Understanding Immunity: Does Low Iron Make it Harder to Fight Infections?

October 13, 2025 •

4 min read

Worldwide, over 40% of children with iron deficiency anemia are frequently associated with infections, highlighting a significant link between this common nutritional deficiency and immune function. So, does low iron make it harder to fight infections? The answer is a clear yes, but the mechanism is surprisingly complex, involving the body's battle not only against pathogens but also over a shared resource: iron.

Quick Summary

Iron is crucial for a healthy immune system, and a deficiency impairs both innate and adaptive immunity, increasing infection risk. The body tightly regulates iron during infection, a process known as nutritional immunity.

Key Points

Immune Cell Impairment: Iron is essential for the function and proliferation of key immune cells, including lymphocytes and neutrophils, and deficiency weakens their effectiveness.
Increased Infection Susceptibility: Untreated iron deficiency anemia can leave you more vulnerable to infections due to a compromised immune system.
Impaired Innate Response: Phagocytic activity and the oxidative burst of innate immune cells are significantly reduced with low iron levels, hindering the body's first line of defense.
Weakened Adaptive Immunity: Iron deficiency can impair adaptive immunity by reducing T-cell proliferation and B-cell antibody production, which are critical for targeted immune responses.
Reduced Vaccine Efficacy: Studies suggest that low iron levels can diminish the effectiveness of vaccinations by compromising the body's ability to generate a robust immune response.
Complex Host-Pathogen Interaction: The body uses a strategy called 'nutritional immunity' to withhold iron from pathogens, but this natural defense can be compromised by chronic iron deficiency.

Yes, low iron levels significantly weaken the immune system and make it more challenging for the body to combat infections. Iron is a fundamental element required for the proper development, proliferation, and function of various immune cells, including lymphocytes, macrophages, and neutrophils. Without sufficient iron, these critical components of the immune response cannot perform their roles effectively, leaving the body more susceptible to invading pathogens.

The Iron-Immunity Connection: A Double-Edged Sword

For decades, experimental evidence has shown that iron is a fundamental element for the normal functioning of the immune system. However, the relationship is a delicate balancing act. While immune cells require iron to function, so do many invading bacteria and other pathogens. This dynamic has led to the evolutionary strategy of "nutritional immunity," where the body reduces the amount of free iron available in the bloodstream during an infection to starve the pathogen.

This strategy is primarily controlled by the hormone hepcidin, which is produced by the liver in response to inflammation. Hepcidin inhibits the absorption of dietary iron and blocks the release of iron from storage cells, trapping it inside macrophages. This creates a state of low plasma iron (hypoferremia), making it difficult for extracellular pathogens to thrive.

However, a chronic state of iron deficiency, rather than a temporary, controlled response, is detrimental. It impairs the very immune cells meant to fight the infection. For example, iron is essential for enzymes involved in DNA synthesis, and a deficiency can diminish the proliferative phase of lymphocyte activation. This impairment compromises both innate and adaptive immune responses, increasing a person's vulnerability to illness.

How Low Iron Impacts Specific Immune Functions

Impact on Innate Immunity

The innate immune system provides the body's first line of defense. Iron deficiency can directly hinder key innate immune cell functions:

Neutrophil function: Studies have found that iron-deficient individuals have significantly lower phagocytic and bactericidal activity in neutrophils. This includes a reduced oxidative burst, a process neutrophils use to kill ingested bacteria.
Macrophage activity: Macrophages require iron for differentiation and to execute antimicrobial mechanisms effectively. A lack of iron can impair their ability to kill pathogens.
Natural Killer (NK) Cells: NK cells are crucial for the early response to viral infections. Sufficient iron is critical for their activation and function. Low iron levels can suppress NK cell activity.

Impact on Adaptive Immunity

Adaptive immunity provides a targeted, long-lasting defense against specific pathogens. The effects of iron deficiency on this system include:

T-cell proliferation: T-cell activation and proliferation are highly iron-sensitive. Low iron impairs the ability of T-cells to multiply and mount an effective response against antigens.
Antibody production: B-cell proliferation and the generation of antibody-secreting plasma cells are impaired by low iron levels. Studies have shown that iron-deficient individuals have a reduced antibody response to certain vaccinations.

Iron and Vaccinations

Emerging research indicates that the level of iron in the bloodstream can be critical for the immune response to vaccines. A weakened immune system due to iron deficiency may respond less effectively to vaccinations, potentially making them less potent and reducing protection against diseases. This highlights the importance of addressing iron deficiency, particularly in populations where both the deficiency and high infection rates are common.

Dietary Strategies for Supporting Immune Function

To ensure adequate iron intake for a robust immune system, a balanced diet rich in both heme and non-heme iron sources is crucial. Pairing non-heme iron with vitamin C can significantly increase absorption.

Heme Iron Sources: Found in animal products, this form is more easily absorbed by the body.
- Red meat (beef, lamb)
- Poultry (chicken, turkey)
- Seafood (fish, shellfish)
Non-Heme Iron Sources: Found in plant-based foods, legumes, and fortified cereals.
- Dark leafy greens (spinach, kale)
- Lentils, chickpeas, and beans
- Nuts and seeds
- Fortified breakfast cereals
- Soy products like tofu

Comparison of Iron-Sufficient vs. Iron-Deficient Immunity


Feature	Iron-Sufficient Immune System	Iron-Deficient Immune System
Immune Cell Proliferation	Optimal; immune cells multiply effectively during an infection.	Impaired; lymphocyte activation and proliferation are diminished.
Innate Immunity (Macrophages, Neutrophils)	Robust; cells exhibit strong phagocytic and bactericidal activity.	Weakened; reduced oxidative burst and microbicidal capacity.
Adaptive Immunity (T-cells, B-cells)	Effective; T-cell activation and B-cell antibody production function optimally.	Suboptimal; compromised T-cell responses and reduced antibody generation.
Infection Risk	Healthy individuals have a lower risk of acquiring infections.	Increased susceptibility to infections and more frequent illnesses.
Vaccination Response	High; strong and effective immune response is generated.	Lower; diminished antibody response and protection from vaccinations.
Overall Energy Levels	Normal; sufficient iron supports energy metabolism and reduces fatigue.	Low; fatigue and lethargy are common symptoms.

Conclusion

Ultimately, the evidence is clear: low iron levels make it harder for the body to fight infections by undermining both the innate and adaptive branches of the immune system. While the body can temporarily restrict iron to fend off pathogens in a process called nutritional immunity, chronic iron deficiency ultimately impairs the very cellular functions needed to mount a robust defense. Addressing low iron through diet or supplements, under medical supervision, can help restore immune resilience, reduce infection risk, and improve the effectiveness of vaccinations.

For more information on iron deficiency, consult a healthcare professional. You can also explore resources from the NHS regarding iron deficiency anemia.

Frequently Asked Questions

Iron deficiency impairs both the innate and adaptive immune systems by limiting the function and proliferation of essential immune cells like T-cells, B-cells, and neutrophils. This weakens the body's ability to fight off infections effectively.

Yes, if you experience more frequent infections than usual, such as common colds, it could be a sign of iron deficiency. A lack of iron weakens the immune system, making you more susceptible to illnesses.

Iron is crucial for many cellular processes in both humans and pathogens, including DNA synthesis and energy production. This creates a competition for iron during an infection, which the body tries to win through a process called nutritional immunity.

Nutritional immunity is the body's strategy to withhold essential nutrients, like iron, from invading pathogens. During an infection, the body increases hepcidin levels to reduce free iron in the bloodstream, limiting the pathogen's access to this vital resource.

For those with an iron deficiency, supplementation can help correct the issue and restore normal immune function. However, always consult a healthcare provider before taking supplements, as excess iron can sometimes worsen infections or cause side effects.

Yes, some studies indicate that a weakened immune system due to iron deficiency may lead to a less effective immune response following a vaccination, making the protection less robust.

Key immune cells affected include neutrophils, which show reduced bacterial killing capacity, and T-lymphocytes, which exhibit impaired proliferation and activation. B-cells also show reduced proliferation and antibody generation.

A diet rich in both heme (animal-based) and non-heme (plant-based) iron, along with sources of vitamin C to enhance absorption, is typically sufficient. However, people with dietary restrictions or underlying conditions may require supplements.