The health benefits of blueberries
Blueberries are a very versatile fruit which originated in North America. They are great as a snack or as an ingredient in more complex dishes, and can also be grown successfully in many other parts of the world. They are packed with really important nutrients and are also very low in calories (1 blueberry is less than 1 calorie!) so they can be enjoyed in large amounts.
100g blueberries (more than 100 individual berries) contains just 57 calories, which tells you immediately that these are a pretty healthy option. It also contains virtually no fat (zero saturated fat, zero monounsaturated fat and just 0.1g of polyunsaturated fat; the healthier fat), no cholesterol and just 1mg sodium. It contains 10% of your recommended daily allowance (RDA) of dietary fibre, and contains 10g sugar.
100g blueberries is also rich in essential vitamins and minerals to help you to remain healthy; manganese, copper, iron, vitamin C and vitamin K.
- 100g of blueberries contain 17% of your RDA of manganese. Manganese helps the body to develop bones and convert proteins, carbohydrates and fats into energy. Blood sugar control is very important, and manganese plays a role in helping enzymes to function properly during the gluconeogenesis process, where glucose is produced from non-carbohydrate sources (i.e. proteins and fat). Glucose is vital for providing energy to the cells and organs of the body.
- Manganese is also a component of the enzyme prolidase, which is necessary for collagen production. Collagen is a structural component of the skin used to keep it firm and supple, but also very important in would healing processes. Furthermore, manganese may be effective as a treatment for osteoporosis (weak and brittle bones) and symptoms of pre-menstrual syndrome (PMS).
- 100g of blueberries contain 3% of your RDA of copper. This may not sound like a lot, but it is a vital mineral for a number of bodily functions. Copper combines with certain proteins to produce enzymes which are catalysts for various processes, including biochemical reactions, transforming melanin for skin pigmentation, maintaining and repairing connective tissues and so forth. This is especially important for maintaining the heart and arteries. Without sufficient copper (and research shows that the UK population isn’t usually getting enough) heart disease is a real possibility.
- 100g of blueberries contain 2% of your RDA of iron, another very important mineral as it is an essential component of haemoglobin. This is a protein within red blood cells which allows them to transfer oxygen around the body. This is vital for ensuring that organs including the brain and heart get enough oxygen to function effectively. In pregnancy, having insufficient iron in the body can put the mother at risk for a premature delivery, or for delivering a baby which is smaller than normal.
- 100g of blueberries contain 16% of your RDA of vitamin C. Vitamin C is essential in the body as it helps to keep cells healthy, maintains connective tissues which support organs and other structures, and it is very important in would healing. 16% for 100g is not particularly high compared to some other fruits (such as strawberries) and vegetables, but the body does not produce vitamin C on its own, and so consuming blueberries to get your RDA is a pretty good idea. It’s a little more interesting than that standard glass of orange juice!
- 100g of blueberries contain 24% of your RDA of vitamin K. This is a vitamin that is less well known (it is actually known as the ‘forgotten vitamin’), but has a very important role in the body nonetheless. It is required for protein modification which increases the functional diversity of proteins, as well as for ensuring that blood clots. Without this process, even a very small cut could lead to a significant amount of blood loss. Thirdly, there is some evidence emerging that vitamin K is necessary for maintaining strong bones, and evidence suggests it is also very good for people who are at risk of heart disease. Unusually for a vitamin, the body does create its own vitamin K, in the bacteria of the intestines. Any vitamin K which is not used is also stored in the liver for future use. This means that it is not an essential in your diet every single day, unlike vitamin A and vitamin C.
Benefits of Blueberries
Alongside the general health benefits found in the nutrients of blueberries, there is evidence that they are excellent for specific medical needs:
- High Blood Pressure
- Memory Problems
- High GI Diets
- Cardiovascular Problems
- Poor Eye Health
- Immune System Function
- Urinary Tract Infections
- Excessive Belly Fat
- Neurological Disorders
1. High Blood Pressure
High blood pressure is the cause of many cardiovascular problems, including incidents of heart attack and stroke. Research has recently been conducted which investigated the effect of blueberries on blood pressure levels (Johnson et al, 2015). 40 women with high blood pressure were asked to eat either blueberry powder daily for eight weeks, or an identical looking and tasting placebo.
The study found that those who ate the blueberry powder showed a 5.1% decrease in systolic blood pressure (pressure caused by the heart squeezing blood through your arteries) and a 6.3% decrease in diastolic pressure (pressure in arteries when heart is between beats).
It was also found that levels of nitric oxide, which relaxes and widens blood vessels, were significantly heightened in those who ate the blueberry powder. None of these changes were witnessed in the placebo group. The researchers suggest that including blueberries in your regular lifestyle can significantly improve outcomes for people at risk and already suffering from high blood pressure.
2. Memory Problems
In recent years scientists have begun to focus significant amounts of research on ageing and memory. In one study by Rendeiro et al (2013) it was found that blueberries may have a significant role in enhancing spatial memory. For six weeks, rats were given a substance which contained either pure anthocyanins, pure flavonols, or was a blueberry extract.
Anthocyanins and flavonols are subclasses of flavonoids, compounds found in plants which have similar effects to antioxidants (these will be discussed later). The subclasses of flavonoids are determined by their chemical structure. Anthocyanins are notable because they give fruits striking pigments, such as the red of a strawberry or the blue of a blueberry.
In fact, blueberries are thought to contain the most anthocyanins of all plants. The researchers ensured that both substances contained levels similar to those found in the blueberry extract. There was also a control group to test normal memory function.
The results showed that all three groups displayed similarly improved spatial working memory (memory for locations and orientation), as well as an increase in Brain-Derived Neurotrophic Factor (BDNF). BDNF is a protein which is responsible for growth, maturation and maintenance of brain cells (known as neurons), and in this study it was shown to be significant in improving spatial memory performance.
Their data also showed that levels of mRNA (messenger ribosomal nucleic acid) from BDNF in the hippocampus were significantly enhanced in the anthocyanins group, but not in the other two experimental conditions, or the control group. MRNA is a molecule which creates a ‘template’ for protein creation. In this case, anthocyanins stimulated production of mRNA which would create the template for creation of BDNF.
Furthermore, they discovered that the group with the most enhanced improvements were the flavonoid only group, but that these levels were very similar to those who had the blueberry supplement.
These results suggest that flavonoids have a causal role in improving spatial working memory, and they do so through enhancing production of BDNF, which improves neuronal functioning. They have also shown that anthocyanins significantly enhance the production of mRNA for the creation of BDNF.
This research strongly suggests that blueberries, which contain both flavonols and anthocyanins, are capable of producing molecular and behavioural changes linked to memory performance in rats.
This animal study has also been backed up by research into human participants. Krikoran et al (2010) assessed the impact of blueberry juice as a preventative measure for dementia in older people. For 12 weeks, participants with an average age of 76 were asked to consume between 444 and 621 millilitres of blueberry juice a day depending on their weight.
A control group consumed a placebo drink. After 12 weeks, it was found that paired association learning task performance and word list recall was significantly improved in the blueberry group, and glucose levels (a risk for diabetes) and depression levels were also reduced.
Both of these studies suggest that blueberries have the potential for significant positive impacts on memory performance. In a society where dementia is becoming a real problem, maintaining a healthy and functional memory is of particular importance. This research suggests that by consuming a small amount of blueberries regularly can significantly improve memory performance, and reduce the risk of developing dementia and Alzheimer’s disease.
3. High GI Diets
GI (glycaemic index) is a way of measuring how much food has an impact on our blood sugar levels. High GI has been associated over the years with increased risk of cardiovascular disease, type 2 diabetes, metabolic syndrome, stroke, depression, chronic kidney disease and certain cancers including breast and prostate.
Blueberries are a low-GI food, meaning that they only have a small impact on blood sugar levels. Not only do low-GI foods mean you aren’t at greater risk for the diseases mentioned above, but they actually decrease the risk of developing these conditions.
Not only do blueberries have a low GI which is good for general health, but it has also been shown that they can have a positive impact on people already suffering with Diabetes. A study by Zunino (2009) assessed the impact of foods containing resveratrol on the health of people with Type 2 Diabetes.
Resveratrol is a plant compound similar to flavonoids, which has anti-inflammatory and antioxidant effects. It was found that consuming foods containing resveratrol, including grapes and blueberries, led to reductions in hyperglycaemia, protection against B-cell loss and improvements in B-cell function.
B-cells are very important for sufferers of Diabetes because they are the cells which produce, store and release insulin, the hormone which controls blood sugar levels. It was suggested that foods containing resveratrol contribute to lowering the GI of blood, something which is extremely important for people with Diabetes.
It has also been found that blueberries can have substantial preventative effects for people at risk of developing Type 2 Diabetes. Wedick (2012) assessed the impact of flavonoid sub-compounds (such as anthocyanins) on the risk of developing diabetes.
Higher consumption of anthocyanin-rich foods was significantly associated with a lower risk for Type 2 Diabetes, and blueberries were particularly beneficial. Again, it is suggested that this may be due to the low-GI content of the fruit.
4. Cardiovascular Problems
Cardiovascular disease is an umbrella term for a number of heart conditions; Coronary Heart Disease (CHD), stroke, peripheral artery disease, and aortic disease. CHD is the biggest killer in the UK (approximately 1 in 6 men and 1 in 10 women die from CHD) and yet it is easily prevented with a healthy lifestyle.
It is caused by a number of factors including high cholesterol, high blood pressure, smoking and diabetes. Symptoms include chest pain, heart attacks and heart failure, and it is defined by a build-up of fatty substances in the blood vessels around the body. This process is known as atherosclerosis.
Diet can have a significant impact on the outcomes of all cardiovascular diseases including CHD, and blueberries are particularly beneficial. Both blueberries themselves and blueberry leaves are rich in antioxidants including polyphenols (which are particularly good for combating heart disease).
Antioxidants attack free radicals – molecules in the body which are missing an electron; as a result of this, they can wreak havoc by destroying cells in their search for a new electron in order to stabilize itself. They are produced as a result of pollution, radiation, toxins and are also created by the body through metabolic processes.
Heart disease can be worsened through the presence of free radicals as they are thought to accelerate the process of atherosclerosis. They can attach to arterial walls and then attract macrophages, a type of white blood cell which absorb and deposit cholesterol within the cell to form ‘foam cells’. These in turn may initiate the formation of an atherosclerotic lesion, which can result in the blockage of blood vessels.
Antioxidants are important in heart disease because they can reverse the build-up of cholesterol on the walls of the arteries, which in turn will improve blood flow to and from the heart. This will reduce the risk of heart attack and stroke. Blueberries are ranked as number one for antioxidant content by the USDA Human Nutrition Centre, and as such are one of the best foods you can eat to reduce the impact of free radicals on heart function.
As well as reducing levels of cholesterol, blueberries are effective at combating metabolic syndrome due to their high polyphenol content. Metabolic syndrome is the medical term for the combination of obesity, high blood pressure and diabetes. Alone, each of these conditions can increase the risk of heart problems, but together the risk is significantly greater. Adding blueberries to your diet are thought to be one way to effectively treat metabolic syndrome.
According to a review by Mohamed (2014), they work in a number of ways. Firstly, anthocyanins found in blueberries have been shown to prevent obesity development and high cholesterol in mammals on a high-fat diet. Secondly, the anti-inflammatory and antioxidant properties found in blueberries can reduce the risk of developing diabetes, hypertension (high blood pressure) and obesity.
Their anti-inflammatory properties have also led to increased insulin-sensitivity in insulin-resistant men and women (and so improved outcomes for diabetes treatment), and the polyphenols found in the fruit can supress the development of fat cells which may lead to obesity.
Adding blueberries to your diet, therefore, have multiple benefits for heart health; they can reduce cholesterol build up in your blood vessels, fight off free-radicals which exacerbate this process, prevent obesity development and enhance responses to diabetic treatments.
5. Poor Eye Health
The retina of the eye is vital for vision. It is the light-sensitive layer at the back of the eye that collects light which has been focused by the lens. Without the retina, vision would be impossible, but it is also particularly susceptible to damage by free radicals.
Photoreceptors in the retina are susceptible to damage due to their high metabolism rates and constant exposure to light, including Ultra Violet. Free radicals form more readily under these conditions (and in any areas of the body which require high levels of oxygen), and cause damage to proteins, DNA and the membrane of the photoreceptors.
Fortunately, anthocyanins found in blueberries can prevent this damage by protecting the retina and by relaxing blood vessels in the eye to ensure good blood flow and prevent blood clots.
Free radicals are also responsible for Age-Related Macular Degeneration (ARMD), the primary cause of sight-loss in people over the age of 65. Anthocyanins in blueberries are responsible for protecting the eye against this sort of damage.
They are so good at doing this that in some cases they can actually reverse sight loss, and in Japan they are referred to as ‘the vision fruit’.
It has been estimated that 1/3 people in the UK population will develop cancer at some point in their lives. It is a devastating disease which can affect any part of the body, and is very hard to treat. Fortunately, there are some ways to prevent this disease from occurring.
One of the ways cancers can develop is through damage caused by free radicals. Therefore, eating a diet rich in antioxidants can help to protect the body against this damage. Blueberries, as already mentioned, contain many antioxidants to help fight off free radicals.
Anthocyanins are the most notable due to their high concentration in the berry, but other notable antioxidants include flavonols such as quercetin, kaempferol and myricetin, hydroxybenzioc acids such as gallic acids and procatchuic acids, and other phytonutrients such as resveratrol and pterostilbene.
Blueberries which have been grown organically are more likely to be beneficial, but the good news is that freezing blueberries won’t reduce their antioxidant properties as it might do in other fruits.
In terms of their ability to help prevent cancer, research has mostly been conducted on blueberries as a preventative treatment for breast cancer, colon cancer, oesophageal cancer and cancers of the small intestine. Nearly all of the research has been completed on animal models or human cells, rather than live patients, but they are showing promising results.
Current evidence from a systematic review (Continuous Update Project, 2011) suggests that the evidence is strong that foods containing dietary fibre can reduce the risk of colorectal cancer. It also states that evidence is fairly good for the ability of fruits in general to reduce the risk of mouth, larynx, oesophagus, lung and stomach cancer. Foods containing vitamin C are particularly good for oesophageal cancer.
Laboratory research has also looked into blueberry-specific properties and their influence on cancer. Vitamin C protects the DNA in cells by trapping free radicals and inhibiting the formation of carcinogens. Blueberry extract, anthocyanins and ellegic acid decrease free radical damage to DNA which can in turn cause cancer to develop.
When cancer has already formed, these substances can also reduce growth of, and stimulate ‘self-destruction’ of cancer cells.
Animal studies have given rise to evidence suggesting that blueberries reduce inflammatory cytokines, oesophageal cancerous and pre-cancerous changes in the colon.
Pterostilbene can decrease the formation of pre-cancerous colon polyps and reduce markers of inflammation, and encourage self-destruction of cancer cells in the lung, stomach, pancreatic and breast.
Although there are very few studies assessing the effects of blueberry properties in human trials, these laboratory and animal studies do provide good evidence that they may be very effective for preventing and treating cancerous cells, and so it is certainly worth adding them to your diet just in case!
7. Immune System Function
Fruits have long been known to be good for the immune system because many of them contain Vitamin C, which as previously mentioned helps support the immune system in a variety of ways. Alongside vitamin C, however, blueberries contain many other immune-supporting nutrients.
Gombart et al (2013) found that blueberries (and red grapes) contain a compound called stilbenoids, which aids vitamin D in increasing expression of the CAMP gene, which is involved in immune function. Specifically, it gives the body the ability to fight bacterial infection, and is particularly useful when antibiotics are not effective.
This research suggests that blueberries can play a very important role in supporting the immune system to function at its highest level. Further research has supported this and suggested that the pterostilbene compound found in blueberries has a similar effect.
8. Urinary Tract Infections
Urinary tract infections (UTIs) affect both men and women, but are more frequently associated with females. They are caused by a number of factors including frequent intercourse, pregnancy, use of soaps and irritating products, and bacterial infections. They are very common, but can be quite painful and uncomfortable.
Symptoms include pain when urinating, an increased need to urinate immediately, and pain in the lower abdomen. Antibiotics can be prescribed, but often UTIs can be treated effectively with home remedies. Cranberry juice is a well-known treatment, but blueberries are equally effective and can also be preventative.
As we now know, blueberries are full of anthocyanins, and they are very good for preventing bacteria from sticking to the walls of the urinary tract. The large amount of vitamin C in blueberries also inhibits the growth of bacteria in the urinary tract, and so can reduce the amount of time the infection is present for.
9. Excessive Belly Fat
Excessive body fat is unhealthy regardless of where it is, but belly fat is the most dangerous. The problem is that as well as having fat just under the skin (subcutaneous fat), belly fat also includes visceral fat, which surrounds the vital organs.
This can be very problematic because having higher levels of visceral fat is linked with an enhanced risk of cardiovascular disease, Type 2 Diabetes and colorectal cancer. It is also associated with premature death, regardless of overall weight.
Despite the dangers of belly fat, however, diet and exercise can quickly reduce the danger. Blueberries contain many substances such as anthocyanins which can have an extremely beneficial effect on excess belly fat.
In fact, a study of rats (Seymore et al, 2011) found that after consuming a diet of 2% blueberries for 90 days, they showed significantly less belly fat, lower blood fats, lower cholesterol, and improved blood sugar and insulin levels. The researchers suggested that blueberries may influence the function of genes responsible for processing sugars and fats from our diets.
A human study in 2010 by Stull and colleagues discovered that drinking a blueberry smoothie twice a day for six weeks can lead to a 10% or greater improvement in insulin sensitivity for pre-diabetic individuals. As they can also help you to lose weight, blueberries may a particularly important addition to the diet of people at risk of diabetes, a disease which is more likely in overweight and obese people.
10. Neurological Disorders
Neurological disorders such as Parkinson’s disease are very difficult to treat and can have devastating effects on the lives of sufferers. Fortunately, dietary changes can improve symptoms. Blueberries have been shown to have some success at both preventing and improving the outcome of neurological disorders.
Rochet et al (2014) investigated the influence of two phytochemicals found in blueberries (anthocyanins and proanthocyanidins) on the degeneration which occurs as a result of Parkinson’s disease. Parkinson’s disease is characterised by the malfunction and death of vital neurons in the brain, leaving a person unable to control movement. Treatment for Parkinson’s disease often causes the classic tremors most people associate with the disorder, but without treatment patients may not be able to move whatsoever.
The study found that blueberry extract alleviated neurodegeneration by stimulating cell’s mitochondria. These are structures within a cell which take in nutrients, break them down and create energy, which can help cells to survive.
The polyphenols (plant compounds with potent antioxidant properties) found in blueberries are also capable of improving general cognitive and motor skills which have degenerated as a result of ageing or pathological conditions (Watson and Preedy, 2015).
A lot of the degeneration which occurs as a result of ageing is down to damage caused by free radicals and the antioxidants found in blueberries are some of the best for fighting free radicals. The anthocyanins in blueberries can both prevent neurodegeneration and stimulate the body to grow new brain cells.
Blueberries contain substances which are able to penetrate the blood-brain barrier. This allows them to enter the brain tissue and be more effective in their delivery of health benefits.
The effects of blueberries on spatial memory performance has previously been discussed, but they have also been shown to improve attention, learning, verbal memory, auditory processing and object recognition. Research has also shown that they can defend against problems at the molecular level including toxicity of proteins, neuro-inflammation and excitotoxicity (the degree to which a substance is toxic to nerve cells through excessive stimulation).
Furthermore, blueberries can aid in restoring synaptic plasticity (adaptability), neurogenesis (the growth of neuronal tissue) and sensitivity to neurotransmitters (chemicals in the brain which control a variety of conscious and subconscious processes).
The evidence discussed here provides good evidence that as well as treating specific diseases, adding blueberries to your diet is an excellent way to improve general cognitive and neurological health.
As well as treating physical health problems, recent evidence has emerged which suggests that blueberries may have some antidepressant qualities. Current statistics suggest that 1 in 4 people will suffer from a mental health problem at some point in their lives, and the causes can be both genetic and environmental. Therefore, anybody is at risk, and so it is important that everybody knows of effective ways they can prevent mental illness.
One of the suspected biological causes of depression is an unstable amount of serotonin. This is a neurotransmitter responsible for transmitting messages throughout the body to do with mood, sexual function and desire, sleep, memory & learning and some social behaviour.
Lower productions of serotonin, or malfunction of the processes involved in serotonin transmission, is thought to be a major cause of depression. In fact, many of the most common antidepressants are called serotonin reuptake inhibitors (SSRIs), and they work by preventing neurons from reabsorbing serotonin, which can help to rebalance the amount of neurotransmitter in the brain. This rebalancing can then lead to improved mood.
A study published in the Archives of Internal Medicine (2004) found that clinical depression is associated with a greater number of c-reactive proteins (CRP). This is a marker for inflammation in the body, which is linked to many health problems including heart disease and degenerative disorders.
In 2011, scientist from the Pittsburgh Medical Centre suggested that not only is there an association, but that inflammation can significantly influence the development of depression. In other words, inflammation can cause depression.
Anti-inflammatory diets, therefore, may be helpful in reducing the risk of depression. Anthocyanins found in blueberries are excellent anti-inflammatory substances and the antioxidant effects can also reduce inflammation caused by free radicals.
Blueberries may also be affective against depression in another way. As mentioned earlier in the article, blueberries contain flavonols and anthocyanins which are excellent at stimulating the creation of brain-derived neurotrophic factor (BDNF). As well as being important for the creation of new cells, BDNF seems to also play a role in depression. A review by Bun-Hee and Yong-Ku (2010) reported that in major depressive disorder, patients consistently show a lower level of BDNF.
Other research has reported that when BDNF is removed from one’s diet, people recovering from depression can relapse, and people with a family history of depression can show significantly lower moods compared to people without a family history.
This implies that BDNF is extremely important in the symptomology of depression, and that a higher level of BDNF may improve symptoms of depression. As blueberries are excellent for stimulating the growth of BDNF, they may have a significant positive role in helping the body to produce anti-depressant compounds, without the need for pharmacological intervention.
Some Things to Be Aware of
Like most fruits, there are not many disadvantages to eating blueberries. Indeed, they appear to be one of the most nutritious foods that exist, but despite this some warnings must be mentioned. As with most things, you can have too much of a good thing.
Despite the nutritional benefits of blueberries, some scientists show concern about overdosing on these substances. The body requires a delicate balance of antioxidants and free-radicals in order to work effectively. Eating blueberries in excessive amounts may upset this balance, and lead to adverse effects, such as breathlessness and impaired muscle function.
For this to occur, however, you would need to eat a very large amount of blueberries, which is unlikely to happen.
We hope you enjoyed reading this article and doing so has enticed you to include more blueberries in your diet. Happy eating!