Blueberries And Digestive Well-Being

Introduction

Our digestive well-being is important to the functioning of our body. Avlin Imaeda, an associate professor of medicine (digestive diseases), states that it can affect our overall well-being in many ways as our immune system, the weight of our body, brain function, etc. 

Many of us may be familiar with foods like yogurt and kimchi being good for the digestive system as they are rich in probiotics, often called ‘healthy’ gut bacteria. But, did you know that blueberries, popularised as “super fruits”, are also good for digestion?¹ In this article, we shall have a brief introduction to the importance of digestive well-being, followed by why blueberries are good for us in this regard.

Importance of digestive well-being

The digestive system is a complex process that transforms food into essential nutrients for the body. It begins with chewing in the mouth and progresses through the oesophagus to the stomach. In the stomach, food mixes with digestive enzymes before slowly entering the small intestine, where further breakdown and nutrient absorption occur. The watery residue then moves to the large intestine, where bacteria break down undigested remnants and water is absorbed.

Key organs involved include the liver, producing bile for fat digestion, stored in the gallbladder, and the pancreas, aiding in the digestion of proteins, fats, and carbohydrates in collaboration with the small intestine. Finally, any undigested food is efficiently expelled through the rectum and anus, completing the digestive process.

From the above process, we can see how good digestive well-being is important for the body to obtain the necessary nutrients, as well as to get rid of waste. It also leads to healthier skin and hair, feeling more energetic, and having a stronger immune system that can impact the prevention of allergens and infections from pathogens.²

Not maintaining good digestive health can lead to disorders that can cause discomfort and suffering, ranging from constipation to bowel cancer. In the UK, disorders of the digestive system account for 1.1 million hospital consultations each year.³ 

The nutritional value of blueberries

The nutritional content, unless specified, in 148g fresh blueberries is highlighted below:

Blueberries and gut microbiota

The gut microbiota refers to a diverse and ever-changing community of microorganisms living in our digestive system. These tiny inhabitants, mainly bacteria, play a crucial role in keeping our immune and metabolic systems balanced and protecting us from harmful invaders.⁴

The makeup of this microbial community is influenced by various factors, with diet being a key player throughout our lives, especially in our early years. Changes in this microbial balance, known as dysbiosis, have been linked to the development of inflammatory diseases and infections.⁴

Polyphenols, like anthocyanins, found in wild blueberries have demonstrated the ability to selectively influence the composition of gut microbiota, offering potential in preventing disorders associated with intestinal and metabolic obesity.⁵ They are an example of prebiotics, typically described as food or substrates for the gut microbiota.⁶ 

The discovered effects indicate that polyphenols may play a role in promoting a balanced environment in the gut, fostering the growth of beneficial bacteria while reducing that of harmful bacteria. This dual action potentially helps alleviate health issues associated with obesity. However, further research is essential to unravel the precise mechanisms involved and identify the specific polyphenols responsible for these beneficial effects.⁵

Fibre in blueberries

In broad terms, dietary fibre refers to the consumable components of plants or comparable carbohydrates that resist digestion and absorption in the small intestine. It contains several compounds like vitamins, minerals and antioxidants which are good for the body.⁷

Consuming foods rich in fibre like blueberries benefits our digestive system and promotes a positive influence on gut bacteria, especially since fibre is also considered a prebiotic. Moreover, as fibre travels through the stomach into the colon, it adds volume to faeces, aiding the peristaltic movements necessary for the effective passage of faeces through the rectum to avoid constipation. This, in turn, supports overall gastrointestinal health.

Blueberries and chronic diseases

Disturbances in gut health have been linked to the progression of chronic diseases such as type 2 diabetes and irritable bowel syndrome (IBS).⁵ The fibre content as well presence of polyphenols in blueberries have been known to lower the risks of these diseases.^1,7

Type 2 diabetes

Type 2 diabetes is a condition where body cells are not responding normally to insulin, a hormone produced by the pancreas that enables the cells to absorb blood sugar to obtain energy.

Polyphenols, particularly anthocyanins play a role in improving insulin sensitivity—a crucial factor in preventing type 2 diabetes. Research in population studies has shown that blueberries reduced the risk of type 2 diabetes by 26%. Furthermore, while examining anthocyanin-rich foods, especially blueberries, having them at least twice a week or even just once a month still shows a significant 23% risk reduction.¹

Many studies have also reported that having more fibre in our diet is linked to a lower risk of diabetes. The way dietary fibre behaves in our digestive system and its thickness seems to be the reasons it can influence the risk factor. These actions might lower how much nutrition our body takes in, reducing the energy we get from what we eat. Also, because dietary fibre is not very energy-dense itself, it could even make the overall energy of our food lower.⁷

Irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a condition that brings about abdominal (belly) pain and irregular bowel habits. These can include diarrhoea, constipation, or a mix of both. People with IBS may also experience bloating, a feeling of fullness, and more gas than usual.

As with diabetes, fibre contributes to feelings of fullness and can also help alleviate symptoms of constipation associated with IBS, though too much fibre as well as certain types of fibre may affect those with IBS. Furthermore, the polyphenolic compounds in blueberries, particularly pterostilbene (PSB), may possess immunosuppressive properties that can aid in managing chronic inflammatory diseases like IBS-D (IBS with diarrhoea). By reducing the production of cytokines, which are part of the body's inflammatory response, PSB helps alleviate symptoms associated with IBS-D.

While further research is necessary, these findings suggest that integrating berries into one's diet could offer a therapeutic approach for individuals managing chronic inflammatory disorders and IBS symptoms.

Precautions and allergies

While blueberry allergy prevalence is relatively low, reactions, especially in those with existing fruit allergies, have been reported. Symptoms vary from mild to severe. Immediate responses, occurring shortly after consumption, might involve oral allergy syndrome (OAS), leading to sensations like itching, tingling, or swelling in the lips, mouth, or throat. 

Additionally, individuals may experience gastrointestinal symptoms, including abdominal pain, nausea, or diarrhoea. In more severe cases, systemic reactions could emerge, featuring hives, persistent itching, difficulty breathing, or, in extreme instances, anaphylaxis.

Accurate diagnosis is crucial. Clinical history, including details of the allergic reaction, is considered during diagnosis. Skin prick tests and specific blood tests help confirm blueberry allergy and assess the severity of the response. Oral food challenges, conducted under medical supervision, determine the threshold of tolerance to blueberries.

The allergy can be managed through strict avoidance of blueberries and products containing them. Reading food labels diligently is important, as blueberries might be present in various processed foods. In cases of accidental ingestion, prompt administration of antihistamines or epinephrine may be necessary to alleviate symptoms or treat anaphylaxis, respectively. 

Summary

Blueberries stand out as digestive powerhouses, fostering overall well-being. Their nutrient-rich composition, featuring vitamins, minerals, and antioxidants, actively supports essential digestive processes. The fibre content in blueberries plays a pivotal role in digestion, acting as a prebiotic that promotes a healthy gut environment and prevents issues like constipation. Polyphenols, and prebiotics too, help balance out gut microbiota, which has the potential to further reduce issues associated with obesity. Additionally, both these components in blueberries demonstrate promise in reducing the risk of chronic diseases, including type 2 diabetes and irritable bowel syndrome (IBS). While mindful of blueberry allergies, their inclusion in a balanced diet becomes a flavorful and beneficial choice for digestive health.