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How to support your immune system before winter

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The OneVit Team

The OneVit Team

Updated on

10th April 2026

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7 min

How to support your immune system before winter

Every autumn it's the same story. The days get shorter, everyone piles indoors, and the coughs start doing the rounds.

So which vitamins for your immune system are actually worth taking? We've gone through the research for you. Here's what holds up, what's still early days, and how to put it together safely.

How does your immune system actually work?

Short version: it works in two layers, and both need the right nutrients to do their job.

Your first line of defence is the innate immune system. That's your skin, the lining of your nose and throat, and fast-acting white blood cells. It reacts within minutes to hours1.

Your second line is the adaptive immune system. It's slower but more targeted1.

Its T cells and B cells learn to recognise specific germs. Then they remember them, so the response is faster next time1. That memory is also how vaccines work.

Both layers rely on a steady supply of vitamins and minerals to work properly.

Why do you get more colds in winter?

There's no single reason. It's a few things stacking up at once.

  • Less vitamin D from sunlight. From about October to March, UK sun is too weak for your skin to make vitamin D2.
  • Cold air in your nose. One theory is that breathing cold air cools the lining of your nose. That may weaken its local defences against cold viruses3.
  • More time indoors. Cold weather keeps people inside together, so viruses have more chances to spread.
  • Winter habits. Darker days often mean moving less, sleeping worse and leaning on comfort food.

So winter's a good time to check the basics.

Vitamin D: the one most of us need in winter

If you only take one supplement this winter, make it vitamin D.

Vitamin D contributes to the normal function of the immune system. Your immune cells carry vitamin D receptors, so they can respond to it directly4.

What the research says

Observational studies have linked low vitamin D to more airway infections, like colds and chest infections4.

A big 2017 analysis pooled data from 25 trials. Taking vitamin D daily or weekly lowered the overall risk of acute respiratory infections5. People who started with the lowest levels saw the biggest benefit5.

How many people run low?

More than you'd think. In the latest national survey, 18% of UK adults aged 19 to 64 were deficient6. Between January and March, that rose to 31%6.

That's why government advice is that everyone should consider a daily vitamin D supplement in autumn and winter2. For most people, 10 micrograms (400 IU) a day is enough2.

Some people are advised to take it all year round. That includes people who rarely get outdoors or who usually cover their skin2.

When to take vitamin D

There's no magic hour. The best time is whenever you'll remember it every day.

Vitamin D is fat-soluble, so taking it with a meal containing some fat may help absorption.

OneVit Vitamin D3 & K2 is a high-strength option. It provides 100 micrograms (4,000 IU) of vitamin D3 a day, which is the upper daily limit for adults2.

It also contains vitamin K2. Vitamin K contributes to the maintenance of normal bones.

Speak to your GP or pharmacist before taking vitamin K2 if you are on blood thinners such as warfarin.

Does vitamin C help your immune system?

Yes, but probably not in the way the cold and flu aisle suggests.

Vitamin C contributes to normal function of the immune system. It also contributes to the protection of cells from oxidative stress7.

Here's what the research actually says

A Cochrane review looked at people taking vitamin C every day8. In the general population, it didn't stop colds from starting8.

It did shorten them a little, though. Colds were 8% shorter in adults and 14% shorter in children8.

The picture changes for people under heavy physical stress. In marathon runners, skiers and soldiers training in the cold, regular vitamin C halved the risk of catching a cold8.

That lines up with a second claim. Vitamin C contributes to maintain the normal function of the immune system during and after intense physical exercise.

Little and often

Your body can't store much vitamin C, so a steady daily intake matters more than the odd big dose7.

Peppers, citrus fruit, broccoli and berries all help. Think of a supplement as backup, not a replacement.

OneVit Vitamin C provides 1,000mg of vitamin C in one daily tablet.

Zinc and your immune system

Zinc contributes to the normal function of the immune system. Your body needs it to develop and run several types of immune cell9.

Zinc and colds: the evidence

A 2012 review pooled 17 trials of zinc started within three days of a cold10. In adults, symptoms cleared about two and a half days sooner on average10. There was no clear effect in children10.

Thing is, the results varied a lot between trials10. Bad taste and nausea were also more common in people taking zinc10.

How much zinc per day?

Men need about 9.5mg of zinc a day, and women about 7mg11. Meat, shellfish, dairy, bread and cereals all provide it11.

Do not take more than 25mg of zinc a day from supplements unless your doctor advises it11.

OneVit Complete Multivitamin includes 5mg of zinc alongside 26 other vitamins and minerals.

What about probiotics?

Your gut does a lot more than digest your lunch. A large share of your immune tissue sits in and around your gut lining12.

The bacteria living in your gut also help shape how your immune system responds12.

What the research says

Probiotics are live bacteria you take on purpose. In a Cochrane review, people taking them were less likely to get upper respiratory infections than people on a placebo13.

But the evidence was low quality, so more research is needed13.

OneVit Probiotics Complex contains 19 billion live cultures from seven bacterial strains. It also includes inulin, a type of plant fibre.

Mushrooms and beta-glucans: where the hype gets ahead of the science

Mushrooms like reishi, shiitake and maitake contain beta-glucans. These are complex sugars found in the mushrooms' cell walls.

In research, beta-glucans appear to interact with certain immune cells14. Some scientists call them immune modulators. That means they may help steady the immune response, rather than ramp it up14.

Sounds promising. But much of this work comes from lab and animal studies14. There's still a lot we don't know about effects in people.

OneVit Mushroom Complex combines five mushroom extracts, including reishi and lion's mane, with zinc and vitamin D. Zinc and vitamin D both contribute to the normal function of the immune system.

How to choose vitamins for your immune system this winter

Start with vitamin D, add what fits your life, and keep an eye on doses.

Start with vitamin D

It's the one supplement government advice covers for everyone in autumn and winter2. So October is a good time to start.

Watch the overlap

Vitamin D turns up in more products than you'd expect. Our Vitamin D3 & K2, Complete Multivitamin and Mushroom Complex all contain it.

Do not take more than 100 micrograms (4,000 IU) of vitamin D a day in total2. Our Vitamin D3 & K2 provides that full amount on its own.

So do not take it alongside other products that contain vitamin D.

Zinc works the same way. Our multivitamin and Mushroom Complex both contain it, so check labels before combining them.

Then build around it

  • Training hard this winter? Vitamin C has its strongest evidence in people under heavy physical stress8.
  • Diet a bit patchy? A multivitamin can help fill the gaps a busy winter leaves.
  • Curious about probiotics or mushrooms? Go in knowing the research is interesting but not settled.

If you are pregnant, breastfeeding or taking any medicines, speak to your GP or pharmacist before starting a new supplement. Do not take the Complete Multivitamin if you are pregnant or trying to get pregnant, as it contains vitamin A.

The bottom line

Supplements can't make up for poor sleep, constant stress or a diet that's mostly beige. But with the basics in place, they can fill gaps.

Vitamin D is the clear starting point for most people in the UK. Vitamin C and zinc both play roles in normal immune function.

Probiotics and mushroom supplements are interesting, but the research is still catching up. Pick the immune support supplements that fit your life and check your doses.

If you keep getting ill, or a cold is not getting better, speak to your GP.

Frequently asked questions

What are the best vitamins for your immune system? Vitamin D and zinc contribute to the normal function of the immune system. Vitamin C contributes to normal function of the immune system. Government advice is that everyone in the UK considers vitamin D in autumn and winter2.

When is the best time to take vitamin D? Any time of day is fine, so pick a time you'll stick to. Taking it with a meal containing some fat may help absorption.

How much vitamin D should I take in winter? For most adults, 10 micrograms (400 IU) a day is enough2. Do not take more than 100 micrograms (4,000 IU) a day2.

How much zinc should I take per day? Men need about 9.5mg a day and women about 7mg, usually from food11. Do not take more than 25mg a day from supplements unless your doctor advises it11.

Can you take vitamin D and zinc together? Yes, they're often combined. Just add up the totals across everything you take, so you stay within the daily limits.

Does vitamin C stop you getting colds? For most people, research suggests it doesn't stop colds starting8. Taking it regularly was linked to slightly shorter colds. People under heavy physical stress saw a bigger effect8.

How do I know if my vitamin D is low? The only reliable way to know is a blood test. If you are worried about your vitamin D levels, speak to your GP.

Can supplements replace a healthy diet? No. Supplements fill gaps. They don't replace a varied, balanced diet.

This article is for informational purposes only and does not constitute medical advice. If you are concerned about your immune health, consult a GP or qualified healthcare professional.

References

  1. Chaplin DD. Overview of the immune response. J Allergy Clin Immunol. 2010;125(2 Suppl 2):S3-23. PMC

  2. NHS. Vitamin D. NHS

  3. Eccles R. An explanation for the seasonality of acute upper respiratory tract viral infections. Acta Otolaryngol. 2002;122(2):183-191. PubMed

  4. Aranow C. Vitamin D and the immune system. J Investig Med. 2011;59(6):881-886. PMC

  5. Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. PMC

  6. Office for Health Improvement and Disparities. National Diet and Nutrition Survey 2019 to 2023: report. 2025. GOV.UK

  7. Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017;9(11):1211. MDPI

  8. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;(1):CD000980. PubMed

  9. Wessels I, Maywald M, Rink L. Zinc as a gatekeeper of immune function. Nutrients. 2017;9(12):1286. MDPI

  10. Science M, Johnstone J, Roth DE, Guyatt G, Loeb M. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012;184(10):E551-E561. PMC

  11. NHS. Vitamins and minerals: others (zinc). NHS

  12. Wiertsema SP, van Bergenhenegouwen J, Garssen J, Knippels LMJ. The interplay between the gut microbiome and the immune system in the context of infectious diseases throughout life and the role of nutrition in optimizing treatment strategies. Nutrients. 2021;13(3):886. MDPI

  13. Hao Q, Dong BR, Wu T. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. 2015;(2):CD006895. PubMed

  14. Akramiene D, Kondrotas A, Didziapetriene J, Kevelaitis E. Effects of beta-glucans on the immune system. Medicina (Kaunas). 2007;43(8):597-606. PubMed

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