The immune system is constantly active and needs energy from macronutrients like carbohydrates, fats and proteins.  Protein also supplies amino acids to build immune cells and enzymes that help destroy pathogens.  These enzymes also require vitamins and minerals as cofactors to function properly.

So, while it may sound obvious, a varied and balanced diet that provides adequate nutrients is the foundation of a healthy immune system.  However, some nutrients receive particular attention for their role in immune health, including vitamins A, C and D, as well as the minerals such as zinc and selenium¹.

There is also evidence for the immune benefits of other nutrients and ingredients, such as long-chain omega-3 fatty acids, probiotics and beta-glucans².

Immunonutrition

Read how each of the nutrients listed below support the immune system.  It is important to bear in mind that micronutrients have additional health benefits to immune health.  Click on each nutrient/non-nutrient below to learn more:

• Vitamin A
• Vitamin C
• Vitamin D
• Selenium
• Zinc
• Probiotics
• Beta Glucans

How the Immune System Works?

The immune system is the body’s way of protecting itself from infection by foreign invaders like bacteria and viruses.  It helps the body stay healthy and recover when illness does occur and is made up of the innate (general) and adaptive (specialised) immune system³.

The innate immune system is the body’s first line of defence.  When pathogens like infectious bacteria or viruses get into the respiratory tract or gastrointestinal system, the innate immune system responds by sending cells like neutrophils or macrophages to remove the threat.  These cells try to engulf the invading pathogen or create enzymes to destroy it.

The adaptive immune system specifically targets the pathogen and takes over from the innate immune system.  It is often described as the ‘memory’ of the immune system.  Once exposed to a pathogen, the immune system can remember the identity of that pathogen for the future and quickly mount a defence specific to that pathogen.

Impact of Age and Physical Activity on Immune Health

Immune health becomes especially important in vulnerable age groups like infants and the elderly. Both physical and psychological stress can also compromise the immune system.  Examples include over-exercising, emotional stress and surgery.

This article was published in March 2022 and updated on June 15, 2026.

Selenium is a mineral that is important for a group of proteins called selenoproteins, which have a few different functions in the body, ranging from helping our reproductive system function to storing selenium in the liver.

Some selenoproteins, called glutathione peroxidases, are important for the body’s antioxidant system, which protects DNA and cells from oxidative damage.  This includes protecting the body’s immune cells from damage^{1, 2}.

Selenium also plays a role in activating immune cells ¹ and helping them function, such as assisting macrophages to more effectively destroy or engulf pathogens.  The role of selenium in the response to vaccines continues to be investigated³.

Figure 1. A summary of selenium and immune responses¹.   © 2018 by the authors ¹. Licensee MDPI, Basel, Switzerland.  Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Recommended Intakes

The recommended daily intake of selenium varies around the world².  The Chinese Nutrition Society⁴ set a Reference Nutrient Intake (RNI) of 60mg per day for adults.  Similarly, in the US the Institute of Medicine has set a Recommended Dily Allowance of 55mg per day⁵.  In addition, the European Food Safety Authority set an adequate intake (AI) of 70mg per day for adults⁶.

Dietary Sources

Meats, eggs, nuts, seeds, seafood and whole grains are good sources of selenium.  The selenium content of foods is linked to the selenium content of the soil (see ‘Deficiency’ section below).

Table 1. Selenium content of common foods in the diet⁷

Deficiency

Selenium deficiency is expected to affect up to 1 billion people worldwide.  This deficiency primarily affects people in areas where the soil is low in selenium⁷ and, as a result, the foods that grow in that soil are low in selenium.

The distribution of selenium in the soil is extremely uneven, with significant differences even within countries.  Regions with lower selenium intakes⁸ include certain areas of New Zealand, China and Italy, among many others.

In areas where the soil is rich in the soil, selenium deficiency is rare.  For example, the average daily intake of selenium in the US is almost twice the daily recommendation.  Certain regions of China, where selenium is plentiful in the soil, also have high intakes of selenium⁹.

Excess Intakes

Selenium has a narrow window between adequate and toxic levels.  Getting too much selenium can lead to symptoms like gastrointestinal or neurological symptoms, hair loss, nausea and fatigue, among others⁷.

For this reason, in the US a tolerable upper limit of selenium has been set at 400mg per day for adults³ .  The EFSA recently revised their upper limit to 255mg per day for adults including pregnant and lactating women¹⁰.  Lower limits are recommended for younger groups.

Selenium Supplementation

People who are deficient in selenium are shown to have impaired immune responses² and studies show that reinstating selenium status through supplementation can improve the body’s ability to fight infection.

Those with adequate selenium intake through their diet are unlikely to see additional benefits.  A recent meta-analysis of selenium¹¹ supplementation trials showed a very mixed picture of effects but no conclusive evidence of an beneficial effect on the immune system beyond the recommended dietary intake.

This article was publishing in March 2020 and updated on April 07, 2026.