Granola: most of the evidence is about the bar

Granola sells as a health food and gets studied as a snack bar. Six of the fourteen findings on this page come from packaged granola bars, and what they show belongs to that product rather than to a jar of oats and nuts baked at home. One more thing before any number. We have no USDA entry for granola in this cohort, so this page carries no composition figures at all, and every figure below comes out of a trial or a product survey. What has been measured, and measured repeatedly, is blood sugar. A review of 72 glycaemic index measurements of oat foods holds 28 for muesli and granola, and they scored 56, against 71 for quick-cooking oats and 75 for instant oatmeal. The authors put the gap down to particle size and how far the starch had been cooked. That number describes how fast the starch turns into blood sugar. It says nothing about how much sugar, fat or energy is in the bowl. A granola rebuilt around a slower starch cut the two-hour glucose rise by 17 to 18 percent in three trials of 40 adults each, and hunger did not move. Those trials were run for the company that makes that granola. Every one of them excluded anyone with diabetes.

How much is actually in it

• Granola built with a slower starch cut the two-hour glucose rise by 17 to 18 percent in three trials of 40 adults each, and hunger did not move. — 160 healthy adults aged 18 to 65, 40 in each study, BMI 21 to under 32 (n = 160, of them 120 in the three granola studies) Evidence B source
  Glucose iAUC 0-2 h lower with the test granola by 17, 18 and 17 percent in the three studies; pooled 98 against 118 mmol x min/l (p<0.001); insulin iAUC 153 against 184 nmol x h/l (p<0.001); no difference in postprandial hunger or in 2 h glucose or hunger increments
• In 19 young Asian men a whole-grain oat protein granola had a glycaemic index of 51, and across the ten foods tested GI fell as protein, fat and fibre rose. — 19 healthy men, 9 Chinese and 10 Indian, mean age 24.7, BMI 21.7, in Singapore (n = 19) Evidence B source
  Whole-grain oat protein granola GI 51 (sem 4), whole-grain oat muesli 55 (sem 4); GI correlated negatively with protein (rs -0.366), fat (rs -0.268) and dietary fibre (rs -0.422), all p<0.001
• Granola bars sold in Quebec scored no better on Nutri-Score in 2023 than in 2018, 234 products against 240, and new products matched the ones withdrawn. — granola bars 240 in 2018 and 234 in 2023, alongside breakfast cereals, sliced breads and yogurts (n = 474 granola bars across two collections) Evidence C source
  Overall nutritional quality stable in all four categories (all p>=0.11); new granola bars similar to discontinued ones (p>=0.06); only reformulated yogurts improved

What a real portion looks like

• The same granola eaten with Greek yogurt gave a 52 percent lower two-hour glucose rise than with a cultured coconut product in 24 young women. — 24 healthy women, mean age 22.7, BMI 22.1 (n = 24) Evidence B source
  2 h blood glucose iAUC 52 percent lower after the dairy than the nondairy breakfast (p<0.0001); protein intake 3 times higher and fibre intake 4 times lower with dairy; both caloric breakfasts suppressed food intake at 2 h similarly against water (p<0.003); postprandial insulin 1.8 times higher after dairy

What cooking and storage change

• Across 28 glycaemic index tests of muesli and granola, inside a review of 72 measurements of oat foods, muesli and granola scored 56, while quick-cooking oats scored 71 and instant oatmeal 75. — 72 glycaemic index measurements from 20 publications and 17 unpublished tests, 28 of them for muesli or granola, each a controlled feeding test in people (n = 72 measurements, 28 for muesli or granola) Evidence A source
  GI 56 (se 1.7) for muesli and granola against 71 (se 2.7) for quick-cooking oats and 75 (se 2.8) for instant oatmeal; steel-cut 55 and large-flake 53; the authors attribute the difference to smaller particle size and greater starch gelatinisation

What it does to your health

• As an afternoon snack in 39 adults, granola bars raised three-hour blood glucose more than a hummus snack with the same 240 kcal, on continuous glucose monitoring. — 39 healthy adults aged 18 to 50, BMI 18 to 32, habitual afternoon snackers, in Indiana (n = 39) Evidence B source
  3-h postsnack blood glucose mean, AUC and variability were higher after both snacks than after no snack (all p<0.05), and lower after hummus than after granola bars (p<0.05); daily glucose responses did not differ between patterns
• The EU allows a box to say oat or barley beta-glucans reduce the blood glucose rise after a meal, and that permission is indexed to the fibre, with 5 beta-glucan claims authorised and 9 refused. — — Evidence E source
  The wording is Authorised; a search of the register for granola returns no entry; for beta-glucan 5 claims are authorised (cholesterol and post-meal glucose) and 9 refused, among them immunity and satiety claims

Safety, limits and interactions

• One reported anaphylaxis after a granola and oatmeal breakfast traced not to oats but to storage mites living in the oat flakes. — a 39-year-old woman in Panama City (n = 1) Evidence C source
  Cutaneous and respiratory allergic symptoms one hour after granola and oatmeal with milk; prick tests negative for the foods and positive for mites; Suidasia pontifica found at high density in the flaked oats
• In a census of 11434 packaged foods in Brazil, granola bars were among the three categories where low-calorie sweeteners were added most often, usually alongside added sugar. — 11434 packaged foods and beverages, subsample of 3491 for child-directed advertising and claims (n = 11434 products) Evidence C source
  9.3 percent of products had a low-calorie sweetener (95% CI 8.8 to 9.9), 14.6 percent among ultra-processed products; about 83 percent of those also had added sugars; sweeteners were most frequent in sweetened beverages, breakfast cereals and granola bars; 40 percent of products with a sweetener carried no related front-of-pack claim

What people believe that the data does not support

• Of 2937 packaged products in five categories including cookies and granola bars, 74.2 percent carried a nutrition or health claim, and 28.9 percent carried one while also meeting the threshold for a high-in warning symbol. — 2937 products collected 2018 to 2022 in Quebec: breakfast cereals 392, cookies and granola bars 983, flavoured milks 202, salty snacks 1063, yogurts 297 (n = 2937 products, 983 of them cookies and granola bars) Evidence C source
  74.2 percent of products had a nutrition or health claim; 28.9 percent had a claim and would require the front-of-pack symbol; products that would require the symbol were less likely to carry a claim
• The heart claim a granola box can carry in the United States belongs to oat beta-glucan and needs 3 g a day of it, and the regulation never names granola. — — Evidence E source
  The claim is conditioned on 3 g or more per day of beta-glucan soluble fiber from whole oats or barley, delivered through eligible sources such as oat bran, rolled oats or whole oat flour; a search of 21 CFR 101 for the word granola returns nothing

Who this works differently for

• Twelve weeks of granola bars in place of snacks left weight, fat mass and energy intake unchanged in 55 adults with overweight, whichever bar they got. — 55 adults with overweight or obesity, 36 women and 19 men, mean age 41, mean BMI 29.4 (n = 55, 29 oligofructose bar and 26 control bar) Evidence B source
  Energy intake, body weight and fat mass did not differ between bars (all p>0.05); both groups lost 0.3 (sd 1.2) kg lean mass (p<0.01) and 2.2 (sd 3.6) cm of waist circumference (p<0.0001) over 12 weeks; the oligofructose group reported less hunger in later weeks (p=0.04)
• Two granola bars a day carrying 10 g of gluten caused no more gut symptoms than gluten-free bars in 33 young people who felt better off gluten, difference on a 100 mm scale -0.01. — 33 adolescents and young adults, median age 20, 32 of 33 female, from a Danish population cohort, with at least four gastrointestinal symptoms and coeliac disease excluded (n = 33 randomised, 32 completed) Evidence B source
  Difference in average symptom VAS -0.01 (95% CI -2.07 to 2.05); no difference in mental health outcomes

What is still unknown

• All 4 granola glucose trials took healthy adults with fasting glucose under 7 mmol/l, so nobody with diabetes has been tested on this. — males and non-pregnant females aged 18 to 65 with BMI 21.0 to under 32.0 and fasting serum glucose under 7.0 mmol/l, recruited from a volunteer pool and web advertisements (n = 160) Evidence B source
  No participant with diabetes, pregnancy or BMI over 32 was eligible; each person took part in one study only

The bottom line

The bar studies are worth reading for what they failed to find. Twelve weeks of granola bars in place of usual snacks left weight, fat mass and energy intake unchanged in 55 adults with overweight, whichever bar they were given, and both groups lost 0.3 kg of lean mass over those weeks. As an afternoon snack in 39 adults, a granola bar raised three-hour blood glucose more than a hummus snack of the same 240 kcal. What you eat granola with may matter more than which one you buy. In 24 young women the same granola gave a 52 percent lower two-hour glucose rise with Greek yogurt than with a cultured coconut product, and the dairy breakfast carried three times the protein and four times less fibre. The label is a separate problem. Of 2937 packaged products collected in Quebec, 983 of them cookies and granola bars, 74.2 percent carried a nutrition or health claim, and 28.9 percent carried one while also crossing the threshold for a high-in warning symbol. Granola bars there scored no better on Nutri-Score in 2023 than in 2018. In a census of 11434 packaged foods in Brazil, granola bars were among the three categories where low-calorie sweeteners turned up most often, and about 83 percent of the products carrying a sweetener had added sugar as well. The heart claim an American box may print belongs to oat beta-glucan and needs 3 g of it a day, and the regulation never names granola. The EU register works the same way. Its permission to say beta-glucans lower the glucose rise after a meal is written against the fibre, 5 beta-glucan claims are authorised and 9 refused, and a search for granola returns nothing. Two questions people ask have thin answers. On gluten, 33 young people who believed they felt better without it ate two bars a day carrying 10 g of gluten and reported no more gut symptoms than on gluten-free bars, a difference of -0.01 on a 100 mm scale. Coeliac disease had been excluded in all of them, so that trial says nothing to anyone who has it. On allergy we hold one case: a woman whose reaction after a granola and oatmeal breakfast traced to storage mites living in the flaked oats, with prick tests negative for the foods themselves. Here is what we could not tell you. We found no work at all on how the nutrients in granola are absorbed. Safety rests on that single case report and one product survey, which leaves this page with no upper limit, no drug interactions, and nothing on pregnancy, children or kidney disease. Everyone in the glucose trials was a healthy adult with fasting glucose under 7 mmol/l. If you have diabetes and want to know what granola does to you, that study has not been run, and the only answer we can point you to is your own meter and the person treating you.

Sources

1. grn-r1-02 · randomised cross-over trials
   TGs1-3 elicited significantly lower glucose iAUC0-2 than CGs1-3 by 17, 18 and 17 %, respectively (similar to the 15 % reduction predicted by the pilot trial)...Neither postprandial hunger nor glucose or hunger increments 2 h after eating differed significantly between TG and CG.
   J Nutr Sci, 2022 · checked 2026-09-23
2. grn-r1-03 · randomised cross-over glycaemic index study
   whereas Western breakfast foods were all of low GI (whole-grain biscuit=54 (sem 5); whole-grain biscuit filled with peanut butter=44 (sem 3); whole-grain oat muesli=55 (sem 4); whole-grain oat protein granola=51 (sem 4); whole-grain protein cereal=49 (sem 3)). The GI of test foods negatively correlated with protein (r s -0·366), fat (r s -0·268) and dietary fibre (r s -0·422) (all P<0·001).
   Br J Nutr, 2018 · checked 2026-09-23
3. grn-r1-10 · repeated cross-sectional study
   Overall nutritional quality remained stable over time in all four main food categories (all p ≥ 0.11)...the overall nutritional quality of new products in the Sliced breads, Granola bars, and Yogurts and dairy desserts categories was similar to that of discontinued products (all p ≥ 0.06)
   Appl Physiol Nutr Metab, 2026 · checked 2026-09-23
4. grn-r1-04 · randomised cross-over trial
   The 2 h blood glucose iAUC was 52% lower after the dairy compared with nondairy treatment (P < 0.0001).
   Appl Physiol Nutr Metab, 2020 · checked 2026-09-23
5. grn-r1-01 · systematic review of glycaemic index feeding tests
   Steel-cut oats (GI=55 (se 2·5)), large-flake oats (GI=53 (se 2·0)) and muesli and granola (GI=56 (se 1·7)) elicited low to medium glycaemic response. Quick-cooking oats and instant oatmeal produced significantly higher glycaemic response (GI=71 (se 2·7) and 75 (se 2·8), respectively) than did muesli and granola or large-flake oatmeal porridge.
   Br J Nutr, 2015 · checked 2026-09-23
6. grn-r1-06 · randomised crossover trial
   Specifically, the BARS and HUMMUS led to greater 3-h postsnack blood glucose mean, AUC, and variability compared with NO SNACK (all P < 0.05). The HUMMUS snack resulted in lower postsnack blood glucose mean, AUC, and variability compared with BARS (both P < 0.05).
   J Nutr, 2020 · checked 2026-09-23
7. grn-r1-13 · regulatory register entry
   POL-HC-6331 Beta-glucans from oats and barley Consumption of beta-glucans from oats or barley as part of a meal contributes to the reduction of the blood glucose rise after that meal Authorised
   EU Register on nutrition and health claims, snapshot 2026-09-21 · checked 2026-09-23
8. grn-r1-08 · case report
   Female patient of 39-years-old was entered an emergency room with allergic cutaneous and respiratory symptoms one hour after ingesting granola and oatmeal with milk at breakfast.
   Rev Alerg Mex, 2019 · checked 2026-09-23
9. grn-r1-11 · cross-sectional study
   LCSs were most frequently added to nonalcoholic sweetened beverages, breakfast cereals, and granola bars.
   J Acad Nutr Diet, 2022 · checked 2026-09-23
10. grn-r1-09 · cross-sectional study
    Overall, 74·2 % of food products had an NHC and 28·9 % had an NHC and would require to display the FOP symbol.
    Public Health Nutr, 2026 · checked 2026-09-23
11. grn-r1-12 · codified federal regulation
    3 g or more per day of β-glucan soluble fiber from either whole oats or barley, or a combination of whole oats and barley.
    21 CFR 101.81, Health claims: Soluble fiber from certain foods and risk of coronary heart disease · checked 2026-09-23
12. grn-r1-05 · randomised controlled trial
    During the intervention, energy intake, body weight and fat mass remained similar in the Co-Bar and OF-Bar groups (all P>0·05). Both groups lost 0·3 (sd 1·2) kg lean mass (P<0·01) and reduced their waist circumference with -2·2 (sd 3·6) cm (P<0·0001) after 12 weeks.
    Br J Nutr, 2018 · checked 2026-09-23
13. grn-r1-07 · blinded randomised cross-over trial
    Compared with a placebo, gluten did not induce gastrointestinal symptoms. The difference in the average VAS was -0.01 (95% confidence interval -2.07 to 2.05).
    Aliment Pharmacol Ther, 2022 · checked 2026-09-23
14. grn-r1-02b · randomised cross-over trials, inclusion criteria
    Participants, who were allowed to participate in only one of the four studies, were males and non-pregnant females aged 18–65 years with body mass index (BMI) ≥21·0 and <32·0 kg/m² and fasting serum glucose <7·0 mmol/l (or whole blood glucose <6·3 mmol/l).
    J Nutr Sci, 2022 · checked 2026-09-23