Blueberries are enjoyed all around the world for their sweet taste and nutritional benefits. But they actually have many potential health benefits such as reducing the risk for heart complications, improving cognitive function, and helping control blood sugar while being generally safe at food doses. Read below to learn more about these fruits and how they may improve your health.
Anthocyanins are a type of flavonoids with potential antioxidant, anticancer, and anti-obesity properties .
However, anthocyanins are very unstable under normal physical conditions and, as a result, are not easily absorbed by the body. Only a small percentage (0.5%-1%) of anthocyanins from food reach the bloodstream [9, 10].
Most health benefits of blueberries are caused by anthocyanins directly in the gut or by traveling to the liver, where they are broken down into metabolites (methylated, sulfated, or glucuronidated conjugates) or just reach the bloodstream unchanged .
Anthocyanins have multiple beneficial and protective effects on the body, especially for the prevention of oxidation or damage to biological structures like fats, proteins, and nucleic acids .
Anthocyanins produce a wide range of colors in plant tissues. They neutralize the potentially harmful effects of free radicals in the body .
Anthocyanins can also detoxify heavy metals (chelation) and exert their effects through direct protein binding. Lab tests have demonstrated that anthocyanins stimulate detoxifying enzymes and antioxidation in cultured cells [20, 21].
- Packed with antioxidant compounds
- Pleasant flavor and easy to snack on
- May improve brain function
- May help prevent heart disease
- May help control blood sugar levels
- May improve arthritis
- May improve mood
- May reduce wrinkles
- Generally safe at normal food doses
- Insufficient evidence for some benefits
- May reduce blood sugar, clotting, and pressure too much
- Tannins may cause digestive issues
- Oxalates may cause kidney stones
- Benzoates may trigger allergic conditions
In a clinical trial on 9 elderly people with early memory decline, blueberry supplementation for 12 weeks improved memory and mitigated neurodegeneration. In another trial on 14 elderly people, blueberry supplementation improved working memory and activity, and blood flow in several brain regions. Dietary blueberry also improved verbal learning and task switching in another trial on 37 elderly people [22, 23, 24].
Similarly, blueberry juice (500 mL/day) reduced the impairment in short-term memory and selective and divided attention caused by general anesthesia in a clinical trial on 26 people .
In another trial on 122 elderly adults, wild blueberry powder (500-100 mg/day) improved working memory in 3 months .
A berry beverage with blueberries, blackcurrant, elderberries, lingonberries, strawberries, and tomatoes had similar effects on working memory in a clinical trial on 40 healthy elderly people .
Blueberries didn’t improve performance in a working memory test but increased the activation of several brain regions (left pre-central gyrus, left middle frontal gyrus, and left inferior parietal lobe) during the test in a clinical trial on 18 elderly people with mild cognitive impairment .
In a clinical trial on 21 children aged 7-10, blueberries improved problem-solving and memory tasks. Higher blueberry consumption led to better testing scores. A blueberry drink improved delayed word recall in another trial on 14 children aged 8-10 [29, 30].
- Can cross the blood-brain barrier and travel to specific areas of the brain (hippocampus) that are associated with learning and memory .
- Inhibit several enzymes in the brain (JNKs, ASK1, and p38 pathways), which decreases inflammation and promotes neuronal health .
- Enhance brain function by stimulating the growth and development of neurons (through changes in synaptic plasticity and neurogenesis) [36, 37].
All in all, limited evidence suggests that blueberries may improve some cognitive areas in both healthy people and those with cognitive impairment. Further research should establish how to use them therapeutically.
A berry beverage with blueberries, blackcurrant, elderberries, lingonberries, strawberries, and tomatoes lowered total and “bad” cholesterol (LDL) in a clinical trial on 40 healthy elderly people .
Blueberry polyphenols have antioxidant properties, which may protect against heart disease .
Oxidative stress in heart cells not only causes inflammation but also causes heart muscle thickening (myocardial hypertrophy), which leads to cell death and heart disease .
In a clinical trial on 48 people with metabolic syndrome, dietary blueberries reduced the levels of oxidized LDL and an oxidative stress marker (MDA). This suggests blueberries may help prevent clogged arteries .
Oxidative stress in the kidneys and blood vessels also contributes to increased blood pressure. Blueberries are rich in anthocyanins and vitamin C, which reduce oxidative stress and lower blood pressure .
In a clinical trial on 16 young cigarette smokers, blueberry consumption helped counteract the increased blood pressure caused by smoking. In another trial on 24 people, blueberry intake improved blood vessel function in both smokers and non-smokers but had no effect on blood pressure [45, 46].
Daily blueberry intake also reduced artery stiffness in a clinical trial on 25 healthy people .
In a clinical trial on 44 people with metabolic syndrome, daily consumption of blueberries for 6 weeks didn’t lower blood pressure but improved blood vessel function .
Daily blueberry consumption for 8 weeks lowered blood pressure and reduced artery stiffness in a clinical trial on 48 postmenopausal women .
Similarly, wild blueberry powder (500-100 mg/day) lowered blood pressure after 6 months in a clinical trial on 122 elderly people .
Again, limited evidence suggests that blueberries may help prevent heart disease by lowering blood cholesterol and improving blood vessel function. You may discuss with your doctor if including them in your diet may help. However, remember that you should never take blueberries in place of what your doctor recommends or prescribes.
Consumption of blueberries may lower the risk of developing type 2 diabetes .
Flavonoids in blueberries (flavonols, flavones, flavanones, flavan-3-ols, and anthocyanins) increase insulin sensitivity in the pancreas, liver, and muscles decreasing glucose concentration and the risk of type 2 diabetes .
In a small trial on 17 healthy people, blueberry consumption had no effect on glucose metabolism but did increase the levels of a protein that controls insulin secretion by the pancreas (pancreatic polypeptide) .
In another trial on 14 healthy people, a high blueberry dose (75 g) improved the antioxidant capacity after a high-carbohydrate breakfast. Blueberries also reduced inflammation after a similar breakfast in another trial on 23 healthy people [52, 53].
In a clinical trial on 32 obese, insulin-resistant people, blueberry intake significantly improved insulin sensitivity without producing any changes in body weight, fat percentage, or energy intake .
In another trial on 30 diabetic children, a supplement with blueberries and sea buckthorn improved their antioxidant status and reduced a marker of poor blood sugar control (glycated hemoglobin) .
In cell-based studies, blueberry extracts showed both insulin-like properties and protection from glucose toxicity. These extracts also enhance the growth and regeneration of beta cells in the pancreas, which is responsible for the secretion of insulin .
To sum up, limited evidence suggests that blueberries may improve blood sugar control and protect from oxidative damage that may lead to health complications. You may use them for this purpose if your doctor determines that they may help as a complementary strategy. Never take blueberries as a replacement for the antidiabetic medication prescribed by your doctor.
In a clinical trial on 63 people with knee osteoarthritis, consuming freeze-dried blueberry powder (40 g/day) reduced joint pain, stiffness, and difficulty to perform daily activities while improving gait performance .
In another trial on over 200 young people with arthritis of unknown cause (juvenile idiopathic arthritis), drinking 50 mL blueberry juice per day enhanced the therapeutic effects of the immunosuppressant etanercept .
Although the results are promising, 2 clinical trials cannot be considered sufficient evidence to claim for certain that blueberries improve arthritis. Further clinical research is needed to confirm these preliminary findings.
In 2 small trials on 21 young adults and 50 children (aged 7-10), a flavonoid-rich blueberry drink increased their propensity to experience positive emotions and interact with others in a positive way .
In another trial on 41 pregnant women, a supplement with blueberry juice and the amino acids tryptophan and tyrosine reduced vulnerability to sadness during the peak of the postpartum blues (3-5 days after giving birth) .
Two small clinical trials are insufficient to support this use of blueberries. Larger, more robust clinical trials are needed to evaluate their effectiveness in people with mood disorders.
In a clinical trial on 20 type 2 diabetic women aged 55+ years, blueberry extract and C-xyloside application to the skin for 12 weeks resulted in significant improvement in skin firmness, wrinkles, and hydration .
Two small clinical trials using blueberries in combination with other compounds are clearly insufficient to back this health benefit. More clinical trials using blueberries alone are warranted.
No clinical evidence supports the use of blueberries for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies should not be interpreted as supportive of any health benefit.
Blueberries are often recommended and used to prevent urinary infections (UTIs) .
In petri dishes, wild blueberry extracts inhibited the growth of the main bacteria responsible for UTIs (E. Coli) .
Although no clinical trials have been carried out on people with UTIs given blueberries, these fruits share many chemical compounds (including anthocyanidins and proanthocyanidins) with cranberries. Multiple clinical trials have shown that cranberries may help prevent recurrent UTIs in women [71, 69].
Fruits such as blueberries with a high fiber content increase satiety and decrease fat storage .
Also, blueberries are rich in anthocyanins, which have beneficial effects on obesity and related metabolic complications .
Blueberry husks supplemented with probiotics (B. infantis, L. gasseri, and L. plantarum) had anti-inflammatory effects in the gut of rats with colitis better than either the husks or the probiotics alone [84, 85].
The husks suppressed inflammatory responses by decreasing inflammatory cytokines and macrophage activity and alleviated symptoms such as bleeding and pain, while the probiotics. Their polyphenols also have antimicrobial effects on harmful bacteria (Enterobacteriaceae) linked to inflammatory bowel disease [84, 85].
Supplementation with probiotics suppresses the growth of harmful bacteria and restores the healthy composition and function of the gut .
The buildup of heavy metals such as arsenic, cadmium, lead, and mercury in the body is toxic because they produce oxidative stress and affect essential functions .
Mice fed with blueberry extracts exhibited less buildup of cadmium in the liver, resulting in a reduced toxicity .
Blueberries have been shown to activate genes involved in anti-aging and decreasing brain function decline :
- SOD produces an enzyme (superoxide dismutase) that has anti-oxidation effects and breaks down cell-damaging molecules called superoxide radicals.
- CAT produces an enzyme (catalase) that protects the body against oxidative stress by breaking down hydrogen peroxide.
Below, we will discuss some preliminary research on the potential anticancer effects of blueberries. It’s still in the animal and cell stage and further clinical studies have yet to determine if this fruit is useful in cancer therapies.
Do not under any circumstances attempt to replace conventional cancer therapies with blueberries or any other foods or supplements. If you want to use them as a supportive measure, talk to your doctor to avoid any unexpected interactions.
Gallic acid from blueberries stopped the spread of cancer cells from the main tumor to other parts of the body by stopping transmission and inducing cell death in mice .
Blueberries are rich in other compounds (flavopiridol, ellagic acid, anethole, and resveratrol) with cancer-preventing properties. These compounds inhibit cancer communication (NF-κB signaling), preventing normal cells from becoming cancerous .
Anthocyanins in blueberries inhibited colon cancer cell growth and increased cell death in cell-based studies .
Anthocyanins are also able to inhibit cellular protein synthesis and alter DNA in cancer cells .
Blueberries slowed colorectal tumor progression in male but not in female rats .
While blueberries are generally safe when consumed at normal food doses, their overconsumption may:
- Lower blood sugar too much: blueberries are rich in anthocyanins with glucose-lowering effects. This can cause the blood sugar levels to drop too low in diabetic people on antidiabetic medication .
- Prevent blood clotting: resveratrol can decrease blood clotting by inhibiting the primary initiation of the blood clotting cascade (tissue factor). This increases the risk of bleeding in people with blood clotting disorders, taking blood thinners, or with a scheduled surgical procedure .
- Lower blood pressure too much: vitamin E and resveratrol can widen the blood vessels, ultimately lowering blood pressure. This effect can be dangerous in people with low blood pressure or taking blood pressure-lowering medication [105, 106, 107].
Additionally, blueberries have some constituents with the potential to cause adverse effects. These include:
- Tannins (hydrolyzable and condensed), which can inhibit digestion and cause digestive and gut issues [73, 108].
- Oxalates, which can bind to calcium and form kidney stones [109, 110, 111].
- Benzoates, which have been associated with chronic hives (urticaria), asthma, atopic dermatitis, rhinitis, and anaphylaxis [112, 113].
Anthocyanins from blueberries can alter the expression of many genes involved in fat breakdown .
Other genes that may be affected by blueberry consumption include:
- RBP4 encodes the main vitamin A transport protein, which also acts as a fat cell transmission molecule (adipokine) in the liver. Blueberry consumption decreases the blood levels of this protein .
- GLUT4 encodes an insulin-dependent glucose transporter. Consumption of blueberries increases insulin sensitivity by increasing the production of this transporter .
- Anthocyanins from blueberries enhance the secretion of a fat cell transmission molecule (adipokine) through stimulation of the PPARγ gene .
- SERPINE1 encodes the protein PAI-1, which promotes blood clotting (thrombosis). Anthocyanins decrease the production of this protein .
- NQO1 encodes an enzyme that functions as an antioxidant. Consumption of blueberries promotes the production of this protein .
- Some variants of the CYP1B1 gene are more sensitive to the protective effects of blueberries against DNA damage than others .