Short answer: the immune system is a network of barriers, cells, tissues and signalling molecules. Skin and mucous membranes help prevent entry; innate immunity responds quickly and broadly; adaptive immunity targets specific threats and can form memory.
That is different from the marketing idea of a single “immunity level” that a supplement can simply boost.
The immune system in three parts
| Part | Main role | Examples |
|---|---|---|
| Physical and chemical barriers | Help stop potentially harmful microorganisms entering tissues | Skin, mucus, tears, stomach acid and airway cilia |
| Innate immune system | Responds quickly and generally to damage or unfamiliar material | Phagocytes, natural killer cells, complement proteins and inflammation |
| Adaptive immune system | Builds a targeted response and can retain memory | B cells, T cells and antibodies |
First line: barriers
Immune defence begins before an immune cell attacks anything. Intact skin forms a physical boundary. Mucous membranes line the respiratory, digestive and genitourinary tracts. Mucus, enzymes, tears and moving cilia help trap, neutralise or remove material.
These barriers are active parts of defence, not merely packaging around the immune system.
Second line: innate immunity
Innate immunity is present from birth and reacts quickly. It recognises broad signs of damage or potentially harmful material rather than one unique target. Cells such as neutrophils and macrophages can engulf material, while proteins and chemical signals coordinate inflammation and recruit other cells.
Inflammation is a controlled biological response. It is not automatically harmful, and “reducing inflammation” should not be treated as a general goal for a food supplement.
Third line: adaptive immunity
Adaptive immunity is more specific. B cells can produce antibodies, while T cells coordinate responses or act on affected cells. Some B and T cells become memory cells, allowing a faster or stronger response after later exposure to the same target.
Vaccines use this ability to learn. The NHS describes vaccination as the most effective way to prevent many infectious diseases; a food supplement is not an alternative to vaccination.
Where nutrients fit
Normal immune function depends on adequate nutrition, and several nutrients have authorised Great Britain health claims. Vitamin C, vitamin D, vitamin A, vitamin B6, vitamin B12, folate, iron, copper, zinc and selenium can each be described as contributing to the normal function of the immune system when the product meets the relevant conditions.
This is a normal-function claim. It does not mean a larger supplement dose creates “super immunity”, nor does it permit claims to prevent or treat infections.
What supports everyday health?
A supplement should sit behind the fundamentals, not replace them:
- eat a varied, balanced diet;
- follow NHS vitamin D advice for autumn and winter;
- keep vaccinations recommended for you up to date;
- avoid smoking;
- move regularly and aim for sufficient sleep; and
- follow hygiene and medical advice when illness is circulating.
If you have frequent or unusual infections, a diagnosed deficiency, a weakened immune system, persistent symptoms or concerns about medication, speak to a healthcare professional rather than self-treating with supplements.
Why “boost your immune system” is a poor description
The immune system needs regulation as well as activity. Too little response can leave the body vulnerable; an inappropriate or excessive response can also cause harm. “Boost” is therefore biologically vague and, in supplement advertising, goes beyond the authorised wording. “Contributes to the normal function of the immune system” is the accurate claim for qualifying nutrients.
Where an immune supplement fits
A supplement can provide a measured source of one or more nutrients when dietary intake or official advice makes supplementation relevant. Compare the exact nutrient amount, %NRV, serving size, overlaps, pack duration and cost.
Our Immunity Pro-Shield contains vitamin C, vitamin D, vitamin B6, zinc and selenium, which contribute to normal immune function. The remaining ingredients are described on the label; they do not inherit those nutrient claims.
Frequently asked questions
What is the difference between innate and adaptive immunity?
Innate immunity responds rapidly and broadly. Adaptive immunity is targeted, involves B and T cells and can create memory. The two systems communicate and work together.
Are antibodies the whole immune system?
No. Antibodies are one part of adaptive immunity. Barriers, innate immune cells, T cells, signalling proteins and lymphoid tissues also have important roles.
Does the gut contain most of the immune system?
The gut contains extensive immune tissue and is an important contact point between the body and the outside environment. Reducing that relationship to a single percentage is misleading, because “how much of the immune system” depends on what is being counted.
Can food supplements prevent infections?
They cannot be advertised as doing so. Food supplements may carry authorised normal-function claims for qualifying nutrients, but disease prevention and treatment claims are not permitted.
When should I seek medical advice?
Use NHS services for persistent, severe or worrying symptoms. If you are immunocompromised, pregnant or breastfeeding, taking medication, or managing a health condition, ask a healthcare professional before starting a multi-ingredient supplement.
How this guide was checked
The immune-system explanation was checked against the US National Library of Medicine’s overview of innate and adaptive immunity. Claim wording was checked against the Great Britain Nutrition and Health Claims Register, and practical guidance against the NHS. Reviewed 3 August 2026.
Sources and further reading
- NCBI Bookshelf — the innate and adaptive immune systems
- NHS — why vaccination is important
- NHS — vitamin D
- Department of Health and Social Care — Great Britain Nutrition and Health Claims Register
- GOV.UK — nutrition, health claims and supplement labelling
Continue reading
- Immune-support nutrients explained
- How to compare UK immune-support supplements
- How to read a supplement label line by line
Written by Barry Lees, founder of The Health Improvers. Educational information only; not medical advice. Food supplements are not a substitute for a varied, balanced diet and healthy lifestyle. Always read the label.
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