Almost everyone will have heard the concept of being able to ‘boost your immune system’ and a simple Google search will reveal a whole host of articles, dietary regimens and supplements that promise to protect you against illnesses and germs. But is there much truth in most of these claims, and is boosting your immune system something you actually want to do?
The immune system is amazingly complex, and you may be concerned by thoughts of expensive supplements that promise to protect you from all forms of infection. Luckily, supporting your immune health doesn’t have to be complicated or expensive!
AXA Health Physiologists and Nutritionists Polly Smith and Thomas Rothwell help to separate fact from fiction and explain how our dietary choices can impact our immune health.
The role of the immune system
We all have probably heard of the immune system at some point and know roughly what it does. ‘It keeps us healthy’ or ‘protects us from illness and disease’ and to be honest you are not technically wrong! But let’s look into the immune system in a little more detail.
The immune system is made up of two parts; the innate and the adaptive immune system.
The innate immune system is our frontline protective barrier against germs and other foreign cells entering the body. This part of the immune system consists of our skin and mucous membranes, like our eyes, mouth, stomach and gut. All of these have their own protective mechanisms to prevent or try and stop infections in their tracks.
For example, if a virus enters the body, scavenger cells, a special type of white blood cell, engulf and digest that virus. Another type of immune cell, called natural killer cells, also help out by locating infected cells and essentially terminating them. The innate immune system is the first to act when a foreign cell is identified in the body, if it can’t destroy the infection, the body’s second line of defence comes into play1.
The second part of the immune system is the adaptive immune system. If the innate system fails, the adaptive immune system takes control and can manage the threat with more accuracy. This second system has the benefit of being able to learn and remember germs, so if we get threatened by this particular germ again, the adaptive system can respond much faster2. Interesting fact, this is how vaccines work!
Can I boost my immune system?
Now you have an understanding of what the immune system is and how it functions you might be wondering how you can potentially boost your immunity? And in fact, the phrase “immune boosting” was a trending search on Google over the last year3. However, despite the plethora of articles that are produced from this search you cannot ‘boost’ your immune system; and it’s not actually something you would want to be able to do either!
‘Boosting’ the immune system in its actual sense would mean having an over-active immune response which is implicated in both allergic reactions, and autoimmune conditions. So, it would be very troublesome to be able to ‘boost’ our immune system, despite the many articles online suggesting we are able to do so through our dietary choices4.
What we can do however, is eat to support and maintain normal immune function which can help to reduce our susceptibility to infection. And we’ll tell you just how to do that in this article.
Nutrition to support the immune system
Before we get started it is important to note that there is no magic pill, food, superfood or diet that can ensure you have 100% protection from infection. Although, there is a lot that you can do support the immune system to make sure it is firing on all cylinders and in the best condition to launch its defences when needed.
Energy – Simply not getting enough energy in the form of calories can have a negative impact on our risk of infection. So, if you are looking to lose weight make sure you are not drastically reducing your calorie intake to extremely low levels. On the other hand, eating too much energy, which can lead to excess fat mass, can also have a negative impact on our immune function5. So it’s important that we are eating enough food to provide us with vital nutrients that keep our immune system ticking over, but not too much so we are storing the excess energy as fat and causing negative interactions with our immune system.
Protein – Many aspects of our immune system rely on proteins as a catalyst to initiate a chain reaction to deploy defensive measures to protect us from a harmful infection. Try and include a rich source of protein with each meal, such as chicken, fish, lean red meats, beans, lentils, nuts or seeds.
Gut health – The gut is home to around 70-80% of the body’s immune cells, meaning that the gut has a major role to play in the function of the immune system. The gut also has an impact on the absorption of nutrients, and so a healthy gut is important for ensuring the nutrients we need to support a flourishing immune system are well absorbed5.
To nourish your gut, aim to eat a diet that is high in fibre such as pulses, legumes, beans, fruits, vegetables and wholegrains. Pre and probiotics are also important for helping our gut microbiota healthy. Prebiotics feed the gut bacteria already found in our gut and can be found in foods such as onions, leeks, asparagus, bananas, barley, apples and oats. Probiotics are live micro-organisms which helps our guts flourish. Probiotics come from foods such as yoghurt, kefir, sauerkraut, tempeh, kimchi and some types of cheese.
Vitamin C – Has a role in both the innate and adaptive immune systems. Citrus fruits, berries, peppers, tomatoes and broccoli top the list for Vitamin C.
Vitamin D – Research now suggests that the sunshine vitamin protects us against upper respiratory tract infections (common cold symptoms etc), and our immune cells even have Vitamin D receptors! It is suggested to take a low dose Vitamin D supplement of 10mcg per day between October and early March if you live in the UK.
Zinc – Zinc supports our T-cells and these are vital as they kickstart the adaptive immune response, detect an infection and remember germs for a future exposure. Whole grains, oysters, scallops, meat, nuts and seeds are good sources of zinc.
Selenium - Studies have shown that increasing selenium levels have been associated with improved immune response. Just two Brazil nuts a day will provide you with the daily recommended amount of selenium so give that a try1.
Omega 3’s – These fatty acids are classed as anti-inflammatories and help our white blood cells to do their job. Oily fish, nuts, seeds and avocados are all strong sources of omega 3’s.
Top Tips
- Eat a varied and colourful diet. Different colours code for different nutrients and these all have an important role to play in ensuring your immune system can function optimally.
- Take a food-first approach and only supplement if you cannot get certain nutrients through a dietary approach. This is because the bioavailability, which is the amount of the compound that will actually be absorbed from a supplement, is hugely variable in supplements and is much lower than in foods where the nutrient is naturally occurring.
- Be mindful of any unrealistic claims you see in the news or online in regards to nutrition and your immune function – if it sounds to good to be true, it usually is!
There are no miracle cures here, simply ensuring you are eating a well-balanced and varied diet is the best thing you can do to support your immune system. Outside of diet, ensuring you are exercising regularly, not smoking and not drinking alcohol excessively will also help you to get the most out of your immune system.
1 Hillion et al. (2020) Clin Rev Allergy Immunol, 58(2):151-154.
2 McComb et al. (2019) Methods Mol Biol, 2024:1-2.
3 Wagner et al. (2020) Allergy Asthma Clin Immunol, 16:76.
4 Rachul et al. (2020) BMJ Open, 10:e040989.
5 Vega Robledo & Rico-Rosillo. (2019) Rev Alerg Mex, 66(3):340-353.
6 So & Tam. (2020) Microorganisms, 8(11):1727.