Last updated: August 2026

Zinc supports your immune system by keeping the tissue that produces and trains your white blood cells working properly, and a genuine zinc deficiency does leave infections lasting longer. What zinc will not reliably do is cut short a cold you have already caught. Trial results are inconsistent, and Cochrane's reviewers have repeatedly described the evidence as low certainty. The practical takeaway is unglamorous but useful: keep your intake at the level your body actually needs, mostly from food, rather than reaching for high dose lozenges once you are already sneezing.

Does zinc actually shorten a cold?

Zinc has not been shown to reliably shorten a cold. Individual trials have reported symptoms clearing roughly a day sooner with high dose lozenges started within 24 hours of the first symptom, but other trials found no benefit at all, and successive Cochrane reviews have graded the overall evidence as low certainty. Treat zinc as plausible and unproven, not as a reliable remedy.

The reason the trials disagree is worth understanding, because it tells you how much weight to put on any headline you read. The studies use different forms of zinc (acetate, gluconate, sulphate), different doses, different formats, and crucially different timing. They also struggle to blind properly, because zinc lozenges have a distinctive metallic taste that tells participants exactly which group they are in. When people can guess their allocation, self reported symptom scores drift, and symptom duration is almost entirely self reported.

None of that means zinc does nothing. It means the honest position is uncertainty, and anyone selling you certainty about zinc and colds is going beyond what the research supports. If you want to help your immune system, the far better bet is making sure you are not short of zinc in the first place, which is a nutrition question rather than a supplement question.

How does zinc support the immune system?

Zinc supports immunity by acting as a structural and catalytic component in hundreds of enzymes and transcription factors, including many that control how immune cells divide and mature. It is needed for the thymus gland to produce functioning T cells, for neutrophils and natural killer cells to work normally, and for wound healing and barrier repair in skin and mucous membranes.

Three parts of the system depend on it most visibly.

The thymus gland. The thymus sits just behind the breastbone and acts as a training school for T cells, the white blood cells that learn to recognise a specific pathogen and then hunt it. Zinc deficiency causes the thymus to atrophy, meaning it physically shrinks and produces fewer competent T cells. This is one of the most consistently reproduced findings in nutritional immunology, and it reverses when zinc is restored.

Lymphoid tissue. Lymph nodes filter fluid from the tissues and act as meeting rooms where immune cells present what they have found to each other. Adequate zinc supports the normal turnover of the cells in those nodes. Deficiency reduces lymphocyte numbers and blunts the coordinated response.

Barriers. Skin and the linings of the nose, throat and gut are the first line of defence, and they are among the fastest dividing tissues in the body. Fast dividing tissue is exactly what suffers first when zinc runs short, which is why one classic sign of deficiency is skin lesions around the mouth and nose alongside slow healing wounds.

This is also why zinc appears on ingredient lists next to a permitted wording rather than a promise. Under GB and EU nutrition rules, zinc is authorised to state that it "contributes to the normal function of the immune system". That is a maintenance claim about a nutrient, not a treatment claim about a product, and the distinction matters.

Why does a zinc deficiency make infections last longer?

Deficiency lengthens infections because it slows the specific arm of immunity that clears a pathogen for good. Innate defences such as inflammation still fire, but the adaptive response, where T cells and antibodies are built against that particular invader, is delayed. A slower adaptive response means the pathogen replicates for longer before it is recognised, so symptoms persist.

You can see the same pattern in populations rather than laboratories. Zinc deficiency is common in parts of the world where diets are cereal based and low in animal protein, and it tracks closely with the burden of childhood diarrhoeal illness and pneumonia. The World Health Organization has recommended zinc supplementation alongside oral rehydration for childhood diarrhoea for years, precisely because correcting a deficiency in a deficient population changes outcomes measurably.

The trap is assuming that logic runs backwards. Correcting a deficiency helps a deficient person. It does not follow that adding more zinc to an already sufficient person produces more immunity. Most adults in the UK eating a mixed diet are not zinc deficient, which is the single biggest reason supplement trials in UK style populations produce such muted results.

Who is most likely to be short of zinc?

Certain groups run genuinely higher risk of low zinc, and this is where testing and correction actually change something. If you recognise yourself in more than one of these, it is worth a conversation with your GP rather than a guess in a health shop.

• Vegetarians and vegans. Not because plants lack zinc, but because phytates in wholegrains, legumes and nuts bind zinc and reduce how much you absorb. Requirements are often estimated to be up to 50 percent higher on a plant based diet.
• People with Crohn's disease, coeliac disease, ulcerative colitis or short bowel syndrome. Absorption happens in the small intestine, so inflammatory and malabsorptive conditions hit zinc directly.
• People who drink heavily. Alcohol reduces absorption and increases urinary losses at the same time.
• Older adults. Intake tends to fall with appetite, and absorption efficiency declines.
• People on long term diuretics or certain other medicines. Some increase zinc excretion. Your pharmacist can check your specific list.
• Pregnant and breastfeeding women. Requirements rise, and deficiency is more consequential.

Signs that should prompt a check rather than self treatment include repeated infections, wounds that heal slowly, a blunted sense of taste or smell, persistent mouth ulcers, skin changes around the nose and mouth, unexplained diarrhoea, and diffuse hair shedding that has lasted more than three months.

Which foods contain the most zinc?

Oysters contain more zinc per gram than any other common food, with a single modest serving typically exceeding a full day's requirement several times over. After that the ranking runs through red meat, other shellfish, seeds, hard cheese, nuts and legumes. Animal sources are absorbed more efficiently than plant sources because they carry no phytate.

The figures below are approximate values from standard food composition tables, given per realistic serving rather than per 100 g, because per 100 g comparisons flatter foods nobody eats 100 g of.

How much zinc do you actually need each day?

UK reference nutrient intakes are 9.5 mg a day for men aged 19 to 64 and 7 mg a day for women. The NHS advises that if you take zinc supplements, staying below 25 mg a day is unlikely to cause harm, and that you should not exceed that without medical advice. Most people eating meat, fish, dairy or a well planned plant based diet reach these levels from food alone.

What are the risks of taking too much zinc?

High dose zinc causes nausea, stomach cramps and a metallic taste in the short term, and in the longer term it competes with copper for absorption, which can produce copper deficiency and anaemia. Sustained intakes well above the NHS ceiling have also been linked to reduced immune function, the exact opposite of the reason most people start taking it.

Two specific cautions are worth naming.

Copper depletion. Zinc and copper use the same intestinal transport route. Take a lot of one over months and you displace the other. Symptoms of copper deficiency include fatigue, pallor and neurological changes, and it is easy to miss because nobody suspects a supplement they take for health.

Intranasal zinc. Zinc sprays and gels applied inside the nose have been associated with lasting loss of smell, and products of that type were withdrawn from the US market after regulatory warnings. Oral zinc does not carry that specific risk, but it is a good reminder that "natural mineral" and "harmless in any form" are not the same statement.

More is not better here. Zinc has a genuine floor and a real ceiling, and the useful range between them is narrower than most supplement marketing implies.

Zinc lozenges, tablets or food: which makes sense?

Food first for everyday intake, a modest supplement if your diet or a medical condition puts you at real risk, and lozenges only as an optional experiment at the first sign of a cold with realistic expectations. The lozenge idea rests on zinc ions contacting the throat directly, which is why the format is different from a swallowed tablet, and also why the evidence is so hard to interpret.

What does zinc have to do with hair?

Zinc contributes to the maintenance of normal hair, and severe or prolonged deficiency is a recognised cause of diffuse shedding because hair follicles are among the body's fastest dividing tissue. What this does not mean is that hair thinning is usually a zinc problem. In most people it is not, and taking zinc when you are not short of it will not thicken anything.

The more common pathway is indirect and worth knowing about, because it explains a lot of confusing timelines. A high fever, a significant infection or any other acute physical stress can push a large batch of follicles out of their growing phase and into resting phase at once. You then shed noticeably around two to three months later, long after you felt better, which is why people rarely connect the two. That pattern is called telogen effluvium, and its triggers and recovery timeline are well described. The same mechanism is behind the shedding many people reported after viral illness, covered in our guide to hair loss after covid and how long recovery takes.

Telogen effluvium after illness is usually self limiting and recovers on its own over six to nine months once the trigger has passed. If your shedding is patchy, is accompanied by scalp pain or scaling, or has not settled after that window, that is a GP or dermatology question rather than a nutrition one. Our guide to working out what is actually causing your thinning walks through how to tell the patterns apart.

GrowPro Hair Growth Gummies, 22.95 GBP

Sugar free vegan gummies providing zinc alongside biotin, vitamin C, MSM and bamboo silica. Zinc and biotin contribute to the maintenance of normal hair, and vitamin C supports normal collagen formation. A sensible way to cover a gap in a plant based or restricted diet, not a replacement for medical advice if you suspect a real deficiency.

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If you are also curious about the other nutrient people reach for first, our honest look at what biotin does and does not do for hair growth covers the same ground with the same scepticism.

How can you support your hair while recovering from illness?

Handle it gently and give it time, because the follicles are still in a resting phase and nothing applied to the scalp speeds that biological clock up. The realistic goal during recovery is reducing mechanical damage to the hair you still have, so that regrowth is not undermined by breakage while it is happening.

That means loosening tight ties and clips, cutting back on heat styling, detangling from the ends upwards with a wide tooth comb on damp rather than soaking wet hair, and using a shampoo and conditioner pairing that leaves the fibre easier to comb through. It is a cosmetic exercise rather than a treatment, and it is worth being clear about that distinction.

Grow Me Hair Growth Shampoo, 14.95 GBP

A sulphate free everyday shampoo formulated with caffeine, biotin, rosemary and hydrolysed lupine protein, made in the UK and vegan. It helps reduce breakage for fuller looking hair while you wait out a recovery phase. It is a cosmetic product and is not a treatment for hair loss or for any medical cause of shedding.

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When should you see a GP about zinc or repeated infections?

See a GP if you are getting infections unusually often, if wounds heal slowly, if your sense of taste or smell has changed without an obvious cause, or if you have a gut condition that affects absorption. Zinc status can be assessed properly in that setting, and self prescribing high doses without knowing your baseline risks doing more harm than good.

Book an appointment sooner rather than later if you notice any of the following.

• Repeated chest, skin or urinary infections over a short period.
• Unexplained weight loss, persistent diarrhoea, or night sweats.
• Skin lesions around the mouth, nose or hands that will not settle.
• Diffuse hair shedding that has continued beyond six months, or any patchy loss.
• You are pregnant, breastfeeding, or taking regular prescription medicines and are considering a supplement.

Nothing on this page is medical advice, and no food or supplement treats an infection. If you feel seriously unwell, contact NHS 111 or your GP rather than reaching for a mineral.

Frequently asked questions

Does zinc prevent you catching a cold?
There is no good evidence that zinc supplements prevent colds in people who already have adequate zinc levels. Correcting a genuine deficiency restores normal immune function, but topping up beyond sufficiency has not been shown to add protection. Handwashing, sleep and vaccination where relevant remain the interventions with real preventive evidence.

How quickly does zinc work for immune function?
If you are genuinely deficient, immune markers begin improving within weeks of restoring adequate intake, and thymus function recovers over a similar timescale. If you are not deficient, there is no "working" to observe, because you are already at the level your immune system needs. This is why testing beats guessing.

Is it better to take zinc with or without food?
Zinc is absorbed better on an empty stomach, but it is far more likely to cause nausea that way. Most people do better taking it with a small meal that is not high in wholegrain or bran, since phytate reduces absorption. Consistency matters more than perfect timing.

Can zinc cause hair loss?
Zinc deficiency can cause shedding, and so can excessive zinc intake, because sustained high doses interfere with copper status. Both ends of the range are problems. This is the clearest argument for staying inside the recommended intake rather than assuming more is safer.

How much zinc is in a typical hair supplement?
Most hair, skin and nails products supply zinc at or near the daily reference intake rather than at therapeutic doses, which is appropriate for a maintenance product. Check the label and add it to anything else you take, because multivitamins, immune blends and hair supplements together can quietly exceed the NHS ceiling.

Do zinc lozenges work better than tablets?
The theory is that lozenges release zinc ions in the throat where a cold virus replicates, which a swallowed tablet does not do. Some trials support a modest shortening of symptoms, others show nothing, and the blinding problem makes results hard to trust. Treat any benefit as possible rather than expected.

Should vegans take a zinc supplement?
Not automatically, but the risk is real enough to be worth checking. Phytate in the staple foods of a plant based diet reduces absorption, so requirements are effectively higher. Soaking, sprouting and fermenting help, and a modest supplement is reasonable if intake still falls short. Discuss it with a GP or registered dietitian.

Can you get too much zinc from food alone?
It is very difficult. Excess intake almost always comes from supplements, fortified products, or from taking several products that each contain zinc without adding up the totals. Food sources self limit long before you reach a problematic dose, which is one more reason to lead with the plate.

The practical summary

Zinc earns its reputation as an immune mineral because deficiency measurably impairs the thymus, lymphoid tissue and barrier repair. It loses that reputation when it is sold as a cold cure, because the trials simply do not support that. Eat oysters, red meat, shellfish, seeds, nuts, dairy or well prepared pulses regularly, stay under 25 mg a day from supplements unless a doctor says otherwise, and see your GP if repeated infections or long term shedding are the pattern you are trying to explain.

Watermans has sold over 5 million bottles since 2012, and every product is vegan and made in the UK. If you are recovering from an illness and want to look after the hair you have while it regrows, the GrowPro gummies cover the nutrient side and Grow Me shampoo handles the everyday care side. Neither is a treatment for illness or for hair loss, and if something feels medically wrong, your GP comes first.