Health Benefits Of Blueberries

Introduction

We’ve all munched on a handful of blueberries now and then. But have you ever wondered how they claimed superfood status? Blueberries have an exceptional nutrient line-up consisting of macro and micronutrients. They also offer a wide range of health benefits when consumed long-term. So let’s explore what they are. 

About blueberries 

Blueberries are native to and grown extensively in North America. The main varieties are:

• Northern highbush berries
• Lowbush berries (Wild blueberries)
• Southern highbush berries
• Rabbit eye berries¹

They’re processed immediately after harvesting as they’re delicate and highly perishable. Even unripe and damaged berries find use in blueberry products. Those not up for immediate consumption are freeze-dried to prevent spoilage and preserve their antioxidants.

Freezing drying, quick freezing, and refrigeration prevent the loss of these heat-sensitive antioxidants in fresh blueberries and blueberry products since these methods use low temperatures and no water.^2,3

The health benefits of blueberries are attributed to their bioactive components. They are:

• Polyphenols (0.3%): They’re phytochemicals with antioxidant, anti-inflammatory, pre-biotic, and anti-allergy properties.4 They lower cholesterol and blood pressure, increase insulin sensitivity, promote mental health, and prevent and treat heart disease, metabolic syndrome, and cancer.^1,2 They’re also responsible for the sweet-sour flavour of blueberries. 100g of blueberries contain 48-304 mg of polyphenols. They include flavonoids, anthocyanins, and phenolic acids² 
  • Anthocyanins: They’re plant pigments responsible for the health benefits of blueberries and their red, blue, and purple colour. 100g of fresh blueberries contain 25-495 mg of anthocyanins, making them one of the highest anthocyanin-containing berries^2,3

The antioxidant potential of blueberries is dependent on their polyphenol content. The order of polyphenol content and antioxidant activity of blueberries based on cultivation and processing method is as follows:

Organic freeze-dried blueberries (49%) > Organic fresh blueberries (43%) > Conventionally grown blueberries (28%).⁴

Health benefits of blueberries

The health benefits of blueberries are:

• Cardiovascular health – They reduce heart disease risk, high blood pressure, arterial stiffness, and metabolic syndrome by improving heart health and the functioning of blood vessels^1,3,6
• Diabetes – They reduce the risk of type 2 diabetes by 23% and prediabetes by improving insulin sensitivity, reducing insulin resistance, and lowering blood sugar levels due to their high anthocyanin content^3,7
• Cancer – They inhibit the growth and kill cancer cell lines of the colon, breast, cervix, ovaries, lung, mouth, prostate, and skin. They also increase their sensitivity to anti-cancer drugs and have anti-mutagenic properties that prevent DNA damage^1,5
• Weight loss – They reduce body weight, correct dyslipidaemia, and lower belly fat due to their dietary fibre and anthocyanin content. Eating blueberries does  not promote weight gain, thus reducing the risk of diabetes and cardiovascular disease^3,5
• Cholesterol reduction – They promote healthy lipid profiles by increasing HDL cholesterol levels and decreasing LDL cholesterol and triglyceride levels, thus reducing the risk of atherosclerosis and heart disease³
• Antioxidant and anti-inflammatory activity – They prevent oxidative stress and cell damage by neutralizing free radicals. They also reduce inflammatory molecules, thus preventing the progression of chronic diseases⁵
• Immunity booster – They can modulate the immune system and trigger the release of immune cells to fight against diseases due to their anthocyanins and Vitamin C content⁵ 
• Brain health – They improve memory, brain function, and cognitive performance in healthy elderly adults and children on long-term consumption. They’ve also shown neuroprotective effects in vitro^3,5,8

Blueberries also have potential prebiotic and antimicrobial effects. They inhibit the growth of pathogens in vitro and promote the growth and diversity of beneficial gut bacteria in elderly adults.^1,5 Two studies have shown that they reduce the risk of cataracts and macular degeneration.³ 

Overall, blueberries are integral to healthy eating. But more human clinical trials should be performed to confirm these health benefits in larger populations, to fix a dietary dosage, to assess efficacy differences between whole blueberries and extracts of their bioactive nutrients, and to determine any interactions with drugs and other foods.^1,3,5,7

Nutrients we can get from blueberries

Blueberries are a low-caloric superfood packed with the following nutrients:

• Carbohydrates (9.7%):

Blueberries mainly contain glucose and fructose. They also have minute quantities of sucrose. Glucose provides energy to the body’s cells, tissues, and organs.^1,2,9

• Proteins (0.6%):

100g of blueberries contain 0.74g of proteins. They include essential amino acids like isoleucine, leucine, phenylalanine, threonine, and valine.^2,10

• Fats (0.4%):

Although blueberries are low in fat, most of it is a polyunsaturated or healthy fat that contains essential fatty acids needed by the body.^1,2 

• Dietary fibre (3-3.5%):

Blueberries are rich in dietary fibre and provide 14% of the daily requirement. They mainly contain soluble fibre that helps with weight loss, lowering cholesterol levels, and controlling blood sugar.^2,11

• Minerals:

Blueberries contain calcium, magnesium, potassium, phosphorous, iron, manganese, zinc, aluminium, boron, and copper. But they only provide 3% of the DRI of these minerals, leaving potassium (77mg/100g) and manganese.

They provide 100% of the DRI of manganese, a mineral that strengthens bones and muscles and helps with blood clotting. Blueberries have very little sodium (1mg/100g), making them ideal for people on low-sodium diets.^1,11 

• Vitamins: Blueberries contain:
  • Vitamin A
  • Vitamin B1
  • Vitamin B2
  • Vitamin B3
  • Vitamin B5
  • Vitamin B6
  • Vitamin C
  • Vitamin E
  • Vitamin K (Phylloquinone)
  • Folate^1,10

They’re good sources of Vitamin C and K since 1 cup provides 24% of Vitamin C’s and 36% of Vitamin K’s daily requirement.¹¹

Vitamin C is an antioxidant and immune booster that helps with iron, calcium, folic acid absorption, and collagen production. Vitamin K promotes bone and heart health and helps with blood clotting.^11,12,13

• The nutritional composition of blueberries varies based on cultivars, cultivation methods, and growth location¹
• DRI (Daily Reference Intakes) are daily nutrient requirements set by nutrition professionals

How to include blueberries in our diet?

There are plenty of ways to include blueberries in your diet. You can eat them as they are or combine them with various fruits and vegetables in many recipes. Whole blueberries are sold fresh or frozen. But there are also many blueberry products available on the market, namely:

• Dried blueberries
• Canned blueberries
• Freeze-dried blueberries
• Blueberry jam and jelly
• Blueberry powder
• Blueberry yoghurt
• Blueberry juice and puree
• Blueberry concentrate
• Blueberry extract
• Blueberry conserve and preserve
• Blueberry baked goods
• Blueberry ice cream
• Blueberry wine and beer^1,2,3,14,15

Blueberries can be blended into smoothies with various vegetables, fruits, and fruit juices following the Blueberry Council’s recommended 2:1 cup ratio of vegetables to fruits. 

Blueberry smoothies double up as well-balanced meals with sources of proteins like Greek yoghurt or nut butter and healthy fats like avocados, chia seeds, or flaxseeds added to them.¹⁴

Blueberries add a subtly sweet flavour to salads, salad wraps, yoghurt, oatmeal, and cereal, in addition to boosting fibre intake. They also pair well with

• Almonds, chicken, mint, or lime or are used as a dressing in the former two
• Lemon, nutmeg, cinnamon, and vanilla in the latter two

Frozen blueberries are great to eat as they are or when made into blueberry ice cream or blueberry crumble. Blueberry ice cubes from fresh blueberries add a healthy touch to party drinks.¹⁴

Blueberry wines and beers are low-alcoholic, flavourful and nutritious beverages that offer plenty of vitamins and minerals. You can also opt for compound blueberry wines with added medicinal herbs like buckwheat, ginseng, and black garlic.¹⁵

But blueberry baked goods are off the table since the high amounts of fat and sugar they have diminished  the health benefits of blueberries.¹⁶

When shopping for blueberries, remember to

• Pick firm, plump, smooth-skinned, dry ones that are either deep purple-blue, blue-black, or reddish.
• Avoid soft, wrinkled, and damaged (stains on the package) ones.

When storing blueberries, make sure to follow these tips:

• Dry blueberries thoroughly before freezing them in airtight containers or resealable plastic bags.
• Keep clean all materials and ingredients needed for canning raw blueberries. 
• Prevent your blueberry stockpile from spoiling by making blueberry jams or preserves. 

How much is enough?

According to NHS’s 5-a-day fruit portions for adults, 80g or 2 handfuls (4 heaped tablespoons) of blueberries is the recommended daily intake. 

However, you need not stop there since a study by Harvard Medical School concluded that 3 or more servings of half of cup of blueberries and strawberries each week reduces the risk of heart attacks by 34%.¹⁶

Another study published in the American Journal of Clinical Nutrition found that eating 1 cup of blueberries (150g)/day promotes blood vessel health, improves lipid profiles, and decreases heart disease risk by 13%.⁶

According to the NIH, adults can eat 22-50g of freeze-dried blueberries for 16 weeks or extracts of whole blueberries and blueberry leaves for medicinal purposes. But always consult a doctor beforehand.¹⁷

Although whole blueberries and blueberry products are considered safe, they have a few side effects, namely:

• Possible allergic reactions and cross-reactivity since they contain lipid transfer proteins¹⁸
• Drinks of freeze-dried blueberries may cause diarrhoea, constipation, nausea, or vomiting¹⁷

There are also precautions when eating blueberries, namely:

• To prevent blood sugar levels from dropping drastically, avoid eating blueberries when taking: 
  • Anti-diabetic medication.
  • Herbal supplements (Bitter melon, cinnamon, aloe, chromium, and prickly pear cactus).¹⁷

• Avoid eating blueberries if you’re:
  • Undergoing surgery to prevent fluctuating blood sugar levels during and after the procedure
  • G6PD deficient to prevent triggering haemolytic anaemia¹⁷
  • Taking warfarin to prevent the risk of increased bleeding¹⁹

• Pregnant and breastfeeding mothers should avoid excessively eating blueberries
• Eat blueberries 1-2 hours before or after drinking milk to prevent an interaction that lowers the health benefits of blueberries¹⁷ 

Summary

Blueberries are a low-calorie and nutrient-dense superfood with many health benefits. They prevent and treat heart disease, cancer, diabetes, and metabolic syndrome.

They’re essential to healthy eating as they are rich in antioxidants, help in weight loss, improve insulin sensitivity, boost immunity, lower blood pressure, and promote brain health. You can enjoy blueberries as they are or in various commercial blueberry products.

They’re easily incorporated into our diets as they pair well with many ingredients. However, remember to be mindful of their side effects and precautions before eating them.