS

Using the international standard method, the GI values were determined for four wheat flatbreads, barley and rye bread, white and brown rice, as well as white and brown rice mixed with lentils. Twelve healthy adults were given 50 g anhydrous glucose three times (as the reference carbohydrate) and the test foods once each throughout the study. Using finger-prick blood samples, capillary blood glucose was measured using a reliable glucometer. The GI was calculated using the trapezoidal method.

RESULTS

The GI values of the following types of bread were: Barley 66, Lavash 72, Taftoon 79, Sangak 82, rye 84, and Barbari 99. The GI values for brown and white rice were 65 and 71, respectively. The mixture of brown rice with lentils had a GI value of 55, and the mixture of white rice with lentils had a GI of 79.

CONCLUSIONS

The most common types of bread and white rice consumed in Iran have high GI values. There is potential to reduce the overall GI values in the Iranian diet by encouraging the consumption of barley bread and brown rice.

Incretin Hormones: The Link between Glycemic Index and Cardiometabolic Diseases

This review aimed to describe the potential mechanisms by which incretin hormones could mediate the relationship between glycemic index and cardiometabolic diseases. A body of evidence from many studies suggests that low glycemic index (GI) diets reduces the risk for type 2 diabetes and coronary heart disease. In fact, despite the extensive literature on this topic, the mechanisms underlying unfavorable effects of high GI foods on health remain not well defined. The postprandial and hormonal milieu could play a key role in the relationship between GI and cardiovascular risk. Incretin hormones, glucagon-like peptide1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are important regulators of postprandial homeostasis by amplifying insulin secretory responses. Response of GIP and GLP-1 to GI have been studied more in depth, also by several studies on isomaltulose, which have been taken as an ideal model to investigate the kinetics of incretin secretion in response to foods’ GI. In addition, extrapancreatic effects of these incretin hormones were also recently observed. Emerging from this have been exciting effects on several targets, such as body weight regulation, lipid metabolism, white adipose tissue, cardiovascular system, kidney, and liver, which may importantly affect the health status.

Anti-Diabetic Effects and Mechanisms of Dietary Polysaccharides

Diabetes mellitus is a multifactorial, heterogeneous metabolic disorder, causing various health complications and economic issues, which apparently impacts the human's life. Currently, commercial diabetic drugs are clinically managed for diabetic treatment that has definite side effects. Dietary polysaccharides mainly derive from natural sources, including medicinal plants, grains, fruits, vegetables, edible mushroom, and medicinal foods, and possess anti-diabetic potential. Hence, this review summarizes the effects of dietary polysaccharides on diabetes and underlying molecular mechanisms related to inflammatory factors, oxidative stress, and diabetes in various animal models. The analysis of literature and appropriate data on anti-diabetic polysaccharide from electronic databases was conducted. In vivo and in vitro trials have revealed that treatment of these polysaccharides has hypoglycemic, hypolipidemic, antioxidant, and anti-inflammatory effects, which enhance pancreatic β-cell mass and alleviates β-cell dysfunction. It enhances insulin signaling pathways through insulin receptors and activates the PI3K/Akt pathway, and eventually modulates ERK/JNK/MAPK pathway. In conclusion, dietary polysaccharides can effectively ameliorate hyperglycemia, hyperlipidemia, low-grade inflammation, and oxidative stress in type 2 diabetes mellitus (T2DM), and, thus, consumption of polysaccharides can be a valuable choice for diabetic control.

Relationship between diet/exercise and pharmacotherapy to enhance the GLP-1 levels in type 2 diabetes

The rapid rise in the prevalence of type 2 diabetes mellitus (T2DM) poses a huge healthcare burden across the world. Although there are several antihyperglycaemic agents (AHAs) available including addition of new drug classes to the treatment algorithm, more than 50% of patients with T2DM do not achieve glycaemic targets, suggesting an urgent need for treatment strategies focusing on prevention and progression of T2DM and its long-term complications. Lifestyle changes including implementation of healthy diet and physical activity are cornerstones for the management of T2DM. The positive effects of diet and exercise on incretin hormones such as glucagon-like peptide-1 (GLP-1) have been reported. We hypothesize an IDEP concept (Interaction between Diet/Exercise and Pharmacotherapy) aimed at modifying the diet and lifestyle, along with pharmacotherapy to enhance the GLP-1 levels, would result in good glycaemic control in patients with T2DM. Consuming protein-rich food, avoiding saturated fatty acids and making small changes in eating habits such as eating slowly with longer mastication time can have a positive impact on the GLP-1 secretion and insulin levels. Further the type of physical activity (aerobic/resistance training), intensity of exercise, duration, time and frequency of exercise have shown to improve GLP-1 levels. Apart from AHAs, a few antihypertensive drugs and lipid-lowering drugs have also shown to increase endogenous GLP-1 levels, however, due to quick degradation of GLP-1 by dipeptidyl peptidase-4 (DPP-4) enzyme, treatment with DPP-4 inhibitors would protect GLP-1 from degradation and prolong its activity. Thus, IDEP concept can be a promising treatment strategy, which positively influences the GLP-1 levels and provide additive benefits in terms of improving metabolic parameters in patients with T2DM and slowing the progression of T2DM and its associated complications.

Impact of Cereal Seed Sprouting on Its Nutritional and Technological Properties: A Critical Review

Sprouting induces activation and de novo synthesis of hydrolytic enzymes that make nutrients available for plant growth and development. Consumption of sprouted grains is suggested to be beneficial for human health. Positive consumer perceptions about sprouted cereals have resulted in new food and beverage product launches. However, because there is no generally accepted definition of "sprouting," it is unclear when grains are to be called sprouted. Moreover, guidelines about how much sprouted grain material food products should contain to exert health benefits are currently lacking. Accordingly, there is no regulatory base to develop appropriate food labeling for "sprouted foods." This review describes the nutritional and technological properties of sprouted grains in relation to processing conditions and provides guidelines to optimize sprouting practices in order to maximize nutritive value. Relatively long sprouting times (3 to 5 days) and/or high processing temperatures (25 to 35 °C) are needed to maximize the de novo synthesis and/or release of plant bioactive compounds. Nutrient compositional changes resulting from sprouting are often associated with health benefits. However, supportive data from clinical studies are very scarce, and at present it is impossible to draw any conclusion on health benefits of sprouted cereals. Finally, grains sprouted under the above-mentioned conditions are generally unfit for use in traditional food processing and it is challenging to use sprouted grains as ingredients without compromising their nutrient content. The present review provides a basis for better defining what "sprouting" is, and to help further research and development efforts in this field as well as future food regulations development.

Whole Grain Intake and Glycaemic Control in Healthy Subjects: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Backgrounds: There is growing evidence from both observational and intervention studies that Whole Grain (WG) cereals exert beneficial effects on human health, especially on the metabolic profile. The aim of this study was to perform a meta-analysis of randomised controlled trials (RCT) to assess the acute and medium/long-term effect of WG foods on glycaemic control and insulin sensitivity in healthy individuals. Methods: A search for all the published RCT on the effect of WG food intake on glycaemic and insulin response was performed up to December 2016. Effect size consisted of mean difference (MD) and 95% CI between the outcomes of intervention and the control groups using the generic inverse-variance random effects model. Results: The meta-analysis of the 14 studies testing the acute effects of WG foods showed significant reductions of the post-prandial values of the glucose iAUC (0–120 min) by −29.71 mmol min/L (95% CI: −43.57, −15.85 mmol min/L), the insulin iAUC (0–120 min) by −2.01 nmol min/L (95% CI: −2.88, −1.14 nmol min/L), and the maximal glucose and insulin response. In 16 medium- and long-term RCTs, effects of WG foods on fasting glucose and insulin and homeostatic model assessment-insulin resistance values were not significant. Conclusions: The consumption of WG foods is able to improve acutely the postprandial glucose and insulin homeostasis compared to similar refined foods in healthy subjects. Further research is needed to better understand the long-term effects and the biological mechanisms.

Bread making technology influences postprandial glucose response: a review of the clinical evidence

Lowering postprandial glucose and insulin responses may have significant beneficial implications for prevention and treatment of metabolic disorders. Bread is a staple food consumed worldwide in a daily basis, and the use of different baking technologies may modify the glucose and insulin response. The aim of this review was to critically record the human studies examining the application of different bread making processes on postprandial glucose and insulin response to bread. Literature is rich of results which show that the use of sourdough fermentation instead of leavening with Saccharomyces cerevisiae is able to modulate glucose response to bread, whereas evidence regarding its efficacy on lowering postprandial insulin response is less clear. The presence of organic acids is possibly involved, but the exact mechanism of action is still to be confirmed. The reviewed data also revealed that the alteration of other processing conditions (method of cooking, proofing period, partial baking freezing technology) can effectively decrease postprandial glucose response to bread, by influencing physical structure and retrogradation of starch. The development of healthier bread products that benefit postprandial metabolic responses is crucial and suggested baking conditions can be used by the bread industry for the promotion of public health.

ОПТИМІЗАЦІЯ СКЛАДУ КОМПОЗИЦІЇ ФЕРМЕНТНИХ ПРЕПАРАТІВ ДЛЯ ПІДВИЩЕННЯ ЯКОСТІ ЗЕРНОВОГО ХЛІБА

У статті обґрунтовано доцільність застосування ферментних препаратів целюлази, ксиланази та глюкозооксидази для підвищення якості полб’яного та пшеничного зернового хліба. Із використанням методів експериментально-статистичного планування та програми MathCAD оптимізовано кількісний склад досліджуваних ферментних препаратів і отримано композиції «Полба» і «Пшениця», додавання яких на стадії замішування тіста дозволяє підвищити питомий об’єм і пористість зернового хліба, а також покращити його органолептичні властивості.

Glycemic responses, appetite ratings and gastrointestinal hormone responses of most common breads consumed in Spain. A randomized control trial in healthy humans

The present study was carried out to determine the glycemic index (GI), glycemic load (GL), insulinemic index (InI), appetite ratings and postprandial plasma concentrations of gastrointestinal hormones related to the control of food intake after the ingestion of the five most common breads consumed in Spain with different compositions and manufacturing processes. Twenty-two healthy adults participated in a randomized crossover study. The breads tested were Ordinary, Precooked-Frozen, Candeal-flour, Alfacar whites and Wholemeal. All breads portions were calculated to supply 50 g of available carbohydrates. In addition, 50 g of glucose was used as a reference. A linear mixed-effects model was used to compare data calculated for all breads with glucose load. The GI value varied from 61 for the Wholemeal, to Alfacar 68, Ordinary 76, and 78 and 86 for the Precooked-Frozen and Candeal-flour breads, respectively. Wholemeal and Alfacar had lower GI than glucose. All tested breads had a lower GL (ranged 9 to 18) compared with glucose. Wholemeal GL was similar to Alfacar, but lower than the other white breads. InI were significantly lower for all breads (ranged 68 to 73) compared with glucose, and similar among them. The intake of the Wholemeal bread led to a higher release of gastric inhibitory polypeptide compared with the Ordinary and Precooked breads and to a higher release of pancreatic polypeptide compared with the Precooked-Frozen bread. All breads affected appetite ratings similarly. In conclusion, based on GL, the Wholemeal bread would be expected to exert a favorable glycemic response.

Cheese 'refinement' with whey B-vitamin removal during precipitation potentially induces temporal 'functional' dietary shortage: homocysteine as a biomarker

Cottage cheese 'refinement' with massive B-vitamin losses (≈70-84%) through whey removal during precipitation may potentially induce an acute imbalance between protein/methionine load and temporal inadequacy/shortage of nutrients critical for their metabolism, i.e. B6 and B12. The temporal effect of cottage cheese consumption was evaluated using increased plasma homocysteine as a B-vitamin shortage marker. In a double-blind study, healthy, normal-weight (BMI = 22-27), premenopausal women aged 25-45 years were first given a methionine load (100 mg kg(-1), n = 15), then cottage cheese alone (500 g, ≈50 g protein, ≈1200 mg methionine, n = 49) at breakfast, and then with added B6 (2 mg, n = 8) and/or B6 + folate (1 mg + 200 mcg, n = 7). Plasma homocysteine was measured preprandially (t0) and then postprandially 5 h (t5) and ≥6-24 h. Cheese-induced homocysteine increased 28.7% (p ≤ 0.001), ≈60% of the free methionine response, remaining higher through ≥6-8 h. Co-supplementation with B6 reduced the Hcy increase by 45.0% (to 14.9%, p = 0.025), and that with B6 + folate reduced the Hcy increase by 72.3% (to 7.5%, p = 0.556, NS). Homocysteine increased more in participants with lower baselines (<5 μM vs. ≥5 μM, p ≤ 0.001) following cheese, ≈3-fold (54.8% vs. 18.5%) or methionine, 47.3% (266.7% vs. 181.1%). Cheese B-vitamin depletion - i.e. to B6 ≈ 2.0-4.0 μg g(-1) protein, far below women's metabolic requirement (15-20 μg g(-1)) - appeared to induce acute relative shortage compared to methionine/protein loads, exemplified by greater homocysteine increases than with other animal proteins (previous data), more so with lower baseline homocysteine. Smaller increases following re-supplementation demonstrated potential for 'functional fortification'/co-supplementation. Unnoted cheese 'refinement', like white bread, potentially induces episodic vitamin shortage effects, warranting consideration for acute/cumulative implications, alternative processing/supplementation technologies, and food combinations, especially for at-risk populations (i.e. with genetic, hormonal/gender, or aging-related predispositions), and for cardiovascular, bone, and brain health.

Germinated grains: a superior whole grain functional food?

Grains are global dietary staples that when consumed in whole grain form, offer considerable health benefits compared with milled grain foods, including reduced body weight gain and reduced cardiovascular and diabetes risks. Dietary patterns, functional foods, and other lifestyle factors play a fundamental role in the development and management of epidemic lifestyle diseases that share risks of developing adverse metabolic outcomes, including hyperglycaemia, hypertension, dyslipidaemia, oxidative stress, and inflammation. Whole grains provide energy, nutrients, fibres, and bioactive compounds that may synergistically contribute to their protective effects. Despite their benefits, the intake of grains appears to be lower than recommended in many countries. Of emerging interest is the application of germination processes, which may significantly enhance the nutritional and bioactive content of grains, as well as improve palatability. Enhancing grain foods in a natural way using germination techniques may therefore offer a practical, natural, dietary intervention to increase the health benefits and acceptability of whole grains, with potentially widespread effects across populations in attenuating adverse lifestyle disease outcomes. Continuing to build on the growing body of in-vitro studies requires substantiation with extended in-vivo trials so that we may further develop our understanding of the potential of germinated grains as a functional food.