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Tuesday, 22 September 2026Global stories. British perspective.

Health

Best Foods to Boost Your Immune System Naturally in the UK: What the Evidence Actually Supports

Only ten nutrients may legally claim an immune effect in Great Britain, and none may say boost. The NHS food source for each, and what the trials found.

By The Global Insight EditorialPublished Updated 20 min read

No food, drink or supplement can boost a healthy immune system, and in Great Britain no food label may say that it does. The law here is unusually clear: of 278 rows in the Government’s health claims register that mention the immune system, exactly twelve are authorised, all of them for named nutrients, and all worded as contributing to the normal function of the immune system rather than improving it. Those nutrients are copper, folate, iron, selenium, vitamins A, B6, B12, C and D, and zinc — and every one of them is easy to get from ordinary food.

Last reviewed: 22 September 2026.

This page is general information, not medical advice, and nobody here is a clinician or a registered dietitian. It exists because the honest answer to this question is not the one most articles give, and because the evidence gap is easy to demonstrate rather than merely assert. If you are having treatment that affects your immune system, or you are unwell now, the sections on those are further down and they are the ones that matter.

What the law lets a food claim, and what it does not

Nutrition and health claims on food sold in Great Britain are controlled. Only claims on the Great Britain nutrition and health claims (NHC) register may be used, and GOV.UK states that plainly: “Only authorised claims in the Great Britain NHC register may be used in Great Britain.”

We downloaded the register — the spreadsheet dated 19 May 2026 — and counted. It holds 2,349 health claim rows. 2,082 are marked non-authorised and 267 authorised.

Filtering to rows where the claim or the health relationship mentions the immune system or the body’s defences gives 278 rows. Twelve are authorised. Here they are in full, with the exact wording the law permits.

Nutrient The authorised claim, verbatim Condition of use
Copper “Copper contributes to the normal function of the immune system” Food must be at least a “source of” copper
Folate “Folate contributes to the normal function of the immune system” At least a “source of” folate
Iron “Iron contributes to the normal function of the immune system” At least a “source of” iron
Selenium “Selenium contributes to the normal function of the immune system” At least a “source of” selenium
Vitamin A “Vitamin A contributes to the normal function of the immune system” At least a “source of” vitamin A
Vitamin B6 “Vitamin B6 contributes to the normal function of the immune system” At least a “source of” vitamin B6
Vitamin B12 “Vitamin B12 contributes to the normal function of the immune system” At least a “source of” vitamin B12
Vitamin C “Vitamin C contributes to the normal function of the immune system” At least a “source of” vitamin C
Vitamin C “Vitamin C contributes to maintain the normal function of the immune system during and after intense physical exercise” Food must provide 200mg a day in addition to the recommended daily intake, and must tell the consumer so
Vitamin D “Vitamin D contributes to the normal function of the immune system” At least a “source of” vitamin D
Vitamin D “Vitamin D contributes to the normal function of the immune system in children” Authorised separately, for children
Zinc “Zinc contributes to the normal function of the immune system” At least a “source of” zinc

Read the wording again, because it is doing careful work. Contributes to the normal function. Not improves, not strengthens, not boosts. The permitted claim is that these nutrients are needed for the immune system to work as it should — which is why a shortage causes a problem and topping up beyond sufficiency does not create an advantage.

The 266 claims that were refused

The other side of the register is the more useful half, because it is a list of exactly the claims the marketing you have read is built on. Every one of these was submitted, assessed and not authorised:

  • “(Anthocyans from) elderberry juice help to: protect cells against oxidative damages — strengthen the immune system”
  • “(Antioxidants from) pomegranate… strengthen the immune system — strengthen the body’s defence”
  • “(Cryptoxanthin from) orange juice participate to strengthen immune system”
  • “(Lycopenes from) tomato juice… strengthen the immune system — strengthen the body’s defences”
  • “Helps to strengthen natural defences / Stimulates immune system / Strengthens resistance of organism” — submitted for a long list of named probiotic strains, every one refused
  • Claims for propolis, royal jelly, beta-glucans and mushroom extracts

We also searched the register for the foods that dominate UK “immune-boosting” listicles. Echinacea, garlic, ginger, turmeric, ginseng, kefir and yoghurt have no authorised immune claim at all — in most cases no immune claim row in the register whatsoever.

Sources: GOV.UK — Great Britain nutrition and health claims (NHC) register (spreadsheet dated 19 May 2026) and GOV.UK — Guidance on nutrition and health claims on foods.

The ten nutrients, and the food the NHS names for each

This is the table that replaces every “15 immune-boosting superfoods” list. The left column is the legally recognised list. The middle column is what the NHS itself names as good sources. The right column is the UK amount for adults aged 19 to 64, as the NHS states it.

Nutrient NHS-named food sources Adults 19–64 need
Vitamin C Citrus fruit and orange juice, peppers, strawberries, blackcurrants, broccoli, brussels sprouts, potatoes 40mg a day
Vitamin D Oily fish (salmon, sardines, trout, herring, mackerel), red meat, egg yolks, fortified fat spreads and breakfast cereals, liver 10 micrograms a day
Vitamin A Cheese, eggs, oily fish, fortified low-fat spreads, milk and yoghurt, liver; plus beta-carotene from spinach, carrots, sweet potatoes, red peppers, mango, papaya, apricots 700µg men, 600µg women
Vitamin B6 Pork, poultry, some fish, peanuts, soya beans, wheatgerm, oats, bananas, milk, some fortified cereals 1.4mg men, 1.2mg women
Vitamin B12 Meat, fish, milk, cheese, eggs, some fortified breakfast cereals about 1.5 micrograms a day
Folate Broccoli, brussels sprouts, leafy greens (cabbage, kale, spring greens, spinach), peas, chickpeas and kidney beans, liver, fortified cereals 200 micrograms a day
Iron Liver, red meat, beans (kidney, edamame, chickpeas), nuts, dried fruit such as apricots, fortified breakfast cereals, soy bean flour 8.7mg men; 14.8mg women 19–49; 8.7mg women 50+
Zinc Meat, shellfish, dairy such as cheese, bread, cereal products such as wheatgerm 9.5mg men, 7mg women
Selenium Brazil nuts, fish, meat, eggs 75µg men, 60µg women
Copper Nuts, shellfish, offal 1.2mg a day

Three of these have NHS text that talks about immunity directly, and it is worth having the wording. The NHS says vitamin A helps “your body’s natural defence against illness and infection (the immune system) work properly”. It says selenium “helps the immune system work properly”. And of copper it says it is “thought to be important for infant growth, brain development, the immune system and strong bones” — note the hedge, which is the NHS’s own.

The NHS’s position on all ten is the same sentence, repeated on page after page: “You should be able to get all the [nutrient] you need from your daily diet.” The single exception is vitamin D.

The practical version of that table

If you want one shopping rule rather than ten: oily fish, eggs, nuts, shellfish or meat, wholegrains or fortified cereal, beans or lentils, leafy greens, peppers or citrus. That combination covers all ten without a supplement aisle, and the two items that carry the most nutrients per portion are oily fish (vitamins D and A, selenium, B12) and brazil nuts (selenium, copper).

Nothing on that list is a superfood. It is the ordinary healthy-eating pattern in the NHS Eatwell Guide, which is the honest reason there is no separate “immune diet”.

Vitamin D: the one thing the UK actually recommends you take

Vitamin D is the exception on this page, and it is the exception for a reason that has nothing to do with immunity headlines.

The NHS position: “From about late March or early April to the end of September, most people should be able to make all the vitamin D they need from sunlight.” But “between October and early March we do not make enough vitamin D from sunlight”, and vitamin D is found in only a small number of foods. In the UK cows’ milk is generally not a good source “because it is not fortified, as it is in some other countries”.

So the Department of Health and Social Care advice is:

Who Advice
Everyone aged 4 and over, including pregnant and breastfeeding women Consider a daily 10 microgram supplement during autumn and winter
People not often outdoors, in care homes, or who usually cover most of their skin A daily 10 microgram supplement all year
People with dark skin — African, African-Caribbean or South Asian background Consider a daily 10 microgram supplement all year
Babies birth to 1 year, if breastfed, or formula-fed on under 500ml a day 8.5 to 10 micrograms daily, all year
Children 1 to 4 10 micrograms daily, all year

Safety limits from the same page: do not exceed 100 micrograms (4,000 IU) a day for adults and children 11–17; children 1–10 no more than 50 micrograms; infants under 12 months no more than 25 micrograms. Too much over a long period “can cause too much calcium to build up in the body (hypercalcaemia)”, weakening bones and damaging the kidneys and heart. You cannot overdose from sunlight.

Women and children who qualify for Healthy Start can get free supplements containing vitamin D.

What the infection trials actually found

This is where the picture is genuinely interesting rather than merely cautionary, and it supports the “correct a deficiency” framing rather than the “boost” framing.

Martineau and colleagues, in the BMJ in 2017, pooled individual participant data from 25 randomised controlled trials covering 11,321 people aged 0 to 95 (DOI 10.1136/bmj.i6583). Their findings:

  • Vitamin D supplementation reduced the risk of acute respiratory tract infection overall: adjusted odds ratio 0.88 (95% CI 0.81 to 0.96).
  • The benefit was in daily or weekly dosing (aOR 0.81, 0.72–0.91), not in large intermittent bolus doses (aOR 0.97, 0.86–1.10).
  • Among those on daily or weekly dosing, the effect was far stronger in people who started with blood levels below 25 nmol/L (aOR 0.30, 0.17–0.53) than in those at or above 25 nmol/L (aOR 0.75, 0.60–0.95).
  • Serious adverse events were not increased. The authors assessed the body of evidence as high quality.

Read the third bullet again. The people who benefited most were the ones who were very deficient. That is the shape of every honest immune-nutrition finding: fixing a shortage helps, and adding more on top of sufficiency does much less.

Do not buy a private vitamin D test on the strength of that

NICE’s public health guideline PH56, recommendation 7, is explicit that health professionals “should not routinely test people’s vitamin D status” unless the person has symptoms of deficiency, is considered to be at particularly high risk (for example, very low exposure to sunlight), or there is a clinical reason such as osteomalacia or having had a fall.

The same guideline tells Public Health England to “Emphasise the limitations of other UK sources of vitamin D (it is only contained in a few foods and sunlight is only effective from the beginning of April to October)” and to make clear what terms like “low sun exposure” and “dark skin” actually mean, because it judged the existing advice confusing.

Sources: NHS — Vitamin D, NICE PH56 — Vitamin D: supplement use in specific population groups (published 26 November 2014, last updated 30 August 2017), SACN vitamin D and health report.

Vitamin C and zinc: what the trials show, stated precisely

These two are the supplements people actually buy for this, so they deserve the numbers rather than a verdict.

Vitamin C Zinc
Best evidence Cochrane review, Hemilä & Chalker 2013 Cochrane review, 2024
Size 29 trial comparisons, 11,306 participants for incidence 34 studies, 8,526 participants
Preventing a cold Pooled risk ratio 0.97 (95% CI 0.94–1.00) in the general community (10,708 people) — no meaningful effect “may have little or no effect on the prevention of colds”
Shortening a cold Regular supplementation reduced duration by 8% in adults (3–12%) and 14% in children (7–21%); 1–2g/day in children shortened colds by 18% “may reduce the duration of ongoing colds”
Taking it once symptoms start “No consistent effect… on the duration or severity of colds” in the therapeutic trials Most treatment trials used lozenges; zinc gluconate at 45–276mg/day for 4.5–21 days
Harm NHS: more than 1,000mg a day can cause stomach pain, diarrhoea and flatulence Cochrane: “an increase in non-serious adverse events”. NHS: high doses reduce copper absorption, which can lead to anaemia and weakened bones

The authors’ own conclusion on vitamin C is worth quoting rather than paraphrasing: “The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise.”

That exercise exception is real and it is the same one the law recognises. In five trials covering 598 marathon runners, skiers and soldiers on subarctic exercises, the pooled risk ratio for catching a cold was 0.48 (95% CI 0.35–0.64). It is also the only place the GB register permits a stronger-sounding vitamin C claim — and only at 200mg a day on top of the normal intake, with that fact disclosed to the consumer.

References: Hemilä H, Chalker E. “Vitamin C for preventing and treating the common cold.” Cochrane Database of Systematic Reviews 2013 (DOI 10.1002/14651858.CD000980.pub4); “Zinc for prevention and treatment of the common cold.” Cochrane Database of Systematic Reviews 2024 (PMID 38719213).

The NHS sentence that answers the question in one line

For all the detail above, the NHS says it in a single sentence on its common cold page:

“There’s little evidence that supplements such as vitamin C, echinacea or garlic prevent colds or help you get better more quickly.”

That page was last reviewed on 22 March 2024, next review due 22 March 2027 — in date, and fresher than most of the nutrient pages cited here.

The same page lists what the NHS says does work for avoiding a cold, and none of it is food:

  • washing your hands with warm water and soap
  • not sharing towels or household items such as cups or children’s toys with someone who has a cold
  • not touching your eyes or nose in case you have come into contact with the virus
  • staying fit and healthy

Two of those four are about not passing it on and one is about washing your hands, which tells you where the evidence actually is. “Staying fit and healthy” is the only lifestyle item, and it is deliberately general — if the specific thing that has gone is your sleep, how to sleep better naturally covers what the NHS recommends rather than what the supplement aisle does.

And one correction the NHS makes that gets repeated wrongly every winter: “The flu vaccine does not prevent colds.” Flu is a different illness. The NHS publishes its own eligibility list for the flu vaccine, and for people in those groups it is the single most evidence-backed seasonal step available — which is a genuinely different claim from anything on a food label.

When not eating enough is the actual problem

The one place where food and infection are firmly linked in NHS material is undernutrition, and it runs the opposite way round from the marketing.

The NHS lists “getting ill often and taking a long time to recover” among the common signs of malnutrition, alongside unintentional weight loss — “losing 5% to 10% or more of weight over 3 to 6 months is one of the main signs” — a BMI under 18.5, a lack of interest in eating and drinking, feeling tired all the time and feeling weak. That last pair is worth taking seriously on its own: iron and vitamin B12 are both on the list above, and both deficiencies show up as exhaustion long before they show up as infections — the blood tests to ask a GP for when you are always tired covers what the NHS says each one rules out.

So the useful question is not “which superfood should I add” but “am I eating enough, and enough variety”. If you are eating far less than usual — because of illness, age, low mood, or because you are on a GLP-1 medicine and your appetite has collapsed — that is the thing to address, and our guide to eating on GLP-1 medicines in the UK covers doing it without losing muscle. If your problem is digestive rather than nutritional, the best foods for gut health in the UK covers what the NHS actually recommends there, including where the popular rules came from.

Source: NHS — Malnutrition (last reviewed 23 May 2023).

If your immune system is already weakened, this page is not for you

Everything above is written for people with a normally functioning immune system. If yours is not — chemotherapy, immunosuppressant medicines, a condition affecting immunity — general food advice does not apply and can be actively wrong, including advice about probiotics, raw foods and supplements.

The NHS makes one specific point on its common cold page for this group: see a GP if “you get cold symptoms and you have a weakened immune system (for example, because you’re having chemotherapy)”. That is a lower threshold for seeking help than for everyone else, and it is the relevant instruction here rather than a shopping list.

Your specialist team’s guidance overrides anything on this page. Ask them before starting any supplement, including vitamin D.

How fresh the NHS pages behind this advice are

Several of the sources everyone cites for this topic are past their own review date. Naming them is more useful than quietly citing them.

Source Last reviewed Next review due Status on 22 September 2026
NHS — Common cold 22 March 2024 22 March 2027 In date
NHS — Malnutrition 23 May 2023 23 May 2026 Past its review date
NHS — Vitamin C 3 August 2020 3 August 2023 Past its review date
NHS — Vitamin D 3 August 2020 3 August 2023 Past its review date
NHS — Vitamin A 3 August 2020 3 August 2023 Past its review date
NHS — B vitamins and folic acid 3 August 2020 3 August 2023 Past its review date
NHS — Iron 3 August 2020 3 August 2023 Past its review date
NHS — Others (copper, selenium, zinc) 3 August 2020 3 August 2023 Past its review date
GB nutrition and health claims register Spreadsheet dated 19 May 2026 Updated on publication Current
NICE PH56 Published 26 November 2014 Last updated 30 August 2017 Live guidance

The whole NHS vitamins and minerals section shares one review date of 3 August 2020 and is six years old. Being past a review date does not make a page wrong — the reference intakes it carries have not changed — but you should know that the nutrient figures on this page rest on a set of NHS pages the NHS has not re-confirmed since 2020, while the legal claims register was refreshed four months ago.

One more freshness note, because articles still cite it: NICE’s COVID-19 rapid guideline on vitamin D, NG187, has been withdrawn. NICE states the reason on the guideline page: “This guideline has been withdrawn because current practice is to manage COVID-19 risk in line with risk of other respiratory infections.”

What we left out, and why

  • Kefir, kimchi, sauerkraut, kombucha, elderberry, echinacea, garlic, ginger, turmeric, manuka honey and mushroom extracts. Every UK immune listicle features them. None has an authorised immune claim in the GB register, and in most cases no NHS recommendation either. They are foods; some are pleasant; there is simply no UK public-health or regulatory basis for passing on an immune claim about them.
  • A number for “how much of X boosts immunity”. No such number exists in UK guidance, because the permitted claim is about normal function, not improvement.
  • Named probiotic strains. Dozens were assessed for immune claims and all were refused. Naming one would imply a confidence the register explicitly does not support.
  • Gram figures for the nutrient content of individual foods. These vary by variety, preparation and portion. We have given the NHS’s named sources and the UK reference intakes instead, which is what the NHS itself publishes.
  • “Boosting” advice for people on immunosuppressants or in cancer treatment. Out of scope, and potentially harmful. That is a conversation for a specialist team.
  • Sleep, exercise and stress as “immune boosters”. All are worth doing; we could not source a UK claim that any of them measurably changes infection rates, so they are not presented here as if we could.

Frequently asked questions

Can any food legally claim to boost your immune system in the UK?

No. The Great Britain nutrition and health claims register contains 278 rows where a claim mentions the immune system or the body’s defences. Twelve are authorised, and every one of them uses the wording “contributes to the normal function of the immune system” for a named nutrient. Claims worded as strengthening, stimulating or boosting immunity are in the non-authorised column, including those submitted for elderberry, pomegranate, orange juice, tomato juice, propolis, royal jelly and dozens of probiotic strains.

Which nutrients are the authorised ones?

Ten: copper, folate, iron, selenium, vitamin A, vitamin B6, vitamin B12, vitamin C, vitamin D and zinc. Vitamin C carries a second authorised claim for intense physical exercise, at a stated 200mg a day in addition to the recommended daily intake, and vitamin D carries one worded specifically for children. All the general claims may only be used on a food that is at least a “source of” that nutrient.

Does vitamin C stop you catching a cold?

Not in the general population. The Cochrane review by Hemilä and Chalker pooled 29 trial comparisons covering 11,306 participants and found a risk ratio of 0.97 (95% CI 0.94 to 1.00) for developing a cold. The authors concluded that this failure to reduce incidence means “routine vitamin C supplementation is not justified”. The exception was 598 marathon runners, skiers and soldiers on subarctic exercises, where the pooled risk ratio was 0.48.

What does the NHS say about immune supplements?

Its common cold page states: “There’s little evidence that supplements such as vitamin C, echinacea or garlic prevent colds or help you get better more quickly.” That page was last reviewed on 22 March 2024 with next review due 22 March 2027, making it one of the fresher NHS pages on this subject.

Is there a UK supplement recommendation that is actually about infection?

There is one population-wide supplement recommendation, but it is not made on infection grounds. The Department of Health and Social Care advises that everyone consider a daily 10 microgram vitamin D supplement during autumn and winter, and that some groups take it all year. Separately, a BMJ meta-analysis of individual participant data from 25 trials found vitamin D reduced the risk of acute respiratory tract infection, with much the largest effect in people whose baseline blood level was below 25 nmol/L.

Should I get my vitamin D level tested?

NICE says not routinely. Recommendation 7 of its public health guideline PH56 is that health professionals “should not routinely test people’s vitamin D status” unless they have symptoms of deficiency, are considered to be at particularly high risk, or there is a clinical reason such as osteomalacia or a fall.

Does zinc help once a cold has started?

Possibly for duration, not for prevention. The 2024 Cochrane review included 34 studies and 8,526 participants and concluded that zinc “may have little or no effect on the prevention of colds but may reduce the duration of ongoing colds, with an increase in non-serious adverse events”. Note also the NHS warning that high doses of zinc reduce how much copper the body can absorb.

What actually reduces how often you get ill?

The NHS names hand washing with warm water and soap, not sharing towels or household items with someone who has a cold, not touching your eyes or nose, and staying fit and healthy. It adds that the flu vaccine does not prevent colds — it is aimed at flu, which is a different illness with its own NHS eligibility list.

Sources