Blueberry

Common Name: Blueberry, Highbush Blueberry

Scientific Name: Vaccinium corymbosum L.

History and Origin

Blueberry belongs to the family Ericaceae. This plant is native to the USA and Southern Canada, growing wild in hilly and woodland regions. The shrubs are medium-sized and bear clusters of dark blue to purple fruit. The USA is the pioneer producer of blubbery. However, the cultivation has now proliferated to Europe, Asia, Africa, and Australia.

The three prominent varieties of the plant are highbush (V. corymbosum, V. ashei), lowbush (V. angustifolium), and evergreen (V. darrowii). ⁽¹⁾

Highbush blueberry is one of the most commercially significant berry crops. European cultivation of highbush blueberry began after 1920, in the Netherlands. In the following years, cultivation spread to Poland and Germany. Production of this crop is on its rise due to the increasing consumer demand for healthy food like the antioxidant-rich blueberry.

Today, European highbush blueberry production is mainly concentrated in Germany, Poland, France, the Netherlands, Lithuania, Romania, Italy, and Spain. ⁽²⁾

Blueberry Plant Structure

Highbush blueberry is a crown-forming shrub with 6 to 12 feet tall. The common name refers to the relatively tall stature of these plants. Twigs are yellow-green (reddish in winter), which are covered with small wart-like dots. Leaves are deciduous, alternate, simple, elliptic or ovate, 2.5 to 8.5 cm long, and slightly waxy above with pubescence (hairs) at least on the veins beneath. The white or pink-tinged flowers are small and urn-shaped with 5 petals. Fruiting occurs about 62 days after flowering. Fruits are blue-black berries with many seeds. ⁽³⁾

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The photo of Vaccinium corymbosum The photo of blueberry fruits

Blueberry Health Benefits

1. Promoting Weight Loss

Scientists studied the effect of a blueberry-enriched powder mixed into the rat diet, as part of either a low or a high-fat diet. They performed the test between the rats consuming the enriched powder and the control rats receiving no blueberries. The rats that were fed by a diet containing blueberry showed a significant reduction in their abdominal fats, triglycerides, and cholesterol levels after 90 days. ^{(4, 5)}

According to a study published in the Journal of medicinal food in 2012, polyphenols of blueberry have been shown to fight adipogenesis, which is the development of fat cells, and induce lipolysis, which is the breakdown of lipids (fat). The reduction of fat cells in rats fed with high and low doses of blueberry were 73% and 27%, respectively. ^{(6, 7)}

Catechin of blueberry reduces abdominal fat and body weight. This component activates the fat-burning genes in the fat cells around the stomach so that it helps to lose weight and fat. Blueberry is a low-calorie fruit and is high in both fiber and water. One cup of blueberry contains 3.6 grams of fiber and 125 grams of water. Its fiber slows the digestion of food and staves off hunger, therefore leads to weight loss. ⁽⁸⁾

2. Improving Brain Function

According to a study published in the Journal of Agricultural and Food Chemistry in 2010, consumption of blueberry or its supplements for 12 weeks improves brain and memory function in elderlies with early memory decline. This is the first human trial assessing the potential benefit of blueberry supplementation on neurocognitive function in older adults with increased risk for dementia. Blueberry anthocyanin increases neuronal signaling in brain centers mediating memory function. The experiment indicated that daily consumption of blueberry improved the learning process and word list recall in elderlies after 12 weeks; it also reduced depressive symptoms and glucose levels. ⁽⁹⁾

3. Regulating Blood Cholesterol Levels

In a study on children with heterozygous familial hypercholesterolemia (HeFH), 10 patients (group A) received blueberry tea (32 mg/kg/day anthocyanins) for 6 months. The results were compared with the control group (10 healthy children, aged between 7 and 11 years) and with group B (10 patients who did not receive blueberry tea).

After one month of blueberry tea consumption, there were no significant changes in lipid level and antioxidative status.

After three and six months, total and LDL cholesterol levels significantly changed in group A.

After 6 months, HDL cholesterol (48.78%), and antioxidants increased and lipid peroxidation products decreased in group A. ⁽¹⁰⁾

One research shows that the daily intake of 50g of blueberry reduced LDL oxidation by 27% over eight weeks in obese people.

Another study shows that consumption of 75 grams of blueberry with a main meal reduces LDL oxidation significantly. ⁽¹¹⁾

4. Regulating Blood Glucose Levels

One cup (148 grams) of blueberry contains 3.6 grams of fiber. ⁽¹²⁾Blueberry anthocyanin improves insulin sensitivity and lowers the risk of metabolic syndrome. In a study on 32 obese subjects with insulin resistance, it was observed that blueberry improved insulin sensitivity and lowered the risk of metabolic syndrome and type 2 diabetes. ^{(11, 13)}

5. Regulating Blood Pressure

According to an 8-week study on obese people, the daily intake of 50 gr of blueberry reduced blood pressure by 4 to 6%. ^{(11, 14)} Another study confirms this effect, especially in postmenopausal women. ⁽¹¹⁾

The results of a study showed blueberry is helpful in reducing arterial stiffness and high blood pressure. Regular consumption of blueberry decreases the risk of pre-hypertension and hypertension disease. The results published in the Journal of the Academy of Nutrition and Dietetics in 2015 indicated that consumption of 22 grams of freeze-dried blueberry powder (equivalent to one cup of fresh blueberry) for a period of eight weeks decreased systolic and diastolic blood pressure in 48 postmenopausal women with pre- and stage-1 hypertension. ^{(15, 16)}

6. Improving Eyesight

In one study, to evaluate the protective effect of blueberry anthocyanins on retinal pigment epithelium (RPE) cells, in vitro cell models of replicative senescent and light-induced damage were established. After purification and fractionation, blueberry anthocyanin extracts (BAE) were yielded with total anthocyanin content and were used.

The results show that BAE is beneficial to RPE cells by protecting these cells against light-induced damage through the suppression of ageing and apoptosis as well as the down-regulation of the over-expressed vascular endothelial growth factor (VEGF) to a normal level.

Malvidin glycosides have been reported to be the predominant anthocyanins found in the eyes after blueberry consumption, and have been confirmed as the main antioxidant constituents in blueberry anthocyanins, representing > 38% of the total anthocyanin content of the fruit. So, malvidin glycosides may be the main bioactive anthocyanins that protect RPE cells against ageing and light-induced damage. ⁽¹⁷⁾

What Are Blueberry Side Effects?

Blueberry fruit is LIKELY SAFE when used in amounts commonly found in foods. But not enough is known about the safety of the larger amounts used for medicine.

So, stay on the safe side and stick to normal food amounts if you are pregnant or breast-feeding.

2. Diabetes

Blueberry may reduce blood sugar levels in people with diabetes. It is important to look for any sign of low blood sugar (hypoglycemia) and monitor your blood sugar level closely if you have diabetes. The dose of your diabetes medications may need to be adjusted by your healthcare provider.

3. Surgery

Blueberry can affect blood glucose levels and can interfere with blood sugar control during and after surgery.

So, stop consuming blueberry at least 2 weeks before a scheduled surgery. ⁽¹⁸⁾

Nutritional Information

The berries are known to be a nutrient storehouse with plentiful fibers, tannins, vitamins (like vitamin C, ascorbic acid, thiamin, riboflavin, Niacin, pantothenic acid, pyridoxine, folic acid, retinol, tocopherol), ellagic acid, omega-3 fatty acids, anthocyanins, proanthocyanidins, and minerals (calcium, copper, iron, magnesium, manganese, phosphorus, potassium, selenium, sodium, zinc). ⁽¹⁾

Blueberry Daily Dosage

The appropriate daily intake of blueberry depends on some factors, such as the user's age, health, and several other conditions. There is not adequate scientific information to determine an appropriate range of doses for blueberry.

Keep in mind that natural products are not necessarily safe, and dosages can be important. Make sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using. ⁽¹⁸⁾

Bioactive Compounds

Blueberry polyphenolic compounds include both flavonoid and nonflavonoid types. Anthocyanin flavonoids account for up to 60% of the total polyphenolics in ripe blueberries. Other classes of flavonoids found in blueberries include proanthocyanidins and flavonols. Abundant nonflavonoid polyphenolic compounds in blueberries are the hydroxycinnamic acid esters (especially chlorogenic acid).⁽¹⁹⁾

Best Time to Consume

2 hours before or after meals.

Possible Drug Interactions

Antidiabetes drugs

Blueberry leaves can reduce blood sugar levels. Diabetes medications are also used to lower blood sugar. Therefore, taking blueberry leaves along with diabetes medications may significantly lower your blood sugar.

Monitor your blood sugar closely. The dose of your diabetes medication may need to be changed.

Several medications used for diabetes include glyburide (DiaBeta, Glynase PresTab, and Micronase), glimepiride (Amaryl), pioglitazone (Actos), insulin, chlorpropamide (Diabinese), glipizide (Glucotrol), rosiglitazone (Avandia), and tolbutamide (Orinase). ⁽¹⁸⁾

Traditional Use

Blueberry possesses anti-diabetic activity. It has been used as a traditional medicine for the treatment of diabetic symptoms such as increased appetite or excessive hunger, increased thirst, and frequent urination. ⁽²⁰⁾

Some Questions about Blueberry

Can too many blueberries be harmful?

1. Dietary fiber is beneficial for our health; it is necessary to take fiber in our daily diet, but having too much fiber is bad for our health. A cup of blueberries contains 3.6 gr fiber; excess consumption of blueberry can result in stomach discomfort, gastrointestinal problems like bloating, flatulence, diarrhea, etc. It can also thwart the absorption of nutrients by our intestines and cause many health problems. Because of the risk associated with high fiber, it is recommended to use blueberry in adequate and moderate quantities. This side effect will be more prominent in people who have digestive diseases like ulcerative colitis or Crohn’s disease. ⁽²¹⁾

2. Bluberries contain 29 micrograms of vitamin K per 1-cup serving, making them a "medium" vitamin K food. Suddenly increasing or decreasing your intake of foods rich in vitamin K without asking your doctor to make changes to prescription blood-thinner dosages can lead to an increased risk of bleeding.

Also, if you take Warfarin (Coumadin), you may need to limit and monitor your Vitamin K intake, Since Vitamin K could affect how these drugs work.

3. Blueberries contain high amounts of salicylates (the active ingredient in aspirin that is also found naturally in many plants), which can cause side effects in people who are sensitive to them. For those who can't tolerate salicylates, blueberries might cause rashes, headaches, or a host of gastrointestinal symptoms, including bloating, vomiting, nausea, reflux, gas, constipation, and diarrhea.

Despite the high amount of salicylates, eating blueberries in small amounts can ease some of the pain and discomfort associated with the ingestion of salicylates.

4. Blueberries are one of the common food culprits that have the potential to stain your teeth because of their intense pigmentation. Whether you eat them fresh, frozen, juiced or preserved in jelly or jam, the deep-blue hue can discolor your tooth enamel or white fillings. It is recommended to:

- Drink something after you eat berries.

- Drink water; it will rinse your mouth and can help keep the staining effect under control.

- Drink a glass of milk; it will neutralize the acidity of the berries and strengthen teeth. ⁽²²⁾

Can blueberries cause an allergic reaction?

Blueberry fruits, although belonging to the Ericaceae family, share at least three IgE-reactive proteins with rosaceous fruits, namely a Mal d 1 and a Mal d 3 homologous protein, and profilin.

Quite recently, a clinical case of anaphylaxis was attributed to a 10 k Da lipid transfer protein of blueberry. However, further clinical investigations are required to understand the impact of blueberry allergens.

Blueberries have a high salicylate content (every 100 g blueberries has 27.6 mg salicylates). If you are allergic to blueberries, it is often due to this compound.

You may have a blueberry allergy if you have some of the following symptoms, after eating or touching blueberries or products that contain blueberries:

- Skin reactions, such as eczema, hives, swelling and redness of the extremities or face

- Gastrointestinal symptoms, such as abdominal pain, nausea, vomiting, or diarrhea.

- Respiratory symptoms, such as a runny or stuffy nose, coughing, sneezing, wheezing, or breathing difficulty.

- Cardiovascular symptoms, such as a drop in blood pressure, lightheadedness, or fainting

Blueberry allergy is not very common. Still, children below 9 months old should not be given blueberries or food with blueberry extracts/components. The reason is that they can develop an allergy easily as their bodies are not yet able to digest the components of blueberry. ⁽²³⁾

Are blueberries good for breakfast?

Blueberry scores the highest in terms of antioxidants and is regarded as a quintessential functional food ingredient.

The fruits are generally processed into jam, syrup, pie, soup, tart, cobbler, smoothie, pancake, muffin, cupcake, salsa, salad, lemonade, waffles, ready-to-eat breakfast cereals, yogurts, and beverages. The berries are known to be nutrient storehouse with plentiful fibers, tannins, anthocyanins, proanthocyanidins, vitamin C, ellagic acid, omega-3 fatty acids, carotenoids, minerals, etc.

A variety of anthocyanins occur in blueberry; the chief types are monoarabinoside, monoglucosides and monogalactosides of cyanidin, petunidin, peonidin, delphinidin, and malvidin. The United States Department of Agriculture (USDA), human nutrition center, recommends its inclusion in the diet.

A study was conducted to determine whether consumption of blueberries could reduce postprandial oxidation when consumed with a typical high-carbohydrate, low-fat breakfast or not. According to the study, a practically consumable quantity of blueberries (75 g) can provide statistically significant oxidative protection in vivo after a high-carbohydrate, low-fat breakfast. Though not tested directly, it is likely that the effects are due to phenolic compounds, either directly or indirectly, as they are a major family of compounds in blueberries with potential bioactive activity. ⁽²⁴⁾

Are blueberries high in sugar content?

In addition to aroma, fruit color and firmness, sugar content is one of the main parameters that affects fruit taste and one of the essential criterion considered in the evaluation of the nutritive value of berries, and nutritional fruit quality; the most abundant sugars are glucose, fructose, and galactose. ⁽²⁵⁾

Blueberries are low in calories and fat yet provide decent amounts of healthy fiber. A 100 gr serving of raw blueberries has 10 grams of sugar.

Can diabetics eat blueberries?

Blueberry has a score of 53 on the glycemic index (GI), which measures how quickly they raise blood sugar levels. As this score is relatively low, blueberries should not cause major spikes in blood sugar. Hence, they are considered safe for people with diabetes.

Also, epidemiological evidence shows that incorporating blueberries into our daily diet can reduce the risk of developing type 2 diabetes (T2DM). These findings are supported by pre-clinical and clinical studies that have shown improvements in insulin resistance, after obese and insulin-resistant rodents or humans consumed blueberries.

Insulin resistance is a public health concern that can initially occur in the prediabetes stage many years before the diagnosis of type 2 diabetes mellitus. ⁽²⁶⁾

According to the finding of one study, daily dietary supplementation with bioactives from whole blueberries improved insulin sensitivity in obese, non-diabetic, and insulin-resistant participants.

For more information, see the “What Are Blueberry Side Effects” section.

Are blueberries good for weight loss?

Blueberry juice has become quite popular in recent years because of the health benefits associated with the nutritious phytochemicals, especially being rich in anthocyanins. Anthocyanins are water-soluble pigments widely found in fruits and vegetables and, therefore, often consumed in a normal diet.

Furthermore, anthocyanins have been attributed to several putative therapeutic roles, including beneficial effects on obesity and related metabolic complications. In this respect, anthocyanins from blueberries prevent the development of obesity in mice fed with a high-fat diet (HFD).

For more information, see the “Blueberry Health Benefits” section.

Are blueberries good for constipation?

Constipation cannot be treated using medication alone. We can achieve better outcomes, in both short and long-term periods, by changing our lifestyles, including a proper daily diet.

Higher dietary fiber intake (fruits, legumes, and vegetables) is associated with a lower incidence of constipation in some studies. So, blueberries are good for constipation, too. One cup has only 84 calories and about 3.6 grams of fiber.

Are frozen blueberries as good as fresh blueberries?

One research shows that frozen blueberries make the antioxidants more bio-available.

Studies, carried out at the South Dakota State University, indicate that freezing blueberries make their powerful antioxidants more available to the human body. This is because anthocyanins, the antioxidant compounds that make blueberries blue, are found in the skin of the berry. Freezing the berries creates tiny ice crystals that disrupt the structure of the cells, which in turn makes it easier for our system to access the anthocyanins contained within the skin. According to Marin Plumb, the researcher behind the study, since commercially-packaged blueberries are frozen soon after they are picked, “they are equal in quality to fresh.” ⁽²⁷⁾

Is blueberry extract good for liver?

Research has shown that blueberries can aid in liver detoxification and health. Consuming blueberries or their extracts increases the activity of important liver enzymes and reduces liver DNA damage. These positive effects are attributed to the high content of antioxidants and polyphenols in blueberries, which help reduce oxidative stress and improve liver function. ⁽²⁸⁾