Diet and The Immune System
We often talk about our immune systems, but if you were asked to describe yours, would you know where to start?
The immune system is comprised of an intricate network of cells, tissues, and organs that all produce substances to help the body fight infections and diseases.
It encompasses the white blood cells, organs, and tissues of the lymph system. These tissues include the spleen, tonsils, bone marrow, thymus, lymph nodes, and lymph vessels.
The immune system’s primary objective is to protect the body from outside invaders like bacteria, fungi, viruses, and toxins. There are two main parts:
- The one you are born with – the innate immune system.
- The adaptive/acquired immune system, which develops when your body is exposed to specific pathogens (organisms capable of causing disease).
The innate immune system
The innate immune system is active from the moment you are born. This is the rapid response element of your immune system and is the first to respond when an ‘invader’ is found in the body. When the immune system identifies the intruder, it gets surrounded and engulfed by the immune system’s ‘killer cells.’ These ‘killer cells,’ known as phagocytes, diligently work to dismantle the invader, rapidly generating additional phagocytes that collaborate to strengthen the defence.
Our innate immune system supports the adaptive/acquired immune system in safeguarding the body against specific invaders. Antibodies, a type of protein present in the blood, recognize specific pathogens within the body. These antibodies are generated by B lymphocytes, persisting in the body in small numbers as a precaution in case the same invader attempts another attack. The initial exposure to a new pathogen takes a few days for the production of pathogen-specific antibodies. Yet, upon future encounters with the same pathogen, the immune system promptly identifies and eliminates it, ensuring a quicker response – excellent news for you!
Visualize your body as a castle with different types of soldiers (antibodies) adept at recognizing various enemies (pathogens). If an enemy, let’s call it a dragon, breaches the outer wall (your skin), one of your soldiers identifies and devises a strategy to neutralize it. This soldier then duplicates itself, ensuring that if another dragon invades later on, the soldiers (more of the same specific antibody) can be produced much faster, preventing harm to your body. With each encounter of a new, distinct pathogen, a similar process unfolds, with another soldier (antibody) responding by learning how to combat it.
How diet affects your immune system
Diet is one of many factors that can boost or suppress immune function, so it is important that we carefully consider what we’re eating. Dietary deficiencies due to a poor diet can impair the production and activity of the immune system’s antibodies and immune cells. However, contrary to the many slogans you may see on packaging in supermarkets or on social media adverts, no products can ‘boost your immunity’. Sarah Stanner, Science Director at the British Nutrition Foundation, explains that “no individual nutrient, food, or supplement will boost immunity or stop us getting highly infectious viruses”. However, having a healthy diet will optimise and support the immune system’s normal functioning, helping to fight off any pathogens and keep you feeling healthy. The following nutrients are essential for ensuring optimum performance of the immune system:
- Vitamins A, B6, B12, C and D
- Zinc
- Selenium
- Iron
- Copper
- Folate
Diet top tips for an optimised immune system!
Eat more fruits and vegetables rich in vitamins C and E, beta carotene, and zinc. Include a wide variety of brightly coloured fruits and vegetables such as berries, kiwis, apples, and kale. Vitamin C can be found abundantly in citrus fruits, however, surprisingly, red peppers contain as much (if not more) Vitamin C than some citrus fruits!
Vitamin C is thought to increase the number of white blood cells produced by the body, which are vital for fighting infections. However, as your body does not store Vitamin C, you must include it regularly in your diet. It is recommended that men consume 90mg daily and women 75mg.
Various mushrooms, including button and Shiitake, provide the body with selenium and B vitamins – excellent for supporting the immune system.
Oysters are rich in zinc, which helps create and activate the white blood cells involved in the immune response to infection. It also helps with wound healing.
Ripe watermelon contains an antioxidant called glutathione, which strengthens the immune system, helping to help fight infection. To get the most glutathione from watermelon, eat the red pulpy flesh near the rind.
Spinach contains a supply of folate, which aids the body in making new cells and repairing DNA, which is essential for the immune system. It is coined as a ‘superfood’ because, as well as folate, it contains fibre, vitamin C, and more.
Teas of many varieties are known for their disease-fighting properties. They contain polyphenols and flavonoids, which seek out and destroy free radicals in the body. This is important as free radicals can cause cell damage, which may lead to disease. However, be mindful of your caffeine intake – too much caffeine can negatively affect your immune system, so moderation is key!
The best things you can do to support your immune system involve eating a diverse, balanced, and fibre-rich diet, following NHS guidelines on alcohol consumption, ensuring a good amount of sleep, exercising regularly, and trying to keep your stress levels down! Read more info, advice, & tips from the NHS:
Dietary habits that inversely affect your immune system
Consuming excessive sugar, whether in food or drinks, hampers the functioning of your immune system. This suppression of immune function may persist for a few hours after consumption.
Excessive alcohol intake, even in the short term, can disrupt the functioning of the immune system. A paper published in the Alcohol Research Journal notes a long-established correlation between excess alcohol intake and a compromised immune system. Excessive drinking not only increases susceptibility to pneumonia but also elevates the risk of developing acute respiratory disorder syndromes (ARDS). Other observed consequences include a heightened risk of sepsis, increased postoperative complications, impaired wound healing, and a slower, less complete recovery from infections.
Too much salt! A study from the University Hospital of Bonn (conducted in mice and humans) concluded that a salt-heavy diet may lead to immune deficiencies. When the kidneys excrete salt, a cascading effect reduces the body’s ability to combat bacterial infections.
In excessive amounts, caffeine can also negatively impact immune function. While caffeine boosts energy levels, it also raises cortisol levels, a stress-response hormone. Sustained high cortisol levels in the blood can diminish the effectiveness of the immune system. Additionally, regular caffeine consumption may impede immune system function by reducing the production of T cells, suppressing lymphocyte function, and decreasing interleukin production—essential components for fighting off infections.
