Part 1 – Nutrition for The Immune System

by | Jun 11, 2020

The Immune System Part 1 – Physical & Biochemical Barriers


The last couple of months, COVID-19 has dominated the headline, focusing on how people can protect themselves, such as using personal protective equipment, hand washing and social distancing. However, the human body comes equipped with an array of defence mechanisms, known as the immune system. Interestingly, there has been minimal discussion concerning what steps we can take to help improve and keep our immune system healthy.

I am going to explore the different layers of the immune system and focus on the pivotal role nutrition plays to keep it healthy and functioning as it should. When the immune system detects something unusual or pathogenic, such as a cut or a virus, it becomes supercharged. When the immune system becomes supercharged, it requires more nutrition to fuel, make and maintain all the components of the immune system to stop us getting sick.

The first layer of the immune system I am going to discuss is the bodies inbuilt PPE (personal protective equipment), physical and chemical barriers. I am also going to look at the critical role specific nutrients have to keep these barriers healthy.

Physical & Biochemical Barriers

Physical and biochemical barriers are our immune systems first line of defence. They help protect us from pathogens such as bacteria, viruses, fungi, parasites, pollen, dust and toxic chemicals entering the body.

The purpose of physical barriers is to trap, filter or move unwanted particles from the body, such as when you cough or sneeze. Biochemical barriers contain compounds such as antimicrobials, enzymes or are highly acidic to help wash away, move or destroy unwanted pathogens.

What are Physical Barriers?

  1. Skin
  2. Gastrointestinal tract
  3. Respiratory tract
  4. Nasopharynx
  5. Eyelashes
  6. Body hair including nose hair
  7. Cilia

What are Biochemical Barriers?

  1. Tears
  2. Saliva
  3. Sweat
  4. Stomach acid
  5. Mucus
  6. Bile

Nutrients to Support the First Line of Immune Defences

Nutrients play a vital role in ensuring the integrity of our physical and biochemical barriers.  Nutrients ensure structurally, and functionally our first line of immune defence is maintained and can keep up with any additional workload if exposed to pathogens. It is becoming clear that we can start to predict a person’s increase the risk of infections and how well they will recover based on their diet.

The Role of Vitamin A

  • Ensures the structural and functional health of your skin and the mucous membrane that lines internal cavities such as your gut, nose and lungs.
  • Vitamin A helps with the composition of good gut bacteria and helps keep the balance of good bacteria and harmful bacteria.
  • Vitamin A assists with the guts immune response by supporting the gut barrier to ensure it is healthy, and the barrier integrity is maintained. 
  • It helps to regulate the immune system by reducing the toxic effects of a type of free radical known as reactive oxygen species (ROS).

The Role of Vitamin D

  • Helps regulate antimicrobial proteins to destroy unwanted pathogens. 
  • Vitamin D helps modify gut bacteria to ensure there is a healthy balance of good bacteria.
  • It helps to support the barrier integrity of the tissue that lines the gut, kidney and eyes.
  • Vitamin D protects the lungs against infections by stimulating the cells that line the respiratory tract to produce antimicrobial compounds to help fight infections.

The Role of Vitamin C

  • Vitamin C is essential to produce collagen, which is one of the primary building blocks for skin and tissue that lines the gut.
  • Vitamin C protects the cell from damage caused by toxic molecules known as free radicals, helping to support the integrity of the skin and tissue that lines the gut.

The Role of Vitamin E

  • Protects cells from free radical damage, helping to support the integrity of our barrier layers such as the skin and gut lining.

The Role of Vitamin B6, B12 and folate

All these B vitamins help support the gut barrier function, and they all have a slightly different role to play.

  • Vitamin B6 helps to regulate the gut immune system by helping to control the migration of immune cells known as Lymphocytes into the intestines when pathogens are detected.
  • Folate helps to prolong the survival of specialised immune systems cells called regulatory T cells so they can fight infections for longer. 
  • Gut bacteria use vitamin B12 for metabolic activities to produce various biological compounds to help support the gut barrier. 

The Role of Iron

  • Barrier tissues such as our skin and the tissue that lines the inside of our gastrointestinal tract are dependent on iron for growth and repair.

The Role of Zinc

  • Zinc is essential for maintenance, repair and integrity of our skin. It is also needed to keep the barrier membrane that lines our digestive tract, lungs, respiratory tract, nose, mouth, eyelids and urinary tract healthy.

What You Can Do Now

Proper nutrition helps create an immune system environment that can respond well to immune challenges. In contrast, poor nutrition creates an immune system environment that cannot react to immune problems.

The table below contains a list of common and readily available whole real foods high in nutrients needed to keep our physical and biochemical barriers healthy. Try to incorporate food from each vitamin groups into your daily meals. 

Immune System Nutrients Found in Foods

Vitamin A

Dairy, eggs, liver, fatty fish, i.e. salmon, sardines or mackerel, butter, lard, olive oil, carrots, sweet potato, pumpkin, kale, spinach, chard, broccoli, orange fruits, i.e. mango, cantaloupe melon, pink or red grapefruit

Vitamin D

Fatty fish, liver, eggs, mushrooms, lard

Vitamin C

Red & green capsicums, berries, kiwi fruit, broccoli, brussels sprouts, tomato, liver

Vitamin E

Sunflower seeds, pine nuts, Almonds, brazil nuts, peanuts, hazelnuts, salmon, trout, avocado, red capsicums, crayfish, lobster, octopus

Vitamin B6

Fish, poultry, red meat, chicken liver, eggs, dairy, green leafy vegetables, carrots, sweet potato, chickpeas, avocado

Vitamin B12

Fish, red meat, shellfish, milk, cheese, eggs


Broccoli, brussel sprouts, green leafy vegetables, green peas, chickpeas


Red meat, liver, shellfish, pork, chicken, lentils, chickpeas, cashew nuts, almonds, macadamia nuts, pumpkin seeds, dark green leafy vegetables, i.e. spinach & kale


Download the Cheat Sheet

Final Word

Changes to your diet or nutrition to manage a health condition should only be undertaken with advice from a suitably qualified nutritional health professional.

This factsheet is for general information only.

Please contact me to discuss your individual needs.