Meta-Analysis of the Association Between Whole and Refined Grain Consumption and Stroke Risk Based on Prospective Cohort Studies

Refined grain intake and cardiovascular disease: Meta-analyses of prospective cohort studies

Refined grains are included as part of an unhealthy, or Western, dietary pattern, which has been shown to be associated with increased risk of cardiovascular disease (CVD). To clarify the association between refined grain intake and CVD risk, Pubmed and Scopus databases were searched for relevant cohort studies from database inception to June 30, 2022. Only studies that examined refined grains as a distinct consumption category and not as part of a dietary pattern, were included. Meta-analyses were performed using Cochrane's RevMan 5.4.1 software, applying inverse variance risk ratios in random effects models for each outcome of interest. Heterogeneity was assessed with Cochrane's Q (chi2) and I2 statistics. Meta-analyses of hazard ratios (HR) and 95% confidence intervals (CI) obtained from 17 prospective cohort studies (>875,000 participants) indicated that refined grain intake was not associated with risk of CVD (HR = 1.08, 95% CI, 0.99-1.18, I2 = 70%; 9 cohorts), stroke (HR = 1.06, 95% CI 0.92-1.23, I2 = 70%; 9 cohorts), or heart failure (HR = 0.95, 95% CI 0.77-1.16, I2 = 10%; 5 cohorts). White rice intake was also not associated with risk of CVD (HR = 0.93, 95% CI 0.86-1.00, I2 = 25%; 7 cohorts) or stroke (HR = 1.03, 95% CI 0.93-1.14, I2 = 22%; 7 cohorts). No significant publication bias was evident (Egger's test P values all > 0.05). The lack of association between refined grain intake and CVD risk was observed in meta-analyses of studies that restricted analyses to only staple grain foods (e.g., bread, cereal, pasta, white rice), as well as for meta-analyses of studies that included both staple and indulgent grain foods (e.g., cakes, cookies, doughnuts, brownies, muffins, pastries). Probable confounding from unmeasured variables in studies included in the meta-analyses diminishes the overall quality of evidence. Although refined grains are included as a component of the Western dietary pattern, the results of the meta-analyses suggest that refined grains do not contribute to the higher CVD risk associated with this unhealthy dietary pattern. This information should be considered in formulation of future dietary recommendations.

The role of cereal soluble fiber in the beneficial modulation of glycometabolic gastrointestinal hormones

According to cohort studies, cereal fiber, and whole-grain products might decrease risk for type 2 diabetes (T2DM), inflammatory processes, cancer, and cardiovascular diseases. These associations, mainly affect insoluble, but not soluble cereal fiber. In intervention studies, soluble fiber elicit anti-hyperglycemic and anti-inflammatory short-term effects, partially explained by fermentation to short-chain fatty acids, which acutely counteract insulin resistance and inflammation. ß-glucans lower cholesterol levels and possibly reduce liver fat. Long-term benefits are not yet shown, maybe caused by T2DM heterogeneity, as insulin resistance and fatty liver disease - the glycometabolic points of action of soluble cereal fiber - are not present in every patient. Thus, only some patients might be susceptive to fiber. Also, incretin action in response to fiber could be a relevant factor for variable effects. Thus, this review aims to summarize the current knowledge from human studies on the impact of soluble cereal fiber on glycometabolic gastrointestinal hormones. Effects on GLP-1 appear to be highly contradictory, while these fibers might lower GIP and ghrelin, and increase PYY and CCK. Even though previous results of specific trials support a glycometabolic benefit of soluble fiber, larger acute, and long-term mechanistic studies are needed in order to corroborate the results.

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

This study aimed to quantitatively summarize earlier findings on the association between whole grain (WG) intake and type 2 diabetes (T2D) risk. We searched related keywords on PubMed/Medline, Scopus, and Google Scholar up to October 2021. Prospective observational studies investigating the association between WG intake and risk of T2D were included. The random-effects model calculates the summary relative risks by contrasting categories and linear and nonlinear dose-response associations. Eleven prospective cohort studies, including 463,282 participants and 37,249 type 2 diabetes incidents, were analyzed. The pooled relative risk (RR) for the highest versus the lowest WG intake category indicated a 21% decrease in T2D risk (95% confidence interval (CI): 0.73-0.85, I 2 = 77%). Each additional 50 grams WG consumption per day was associated with a 23% reduced risk of T2D. The nonlinear association of WG and T2D revealed that 60 grams WG intake per day would give the highest benefit to prevent T2D (Pnonlinearity < 0.001). The findings were not affected by any individual study. No evidence of publication bias was documented. In conclusion, a high intake of WG was associated with a lower risk of T2D. Randomized controlled trials are needed to confirm our results.

Role of diet in stroke incidence: an umbrella review of meta-analyses of prospective observational studies

BACKGROUND

Stroke is one of the major challenges for the global healthcare system, which makes it necessary to explore the relationship between various modifiable factors and stroke risk. Recently, numerous meta-analyses of prospective observational studies have reported that dietary factors played a key role in the occurrence of stroke. However, the conclusions of previous studies have remained controversial and unclear. Accordingly, we conducted an umbrella review synthesizing and recalculating available evidence to assess the certainty of the associations between dietary factors and stroke.

METHODS

Relevant meta-analyses examining the associations between dietary factors and stroke were searched in PubMed and Embase databases up to September 1, 2021. For each eligible meta-analysis, two independent reviewers appraised the methodologic quality using the AMSTAR 2 criteria and estimated the summary effect size, 95% confidence intervals, 95% prediction intervals, heterogeneity between studies, and small-study effects. Moreover, we further assessed the associations between dietary factors and ischemic stroke as well as hemorrhagic stroke. Lastly, a set of pre-specified criteria was applied to qualitatively evaluate the epidemiological credibility of each dietary factor.

RESULTS

Overall, our umbrella review included 122 qualified meta-analyses for qualitative synthesis, involving 71 dietary factors related to food groups, foods, macronutrients, and micronutrients. Using the AMSTAR 2 criteria, 5 studies were assessed as high quality, 4 studies as moderate quality, and 113 studies as low or critically low quality. We identified 34 dietary factors associated with stroke occurrence, 25 dietary factors related to ischemic stroke, and 11 factors related to hemorrhagic stroke. Among them, high/moderate certainty epidemiological evidence demonstrated an inverse association between intake of fruits (RR: 0.90) and vegetables (RR: 0.92) and stroke incidence, but a detrimental association between red meat (RR: 1.12), especially processed red meat consumption (RR:1.17), and stroke incidence. Besides, the evidence of high/moderate certainty suggested that the intake of processed meat, fruits, coffee, tea, magnesium, and dietary fiber was associated with ischemic stroke risk, while consumption of tea, fruits, and vegetables was relevant to hemorrhagic stroke susceptibility.

CONCLUSIONS

Our study has reported that several dietary factors have a significant impact on stroke risk and offered a new insight into the relationship between dietary modification and stroke occurrence. Our results may provide an effective strategy for stroke prevention.

Evaluation of the Quality of Evidence of the Association of Foods and Nutrients With Cardiovascular Disease and Diabetes: A Systematic Review

IMPORTANCE

Poor diet is a leading global factor associated with cardiometabolic disease (CMD). Understanding the quality of evidence of the associations between specific dietary factors and CMD, including effect size (relative risk [RR]) and uncertainty, is essential to guide policy and consumer actions to achieve healthy diet and public health goals.

OBJECTIVE

To assess the quality of evidence of the associations between specific dietary factors and CMD as well as the quantitative evidence for RRs and the uncertainty of these risk estimates.

EVIDENCE REVIEW

PubMed and the reference lists of eligible articles were searched between May 1, 2015, and February 26, 2021, for systematic reviews with meta-analyses of randomized clinical trials and prospective cohort studies that analyzed the consumption of 1 or more of the dietary factors of interest; reported dose-response meta-analyses; included healthy adults; and assessed 1 or more of the outcomes of interest. Study characteristics and RR estimates were extracted in duplicate. For identified associations, quality of evidence was assessed using the Bradford-Hill criteria for causation.

FINDINGS

A total of 2058 potentially relevant reports were identified, from which 285 full-text articles were assessed for eligibility. The final selection of articles included 28 meta-analyses representing 62 associations between diet and CMD. Among these associations, 10 foods, 3 beverages, and 12 nutrients had at least probable evidence of associations with coronary heart disease, stroke, and/or diabetes. Most RRs ranged from 0.87 to 0.96 per daily serving change for protective associations and from 1.06 to 1.15 per daily serving change for harmful associations. Most identified associations were protective (n = 38) and a smaller number were harmful (n = 24), with a higher risk associated with higher intake.

CONCLUSIONS AND RELEVANCE

This systematic review summarized the current quality of evidence of the associations of specific dietary factors with coronary heart disease, stroke, and diabetes. These findings may inform dietary guidance, the assessment of disease burden in specific populations, policy setting, and future research.

Do Refined Grains Have a Place in a Healthy Dietary Pattern: Perspectives from an Expert Panel Consensus Meeting

Although dietary guidance recommends increasing consumption of whole grains and concurrently limiting consumption of refined and/or enriched grain foods, emerging research suggests that certain refined grains may be part of a healthy dietary pattern. A scientific expert panel was convened to review published data since the release of 2015 dietary guidance in defined areas of grain research, which included nutrient intakes, diet quality, enrichment/fortification, and associations with weight-related outcomes. Based on a 1-d roundtable discussion, the expert panel reached consensus that 1) whole grains and refined grains can make meaningful nutrient contributions to dietary patterns, 2) whole and refined grain foods contribute nutrient density, 3) fortification and enrichment of grains remain vital in delivering nutrient adequacy in the American diet, 4) there is inconclusive scientific evidence that refined grain foods are linked to overweight and obesity, and 5) gaps exist in the scientific literature with regard to grain foods and health.

The associations of major foods and fibre with risks of ischaemic and haemorrhagic stroke: a prospective study of 418 329 participants in the EPIC cohort across nine European countries

AIM

To investigate the associations between major foods and dietary fibre with subtypes of stroke in a large prospective cohort.

METHODS AND RESULTS

We analysed data on 418 329 men and women from nine European countries, with an average of 12.7 years of follow-up. Diet was assessed using validated country-specific questionnaires which asked about habitual intake over the past year, calibrated using 24-h recalls. Multivariable-adjusted Cox regressions were used to estimate hazard ratios (HRs) for ischaemic and haemorrhagic stroke associated with consumption of red and processed meat, poultry, fish, dairy foods, eggs, cereals, fruit and vegetables, legumes, nuts and seeds, and dietary fibre. For ischaemic stroke (4281 cases), lower risks were observed with higher consumption of fruit and vegetables combined (HR; 95% CI per 200 g/day higher intake, 0.87; 0.82-0.93, P-trend < 0.001), dietary fibre (per 10 g/day, 0.77; 0.69-0.86, P-trend < 0.001), milk (per 200 g/day, 0.95; 0.91-0.99, P-trend = 0.02), yogurt (per 100 g/day, 0.91; 0.85-0.97, P-trend = 0.004), and cheese (per 30 g/day, 0.88; 0.81-0.97, P-trend = 0.008), while higher risk was observed with higher red meat consumption which attenuated when adjusted for the other statistically significant foods (per 50 g/day, 1.07; 0.96-1.20, P-trend = 0.20). For haemorrhagic stroke (1430 cases), higher risk was associated with higher egg consumption (per 20 g/day, 1.25; 1.09-1.43, P-trend = 0.002).

CONCLUSION

Risk of ischaemic stroke was inversely associated with consumption of fruit and vegetables, dietary fibre, and dairy foods, while risk of haemorrhagic stroke was positively associated with egg consumption. The apparent differences in the associations highlight the importance of examining ischaemic and haemorrhagic stroke subtypes separately.

Perspective: Whole and Refined Grains and Health-Evidence Supporting "Make Half Your Grains Whole"

Research-based dietary guidelines suggest that consumers "make half their grains whole." Yet some advocate ingesting only whole-grain foods (WGFs) and avoiding all refined-grain foods (RGFs). Some even recommend avoiding all grain-based foods (GBFs). This article will provide arguments to counter negative deductions about GBFs and RGFs, especially staple ones, and to support dietary guidance recommending a balance of GBFs-achieved through the right mix, type, and quantity of WGFs and RGFs. Studies looking at early mortality, body weight, and glucose tolerance and diabetes will be used as examples to characterize the literature about GBFs. The following issues are highlighted: 1) inconsistent findings between epidemiological and interventional studies and impacts of GBFs on health outcomes, and the underreporting of findings showing RGFs neither raise nor lower health risks; 2) multiple confounding and potential interactions make adequate statistical adjustment difficult; 3) nonuniform WGF definitions among studies make comparison of results challenging, especially because some WGFs may contain 49-74% refined grain (RG); 4) binary categorization of GBFs creates bias because nearly all categories of WGFs are recommended, but nearly half the RGF categories are not; 5) ingestion of >5 (30-g) servings RGFs/d and <1 serving WFGs/d creates dietary imbalance; 6) pattern names (e.g., "white bread") may impugn RGFs, when names such as "unbalanced" or "few fruits and vegetables" may more fairly characterize the dietary imbalance; 7) avoidance of all enriched RGs may not only impair status of folate and other B vitamins and certain minerals such as iron and zinc but also decrease acceptability of WGFs; 8) extrapolation beyond median documented intakes in high-WGF consumers (∼48 g whole grain/d) in most cohorts is speculative; 9) recommended dietary patterns such as the Mediterranean diet demonstrate that the right mix of WGFs and RGFs contributes to positive health outcomes.

Whole grain consumption and human health: an umbrella review of observational studies

Whole grains have been associated with a number of health benefits. We systematically reviewed existing meta-analyses of observational studies and evaluated the level of evidence for their putative effects based on pre-selected criteria. Of the 23 included studies, we found convincing evidence of an inverse association between whole grain consumption and risk of type-2 diabetes and colorectal cancer; possible evidence of decreased risk of colon cancer and cardiovascular mortality with increased whole grain intake, as well as increased risk of prostate cancer. Limited or insufficient evidence was available for all other outcomes investigated. Overall findings are encouraging for a positive effect of whole grain consumption on certain diseases, especially highly prevalent metabolic diseases, however, uncertainty of some negative associations deserves further attention.

Substitutions of Oatmeal and Breakfast Food Alternatives and the Rate of Stroke

Background and Purpose- Studies indicate that consuming breakfast every day, and particularly oatmeal, is associated with lower risk of stroke. However, few studies have considered replacement foods when considering foods usually consumed at breakfast. We, therefore, aimed to model substitutions between the breakfast food products oatmeal, eggs, yogurt, or white bread and subsequent risk of stroke. Methods- Participants from the Danish cohort study (Diet, Cancer and Health; n=55 095) were followed for 13.4 years, during which 2260 subjects experienced a first-ever stroke. Breakfast foods were assessed using a validated 192-item food-frequency questionnaire at baseline. Cox proportional hazards models were used to estimate adjusted hazard ratios and 95% CIs for associations between hypothetical substitutions of standard portion sizes of breakfast foods and stroke. Results- Modeling replacement of white bread or eggs with oatmeal was associated with a lower rate of total stroke (hazard ratio [HR]=0.96 [95% CI, 0.95-0.98]; HR=0.96 [95% CI, 0.93-0.98], respectively), total ischemic stroke (HR=0.96 [95% CI, 0.94-0.98]; HR=0.96 [95% CI, 0.94-0.99], respectively), and ischemic stroke due to small-artery occlusion (HR=0.95 [95% CI, 0.93-0.98]; HR=0.95 [95% CI, 0.91-0.99], respectively). Furthermore, modeling replacement of eggs with oatmeal was associated with a lower rate of total hemorrhagic stroke (HR=0.94 [95% CI, 0.89-0.99]). Modeling replacement of yogurt with oatmeal was not associated with stroke. Conclusions- Our findings suggest that a diet containing oatmeal instead of white bread or eggs may be associated with a lower rate of stroke.

Biomarkers of cereal food intake

Background/objectives

Cereal foods are major contributors to the daily energy, protein, and dietary fiber intake all over the world. The role of cereals in human health is dependent on whether they are consumed as refined or whole grain and on cereal species. To unravel the underlying mechanisms of health effects attributed to specific cereal foods and to provide more precise dietary advice, there is a need for improved dietary assessment of whole-grain intake. Dietary biomarkers of specific cereals, different fractions or cereal-containing foods could offer such a possibility. The aim of this review was to summarize the current status on biomarkers of different cereals, fractions, and specific cereal foods.

Subjects and methods

A literature review was conducted and putative biomarkers of different cereals and pseudo-cereals (wheat, oats, rye, barley, rice, and quinoa) as well as for different grain fractions (whole grain, refined grain, bran) and foods were summarized and discussed.

Results

Several putative biomarkers have been suggested for different cereals, due to their unique presence in these grains. Among the biomarkers, odd-numbered alkylresorcinols are the most well-studied and -evaluated biomarkers and reflect whole-grain wheat and rye intake. Even-numbered alkylresorcinols have been suggested to reflect quinoa intake. Recent studies have also highlighted the potential of avenanthramides and avenacosides as specific biomarkers of oat intake, and a set of biomarkers have been suggested to reflect rice bran intake. However, there are yet no specific biomarkers of refined grains. Most biomarker candidates remain to be evaluated in controlled interventions and free-living populations before applied as biomarkers of intake in food and health studies.

Conclusion

Several putative biomarkers of different cereals have been suggested and should be validated in human studies using recently developed food intake biomarker validation criteria.

Perspective: Refined Grains and Health: Genuine Risk, or Guilt by Association?

Refined grain intake is widely assumed to be associated with adverse health outcomes, including increased risk for cardiovascular disease (CVD), type 2 diabetes (T2D), and obesity. The 2015 Dietary Guidelines Advisory Committee recommended that to improve dietary quality, the US population should replace most refined grains with whole grains. This recommendation was based largely on results from studies that examined dietary patterns, not separate food groups. A Western dietary pattern typically includes red and processed meat, sugar-sweetened foods and beverages, French fries, and high-fat dairy products, as well as refined grains, and has been linked to increased risk of many chronic diseases. However, when evaluated as a distinct food category, 11 meta-analyses of prospective cohort studies, which included a total of 32 publications with data from 24 distinct cohorts, demonstrated that refined grain intake was not associated with all-cause mortality, T2D, CVD, coronary heart disease (CHD), stroke, hypertension, or cancer. By contrast, consumption of red and processed meat was consistently associated with increased risk of these same health outcomes. Refined grain consumption up to 6-7 servings/d (1 serving = 30 g) was not associated with higher risk of CHD, T2D, hypertension, or all-cause mortality. Moreover, total grain intake was not associated with risk of CVD, CHD, stroke, or cancer, but was associated with lower risk of all-cause mortality. Consequently, the recommendation to reduce refined grain intake based on results from studies linking a Western dietary pattern to numerous adverse health outcomes is contrary to a substantial body of published scientific evidence. Future research needs to better define refined grain intake to distinguish between staple grain foods and indulgent grain foods, and to better design randomized controlled trials to resolve discrepancies between results from observational studies and such trials with regard to determining the benefits of whole grains compared with refined grains.

How Important are Cereals and Cereal Products in the Average Polish Diet?

The main aim of this study was to identify the food sources of energy and 28 nutrients from cereals and cereal products in the average Polish diet based on data from a nationally representative sample of the Polish population attending in 2016 Household Budget Survey (i.e., 36,886 households). The contribution of energy and nutrients from cereals and cereal products were compared with reference values. The detailded analysis included five main groups and nine sub-groups of cereal food category. Our findings indicated that cereals and cereal products contributed 30.4% of total dietary energy supply, providing a significant percentage of six nutrients to the average Polish diet (i.e., 64.1% of manganese, 51% of carbohydrates, 48.5% of dietary fibre, 34.1% of iron, 33.6% of folate, and 31.3% of copper). Supply at the level of 20⁻30% was observed for protein, thiamin, phosphorus and zinc, and at 10⁻20% for polyunsaturated fatty acids (PUFA), sodium, potassium, calcium, riboflavin, niacin, and vitamin B6. For other nutrients i.e., total fat, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), cholesterol, iodine, vitamins: A, D, B12, and C, the share of cereals and cereal products contribution was below 10%. Cereals and cereal products were the major food category in meeting the reference values for the Polish population in case of manganese, carbohydrates (approximately100%), and sodium (50%). The reference values was reached at the level of 30⁻40% for dietary fibre, protein, iron, copper, zinc, phosphorus and thiamin, and 20⁻30% for energy, magnesium, folate, niacin, riboflavin, vitamins B6 and E. For such nutrients as total fat, SFA, and potassium, the fulfillment of the reference values amounted to 10⁻20%. Our results document the importance of cereals and cereal products in the Polish diet, which should be emphasized from a nutritional and health point of view.

Plasma alkylresorcinol metabolite, a biomarker of whole-grain wheat and rye intake, and risk of ischemic stroke: a case-control study

Background

Epidemiologic studies on whole grains and risk of stroke have reported inconsistent results, with some suggesting a protective effect but others showing a null association.

Objectives

The aim of this study was to examine whether plasma 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), a biomarker of whole-grain wheat and rye intake, is associated with risk of ischemic stroke.

Methods

A hospital-based case-control study was conducted between March 2011 and May 2016. Cases (n = 990) with first ischemic stroke were matched to controls (n = 990) by sex and age. Concentrations of plasma DHPPA were determined by high-performance liquid chromatography-tandem mass spectrometry. We calculated ORs for the association of plasma DHPPA concentrations with ischemic stroke risk through the use of logistic regression.

Results

Plasma DHPPA was inversely associated with ischemic stroke risk. After adjustment for potential confounding factors, the ORs for ischemic stroke across increasing quartiles of plasma DHPPA concentrations were 1 (referent), 0.76 (95% CI: 0.58, 0.99), 0.71 (95% CI: 0.54, 0.92), and 0.59 (95% CI: 0.45, 0.77), respectively (P-trend = 0.001). The inverse association was also observed in all subgroups of participants according to sex, age, body mass index, smoking status, alcohol consumption, history of hypertension, and history of diabetes.

Conclusions

Our study showed that higher plasma DHPPA concentrations were associated with lower risk of ischemic stroke. This finding provides further evidence to support the health benefits of whole-grain consumption.

Bread Consumption Is Associated with Elevated Blood Pressure among Adults Living in Mexico City⁻A Sub-Analysis of the Tlalpan 2020 Study

Excessive dietary sodium is associated with elevated blood pressure (EBP). Bread products are identified as one of the main sources of daily sodium intake. The objective of this cross-sectional study was to evaluate the association between bread and others cereal products consumption with EBP. Frequency intake of a standard serving of bread and other cereal products was recorded and categorized as: ≤3 times/month or never (reference category group) and ≥ once/week. EBP was defined as systolic blood pressure (SBP) ≥120 mmHg and/or diastolic blood pressure (DBP) ≥80 mmHg. Raw and adjusted odds ratios (OR) for the association between consumption of the studied food products and blood pressure status were estimated. Overall, 2011 participants aged 37.3 ± 9.1 years old were included. In the models adjusted for relevant covariates, consumption of one piece of bolillo or telera (OR = 1.39; 95% CI = 1.01–1.89) ≥ once/week was associated with an increased risk of EBP, compared to the reference category. Also, participants consuming one bowl of high-fiber breakfast cereal once/week were less likely to have EBP (OR = 0.73; 95% CI = 0.53–0.98). Initiatives to reduce sodium levels in bread products such as bolillo and telera are needed in Mexico to help manage the cardiovascular risk at the population level.

Whole Grain Consumption and Risk of Ischemic Stroke: Results From 2 Prospective Cohort Studies

BACKGROUND AND PURPOSE

Higher intake of whole grains may exert cardiometabolic benefits, although findings on stroke risk are inconclusive. The potentially differential effects of individual whole grain foods on ischemic stroke have not been examined.

METHODS

We analyzed whole grain consumption in relation to ischemic stroke among 71 750 women from the Nurses' Health Study and 42 823 men from the Health Professionals Follow-up Study who were free of cardiovascular disease, diabetes mellitus, and cancer at baseline (1984 and 1986, respectively) through 2010 using a Cox proportional hazards model. Validated semiquantitative food frequency questionnaires were used to assess consumption of whole grain intake, including whole grain cold breakfast cereal, dark bread, oatmeal, brown rice, popcorn, bran, and germ. Self-reported incident cases of ischemic stroke were confirmed through medical record review.

RESULTS

During 2 820 128 person-years of follow-up in the 2 cohorts, 2458 cases of ischemic stroke were identified and confirmed. Intake of total whole grains was not associated with risk of ischemic stroke after adjustment for covariates: the pooled hazard ratio (95% confidence interval) comparing extreme intake levels was 1.04 (0.91-1.19). However, intake of whole grain cold breakfast cereal and total bran was inversely associated with ischemic stroke after multivariate adjustment: the pooled hazard ratios (95% confidence intervals) were 0.88 (0.80-0.96; Ptrend=0.008) and 0.89 (0.79-1.00; Ptrend=0.004), respectively. Other whole grain foods were not associated with a lower risk of ischemic stroke.

CONCLUSIONS

Although overall consumption of whole grains was not associated with lower risk of ischemic stroke, greater consumption of whole grain cold breakfast cereal and bran was significantly associated with a lower risk of ischemic stroke. More studies are needed to replicate these associations between individual whole grain foods and risk of ischemic stroke among other populations.

Health Benefits of Dietary Whole Grains: An Umbrella Review of Meta-analyses

OBJECTIVE

The purpose of this study is to review the effectiveness of the role of whole grain as a therapeutic agent in type 2 diabetes, cardiovascular disease, cancer, and obesity.

METHODS

An umbrella review of all published meta-analyses was performed. A PubMed search from January 1, 1980, to May 31, 2016, was conducted using the following search strategy: (whole grain OR whole grains) AND (meta-analysis OR systematic review). Only English language publications that provided quantitative statistical analysis on type 2 diabetes, cardiovascular disease, cancer, and weight loss were retrieved.

RESULTS

Twenty-one meta-analyses were retrieved for inclusion in this umbrella review, and all the meta-analyses reported statistically significant positive benefits for reducing the incidence of type 2 diabetes (relative risk [RR] = 0.68-0.80), cardiovascular disease (RR = 0.63-0.79), and colorectal, pancreatic, and gastric cancers (RR = 0.57-0.94) and a modest effect on body weight, waist circumference, and body fat mass. Significant reductions in cardiovascular and cancer mortality were also observed (RR = 0.82 and 0.89, respectively). Some problems of heterogeneity, publication bias, and quality assessment were found among the studies.

CONCLUSION

This review suggests that there is some evidence for dietary whole grain intake to be beneficial in the prevention of type 2 diabetes, cardiovascular disease, and colorectal, pancreatic, and gastric cancers. The potential benefits of these findings suggest that the consumption of 2 to 3 servings per day (~45 g) of whole grains may be a justifiable public health goal.