Blueberries are not blue because of a blue pigment. Their skin holds dark pigments, and the blue comes from a waxy coating called bloom, which scatters blue and ultraviolet light. In a 2024 study, researchers grew that wax again in the lab, and the blue look came back.
A cup (148 g) of raw blueberries has 84 calories, 3.6 g of fiber and 24% of the Daily Value of vitamin K. Our data also show 242 mg of anthocyanins, the blue-to-purple pigments behind most of the research. Blueberries are one of only 4 foods in our database with a measured amount of petunidin, one of those pigments (31.5 mg per 100 g).
Most of the trial evidence comes from freeze-dried blueberry powder, not from handfuls of fresh berries. Much of it was funded by two industry groups, the US Highbush Blueberry Council and the Wild Blueberry Association of North America. We say so on each card where the paper does.
Health benefits of blueberries
The top findings from 30 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★★Slightly better artery functionIn 14 trials in healthy people, blueberries improved artery function by 1.11% (flow-mediated dilation, how well arteries widen). Powder gave 1.45% in adults with metabolic syndrome.
- ★★Little or no effect on blood pressureThe top number barely moved in 14 trials in healthy people (0.11 mm Hg) or in 6 supplement trials (0.28 mm Hg), both not significant. A pooled review of 12 trials did find a lower bottom number.
- ★★Lower fasting blood sugar in diabetesIn people with diabetes, blueberry or cranberry supplements lowered fasting blood sugar (17.72 mg/dL) and average blood sugar (HbA1c, 0.32%). The two berries were pooled, and people without diabetes saw no significant change.
- ★★Lower cholesterol and bottom blood pressure numberIn 12 pooled trials of blueberry powder, extract, fruit, juice and frozen berries, total cholesterol, LDL and the bottom blood pressure number (diastolic) fell. Blood sugar markers and body measurements did not change significantly.
- ★★Slightly better memory for events in older adultsIn older adults with memory complaints or mild cognitive impairment, pooled trials found a small gain in episodic memory, memory for events. Processing speed and working memory did not change significantly.
All 30 studies, strongest evidence first
In healthy people, blueberries improved artery function 1.11%, not blood pressure
This meta-analysis pooled 14 randomized trials in 632 healthy people, measuring artery function as flow-mediated dilation. Systolic pressure changed by only 0.11 mm Hg and diastolic by 0.46 mm Hg, neither significant. Executive function and mood did not change significantly either. The trials differed in blueberry dose, form, length and the age of the people.
Blueberry powder improved artery function 1.45%, not insulin resistance, in metabolic syndrome
This double-blind trial in 115 adults (average age 63) ran for 6 months. It compared powder equal to 1 cup (150 g) of berries a day, half a cup (75 g) and a matched placebo. The 1-cup dose also lowered arterial stiffness (augmentation index, down 2.24%) and raised HDL cholesterol in people not taking statins. Insulin resistance, the main goal, blood pressure and pulse wave velocity did not change, and half a cup had no effect. The US Highbush Blueberry Council funded the trial and supplied the berries.
Blueberry powder improved artery function, lowered systolic pressure in healthy older adults
In this double-blind trial, 61 healthy adults aged 65 to 80 took a daily 26 g of freeze-dried wild blueberry powder for 12 weeks. The powder held 302 mg of anthocyanins and equals about 178 g of fresh berries, and the placebo held none. Flow-mediated dilation rose 0.86%, 24-hour systolic pressure fell 3.59 mm Hg, and word-learning recall and task-switching accuracy improved. Brain blood flow and gut bacteria did not change, and the Wild Blueberry Association of North America gave an unrestricted grant and the test products.
Blueberry supplements did not lower blood pressure across 6 trials
This meta-analysis pooled results from 204 people. Systolic pressure changed by only 0.28 mm Hg and diastolic by 0.5 mm Hg, neither significant. The trials differed a lot from one another, and the authors call for larger, better designed trials.
Blueberry or cranberry supplements did not clearly lower blood pressure in patients
This meta-analysis of 17 articles covered people with heart or metabolic disease. Pooled systolic pressure fell by 0.81 mm Hg and diastolic by 0.15 mm Hg, neither significant. Only two of the studies found a significant drop, and the result held whatever the trial length or the age of the people. The two berries were analyzed together.
Blueberry powder did not improve memory, attention or mood in metabolic syndrome
This secondary analysis of a double-blind trial covered 115 people with metabolic syndrome over 6 months. They took freeze-dried powder equal to half or a full cup a day, and 33 people also had a 24-hour test. Self-rated calmness rose 11.6% after 1 cup, but all other mood, sleep and thinking measures were unchanged. The US Highbush Blueberry Council funded the trial.
Blueberries slightly improved episodic memory in older adults with memory problems
This meta-analysis pooled 9 randomized trials with 513 older adults with mild cognitive impairment or memory complaints. Episodic memory improved by a small amount (standardized difference 0.34), and language memory improved in people with mild cognitive impairment (0.30). Processing speed, recognition memory, visuospatial learning and working memory did not change significantly. The authors ask for larger multicenter trials.
Blueberry supplements lowered cholesterol and diastolic pressure, not blood sugar
This systematic review covered 18 randomized trials on risk factors for metabolic syndrome, and 12 of them were pooled. Total cholesterol, LDL cholesterol and diastolic blood pressure fell. Powder, extract, fruit, juice and frozen berries were all counted, and the trials differed in dose, length and the people studied. Glycemic markers and body measurements did not change significantly.
In diabetes, blueberry or cranberry supplements lowered fasting blood sugar
This meta-analysis pooled 22 randomized trials. In people with diabetes, fasting blood sugar fell 17.72 mg/dL and HbA1c 0.32%, with no effect on insulin resistance. In people without diabetes the results were not significant, apart from one sensitivity analysis for fasting glucose. The two berries were pooled, so the result does not isolate blueberries.
Blueberry supplements did not significantly change heart risk factors
This meta-analysis pooled 11 randomized trials. Triglycerides fell by 0.27 mmol/L, only a hint and not significant, and no other outcome differed. Weight loss appeared only in trials longer than 6 weeks or using blueberry powder or freeze-dried blueberry. The authors say the evidence is insufficient to show a benefit.
In postmenopausal women, blueberry powder improved artery function, not blood pressure
This placebo-controlled trial included 43 postmenopausal women aged 45 to 65 with raised blood pressure. They took 22 g of freeze-dried highbush blueberry powder a day for 12 weeks. Flow-mediated dilation, adjusted for blood flow, was 96% higher than at the start, with no change on placebo. A vitamin C infusion suggested the gain came from less oxidative stress, and blood pressure, arterial stiffness and blood markers showed no major differences. The US Highbush Blueberry Council was among the funders.
After menopause, powder cut systolic pressure from 138 to 131 mm Hg
This placebo-controlled trial gave 48 postmenopausal women with pre- or stage 1 hypertension 22 g of freeze-dried blueberry powder a day for 8 weeks. Diastolic pressure fell from 80 to 75 mm Hg. Brachial-ankle pulse wave velocity, a measure of arterial stiffness, dropped from 1,498 to 1,401 cm/second. Nitric oxide levels rose, and the placebo group did not change.
Freeze-dried blueberries cut systolic pressure 6% and diastolic 4% in metabolic syndrome
In this randomized trial, 48 obese adults, 44 of them women, had 50 g of freeze-dried blueberries a day for 8 weeks, or water. The drink was made from about 350 g of fresh berries. Oxidized LDL fell 28%, against 9% in the control group, while blood sugar and blood fats did not change. The US Highbush Blueberry Council supported the study.
Blueberry smoothies improved insulin sensitivity in obese, insulin-resistant adults
In this double-blind trial, 32 people drank blueberry or placebo smoothies twice a day for 6 weeks. Insulin sensitivity, measured with a clamp test, rose by 1.7 with blueberries and 0.4 with placebo (mg per kg of lean mass per minute). The smoothie held 22.5 g of blueberry bioactives, and inflammation markers and body fat did not change. One author received research funds from the US Highbush Blueberry Council, which also prepared the freeze-dried powder.
Blueberry smoothies improved blood vessel function but not blood pressure
In this double-blind trial, 44 adults with metabolic syndrome drank blueberry or placebo smoothies twice a day for 6 weeks. Endothelial function, the health of the vessel lining, improved: reactive hyperemia index rose 0.32, against a fall of 0.33 on placebo. Blood pressure and insulin sensitivity did not differ between the groups. The smoothie held freeze-dried blueberry powder supplied by the US Highbush Blueberry Council, which helped fund the study.
Blueberry powder lowered glucose and insulin 3 hours after a rich drink
In this double-blind trial, 45 people with metabolic syndrome had a 969-calorie high-fat, high-sugar drink. It came with 26 g of blueberry powder (equal to 1 cup) or a matched placebo. At 3 hours, insulin was 23.4 against 52.9 pmol/L and glucose 4.3 against 5.1 mmol/L. But glucose peaked higher at 1 hour (8.2 against 6.9), and artery function, arterial stiffness and blood pressure did not change. The US Highbush Blueberry Council funded the trial.
Freeze-dried blueberry powder did not improve weight, blood pressure, fats or glucose
This placebo-controlled trial gave 49 adults at risk of metabolic syndrome 50 g of freeze-dried blueberry powder a day for 8 weeks. Insulin resistance did not improve either, and a triglyceride difference disappeared after adjusting for age, sex, BMI and starting values. The powder did change 49 genes and 35 metabolites, mostly in immune pathways, and the authors say longer or higher doses may be needed. The US Highbush Blueberry Council funded the study and supplied the powder.
Juice did not change blood sugar, insulin or blood pressure in at-risk women
In this crossover trial, 19 women aged 39 to 64 at risk of type 2 diabetes drank wild blueberry juice. They had 240 mL a day for 7 days, juice rather than whole berries. Systolic pressure trended lower (116.0 against 120.8 mm Hg), but not significantly. Nitrate and nitrite, a sign of nitric oxide, rose from 2.9 to 4.1 µM. The Wild Blueberry Association of North America gave grant support to several authors.
Blueberries did not change blood pressure or cholesterol in healthy young adults
This crossover trial compared fresh blueberries, freeze-dried powder and a control in 37 healthy young adults, each for 1 week. Arterial stiffness did not change either. Blood nitrite rose 68.66% after whole blueberries and 4.34% after powder, but the differences were not significant, and the two forms did not differ. The authors report no outside funding.
Blueberry powder improved word-finding and memory interference in people with memory complaints
This randomized trial covered overweight men and women aged 50 to 65 with memory complaints (subjective cognitive decline) and insulin resistance. The blueberry group scored better on lexical access, or word-finding, and on memory interference. They also reported fewer memory-encoding problems in daily life, and high insulin levels fell toward normal. The US Highbush Blueberry Council funded the trial and supplied the powder.
Wild blueberry powder improved processing speed in mild cognitive decline
This double-blind trial gave freeze-dried wild blueberry powder for 6 months to 44 older adults with cognitive issues, against 42 on placebo. A reference group of 45 people had no memory problems, and the blueberry group rose up to their level. Brain-wave recordings agreed with the speed-of-processing result, and the gain was biggest in people aged 75 to 80. The abstract reports gains in speed of processing only.
Freeze-dried blueberry cut memory errors and task-switching cost, not gait or balance
In this double-blind trial, 37 adults aged 60 to 75 (13 men and 24 women) took blueberry or a placebo for 90 days. The daily dose was 24 g of freeze-dried blueberry, equal to 1 cup of fresh berries. The blueberry group made fewer repetition errors on a verbal learning test and had a smaller switch cost on a task-switching test. Gait and balance did not improve, and the US Highbush Blueberry Council was among the funders.
A single blueberry drink lowered after-meal glucose and insulin, kept word recognition
In this crossover trial, 35 adults aged 40 to 65 had breakfast with a drink equal to 1 cup of berries or a matched placebo. They were followed for 8 hours. Glucose and insulin were lower over the first 2 hours, and responses on a demanding Go/No-Go task were faster at 4 and 8 hours. Triglycerides did not change, and the Wild Blueberry Association of North America funded the study.
3 extra weekly blueberry servings went with 26% lower diabetes risk
These three large US cohorts were the Nurses’ Health Study, Nurses’ Health Study II and Health Professionals Follow-up Study. They recorded 12,198 cases of type 2 diabetes over 3,464,641 person-years, and the hazard ratio for blueberries was 0.74. Grapes and raisins (0.88) and apples and pears (0.93) also went with lower risk, while strawberries showed no link (1.03). Fruit juice went with higher risk (1.08), and a link is not proof of cause.
Older women eating more blueberries had slower cognitive decline
This Nurses’ Health Study analysis covered 16,010 women aged 70 or older, tested twice 2 years apart, with diet averaged from 1980. Comparing the extremes of blueberry intake, the difference on a global score was 0.04, equal to up to 2.5 years of delayed aging. Strawberries showed a similar link (0.03), and the California Strawberry Commission funded the work in part. Food questionnaires are imperfect, and a link is not proof of cause.
Young women eating most anthocyanins had 32% lower heart attack risk
The Nurses’ Health Study II followed 93,600 women aged 25 to 42 for 18 years, with 405 heart attacks. Women with the highest anthocyanin intake had 0.68 times the risk of those with the lowest. More than 3 servings a week of blueberries and strawberries together only tended to lower risk (0.66), and this was not significant. Anthocyanins come from many foods, and a link is not proof of cause.
Top anthocyanin intake went with 8% lower risk of high blood pressure
This pooled analysis of three US cohorts followed people for 14 years, with 29,018 cases in women and 5,629 in men. In the top fifth of intake, anthocyanins came mainly from blueberries and strawberries. The drop was 12% in people aged 60 or younger and not significant in older people (0.96). Intake came from food questionnaires, and a link is not proof of cause.
UK adults eating the most flavonoid-rich foods had 28% lower dementia risk
This UK Biobank analysis followed 121,986 adults for 9.2 years, with 882 cases of dementia (hazard ratio 0.72). The score covers tea, red wine and berries together, not blueberries alone. The biggest drop (0.62) came with at least 2 of these a day: 5 servings of tea, 1 of red wine and 0.5 of berries. One author reported grants and fees from the US Highbush Blueberry Council.
Frozen blueberries kept their anthocyanins for 3 months; drying cut them
This lab test on highbush blueberries is a measurement of the fruit, not a study in people. Fresh berries held 7.2 mg of anthocyanins per gram of dry matter, and frozen berries stored at −20 °C showed no significant drop. Drying cut anthocyanins by 41 to 49%. Antioxidant activity did not differ between fresh, dried and frozen berries.
Blueberry powder kept glucose tolerance normal and prevented fatty liver in mice
This was a study in mice, not people, after chemically induced menopause. The mice ate a high-fat diet with or without 4% blueberry powder for 12 weeks. The berry-fed mice were still heavier and fatter than controls, so the benefits did not come from weight loss.
Who should be careful with blueberries
Most people can eat blueberries freely. Take a little care if one of these applies:
- Warfarin. Blueberries contain vitamin K (28.6 µg in a cup, 24% of the Daily Value). A Cambridge University Hospitals leaflet lists them among vitamin K fruits. You do not need to avoid them: keep the amount steady from week to week. Tell your clinic before starting a daily smoothie or powder.
- Blood sugar. A cup (148 g) has 21.4 g of carbohydrate, 14.7 g of it sugars, and a glycemic index of 53 in our data. That is a modest load and a small concern. But if you count carbs or take diabetes medicine, count blueberries too and watch your own readings.
- Irritable bowel syndrome. Monash University lists blueberries among its low FODMAP fruit examples, so they are usually an easy pick. Its app gives tested serving sizes if you are sensitive.
How to choose, store and eat blueberries
- Fresh or frozen: in a lab test, frozen blueberries kept their anthocyanins for 3 months, so frozen is a fair swap for fresh.
- Dried: drying cut anthocyanins by 41 to 49% in the same lab test, so dried berries are a different food from fresh.
- As in the trials: 1 cup a day, given as 26 g of powder, improved artery function over 6 months. Half a cup did not. Most trial powders were freeze-dried, so a handful of berries is not an exact match.
Pick plump, firm berries with a dark blue color and a silvery, waxy bloom, and skip dull or soft ones. Keep them unwashed in a covered container in the fridge for 3 to 5 days, and rinse them just before eating.
Residues are no reason to skip them. In USDA tests of 482 fresh blueberry samples in 2022, 2 had a residue above the legal limit, and none of 51 frozen samples did.
Sources
- Dietary advice for patients taking warfarin. Cambridge University Hospitals NHS Foundation Trust.
- Anticoagulant medicines: considerations. NHS.
- High and low FODMAP foods. Monash University FODMAP.
- Blueberries, raw (FDC 171711). USDA FoodData Central.
- Curtis PJ, van der Velpen V, Berends L, et al. Blueberries improve biomarkers of cardiometabolic function in participants with metabolic syndrome: results from a 6-month, double-blind, randomized controlled trial. Am J Clin Nutr. 2019.
- Lohachoompol V, Srzednicki G, Craske J. The change of total anthocyanins in blueberries and their antioxidant effect after drying and freezing. J Biomed Biotechnol. 2004.
- Selecting, storing, and serving Ohio blueberries, blackberries, and raspberries. Ohio State University Extension.
- Pesticide Data Program annual summary, calendar year 2022. USDA Agricultural Marketing Service.
History of blueberries
Two wild species supplied most of the blueberries people eat. The northern highbush, Vaccinium corymbosum, is the most common cultivated blueberry in North America. The lowbush, Vaccinium angustifolium, grows wild from the Atlantic provinces of Canada west to Quebec and south to Michigan and West Virginia.
People managed wild blueberries long before anyone farmed them. Native Americans regularly burned away trees and shrubs in parts of eastern Maine to stimulate blueberry growth. Growers still burn lowbush fields every few years. Acadian French even calls a blueberry field a brûlis, from the word for burnt.
Growing blueberries as a crop is only about a century old. In 1910 the US Department of Agriculture botanist Frederick Coville published Experiments in Blueberry Culture (Bulletin 193). He had found that blueberries need acidic soil and cannot pollinate themselves.
Elizabeth White, whose family ran a large cranberry farm at Whitesbog in New Jersey, read it and invited him to her land in 1911.
White paid her neighbors in the New Jersey Pine Barrens for wild plants with large berries. A good bush was named after the person who found it. Of about 100 wild plants tested over five years, only a few were worth breeding.
The best, found by Rube Leek, was named Rubel, and farmers still grow it. The first containers of cultivated blueberries went to market in 1916.
White also sold the first fruit wrapped in cellophane, an idea she took from candy, and she organized the first blueberry growers’ cooperative. According to the blueberry breeder James Hancock, about 75% of blueberry acreage in the 1990s grew Coville’s hybrids. In 2024 the United States grew 29% of the world’s blueberries, ahead of Peru with 25% and Canada with 12%.
Sources
- Blueberry. Wikipedia.
- Vaccinium angustifolium. Wikipedia.
- Coville FV. Experiments in blueberry culture. US Department of Agriculture, Bureau of Plant Industry, Bulletin 193. 1910.
- The delicious origins of the domesticated blueberry. JSTOR Daily.
- Frederick Vernon Coville. Wikipedia.
- Elizabeth Coleman White. Wikipedia.
- Middleton R, Tunstad SA, Knapp A, et al. Self-assembled, disordered structural color from fruit wax bloom. Sci Adv. 2024.
Frequently asked questions about blueberries
Are blueberries good for you?
For most people, yes, but the evidence is moderate at best. A cup (148 g) has 84 calories, 3.6 g of fiber and 24% of the Daily Value of vitamin K. In a meta-analysis of 14 trials, blueberries improved artery function by 1.11% but did not change blood pressure. No study here reaches strong evidence, and many were funded by blueberry industry groups.
How many blueberries should you eat a day?
No study here sets an ideal amount. The 6-month trial that improved artery function used powder equal to 1 cup (150 g) a day. Half a cup (75 g) had no effect. Other trials used 22 to 26 g of freeze-dried powder a day for 8 to 13 weeks.
Are frozen blueberries as healthy as fresh?
Probably, but no trial here compares them directly. In a lab test, frozen blueberries kept their anthocyanins for 3 months, while drying cut them by 41 to 49%. In a crossover trial of 37 healthy adults, fresh blueberries and freeze-dried powder did not differ in their effect on blood pressure or cholesterol.
Do blueberries improve memory?
Maybe a little, but the results are mixed. A meta-analysis of 9 trials in 513 older adults with mild cognitive impairment found better episodic memory (0.34) but no change in processing speed. A 6-month trial in people with metabolic syndrome found no gain in memory, attention or mood. Older women who ate more blueberries had slower decline in a cohort study (0.04), which cannot prove cause.
Do blueberries lower blood pressure?
Not reliably. Systolic pressure changed only 0.28 mm Hg (6 trials), 0.81 mm Hg (17 articles) and 0.11 mm Hg (14 trials) in meta-analyses, none significant. Single trials did find drops, such as 3.59 mm Hg over 24 hours in older adults taking 26 g of powder. So the effect may depend on who is studied.
Are blueberries good for people with diabetes?
They can fit, but the evidence is mixed. In a meta-analysis, blueberry or cranberry supplements lowered fasting blood sugar by 17.72 mg/dL and HbA1c by 0.32% in people with diabetes. Trials on insulin sensitivity split: one improved it, while a 6-month trial in 115 people and another in 44 did not. Check portions and choices with your care team.
Are blueberries high in sugar?
A cup (148 g) has 14.7 g of sugars, about 10 g per 100 g, along with 3.6 g of fiber. Our data give a glycemic index of 53. In three large US cohorts, 3 more servings of blueberries a week went with a 26% lower risk of type 2 diabetes. Fruit juice went with a higher risk.
Are wild blueberries healthier than regular ones?
No trial here compares them, so nobody can say, though both have been tested. Wild blueberry powder (26 g a day) raised artery function by 0.86% in older adults. Highbush blueberry powder (1 cup a day) raised it by 1.45% in people with metabolic syndrome. The doses and people differed, so the two results cannot be ranked.