Contents
What it is
The blueberry is the fruit of a shrub in the heath family. It is native to North America and is a relatively new crop, only seriously cultivated from the twentieth century. The pale dusty film on the skin is the bloom, and the fresher the fruit the better it survives. The near-navy colour comes from anthocyanin. Blueberries are eaten fresh, and because freezing does not turn them to mush a great deal of the crop is sold frozen; they also go into jam and baking. Washing shortens their life, so rinse them just before eating.
Scientific name Vaccinium
Blueberries attract an unusual amount of research because of their anthocyanin content. The deep blue-purple pigment in the skin is both a potent antioxidant and, it seems, something that acts directly on the cells lining your blood vessels.
"Superfood" is a marketing word, but for blueberries the human evidence is genuinely stacked up. Just remember that most of it involves 100–250 g a day — about a cup — eaten consistently for weeks.
Key benefits
- Moderate evidence
It supports memory and cognition
The results conflict. In a randomised trial of 61 healthy adults aged 65–80, twelve weeks of 26 g freeze-dried powder (equivalent to 178 g of fresh berries) improved immediate recall and task-switching accuracy. But a meta-analysis pooling randomised trials concluded there was no significant effect on executive function or mood in healthy people. One well-run trial and the pooled analysis point in different directions.[1]
- Moderate evidence
It improves vascular function
A meta-analysis of randomised trials found blueberry intake improved endothelial function (flow-mediated dilation) by 1.11 percentage points. The explanation involves anthocyanins acting on the nitric oxide pathway that widens vessels. The same analysis found no significant change in systolic or diastolic blood pressure.[2]
- Early research
It lowers oxidative stress and inflammation
The evidence is a single randomised trial: 40 postmenopausal women with pre- or stage-1 hypertension took 22 g of freeze-dried powder for eight weeks. A marker of oxidative DNA damage (8-OHdG) was lower at four weeks but the difference had gone by eight weeks, and none of the other inflammation or antioxidant markers measured moved at all. There is a direction, but it did not hold.[3]
- Early research
It raises blood sugar slowly for something this sweet
Despite the sugar, blueberries have a relatively low glycaemic index. But a meta-analysis of randomised trials found no significant change in glycaemic markers — in contrast to the drops it did find in total and LDL cholesterol. The low glycaemic index is a property of the fruit; evidence that it translates into better glucose control is still thin.[4]
How to eat it well
- A handful a day (80–150 g) lands close to the amounts used in research. Small and daily beats large and occasional.
- Frozen is fine. Flash freezing preserves anthocyanins well, and some reports suggest the ruptured cell walls even improve absorption.
- Rinse and eat. The pale bloom on the skin is natural wax, not pesticide — no need to scrub it off.
- Spooned over yoghurt, oatmeal or a salad, they get eaten without any cooking at all.
- Long cooking degrades anthocyanins, so fresh or frozen beats jam.
How to read the grades
Each benefit carries a label showing how far research on people supports it. Grades differ between items even within the same ingredient.
- Nutrition data
- A fact verifiable from food composition databases or health authorities. This is a different kind of statement from a clinical effect.
- Strong evidence
- Consistently confirmed across randomised controlled trials or meta-analyses.
- Moderate evidence
- Human studies exist, but effect sizes are small or results are mixed.
- Early research
- Cell or animal work, or small preliminary studies.
- Not established
- Commonly claimed, but not confirmed in studies on people.
What to watch out for
- If you take warfarin, keep vitamin K intake steady rather than suddenly increasing it.
- They do contain fruit sugar, so set a daily amount if you are managing blood glucose.
- People sensitive to salicylates occasionally get hives or digestive symptoms.
- A large portion at once can cause bloating or loose stools thanks to the fibre.
Nutrition
Approximate values per 100 g edible portion.
- Calories
- 57 kcal3%
- Carbohydrates
- 14.5 g5%
- Sugars
- 10.0 g
- Fiber
- 2.4 g9%
- Protein
- 0.7 g1%
- Vitamin C
- 9.7 mg11%
- Vitamin K
- 19.3 µg16%
- Manganese
- 0.34 mg15%
Percentages are of the US FDA Daily Value for adults and children 4 and over. National reference intakes differ by sex and age.
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Sources
The databases and health authorities this article's nutrition figures and health statements draw on.
- 1Wild blueberry (poly)phenols can improve vascular function and cognitive performance in healthy older individuals: a double-blind randomized controlled trialClinical trialWood E, et al. Am J Clin Nutr 2023PMID 36972800
- 2Blueberry consumption enhances vascular function but not cognitive abilities in healthy individuals: a systematic review and meta-analysisMeta-analysisHe Y, et al. Nutr Res 2026PMID 41974068
- 3Effects of daily blueberry consumption on circulating biomarkers of oxidative stress, inflammation, and antioxidant defense in postmenopausal women with pre- and stage 1-hypertension: a randomized controlled trialClinical trialJohnson SA, et al. Food Funct 2017PMID 28059417
- 4Blueberry intervention improves metabolic syndrome risk factors: systematic review and meta-analysisMeta-analysisCarvalho MF, et al. Nutr Res 2021PMID 34139510
- 5USDA FoodData CentralFood composition database
- 6NIH Office of Dietary SupplementsHealth authority
- 7PubMedResearch literature
