How does diet affect the immune system?

Guest post:

Supporting young up and coming nutritionists is an important part of being a RNutr. A big thanks to Tanya for this post on diet and the immune system. Tanya is a recently registered Associate Nutritionist with the Association for Nutrition (AfN). Her interests include osteoporosis, healthy ageing and all things food. Her blog is here

Diet can have an affect on your immunity. But how does the food we eat affect the immune system? What foods best support the immune system?

A varied diet supports the immune system

There is a lot of interest in the immune system right now as a result of the current pandemic. Diet is one of many factors that affect the immune system. Different nutrients in the food we consume are needed by different parts of the delicate and complicated immune system.  Eating well can support your immune system to function optimally.

What is the immune system?

The immune system is a network of different cells and tissues in your body working together to protect us from infections. There are several lines of defence to protect the body from invading pathogens (germs).

Firstly, physical barriers such as skin and mucous membranes stop the invading pathogens from entering the body. Secondly, if the barrier is breached cells such as macrophages identify and destroy any pathogens before they can cause any harm. Finally, as a future layer of protection lymphocytes remember pathogens so that the immune response is swifter and more effective.

Different parts of the immune system

No special food or supplement will boost immune system

There is no single magic nutrient that will boost your immune system allowing you to fight off any infection that comes your way. The British Dietetic Association states that you “cannot “boost” your immune system through diet”. However, a varied and balanced diet will help you to get all the nutrients your immune system needs.

Your immune system needs protein to build and maintain the important structures that make the immune system. Fats are important for the process of inflammation regulation and the cytokines that act as chemical messengers within the immune system.

There are many micronutrients which can support your immune system such as vitamins A, C, D, B6 and B12 and the minerals copper, iron, zinc and selenium. Zinc, Vitamin C and Vitamin D have been shown to have the strongest evidence for being effective for immune support.

As you age your immunity declines

Over time your immune system will not be able to battle infections as quickly. Therefore, you are more likely to catch infections, and it may take you longer to recover. This gradual deterioration of immunity is known as immunosenescence.

What can we do to maintain a healthy immune system as we age?  An increased intake of polyunsaturated fatty acids (PUFA) can reduce inflammation which can have a negative impact on the body’s organs. Sources of PUFA include oily fish e.g. sardines and rapeseed oil. A study has shown that an increased Vitamin E intake (higher than the recommended levels; 3mg a day for women, 4mg a day for men) has been shown to reduce inflammation and lower the risk of infection in the older population. 

Eat a varied and balanced diet

Poor nutrition can have a negative effect on the immune system. As a result. those with poor nutrition might be more suseceptible to infections, be ill for longer and recovery afterwards can be slower.

The eatwell guide is the UK government’s model for a balanced diet for adults and children aged over 5. It recommends eating a variety of food from different food groups in order to get all the nutrients and energy we need. 

Image caption: The Eatwell Guide

There are five main food groups in the Eatwell Guide. They are:

  • Fruit and vegetables
  • Potatoes, bread, rice, pasta and other starchy carbohydrates
  • Dairy and alternatives
  • Beans, pulses, fish, eggs, meat and other protein
  • Oils and spreads

It does not represent what you should eat at every meal but it represents the type of food you should be eating over a week. The British Nutrition Foundation has made a resource that explains more about healthy eating. If anyone has any medical conditions or dietary requirements they might need to ask their GP for specific healthy eating advice. 


Good nutrition means that the body is prepared for immune system challenges. There are no foods that can “boost” immunity.  Ageing can cause the immune system to be less effective. Eating a balanced diet throughout your life will supply important nutrients to the body so it can fight off infection. 

For more information there is a recent Association for Nutrition (AfN) Twitter chat about Lockdown Nutrition took place on 19th May 2020. 

Tanya is a recently registered associate Nutritionist with the Association for Nutrition (AfN). Her interests include osteoporosis, healthy ageing and all things food. Her blog is here

2 Comments Add yours

  1. africanutritionzim says:

    Well said, most bloggers tend to overemphasize the role of food as immune boosters.

    1. Thank you for your comment!! Totally agreed. The idea that we can ‘boost’ the immune system with one thing shows a lack of understanding of the complexity of the immune system!! That a ‘boosted’ immune system usually means bad things like auto immune disease or allergy. That there are so many points in the immune response that need different nutrients that the only way to truly support it well is through a varied healthy diet!

      Then of course there is the gut microbiome and its link to the immune system but that’s another story!

      And right now, with Covid-19 with us, the immune ‘boosting’ stuff seems even more prominent than ever.

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