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Whole grains

Pooled cohorts link about three daily servings of whole grains to roughly 20% less heart disease and death, and to less type 2 diabetes. Trials found a small LDL cholesterol fall, mostly with oats, and no change in body weight. Refined grains and white rice were linked to harms in some cohorts. Celiac disease affects about 0.8% of people.

Add to Bio HackChecked 2026-11-13
Status
A food, not a regulated health product. The Dietary Guidelines for Americans, 2025-2030 say to prioritize fiber-rich whole grains, with a goal of 2 to 4 servings a day, and to significantly reduce highly processed refined carbohydrates such as white bread, packaged breakfast options, flour tortillas and crackers [1]. Wheat is one of the nine major food allergens under US law [2].
Also called
whole grain, wholegrain, whole wheat, whole-wheat bread, wholemeal, brown rice, oats, oatmeal, barley, rye, quinoa, bulgur, bran, refined grains, white bread, white rice, white flour
Studied for
heart health, cholesterol, longer life, type 2 diabetes prevention, blood sugar, weight loss, digestion, constipation, gut health, inflammation

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help5

Reported risks5

What it was studied for, and what was found

Shown to help5

Strong

Heart disease and stroke

Linked to 19% lower coronary heart disease and 22% lower cardiovascular disease per three daily servings of whole grains, in pooled cohorts. The stroke link did not reach significance.

Compared with 90 g a day less whole grain, in a dose-response model [3]; the lowest whole grain intake [4]

The numbers and sources
Effect
Per extra 90 g a day of whole grain, about three servings, the relative risk was 0.81 (95% CI 0.75 to 0.87) for coronary heart disease, 0.78 (95% CI 0.73 to 0.85) for cardiovascular disease and 0.88 (95% CI 0.75 to 1.03) for stroke [3]. The highest against the lowest whole grain intake was linked to lower cardiovascular death (RR 0.82, 95% CI 0.79 to 0.85, I² 0%), and each extra 16 g a day, about one serving, to 9% lower cardiovascular death [4]. A Lancet series of reviews observed similar findings for whole grains as for dietary fiber, where the highest intakes were linked to 15% to 30% lower death, coronary heart disease and stroke, and graded the whole grain evidence low to moderate in certainty [5].
Population
45 prospective studies [3]. 786,076 participants and 23,957 cardiovascular deaths in 14 cohorts [4]. 185 prospective studies and 58 trials [5].
Sources
[3], [4], [5]
Caveats
Observational. People who eat more whole grains differ in other habits such as smoking and exercise (confounding), and illness can change diet (reverse causation). The certainty was graded low to moderate [5].
Strong

Death from any cause

Linked to 16% to 17% lower death from any cause at the highest whole grain intake or per three daily servings, in pooled cohorts.

Compared with 90 g a day less whole grain, in a dose-response model [3]; the lowest whole grain intake [4]

The numbers and sources
Effect
Per extra 90 g a day, the relative risk was 0.83 (95% CI 0.77 to 0.90, I² 83%) for death from any cause, 0.85 (95% CI 0.80 to 0.91) for cancer death and 0.78 (95% CI 0.70 to 0.87) for respiratory death. Lower risks were seen up to 210 to 225 g a day [3]. The highest against the lowest intake was linked to lower total death (RR 0.84, 95% CI 0.80 to 0.88) and cancer death (RR 0.88, 95% CI 0.83 to 0.94), and each extra 16 g a day to 7% lower total death (RR 0.93, 95% CI 0.92 to 0.94) [4].
Population
45 prospective studies [3]. 786,076 participants and 97,867 deaths in 14 cohorts [4].
Sources
[3], [4]
Caveats
Observational, with high heterogeneity for total death (I² 83% and 74%) [3][4]. Confounding and reverse causation as above.
Moderate

Type 2 diabetes

Linked to 32% lower type 2 diabetes per three daily servings of whole grains in pooled cohorts. Brown rice was linked to 11% lower risk.

Compared with three fewer servings a day, in a dose-response model [6]; the lowest brown rice intake [7]

The numbers and sources
Effect
Per extra 3 servings a day, the relative risk of type 2 diabetes was 0.68 (95% CI 0.58 to 0.81, I² 82%) for whole grains and 0.95 (95% CI 0.88 to 1.04) for refined grains. Whole grain bread, whole grain cereals, wheat bran and brown rice were each linked to lower risk, in few studies [6]. Brown rice at the highest intake was linked to lower risk (RR 0.89, 95% CI 0.81 to 0.97), and each 50 g a day serving to 13% lower risk [7].
Population
16 cohort studies [6]. 3 estimates covering 197,228 participants and 10,507 cases for brown rice [7].
Sources
[6], [7]
Caveats
Observational, with high heterogeneity (I² 82%) [6]. The brown rice estimate rests on 3 estimates [7].
Strong

LDL cholesterol

Shown to lower LDL cholesterol slightly, by 0.09 mmol/L, against refined-grain control foods in pooled trials, with whole-grain oats lowering cholesterol most.

Compared with non-whole-grain control foods [8]; refined grains or placebo [9]

The numbers and sources
Effect
Whole grain intake lowered LDL cholesterol by 0.09 mmol/L (about 3.5 mg/dL, 95% CI -0.15 to -0.03) and total cholesterol by 0.12 mmol/L (95% CI -0.19 to -0.05), with no effect on HDL cholesterol. Triglycerides tended to fall (-0.04 mmol/L, 95% CI -0.08 to 0.01). Oats had the largest effect on total cholesterol (-0.17 mmol/L) [8]. In a second review, whole-grain oats improved total cholesterol (SMD -0.54, 95% CI -0.95 to -0.12) and LDL cholesterol (SMD -0.57, 95% CI -0.84 to -0.31), and whole-grain rice improved triglycerides [9].
Population
24 randomized trials in apparently healthy adults [8]. 25 randomized trials of 2 to 16 weeks in adults with or without cardiovascular risk factors [9].
Sources
[8], [9]
Caveats
Small changes over weeks. The second review found the LDL effect for oats, not for all whole grains combined [9]. Beta-glucan from oats is on its own page.
Moderate

Bowel habits

Shown to raise stool weight by 3.7 g per extra gram of wheat fiber a day, and to shorten slow gut transit, in pooled intervention studies.

Compared with lower intakes of wheat fiber, in a regression across intervention studies [14]

The numbers and sources
Effect
Each extra gram a day of wheat fiber raised total stool weight by 3.7 g a day (95% CI 3.50 to 3.84) and stool frequency by 0.004 times a day. In people whose transit time was over 48 hours, it shortened by 0.78 hours per extra gram (95% CI 0.53 to 1.04). Too few studies of non-wheat cereal fibers allowed analysis [14].
Population
65 intervention studies in generally healthy people [14].
Sources
[14]
Caveats
Most of the effect came from wheat bran [14]. Fiber in general is on its own page.

Mixed results2

Moderate

C-reactive protein and inflammation

Mixed results: two pooled analyses of trials found whole grains lowered C-reactive protein slightly, while a third found no significant change.

Compared with refined grains [11]; refined grains or placebo [9]; control diets low in or without whole grains [10]

The numbers and sources
Effect
Whole grains lowered high-sensitivity C-reactive protein (Hedges' g -0.22, 95% CI -0.45 to 0.00) and interleukin-6, with no change in TNF-alpha, and high heterogeneity (I² 69%) [11]. Another review found lower C-reactive protein (SMD -0.22, 95% CI -0.44 to 0.00) [9]. A third found no significant change in C-reactive protein (-0.29 mg/L, 95% CI -1.10 to 0.52), interleukin-6 or TNF-alpha, with effects in people with raised C-reactive protein and in trials with matched calories [10].
Population
466 participants in 13 trials [11]. 25 trials [9]. 1,238 adults in 14 trials [10].
Sources
[11], [9], [10]
Caveats
Heterogeneity was high across reviews [10][11]. The intervals of the two reviews that found a fall reach zero.
Moderate

Blood sugar in trials

Shown to lower the rise in blood sugar after a meal against refined foods. Longer trials found no change in fasting glucose, and one review found HbA1c fell.

Compared with similar refined foods [12]; refined grains or placebo [9]

The numbers and sources
Effect
In 14 single-meal trials, whole grain foods reduced the 2-hour glucose response by 29.71 mmol·min/L (95% CI -43.57 to -15.85) and the insulin response. In 16 trials lasting weeks to months, fasting glucose, fasting insulin and HOMA-IR did not change significantly [12]. Another review found whole grains lowered HbA1c (SMD -0.33, 95% CI -0.61 to -0.04) [9].
Population
Healthy adults in 30 trials [12]. 25 trials of adults with or without cardiovascular risk factors [9].
Sources
[12], [9]
Caveats
Most longer trials enrolled healthy people with normal blood sugar [12].

Not shown to help1

Moderate

Body weight

Not shown to change body weight in pooled trials against non-whole-grain foods. Body fat was 0.48 percentage points lower.

Compared with non-whole-grain control foods [13]

The numbers and sources
Effect
Whole grain intake did not change body weight (0.06 kg, 95% CI -0.09 to 0.20) and lowered body fat percentage slightly (-0.48%, 95% CI -0.95 to -0.01). The whole grain dose did not predict the difference [13].
Population
2,060 apparently healthy adults in 26 randomized trials of up to 16 weeks [13].
Sources
[13]
Caveats
Trials were short, which the authors say may explain the lack of difference [13].

Amounts studied

Cohort reviews modeled risk per 90 g a day of whole grain, about three servings such as two slices of whole grain bread and one bowl of cereal, with lower risks seen up to 210 to 225 g a day [3]. Another modeled per 16 g a day of whole grain ingredient, about one serving, and most populations ate under 50 g a day [4]. The diabetes review modeled per 3 servings a day [6], and the rice review per 158 g serving of white rice and 50 g serving of brown rice [7]. The PURE cohort compared 350 g or more of refined grains a day, about 7 servings, with under 50 g [15]. Trials lasted up to 16 weeks for weight [13] and 2 to 16 weeks for heart risk factors [9]. The Dietary Guidelines set a goal of 2 to 4 servings of whole grains a day [1].

Risks

Reported risks4

ModerateUncommon

Celiac disease

A global meta-analysis found 1.5% of the general population tested positive for celiac antibodies and 0.8% had celiac disease confirmed by biopsy.

The numbers and sources
How common
Uncommon: between 1 in 1,000 and 1 in 100 people.
Effect
Global seroprevalence was 1.5% (95% CI 1.3 to 1.8%) and biopsy-confirmed prevalence 0.8% (95% CI 0.6 to 1.0%). Prevalence was 50% higher in females and nearly double in children, and 41.4% of biopsy-confirmed patients had no symptoms [16].
Population
394,274 participants in 87 general population studies [16].
Sources
[16]
Caveats
Heterogeneity was very high (I² 97.1%), and 36.6% of people testing positive did not have a biopsy [16]. Celiac disease is triggered by gluten in wheat, barley and rye.
LimitedUncommon

Wheat allergy

A national survey estimated convincing wheat allergy in 0.8% of US adults.

The numbers and sources
How common
Uncommon: between 1 in 1,000 and 1 in 100 people.
Effect
Convincing wheat allergy was estimated at 0.8% (95% CI 0.7 to 0.9) of US adults, about 2.0 million people [17]. Wheat is one of the nine major food allergens under US law [2].
Population
40,443 US adults surveyed [17].
Sources
[17], [2]
Caveats
The estimate rests on reported symptoms consistent with allergy, not food challenge testing [17].
ModerateHow often is not known

White rice and type 2 diabetes

Linked to 16% more type 2 diabetes at the highest white rice intake than the lowest, and 13% more per 158 g serving above about 300 g a day.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The highest against the lowest white rice intake was linked to higher type 2 diabetes (RR 1.16, 95% CI 1.02 to 1.32). Above about 300 g a day, each 158 g a day serving was linked to 13% (95% CI 11% to 15%) higher risk [7].
Population
577,426 participants and 25,956 cases in cohort studies [7].
Sources
[7]
Caveats
Observational. White rice intake was highest in Asian cohorts [7].
LimitedHow often is not known

Inorganic arsenic in rice

FDA states long-term inorganic arsenic exposure is linked to skin, bladder and lung cancers, names children as most vulnerable, and sets an action level for infant rice cereal.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The FDA states that long-term exposure to inorganic arsenic has been associated with skin disorders, skin, bladder and lung cancers, and cardiovascular disease, and that high exposure during brain development is associated with learning disabilities and lowered IQ. It names fetuses, infants and children as particularly vulnerable, and publishes testing of rice and rice products [18]. In 2020 it issued an action level for inorganic arsenic in rice cereals for infants [19].
Population
US food supply, as assessed by the FDA [18][19].
Sources
[18], [19]
Caveats
Regulator statements about arsenic from all food sources, not a measured rate of harm from eating rice.

Mixed results1

ModerateHow often is not known

Refined grains and heart events

Mixed results: one 21-country cohort linked high refined grain intake to 27% higher death and 33% more major heart events, while pooled cohorts found little link.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
At 350 g or more of refined grains a day against under 50 g, death from any cause was higher (HR 1.27, 95% CI 1.11 to 1.46) and so were major cardiovascular events (HR 1.33, 95% CI 1.16 to 1.52). Higher refined grain intake was linked to higher systolic blood pressure. Whole grains and white rice were not linked to outcomes in this cohort [15]. A meta-analysis of 45 studies found little evidence of a link between refined grains, white rice or total grains and cardiovascular disease or death [3], and another found no link between refined grains and type 2 diabetes (RR 0.95, 95% CI 0.88 to 1.04) [6].
Population
137,130 adults in 21 countries followed a median 9.5 years [15]. 45 prospective studies [3]. 6 cohorts for refined grains [6].
Sources
[15], [3], [6]
Caveats
Observational. What counts as a refined grain food differs between countries.

Claims tested and not found

  1. That whole grains lead to weight loss. Pooled trials found no change in body weight against non-whole-grain foods [13].
  2. That whole grains lower fasting blood sugar in healthy people. Trials lasting weeks to months found no significant change in fasting glucose, fasting insulin or HOMA-IR [12].
  3. That whole grains raise HDL cholesterol. Pooled trials found no effect on HDL cholesterol [8].

Related

Fiber supplementsBeta-glucanGluten-free diet

Sources

  1. US Department of Agriculture and US Department of Health and Human Services. Dietary Guidelines for Americans, 2025-2030. realfood.gov. 2026. https://cdn.realfood.gov/DGA.pdf
  2. US Food and Drug Administration. Food Allergies. FDA. Content current as of 2026-03-11. https://www.fda.gov/food/nutrition-food-labeling-and-critical-foods/food-allergies
  3. Aune D, Keum N, Giovannucci E, et al. Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies. BMJ. 2016. https://doi.org/10.1136/bmj.i2716
  4. Zong G, Gao A, Hu FB, Sun Q. Whole Grain Intake and Mortality From All Causes, Cardiovascular Disease, and Cancer: A Meta-Analysis of Prospective Cohort Studies. Circulation. 2016. https://doi.org/10.1161/circulationaha.115.021101
  5. Reynolds A, Mann J, Cummings J, et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet. 2019. https://doi.org/10.1016/s0140-6736(18)31809-9
  6. Aune D, Norat T, Romundstad P, Vatten LJ. Whole grain and refined grain consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies. European Journal of Epidemiology. 2013. https://doi.org/10.1007/s10654-013-9852-5
  7. Yu J, Balaji B, Tinajero M, et al. White rice, brown rice and the risk of type 2 diabetes: a systematic review and meta-analysis. BMJ Open. 2022. https://doi.org/10.1136/bmjopen-2022-065426
  8. Hollænder PL, Ross AB, Kristensen M. Whole-grain and blood lipid changes in apparently healthy adults: a systematic review and meta-analysis of randomized controlled studies. The American Journal of Clinical Nutrition. 2015. https://doi.org/10.3945/ajcn.115.109165
  9. Marshall S, Petocz P, Duve E, et al. The Effect of Replacing Refined Grains with Whole Grains on Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials with GRADE Clinical Recommendation. Journal of the Academy of Nutrition and Dietetics. 2020. https://doi.org/10.1016/j.jand.2020.06.021
  10. Rahmani S, Sadeghi O, Sadeghian M, et al. The Effect of Whole-Grain Intake on Biomarkers of Subclinical Inflammation: A Comprehensive Meta-analysis of Randomized Controlled Trials. Advances in Nutrition. 2020. https://doi.org/10.1093/advances/nmz063
  11. Hajihashemi P, Haghighatdoost F. Effects of Whole-Grain Consumption on Selected Biomarkers of Systematic Inflammation: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Journal of the American College of Nutrition. 2019. https://doi.org/10.1080/07315724.2018.1490935
  12. Marventano S, Vetrani C, Vitale M, et al. Whole Grain Intake and Glycaemic Control in Healthy Subjects: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2017. https://doi.org/10.3390/nu9070769
  13. Pol K, Christensen R, Bartels EM, et al. Whole grain and body weight changes in apparently healthy adults: a systematic review and meta-analysis of randomized controlled studies. The American Journal of Clinical Nutrition. 2013. https://doi.org/10.3945/ajcn.113.064659
  14. de Vries J, Miller PE, Verbeke K. Effects of cereal fiber on bowel function: A systematic review of intervention trials. World Journal of Gastroenterology. 2015. https://doi.org/10.3748/wjg.v21.i29.8952
  15. Swaminathan S, Dehghan M, Raj JM, et al. Associations of cereal grains intake with cardiovascular disease and mortality across 21 countries in Prospective Urban and Rural Epidemiology study: prospective cohort study. BMJ. 2021. https://doi.org/10.1136/bmj.m4948
  16. Karimzadhagh S, Abbaspour E, Shamsi P, et al. Global Prevalence of Celiac Disease and Clinical Characteristics in the General Population: A Systematic Review and Meta-Analysis. Gastroenterology. 2026. https://doi.org/10.1053/j.gastro.2026.07.028
  17. Gupta RS, Warren CM, Smith BM, et al. Prevalence and Severity of Food Allergies Among US Adults. JAMA Network Open. 2019. https://doi.org/10.1001/jamanetworkopen.2018.5630
  18. US Food and Drug Administration. Arsenic in Food. FDA. Content current as of 2024-03-05. https://www.fda.gov/food/environmental-contaminants-food/arsenic-food
  19. US Food and Drug Administration. Guidance for Industry: Action Level for Inorganic Arsenic in Rice Cereals for Infants. FDA. Content current as of 2020-08-05. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-action-level-inorganic-arsenic-rice-cereals-infants

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