Can Food Really 'Boost' Your Immune System?

Let’s be clear from the start, there are important links between nutrition and immunity.

In order for the immune system to deal with foreign invaders such as viruses and bacteria, there must be a supply of energy from fuel sources that come from food - including glucose and fatty acids.

Amino acids (the building blocks of proteins) are also particularly important for producing different components of the immune system.

Finally, vitamins and minerals also play important roles in ensuring protecting immune health. 

This relationship between nutrition and immunity is especially apparent in developing countries, where malnutrition leads to compromised immunity and infection-related deaths. However, if food intake is adequate and varied, there is very little evidence to suggest any foods or individual nutrients actually ‘boost’ immunity. According to Prof. Neil Walsh (Liverpool John Moores University), the current view in the scientific community is that we should not be so concerned with asking whether a nutritional intervention will stop us from getting sick, but whether the nutritional intervention can reduce how sick we will get (this is a really key point!).

But what does this mean in terms of food and, importantly, how can we use this information? 

We use food to nourish the body. That is, to provide it with key nutrients required to keep us energised, alert, resistant to illness and injury, and performing to the best of its ability. Where immunity is concerned, there are a few priorities to focus on to ensure that we’re providing the body, and the immune system itself, with plenty of the specific nutrients it needs to function well. We’d recommend focusing on: 

1. Avoiding severe energy (calorie) restriction: the immune system relies on a regular supply of energy (in the form of calories from food), especially carbohydrates, as well as an adequate supply of vitamins, minerals and healthy fats (low fat isn’t always better!). Try your best to stick to a regular meal structure and don’t unnecessarily restrict particular food groups as doing so may deprive your immune system of essential nutrients.
2. Hydration: Our ‘first line of defence’ against bacteria is in the mouth (saliva) and nose (mucus); both of which heavily depend on your hydration status. Drinking plenty of water and consuming foods with a high water content helps to ensure that the antibodies in these areas are able to function properly - helping to prevent an onset of illness. 
3. Protein: protein is essential for our immune cells to function properly. As such, it’s important to consume high-quality serves of protein regularly throughout the day. Remember to include a serve of protein (such as meat, fish, eggs or soya products) at each meal time. In particular, plant proteins such as pulses, tempeh and tofu also support the diversity of the gut and contain many other nutrients that the immune system needs. They are great meal additions!
4. Vitamin C rich foods: vitamin C is crucial for the normal function of white blood cells that function to protect us against infection. Vitamin C also improves the uptake of iron in the body, and iron is important for the development of immune cells. Focus on including at least one serve of one of the following in each meal to up your vit C intake: citrus fruits (orange, lemon, lime), berries, peppers, broccoli, spinach or tart cherries are all good choices.

Once you have the basics covered, it’s time to up your game! The following foods not only help flavour-boost your dishes, they also support your immune-health:

1. Herbs & spices: many herbs and spices have antioxidant properties which may help to manage inflammation, as well as antiviral properties that may help combat common colds and viruses.
2. Fermented foods (containing probiotics): these foods  diversify and increase the number of good bacteria in the gut, which can positively influence the immune system and help combat common acute illnesses. Some of our favourite probiotic-rich foods include: natural (unsweetened) yoghurt, kefir, sauerkraut, kimchi and tempeh - there’s something for everyone! 

During periods of high infection risk, such as during air travel or if you experience the first signs of a common cold, there are a couple of evidence-based supplements that may reduce the severity and duration of illness. If you're an athlete, you must ensure that any supplement has undergone batch testing (you can search for products here to minimise contamination risk):

1. Zinc lozenges: at the onset of a common cold dissolve zinc lozenges in the mouth. 75 mg per day of elemental zinc.
2. Vitamin C supplement: consider vitamin C supplementation during heightened infection risk, e.g., traveling. 0.25–1.0 g per day.
3. Probiotic supplement: consider probiotic supplementation if illness prone and/or traveling. ~10¹⁰ live bacteria per day. 

Summary

It’s misleading when headlines claim that foods or supplements can ‘boost’ immunity, as the science simply doesn’t support this. You cannot ‘boost’ your immune system, but good nutrition is crucial for protecting your immune health. Getting the basics right is the most important thing, then bolt-ons such as supplemental vitamin C, probiotics and zinc may improve tolerance to infections during periods of heightened risk. For a deep dive on this, see this free article from Prof. Neil Walsh. One other nutrient worth considering where immunity is concerned is vitamin D, that unfortunately cannot be obtained in high enough quantities in the diet when sun exposure is limited. We’ll be covering everything you need to know on vitamin D in our next blog post, so be sure to keep an eye out!