The importance of a healthy immune system and the role of nutrition in supporting immunity

Let’s talk about our unsung heroes: immune cells. They’re constantly on the job, defending us from sneaky invaders like bacteria, viruses and fungi. They even patrol our bodies to sniff out cancer cells and repair any wounds or tissue damage. For this reason, keeping our immune system in top form is crucial for our overall well-being.

But how can we support this tireless team? One of the answers lies in our diet. Because we get infected with millions of new pathogens every day, our crew needs to be provided with the best tools to fight and prevent disease. A well-balanced diet, for example, rich in immune-boosting nutrients like vitamin C and flavonoids can work wonders. Fortunately for us, blueberries comprise huge amounts of these, making them the star of the show. Truly, incorporating these tiny fruits in your diet will make your immune system thank you, at least in their own way.

In this article, we’ll embark on a journey to discover the tiny yet mighty blueberries. We’ll uncover their nutritional secrets and explore how they hold the power to supercharge and balance our immune system while supporting our microbiome.

Nutritional Profile of Blueberries

Blueberries are like nature’s nutritional gems. They may be small, but they’re bursting with superpowers. Picture them as the superheroes of the fruit world, dressed in deep blue or purple capes, ready to defend your body against the villains of illness and the detrimental effects of ageing. These delicious, sweet-tart orbs are not only a treat for your taste buds but also a powerful boost to your well-being, and especially to your immune system.

Despite being low in calories and mostly water, blueberries are nutritional powerhouses. In just 1 cup (148 grams) serving you get:¹

• Vitamin C – 16% of daily value (DV)
• Flavonoids, including anthocyanin: A whopping 1480 milligrams of these antioxidants ²
• Vitamin K (phylloquinone) – 24% of the DV
• Manganese – 22% of the DV
• Carbohydrates – 21.5 grams
• Dietary fibre - 3.6 grams

The Immune System: Your Body’s Defense Brigade

Our immune system is a complex army of cells that work in harmony to protect us. They each have unique roles, like specialised soldiers, to combat different threats. For example, natural killer cells are excellent virus hunters and cancer cell assassins. Other cells, like dendritic cells, are excellent communicators, as they sample the environment where they live (usually below the skin, our lungs, and guts) on the lookout for pathogens. When they detect one, they alert other immune cells, like lymphocytes such as T cells, for them to prepare accurate defences and recruit further troops (immune cells) to the infection site.³

When there’s no threat, our immune system is ‘on standby’, so that it doesn’t damage our own tissues and cells. However, when danger lurks, our immune system needs to become activated, generally after recognising a pathogen. Nonetheless, balance is key; deactivating the immune system when the infection has been resolved is equally as important as activating it. Failure to deactivate the immune system when required could cause problems like autoimmunity, where our body mistakenly believes our own cells are dangerous and attacks them, causing persistent inflammation which can lead to chronic diseases and tissue damage.⁴

So, where do blueberries come in?

Blueberries and Immunity

Role of antioxidants like vitamin C and flavonoids in immune support

Vitamin C, also known as ascorbic acid, is a potent antioxidant found in blueberries and plays a crucial role in supporting immune function. It achieves this by both activating and balancing our immune system, ensuring efficient activation when needed and preventing over active responses.

It was shown that this vitamin enhances the activity of natural killer cells (the virus and cancer cell hunters), the activation and multiplication of lymphocytes (the cells that dendritic cells communicate with), and facilitates the movement of immune cells to infection sites.^5,6 This is essential for eliminating harmful pathogens.   

Interestingly, although most animals can synthesise vitamin C from glucose, humans and guinea pigs lost the enzyme needed to make this reaction through evolution, making its intake more critical than ever.⁷ Moreover, because vitamin C is water-soluble, the risk of overdose is virtually non-existent since our bodies can easily eliminate any excess.  So, rest assured if you find yourself indulging in blueberries on a summer afternoon - your kidneys won’t mind.

But there’s more to these tiny powerhouses. Blueberries are also packed with flavonoid antioxidants, especially one called anthocyanin (let’s call it ACN for short), which accounts for around 60% of the total polyphenolic content in ripe blueberries.⁸  

So what’s so special about ACNs? Well, multiple studies have shown that ACNs play a key role in both activating and balancing the activity of our immune cells. For example, ACNs have been demonstrated to activate a specific type of T cells, the gamma-delta subset, which reside in our gut and lung linings. These are areas where troublemakers like foodborne pathogens or airborne viruses try to sneak in.

When these T cells become excited, they have a positive impact further activating other branches of our immune system, acting as a superhero team-up. Gamma-delta T cells then communicate with other immune components, such as natural killer cells and other lymphocytes, which together can keep the pesky invaders at bay, preventing disease.⁹

But that’s not all! They’re also peacekeepers. They also help your immune system find its zen by reducing the release of inflammatory molecules and promoting anti-inflammatory pathways. This is especially crucial after the threat (like an infection) has passed. In addition, ACNs also neutralise free radicals, which are molecules that go haywire during stressful times in your cells, like during sun exposure, inflammation, or intense workouts, in a process known as oxidative stress. Free radicals can accelerate the ageing process and even damage your cells and DNA. Thus, by protecting immune cells from oxidative stress, ACNs may additionally improve immune function.⁹

In a nutshell, ACNs act like the guardians of your immune cells, protecting them from stress while helping them function at their best.

Scientific studies on blueberries and immune function

As mentioned above, we all know that exercising can sometimes lead to the feeling of being wiped out and sore, generating oxidative stress and inflammation. But here’s where blueberries can come to the rescue. Imagine this: a group of brave people participated in a study where the scientists measured their inflammation levels, oxidative stress, and any immune system changes. These people incorporated blueberries into their diet daily for 6 weeks, and on top of this, they were additionally treated with a 375g blueberry dose before going for a run. They observed the group that had the blueberries showed higher natural killer cell populations and higher levels of Interleukin-10, a molecule that’s like a peacemaker in your body, with a key role in reducing inflammation. This is great news as daily blueberry consumption for this period seemed to enhance their immune function, while helping soothe the excessive inflammation that comes with strenuous exercise.¹⁰

But that’s not all, in another study, researchers looked at dendritic cells, and also at the production of reactive oxygen species (ROS). These ROS molecules are involved in oxidative stress and hence cellular damage. The researchers observed that the group consuming blueberries had higher numbers of dendritic cells and fewer ROS when compared to the placebo group. This is more proof that blueberries are like your immune system’s best friends, keeping them happy and healthy.¹¹

The Gut-Immune Connection

And guess what? Blueberries aren’t just great for your muscles and immune system – they’re also superheroes for your gut. The gut microbiota is the complex community of millions of microorganisms that reside in the intestinal tract and provide crucial benefits to us. Some of these microorganisms are beneficial, others just reside without causing any good or harm, and a few can become harmful and attempt to invade us if given the opportunity. When they are in harmony, our beneficial bacteria prevent harmful bacteria from invading us, produce nutrients and regulate our immune system to prevent excessive inflammation. 

Importantly, because the microbiota have an intimate relationship with our immune cells, when the gut microbiota is disturbed, for example as a result of stress or disease, the immune system becomes altered too, sometimes leading to digestive inflammatory disorders and autoimmunity.  For this reason, keeping a healthy microbiome is essential for not only maintaining overall good health but also a happy immune system.¹²

Now, here’s the juicy part - blueberries can have an impact on the gut microbiota populations, encouraging the proliferation of beneficial bacteria.¹³ For example, a recent study assessed the gut microbiota of rats that were given a high-fat diet. When supplemented with blueberries, rats’ microbiota composition changed, presenting an increase in Gammaproteobacteria abundance. This study suggests that blueberries can impact the gut microbiota populations.¹⁴ Another study found similar results in rats’ friends- mice, where an extract obtained from blueberries was given to obese mice that were also fed a high-fat diet. The researchers observed that supplementation had a positive impact on the beneficial gut microbiota, as it helped restore the mucus layer of the colon (that the friendly bacteria love), making the environment even cosier for them.¹⁵

And it’s not just for the animals. Humans, too, can enjoy these gut-loving benefits. A study showed that blueberries had prebiotic-like effects on the gut, increasing Bifidobacterium species relative abundance.¹⁶ Bifidobacteria are healthy bacteria which help us digest fibre, stop infections, and produce important vitamins like B vitamins.¹⁷ 

So there you have it – blueberries are your gut microbiota protectors, demonstrating their potential to promote optimal immune function by keeping a healthy microbiome.

Practical Ways to Include Blueberries in Your Diet 

As you have learnt from this article, incorporating blueberries into your diet is both delicious and incredibly nutritious. An easy way to incorporate them into your diet is by blending them into smoothies for a refreshing treat. Additionally, blueberries make a fantastic addition to salads, providing a burst of flavour and antioxidants. 

But there’s more. If the birthday of someone you love is coming up, it is a great idea to use them in baking, such as in muffins and pancakes for a delightful surprise. It is however worth noting that, although blueberries are a fantastic addition to your diet, their benefits are still limited. Therefore, a well-balanced diet containing more vitamins, lipids and proteins is necessary to maintain a long-term happy immune system and intestinal microbiota, which will translate into long-term health and longevity.

Summary

Blueberries are nutrition-packed gems, containing manganese, vitamins K and C, and flavonoids like anthocyanin. These nutrients, especially vitamin C and flavonoids play a crucial role in supporting immune cells to ensure their optimal function. These antioxidants achieve this by enhancing the activity of immune cells like natural killer cells, dendritic cells, and lymphocytes like gamma-delta T cells, which in turn fight pathogens and prevent disease. Accordingly, these antioxidants also help lower inflammation and reduce oxidative stress, two key factors required to maintain a well-functioning and well-balanced immune system.

In addition, blueberries can impact our gut microbiota, the community of microorganisms living in our intestinal lining. The gut microbiota and our immune cells are intimately associated, and hence a healthy gut microbiome is linked to a healthy immune system. Some animal and human studies have shown that blueberries promote the proliferation of beneficial gut bacteria, suggesting these fruits may contribute to maintaining a healthy immune system in this way too. For this reason and due to their versatility, blueberries make a great addition to our diet, being easily incorporated into smoothies, salads, and cakes. However, it is worth noting that while they offer excellent immune support, a well-balanced diet with a variety of nutrients is essential for long-term health and a strong immune system.