Whole Grains and Ancient Grains: What Research Shows
What counts as a whole grain, what cohort studies and trials found for whole grains, brown rice, quinoa and ancient wheats, and which grains contain gluten.
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A whole grain is a grain kernel that still has all of its parts. A 2021 consensus statement from the Whole Grain Initiative says the endosperm, germ and bran must all be present in the same relative proportions as in the intact kernel. [1] Whole grains are studied in large population studies and in some trials, and the strongest links are for heart disease, type 2 diabetes and early death. These are links seen in people who eat more whole grain, which is not the same as proof that the grain causes the benefit.
Gluten note first. Wheat, barley and rye contain gluten, and so do types of wheat such as durum, emmer and spelt. [2] The "ancient" wheats are not gluten-free (see below). If you think you might have celiac disease, ask a doctor about testing before you stop eating gluten, because avoiding it first can make the tests inaccurate. [2]
What the term means
- Whole grain: all three kernel parts present, as above. [1]
- 100% whole-grain food: the US Dietary Guidelines for Americans 2020-2025 say a food is 100% whole grain if the only grains in it are whole grains. [3]
- Refined grain: the Guidelines say people who eat refined grains should choose enriched ones. [3]
- On a label: the Guidelines suggest the whole grain should be the first ingredient (or the second after water), or that whole-grain ingredients make up at least 50 percent of the product's weight. [3] See fiber and "whole grain" claims on packages.
The Guidelines (US, 2020-2025) also say at least half of total grains should be whole grains, and that 98 percent of Americans fall below the whole-grain recommendation. [3]
What research shows
| Question | What the source found | Strength of evidence |
|---|---|---|
| Whole grains and heart disease or early death | A meta-analysis of 45 cohort studies found that, per 90 g a day (about three servings) of whole grain, the relative risk was 0.78 for cardiovascular disease and 0.83 for death from any cause. [4] | Promising but limited (observational) |
| Whole grains and type 2 diabetes | A meta-analysis of 16 cohort studies found a relative risk of 0.68 per 3 servings a day for whole grains and 0.95 for refined grains. [5] | Promising but limited (observational) |
| Whole grains and body weight | Whole-grain intake was inversely linked to body mass index in observational studies, but nine trials (973 people, up to 16 weeks) found no significant weight difference. [6] | Mixed |
| Certainty of the overall evidence | A 2019 Lancet series of reviews graded certainty as low to moderate for whole grains and moderate for dietary fiber. [7] | Graded by the authors |
| Brown rice instead of white rice in prediabetes or type 2 diabetes | Seven trials (417 adults) found no effect on HbA1c or fasting glucose, but lower body weight and higher HDL cholesterol with brown rice. [8] | Mixed |
| Quinoa (Chenopodium quinoa) seeds | Seven trials (258 adults, 15 to 50 g a day, 28 to 180 days) found a benefit for fasting glucose but not for body weight or body mass index. [9] | Insufficient evidence (small trials; authors call for more) |
| Ancient wheats (einkorn, emmer, spelt, Khorasan) | A review found human trials are too few to conclude they are better than modern wheat at lowering chronic disease risk. [10] | Insufficient evidence |
Two cautions apply to this table. First, a separate review of "superfoods" found only one controlled trial of quinoa on metabolic syndrome measures. [11] Second, the brown rice trials compared brown with white rice; they did not compare rice with no rice.
Ancient grains and gluten
There is no clear definition of "ancient grains", but the term usually includes einkorn, emmer, spelt and Khorasan wheat. [12] A 2022 review reports that gluten is present in all wheat grains, that ancient wheats contain more protein and gluten than bread wheat, and that no single wheat type can be recommended as better for celiac disease. [12] The same review notes that bloating in people who feel "gluten sensitive" may sometimes come from fermentation of fructans in wheat rather than gluten. [12]Naturally gluten-free flours named by the US National Institute of Diabetes and Digestive and Kidney Diseases include amaranth, quinoa, buckwheat, rice and corn. [2] Cross-contact with gluten during growing, processing or cooking is a concern for people with celiac disease. [2] The NHS notes that oats do not contain gluten but can cause a reaction if produced alongside wheat, barley and rye. [13] Oats have their own page: oats.
Related pages
Beta-glucan in foods, barley and fiber amounts and side effects.Frequently asked questions
What counts as a whole grain?
A grain with the endosperm, germ and bran all present in their natural proportions. [1] A food made only from whole grains is called 100% whole grain in the US Dietary Guidelines. [3]
Is brown rice better than white rice for blood sugar?
In seven trials of adults with prediabetes or type 2 diabetes, brown rice did not change HbA1c or fasting glucose compared with white rice, though body weight was lower and HDL cholesterol higher. [8] Anyone managing diabetes should follow their own care team's plan.
Are ancient grains healthier than modern wheat?
Human trials are too few to say so. [10] They also contain gluten, so they are not suitable for people who must avoid it. [12]
Are quinoa and buckwheat gluten-free?
NIDDK lists quinoa and buckwheat flours among flours that are safe for people with celiac disease, while warning about cross-contact in growing, processing or serving. [2]
How much whole grain do official guidelines suggest?
The US Dietary Guidelines for Americans 2020-2025 say at least half of total grains should be whole grains. [3] A clinician or dietitian can advise on personal needs.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask a clinician
- Celiac disease or suspected celiac disease: follow your doctor or dietitian. A gluten-free diet started without advice may not give enough fiber, iron and calcium. [2]
- Cooked rice and grains: the NHS says spores of some food-poisoning bacteria survive cooking and can multiply if cooked rice or grains stand at room temperature; reheating does not remove the toxins. [14] Its advice is to cool them within 1 hour and keep them refrigerated. [14] More in food safety basics.
- Metals in rice and other foods: see heavy metals and contaminants in foods.
- Medicines: interactions between whole grains and medicines are not described in the sources we read for this page.
References
- van der Kamp JW et al. Consensus, Global Definitions of Whole Grain as a Food Ingredient and of Whole-Grain Foods Presented on Behalf of the Whole Grain Initiative. Nutrients 2021. PMID 35011013. Read 2026-10-23.
- NIDDK (US National Institutes of Health). Eating, Diet, & Nutrition for Celiac Disease. Last reviewed October 2020. Read 2026-10-23.
- US Department of Agriculture and US Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th edition. Read 2026-10-23.
- Aune D 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 (Clinical research ed.) 2016. PMID 27301975. Read 2026-10-23.
- Aune D et al. 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. PMID 24158434. Read 2026-10-23.
- Maki KC et al. The Relationship between Whole Grain Intake and Body Weight: Results of Meta-Analyses of Observational Studies and Randomized Controlled Trials. Nutrients 2019. PMID 31159235. Read 2026-10-23.
- Reynolds A et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet (London, England) 2019. PMID 30638909. Read 2026-10-23.
- Abdul Rahim AF et al. The effect of a brown-rice diets on glycemic control and metabolic parameters in prediabetes and type 2 diabetes mellitus: a meta-analysis of randomized controlled trials and controlled clinical trials. PeerJ 2021. PMID 34123581. Read 2026-10-23.
- Atefi M et al. Does Quinoa (Chenopodium quinoa) Consumption Improve Blood Glucose, Body Weight and Body Mass Index? A Systematic Review and Dose-Response Meta-Analysis of Clinical Trials. Current medicinal chemistry 2024. PMID 36847233. Read 2026-10-23.
- Dinu M et al. Ancient wheat species and human health: Biochemical and clinical implications. The Journal of nutritional biochemistry 2018. PMID 29065353. Read 2026-10-23.
- van den Driessche JJ et al. Effects of superfoods on risk factors of metabolic syndrome: a systematic review of human intervention trials. Food & function 2018. PMID 29557436. Read 2026-10-23.
- Brouns F et al. Do ancient wheats contain less gluten than modern bread wheat, in favour of better health?. Nutrition bulletin 2022. PMID 35915783. Read 2026-10-23.
- NHS. Coeliac disease. Page last reviewed 31 March 2023. Read 2026-10-23.
- NHS. Starchy foods and carbohydrates. Read 2026-10-23.