Eating for Immune Strength: How Nutrition Supports Your Body's Defence System

Published: 1 November 2025

Immunotherapy activates your immune system to fight cancer. But your immune system doesn't perform well on inadequate fuel. Protein deficiency, micronutrient gaps, and inflammatory eating patterns undermine immune function despite medication designed to enhance it[1][2].

Strategic nutrition directly supports your immune system's ability to respond to treatment and defend against infection—a critical concern during cancer treatment when immune function is already compromised[1][2][3].

How Nutrition Fuels Immune Function

Your immune system is metabolically expensive. Immune cells (white blood cells, antibodies, inflammatory molecules) are made from protein, rely on micronutrients for function, and are directly affected by inflammatory status[1][2].

Protein and amino acids: White blood cells and antibodies are made of protein. Adequate protein intake (1.2–1.5g/kg daily) ensures your immune system has building blocks[1][2]. Specific amino acids matter: glutamine (used heavily by immune cells), arginine (supports white blood cell function), and leucine (signals immune cell production)[1].

Micronutrient status: Vitamin D, selenium, zinc, and vitamins A, C, and E are essential for immune cell function and antibody production[1][2]. Deficiency in any impairs immune response[1].

Gut health and fibre: Over 70% of your immune tissue lives in your gut. Dietary fibre feeds beneficial bacteria, which produce compounds that support gut immunity and reduce systemic inflammation[2][3]. This is particularly important during immunotherapy, where your immune system needs to be precisely calibrated—strong enough to attack cancer, not so hyperactive it attacks healthy tissue[2].

Inflammatory status: Ultra-processed foods high in refined carbohydrates and seed oils increase overall inflammation, which can suppress appropriate immune function[1][3]. Anti-inflammatory eating (Mediterranean pattern) optimises immune balance[1][2].

The Specific Nutrients

Protein and leucine-rich foods:Eggs, fish, poultry, Greek yoghurt, legumes, nuts. Prioritise variety; different sources provide different amino acid profiles and accompanying nutrients.

Vitamin D:Oily fish, egg yolks, fortified milk, mushrooms. Testing and supplementation may be needed (target 50–100 nmol/L).

Zinc:Meat, fish, shellfish, legumes, nuts, seeds. Critical for white blood cell development and function. Deficiency particularly problematic during treatment.

Selenium:Brazil nuts (just 2–3 daily), seafood, chicken, eggs. Supports immune cell function and antioxidant protection.

Vitamin C:Citrus fruits, berries, tomatoes, peppers, broccoli. Supports white blood cell function and antibody production. Doesn't prevent illness but supports immune response.

Vitamin A:Leafy greens, carrots, sweet potato, squash. Essential for white blood cell development and gut barrier integrity.

Fibre (for gut health):Whole grains, legumes, vegetables, fruits. Feeds beneficial bacteria that support immune function. Aim for 25–30g daily if tolerated.

Practical Daily Structure for Immune Support

Breakfast:Eggs with whole grain toast, tomato, and leafy greens (protein, vitamin A, vitamin C, whole grain fibre)

Mid-morning snack:Brazil nuts and orange (selenium, vitamin C)

Lunch:Baked salmon with sweet potato and broccoli (protein, omega-3s, vitamin D, vitamin C, fibre)

Afternoon snack:Greek yoghurt with berries (protein, zinc, vitamin C)

Dinner:Lentil and vegetable stew (protein, zinc, fibre, polyphenols from vegetables)

This provides substantial protein, multiple immune-supporting micronutrients, adequate fibre, and anti-inflammatory components.

Avoiding Immune Suppression

Foods that may worsen immune function during treatment:

·       Ultra-processed foods: High in refined carbohydrates and seed oils; increase inflammation and worsen metabolic parameters[1][3]

·       Excessive refined sugar: Suppresses immune function and worsens inflammation[1]

·       Excessive alcohol: Impairs immune function and increases inflammation[1]

These don't need to be eliminated entirely (psychological well-being matters too), but during active treatment, minimising them supports immune function.

Supplements Specifically for Immune Support

What the evidence supports:

·       Correction of specific documented deficiencies (vitamin D, zinc, selenium) based on testing[1][2]

·       Standard multivitamin if diet is very limited[2]

What the evidence does NOT clearly support:

·       High-dose vitamin C for immune boost (evidence mixed; some concern it might interfere with certain immunotherapies)[1]

·       Echinacea, elderberry, or other botanical "immune boosters"; limited evidence and interaction potential[1][2]

·       Probiotics; evidence mixed and some strains may not be appropriate during active treatment[2]

Discuss any supplements with your team before starting. Immune support sounds universally beneficial, but during cancer treatment, you want immune modulation, not indiscriminate "boosting."

Timing Considerations

Immune function follows circadian rhythms (daily cycles). Adequate sleep supports immune function[3]. So does moderate (not excessive) physical activity. Chronically elevated stress suppresses immunity[3].

Nutrition is one pillar of immune support. Sleep, gentle movement, and stress management are equally important[1][3].

During Active Infection or Immune Compromise

If your white blood counts drop significantly or you develop infection, your nutritional needs shift:

·       Protein intake may need to increase further

·       Micronutrient needs intensify

·       Your team may recommend specific foods to avoid (unpasteurised dairy, certain raw vegetables) due to infection risk

·       Oral nutrition supplements become more important if eating is difficult

Work closely with your team during these periods; immune compromise is serious.

The Integration

Strong nutrition supports immune function, which is precisely what immunotherapy relies on. You're not just eating for energy and fatigue management. You're eating to fuel the immune system that's your primary treatment tool[1][2][3].

This reframing—nutrition as immune support, not just symptom management—can be motivating on difficult days.

Bottom Line

Immunotherapy works by activating your immune system. Adequate protein, key micronutrients, fibre for gut health, and anti-inflammatory eating patterns directly support immune function and treatment effectiveness[1][2][3]. Deficiencies and poor eating patterns undermine the very system you're trying to activate.

Strategic nutrition isn't just about managing fatigue—it's about fuelling your body's primary treatment mechanism.

Want a detailed immune-support nutrition plan for your specific immunotherapy regimen? Contact me; we can build a personalised eating strategy optimised for immune function.

References

[1] Calder, P. C., et al. (2020). Optimal nutritional status for a well-functioning immune system is an important factor to protect against viral infections. Nutrients, 12(4), 1181.

[2] Arends, J., et al. (2017). ESPEN expert group recommendations for optimal nutritional care of cancer patients. Clinical Nutrition, 36(1), 11-48.

[3] Elinav, E., et al. (2022). Diet and oncogenesis—the microbiome connection. Nature Reviews Cancer, 22(12), 663-672.