Consumption of whole grains and risk of type 2 diabetes: A comprehensive systematic review and dose-response meta-analysis of prospective cohort studies

Long-term clinical efficacy of dietary fiber supplementation in middle-aged and elderly prediabetic patients

AIMS

Dietary fiber (DF) can be separated from food and convenient to take, and has an important role in diabetes prevention, but long-term intervention data are lacking. This study evaluated the long-term benefits of DF supplementation on body composition, glucose-lipid metabolism, and clinical regression in middle-aged and elderly patients with prediabetes.

METHODS

A randomized, controlled, open clinical study was conducted. Participants were randomized into a control group receiving health education and an intervention group consuming DF supplements daily before meals (15 g of mixed fiber per serving) for 6 consecutive months based on health education. Follow-up was 1 year with a 6-month cycle. Blood and anthropometric parameters were assessed at baseline and 6 months and 12 months of follow-up.

RESULTS

Fifty-four participants were included in the study, 27 in each group. After 6 months, waist circumference, waist-to-hip ratio, fasting plasma glucose (FPG), 2 hour plasma glucose (2h PG), and postprandial insulin levels were significantly lower in the intervention group compared to baseline. FPG, 2h PG, glycosylated hemoglobin, triglyceride/high-density lipoprotein cholesterol values and diabetes incidence were lower than in the control group. After 12 months, blood glucose and diabetes incidence remained lower in the intervention group.

CONCLUSIONS

DF supplementation can reduce the degree of central obesity, the levels of FPG and 2h PG, and the incidence of diabetes in middle-aged and older patients with prediabetes.

Oat polar lipids and sunflower lecithin similarly improve cardiometabolic risk markers and appetite controlling hormone responses after breakfast and a subsequent lunch. A randomized crossover study in healthy adults

Introduction

The alarming global increase in lifestyle-related disorders such as obesity and type 2 diabetes mellitus (T2DM) has increased during the last several decades. Poor dietary choices significantly contribute to this increase and prevention measures are urgently needed. Dietary intake of bioactive compounds found in foods are linked to a decrease likelihood of these disorders. For this purpose, a randomized crossover meal study was performed to compare the postprandial metabolic effects of lecithin and oat polar lipids in healthy subjects.

Materials and methods

Eighteen young healthy subjects ingested test meals enriched with lecithin, oat polar lipids (PLs) or rapeseed oil. There were four test meals (i) 15 g oat polar lipids: OPL, (ii) 18 g sunflower lecithin (of which 15 g were polar lipids): LPL, (iii) 18 g rapeseed oil: RSO, and (iv) reference white wheat bread: WWB. Lipid-enriched test meals contained equivalent amounts of total fat (18 g), and all breakfast meals contained 50 g available carbohydrates. The meals were served as breakfast followed by a standardised lunch (white wheat bread and meat balls) after 3.5 h. Test variables were measured at fasting and repeatedly during 5.5 h after ingestion of the breakfast.

Results

Our study demonstrated that both LPL and OPL had beneficial effects on postprandial glucose and insulin responses, and appetite regulating gut hormones, as compared to RSO and WWB. Significant increase in GLP-1, GIP, and PYY concentrations were seen after consuming breakfast meals with LPL and OPL, and ghrelin concentration was reduced compared to meals with RSO and WWB (p < 0.05). Furthermore, triglycerides (TG) concentration was significantly reduced after OPL compared to RSO (p < 0.05). Our data show that there were no significant variations in glycaemic and insulin responses, TG, and gut hormone concentrations between LPL and OPL during breakfast (0-210 min) or over the whole study period (0-330 min).

Conclusion

Our study revealed that the consumption of both lecithin and oat PLs included in breakfast meal may similarly enhance postprandial glucose tolerance, reduce TG, and enhance the secretion of incretins and appetite regulating hormones in healthy young adults.

Clinical trial registration

ClinicalTrials.gov, identifier NCT05139355.

Adherence to the dietary approaches to stop hypertension diet reduces the risk of diabetes mellitus: a systematic review and dose-response meta-analysis

BACKGROUND

Despite several epidemiological studies reporting a significant association between adherence to the Dietary Approaches to Stop Hypertension (DASH) diet and the risk of diabetes mellitus, the results remain controversial. In this systematic review and meta-analysis, we aimed to summarize the existing evidence from published observational studies and evaluate the dose-response relationship between adherence to the DASH diet and diabetes mellitus risk.

METHODS

We performed a systematic search for relevant articles published up to September 2023 using electronic databases of PubMed, Embase, Scopus, and China National Knowledge Infrastructure (CNKI). A random-effects model was applied to calculate the combined relative risks (RR) with 95% confidence intervals (CIs) for the highest compared to the lowest categories of DASH score in relation to diabetes mellitus risk. Heterogeneity among the included studies was assessed using the Cochran's Q test and I-squared (I2) statistic. Literature search, study selection, data extraction, and quality assessment were performed by two independent reviewers.

RESULTS

Fifteen studies involving 557,475 participants and 57,064 diabetes mellitus cases were eligible for our analyses. Pooled analyses from included studies showed that high adherence to the DASH diet was significantly associated with a reduced risk of diabetes mellitus (RR: 0.82; 95% CI: 0.76-0.90, P < 0.001). Moreover, the dose-response meta-analysis revealed a linear trend between adherence to the DASH diet and diabetes mellitus (RR:0.99; 95%CI: 0.97-1.02, Pdose-response = 0.546, Pnonlinearity = 0.701). Subgroup analyses further revealed a significant inverse association between adherence to the DASH diet and diabetes mellitus risk in case-control studies (RR: 0.65; 95%CI: 0.29-1.43, P < 0.001), with a marginal inverse association in cohort studies (RR:0.83; 95%CI: 0.76-0.91, P < 0.001). Additionally, we conducted analyses separately by comparison and found a significant inverse association between DASH diet and diabetes mellitus risk in T3 vs T1 comparison studies (RR = 0.74; 95%CI: 0.64-0.86, P = 0.012).

CONCLUSION

The findings of this study demonstrate a protective association between adherence to the DASH diet and risk of diabetes mellitus. However, further prospective cohort studies and randomized controlled trials are needed to validate these findings.

Grains in a Modern Time: A Comprehensive Review of Compositions and Understanding Their Role in Type 2 Diabetes and Cancer

Globally, type 2 diabetes (T2D) and Cancer are the major causes of morbidity and mortality worldwide and are considered to be two of the most significant public health concerns of the 21st century. Over the next two decades, the global burden is expected to increase by approximately 60%. Several observational studies as well as clinical trials have demonstrated the health benefits of consuming whole grains to lower the risk of several chronic non-communicable diseases including T2D and cancer. Cereals grains are the primary source of energy in the human diet. The most widely consumed pseudo cereals include (quinoa, amaranth, and buckwheat) and cereals (wheat, rice, and corn). From a nutritional perspective, both pseudo cereals and cereals are recognized for their complete protein, essential amino acids, dietary fibers, and phenolic acids. The bran layer of the seed contains the majority of these components. Greater intake of whole grains rather than refined grains has been consistently linked to a lower risk of T2D and cancer. Due to their superior nutritional compositions, whole grains make them a preferred choice over refined grains. The modulatory effects of whole grains on T2D and cancer are also likely to be influenced by several mechanisms; some of these effects may be direct while others involve altering the composition of gut microbiota, increasing the abundance of beneficial bacteria, and lowering harmful bacteria, increasing insulin sensitivity, lowering solubility of free bile acids, breaking protein down into peptides and amino acids, producing short-chain fatty acids (SCFAs), and other beneficial metabolites that promote the proliferation in the colon which modulate the antidiabetic and anticancer pathway. Thus, the present review had two aims. First, it summarized the recent knowledge about the nutritional composition and bioactive acids in pseudo cereals (quinoa, amaranth, and buckwheat) and cereals (wheat, rice, and corn); the second section summarized and discussed the progress in recent human studies, such as observational (cross-sectional studies, case-control studies, and cohort studies) and intervention studies to understand their role in T2D and cancer including the potential mechanism. Overall, according to the scientific data, whole grain consumption may reduce the incidence of T2D and cancer. Future studies should carry out randomized controlled trials to validate observational results and establish causality. In addition, the current manuscript encourages researchers to investigate the specific mechanisms by which whole grains exert their beneficial effects on health by examining the effects of different types of specific protein, dietary fibers, and phenolic acids that might help to prevent or treat T2D and cancer.

[Bioactive components of whole grain and their effect on health]

Introduction

Non-communicable diseases represent a global health burden with increasing prevalence. To prevent or improve this type of diseases, dietary strategies based on healthy foods have been suggested. Cereals are the most consumed foods in the world and preventive effects of whole grains on health have been described. The germ and bran of cereals are abundant in bioactive compounds, including phytochemicals, vitamins, minerals and fibers, and these compounds are effective in preventing and improving non-communicable diseases. This review analyzes the content and distribution of the primary components of whole grains (wheat, barley, oats, rice and black wheat) and their fractions, focusing on the mechanisms by which phenolic acids and dietary fiber contribute to reducing the risk of metabolic and cardiovascular diseases and cancer. There is clear evidence of the broad cellular and physiological effects of bioactive compounds in whole grains, supporting the health value of a diet rich in whole grains.

The protective role of carnosine against type 2 diabetes-induced cognitive impairment

The morbidity and mortality associated with type 2 diabetes mellitus (T2DM) have grown exponentially over the last 30 years. Together with its associated complications, the mortality rates have increased. One important complication in those living with T2DM is the acceleration of age-related cognitive decline. T2DM-induced cognitive impairment seriously affects memory, executive function, and quality of life. However, there is a lack of effective treatment for both diabetes and cognitive decline. Thus, finding novel treatments which are cheap, effective in both diabetes and cognitive impairment, are easily accessible, are needed to reduce impact on patients with diabetes and health-care systems. Carnosine, a histidine containing dipeptide, plays a protective role in cognitive diseases due to its antioxidant, anti-inflammation, and anti-glycation properties, all of which may slow the development of neurodegenerative diseases and ischemic injury. Furthermore, carnosine is also involved in regulating glucose and insulin in diabetes. Herein, we discuss the neuroprotective role of carnosine and its mechanisms in T2DM-induced cognitive impairment, which may provide a theoretical basis and evidence base to evaluate whether carnosine has therapeutic effects in alleviating cognitive dysfunction in T2DM patients.

Effects of whole grains on glycemic control: a systematic review and dose-response meta-analysis of prospective cohort studies and randomized controlled trials

PURPOSE

Whole grains have recently been promoted as beneficial to diabetes prevention. However, the evidence for the glycemic benefits of whole grains seems to conflict between the cohort studies and randomized control trials (RCTs). To fill the research gap, we conducted a meta-analysis to determine the effects of whole grains on diabetes prevention and to inform recommendations.

METHODS

We searched PubMed, Clarivate Web of Science, and Cochrane Library until March 2024. We used the risk ratio (RR) of type 2 diabetes to represent the clinical outcomes for cohort studies, while the biomarkers, including fasting blood glucose and insulin, HbA1C, and HOMA-IR, were utilized to show outcomes for RCTs. Dose-response relationships between whole grain intakes and outcomes were tested with random effects meta-regression models and restricted cubic splines models. This study is registered with PROSPERO, CRD42021281639.

RESULTS

Ten prospective cohort studies and 37 RCTs were included. Cohort studies suggested a 50 g/day whole grain intake reduced the risk of type 2 diabetes (RR = 0.761, 95% CI: 0.700 to 0.828, I2 = 72.39%, P < 0.001) and indicated a monotonic inverse relationship between whole grains and type 2 diabetes rate. In RCTs, whole grains significantly reduced fasting blood glucose (Mean difference (MD) = -0.103 mmol/L, 95% CI: -0.178 to -0.028; I2 = 72.99%, P < 0.01) and had modest effects on HbA1C (MD = -0.662 mmol/mol (-0.06%), 95% CI: -1.335 to 0.010; I2 = 64.55%, P = 0.05) and HOMA-IR (MD = -0.164, 95% CI: -0.342 to 0.013; I2 = 33.38%, P = 0.07). The intake of whole grains and FBG, HbA1C, and HOMA-IR were significantly dose-dependent. The restricted spline curves remained flat up to 150 g/day and decreased afterward. Subgroup analysis showed that interventions with multiple whole-grain types were more effective than those with a single type.

CONCLUSION

Our study findings suggest that a daily intake of more than 150 g of whole grain ingredients is recommended as a population approach for diabetes prevention.

Association of plant-based dietary patterns with the risk of type 2 diabetes mellitus using cross-sectional results from RaNCD cohort

The prevalence of type 2 diabetes mellitus (T2DM) is increasing in middle- and low-income countries, and this disease is a burden on public health systems. Notably, dietary components are crucial regulatory factors in T2DM. Plant-based dietary patterns and certain food groups, such as whole grains, legumes, nuts, vegetables, and fruits, are inversely correlated with diabetes incidence. We conducted the present study to determine the association between adherence to a plant-based diet and the risk of diabetes among adults. We conducted a cross-sectional, population-based RaNCD cohort study involving 3401 men and 3699 women. The plant-based diet index (PDI) was developed using a 118-item food frequency questionnaire (FFQ). Logistic regression models were used to evaluate the association between the PDI score and the risk of T2DM. A total of 7100 participants with a mean age of 45.96 ± 7.78 years were analysed. The mean PDI scores in the first, second, and third tertiles (T) were 47.13 ± 3.41, 54.44 ± 1.69, and 61.57 ± 3.24, respectively. A lower PDI was significantly correlated with a greater incidence of T2DM (T1 = 7.50%, T2 = 4.85%, T3 = 4.63%; P value < 0.001). Higher PDI scores were associated with significantly increased intakes of fibre, vegetables, fruits, olives, olive oil, legumes, soy products, tea/coffee, whole grains, nuts, vitamin E, vitamin C, and omega-6 fatty acids (P value < 0.001). After adjusting for confounding variables, the odds of having T2DM were significantly lower (by 30%) at T3 of the PDI than at T1 (OR = 0.70; 95% CI = 0.51, 0.96; P value < 0.001). Our data suggest that adhering to plant-based diets comprising whole grains, fruits, vegetables, nuts, legumes, vegetable oils, and tea/coffee can be recommended today to reduce the risk of T2DM.

The Relationship between Whole-Grain Intake and Measures of Cognitive Decline, Mood, and Anxiety-A Systematic Review

Greater intake of whole grains, compared to refined grains, is consistently associated with a reduced risk of cardiovascular disease and type 2 diabetes, both of which are associated with cognitive decline. To better understand the relationship between whole-grain intake, cognition, mood, and anxiety, a systematic review was conducted to synthesize available evidence linking whole grains to these outcomes. Four electronic databases were searched from inception to August 2021 for potentially relevant observational and interventional studies. Risk of bias (RoB) assessments were performed using the newly developed Nutrition Quality Evaluation Strengthening Tools, and the Grades of Recommendation, Assessment, Development, and Evaluation approach was used to determine the strength of evidence for each outcome. In total, 23 studies [4 randomized controlled trials (RCTs) and 19 observational studies] met the predefined eligibility criteria. Of these,12 studies included analysis of whole-grain intake and cognitive decline, 9 included mood outcomes, and 2 included both cognition and mood outcomes. The overall evidence for an association between whole-grain intake and cognition is inconclusive. With respect to mood outcomes, evidence from RCTs prospective cohort and case-control studies suggest that higher intake is linked to improved outcomes for mood and depression although the evidence is mixed for cross-sectional studies. Reporting of whole-grain intake fell short of suggested standards, and the strength of available evidence was low or very low for all outcomes. A high RoB toward studies reporting results was also noted, complicating both the interpretation of some studies and the combined evidence. Of note, few well-designed RCTs assessing the effect of whole-grain intake on measures of cognition, mood, and anxiety were identified, highlighting the need for more studies in this area. The available, although limited, evidence suggests that greater whole-grain intake is associated with better mood and anxiety-related scores and is inconclusive regarding cognitive outcomes. PROSPERO registration: CRD42021266355.

Risk assessment of dietary factors in global pattern of ischemic heart disease mortality and disability-adjusted life years over 30 years

Objectives

The aim of this study was to investigate differences in the burden of ischemic heart disease (IHD)-related mortality and disability-adjusted life years (DALYs) caused by dietary factors, as well as the influencing factors with age, period, and cohort effects, in regions with different social-demographic status from 1990 to 2019.

Methods

We extracted data on IHD mortality, DALYs, and age-standardized rates (ASRs) related to dietary risks from 1990 to 2019 as IHD burden measures. Hierarchical age-period-cohort analysis was used to analyze age- and time-related trends and the interaction between different dietary factors on the risk of IHD mortality and DALYs.

Results

Globally, there were 9.2 million IHD deaths and 182 million DALYs in 2019. Both the ASRs of death and DALYs declined from 1990 to 2019 (percentage change: -30.8% and -28.6%, respectively), particularly in high and high-middle socio-demographic index (SDI) areas. Low-whole-grain, low-legume, and high-sodium diets were the three main dietary factors that increased the risk of IHD burden. Advanced age [RR (95%CI): 1.33 (1.27, 1.39)] and being male [1.11 (1.06, 1.16)] were independent risk factors for IHD mortality worldwide and in all SDI regions. After controlling for age effects, IHD risk showed a negative period effect overall. Poor diets were positively associated with increased risk of death but were not yet statistically significant. Interactions between dietary factors and advanced age were observed in all regions after adjusting for related variables. In people aged 55 and above, low intake of whole grains was associated with an increased risk of IHD death [1.28 (1.20, 1.36)]. DALY risks showed a similar but more obvious trend.

Conclusion

IHD burden remains high, with significant regional variations. The high IHD burden could be attributed to advanced age, sex (male), and dietary risk factors. Dietary habits in different SDI regions may have varying effects on the global burden of IHD. In areas with lower SDI, it is recommended to pay more attention to dietary problems, particularly in the elderly, and to consider how to improve dietary patterns in order to reduce modifiable risk factors.

Whole grains-derived functional ingredients against hyperglycemia: targeting hepatic glucose metabolism

Type 2 diabetes mellitus (T2DM) is characterized by the dysregulation of glucose homeostasis, resulting in hyperglycemia. However, concerns have been raised about the safety and efficacy of current hypoglycemic drugs due to undesirable side effects. Increasing studies have shown that whole grains (WG) consumption is inversely associated with the risk of T2DM and its subsequent complications. Thus, dietary strategies involving functional components from the WG provide an intriguing approach to restoring and maintaining glucose homeostasis. This review provides a comprehensive understanding of the major functional components derived from WG and their positive effects on glucose homeostasis, demonstrates the underlying molecular mechanisms targeting hepatic glucose metabolism, and discusses the unclear aspects according to the latest viewpoints and current research. Improved glycemic response and insulin resistance were observed after consumption of WG-derived bioactive ingredients, which are involved in the integrated, multi-factorial, multi-targeted regulation of hepatic glucose metabolism. Promotion of glucose uptake, glycolysis, and glycogen synthesis pathways, while inhibition of gluconeogenesis, contributes to amelioration of abnormal hepatic glucose metabolism and insulin resistance by bioactive components. Hence, the development of WG-based functional food ingredients with potent hypoglycemic properties is necessary to manage insulin resistance and T2DM.

Integrated metabolite analysis and health-relevant in vitro functionality of white, red, and orange maize (Zea mays L.) from the Peruvian Andean race Cabanita at different maturity stages

The high maize (Zea mays L.) diversity in Peru has been recognized worldwide, but the investigation focused on its integral health-relevant and bioactive characterization is limited. Therefore, this research aimed at studying the variability of the primary and the secondary (free and dietary fiber-bound phenolic, and carotenoid compounds) metabolites of three maize types (white, red, and orange) from the Peruvian Andean race Cabanita at different maturity stages (milk-S1, dough-S2, and mature-S3) using targeted and untargeted methods. In addition, their antioxidant potential, and α-amylase and α-glucosidase inhibitory activities relevant for hyperglycemia management were investigated using in vitro models. Results revealed a high effect of the maize type and the maturity stage. All maize types had hydroxybenzoic and hydroxycinnamic acids in their free phenolic fractions, whereas major bound phenolic compounds were ferulic acid, ferulic acid derivatives, and p-coumaric acid. Flavonoids such as luteolin derivatives and anthocyanins were specific in the orange and red maize, respectively. The orange and red groups showed higher phenolic ranges (free + bound) (223.9-274.4 mg/100 g DW, 193.4- 229.8 mg/100 g DW for the orange and red maize, respectively) than the white maize (162.2-225.0 mg/100 g DW). Xanthophylls (lutein, zeaxanthin, neoxanthin, and a lutein isomer) were detected in all maize types. However, the orange maize showed the highest total carotenoid contents (3.19-5.87 μg/g DW). Most phenolic and carotenoid compounds decreased with kernel maturity in all cases. In relation to the primary metabolites, all maize types had similar fatty acid contents (linoleic acid > oleic acid > palmitic acid > α-linolenic acid > stearic acid) which increased with kernel development. Simple sugars, alcohols, amino acids, free fatty acids, organic acids, amines, and phytosterols declined along with grain maturity and were overall more abundant in white maize at S1. The in vitro functionality was similar among Cabanita maize types, but it decreased with the grain development, and showed a high correlation with the hydrophilic free phenolic fraction. Current results suggest that the nutraceutical characteristics of orange and white Cabanita maize are better at S1 and S2 stages while the red maize would be more beneficial at S3.

Differences in health behavior and nutrient intake status between diabetes-aware and unaware Korean adults based on the Korea national health and nutrition examination survey 2016-18 data: A cross-sectional study

Background

The aim of this study was to investigate the nutritional intakes and treatment regimens of Korean patients with type 2 diabetes who were aware of their condition.

Methods

Participants (n = 16582) aged ≥ 19 years from the 2016-18 National Health and Nutrition Survey were divided into diabetes-aware and unaware groups and the variables were compared.

Results

Among 1,906 (11.5%) diabetic adults, 1,433 (75.2%) were aware of their condition; 130 (9.1%) had nutrition education, and 1,340 (93.5%) were in the diabetes-aware treatment group. The diabetes-aware group had higher average age (P < 0.0001) and lower average BMI (P = 0.0015) than the unaware group. Intake of total fat (P = 0.0034), saturated fatty acids (P = 0.0021), riboflavin (P = 0.0035) and niacin (P = 0.0228) was significantly higher in the unaware group than in the diabetes-aware group, after adjusting energy intake for age and sex. Current smoking (P = 0.0046) and heavy drinking (P < 0.0001) rates were higher in the unaware group, whereas fiber intake (P = 0.0054) was lower in the unaware group. Higher levels of glycated hemoglobin were found in the group treated for diabetes (7.2%) than in the no-treatment (6.8%) group (P = 0.0048). Diabetes control was significantly better in the high income group.

Conclusions

There is a need to strengthen nutritional education to prevent diabetes and improve the health status of diabetic patients in Korea.