Home Blog Best Vitamins for Immune Function: Support Your Defences Naturally

Onevit health hub

Best Vitamins for Immune Function: Support Your Defences Naturally

written by

The OneVit Team

The OneVit Team

Updated on

14th August 2026

reading time

8 min

Best Vitamins for Immune Function: Support Your Defences Naturally

Search for the best vitamins for immune system support and you'll find bottles promising to "boost" or "supercharge" your defences overnight. That's not really how immunity works - your immune system is a complex network of cells and signals, and not simply a dial you can turn up. That doesn't mean nutrition is irrelevant - there's several nutrients that are proven support normal immune function, and one is particularly important for those in the UK.

Here's what the evidence actually supports.

How your immune system actually works

Your immune system isn't a single organ you can "boost". It's better understood as several defence layers working together, each doing a different job.

The first layer is physical: your skin, mucous membranes, and the lining of your gut and airways act as barriers that stop most pathogens getting in at all. Behind that sits your innate immune system - white blood cells such as neutrophils and macrophages that respond quickly and non-specifically to anything that gets past the barrier, engulfing invaders and triggering the inflammation you feel as swelling, heat or a raised temperature. If a threat persists, your adaptive immune system takes over. T cells and B cells that learn to recognise a specific pathogen, produce antibodies against it, and remember it for the future.

All of this activity happens across your blood, skin, gut lining and lymph nodes, coordinated by signalling proteins called cytokines that tell different immune cells when and where to respond. It's a complex system - not a switch that can be turned up beyond its normal operating range.

Nutrition's role in this is more foundational than people often expect. Building new white blood cells, producing antibodies, maintaining the physical barriers that keep pathogens out, generating the energy immune cells need to multiply rapidly during an infection - every part of that process depends on an adequate supply of specific nutrients. Being short on a key vitamin or mineral doesn't necessarily mean you'll get sick more often, but your immune response may be slower or less effective than it would be with good nutrient status. That's the mechanism behind most of the nutrients covered in this guide. They're making sure a demanding, active system has what it needs to run as intended.

Keep reading to learn about the established nutrients proven to help immune function, as well as ones with exciting research and potential behind them.

Vitamin D and immune function

Vitamin D is the clearest case among the vitamins for immune system support, especially for people in the UK. Between October and early March, UK daylight isn't strong enough for most people's skin to make sufficient vitamin D, which is why the NHS advises everyone to consider a daily 10-microgram supplement during autumn and winter.1 Around one in five UK adults have low vitamin D status even accounting for seasonal variation, rising well above that during winter months.2,5

The immune angle isn't incidental. A large 2017 meta-analysis of individual participant data, published in the BMJ, found that regular vitamin D supplementation reduced the risk of acute respiratory tract infections overall, with the strongest protective effect seen in people who started off with the lowest vitamin D levels.3

OneVit Vitamin D3 & K2 pairs the standard 10mcg dose with vitamin K2, which works alongside vitamin D in calcium regulation.

Vitamin C and immune function

Vitamin C is probably the most recognisable name on any list of vitamins for immune system support. It's very commonly taken as a remedy for colds or to help prevent getting ill in the first place - but how much of that is grounded in evidence? The truth is a bit more modest than its reputation.

A Cochrane review pooling data from thousands of participants found that regular vitamin C supplementation did not reduce how often people caught a cold in the general population, but it did produce a modest, consistent reduction in how long colds lasted - around 8% shorter in adults.4 The effect was considerably larger in people under short bursts of intense physical stress, such as marathon runners, where regular supplementation roughly halved cold risk in the trials reviewed.4 Vitamin C also contributes to normal collagen formation and helps protect cells from oxidative stress, which is why it's often paired with other immune-relevant nutrients rather than taken in isolation.

OneVit Vitamin C is a straightforward way to cover this, particularly if your diet is light on fresh fruit and vegetables during the colder months when fewer varieties are in season.

Zinc and the other nutrients in a complete multivitamin

Zinc doesn't get the same headline treatment as vitamin C or D, but it's proven to contribute to normal function of the immune system, alongside roles in cognitive function and skin health. It's a mineral that's easy to under-consume if your diet is light on meat, shellfish or legumes, which is one reason it's usually included in multivitamins.

A well-formulated multivitamin is a way of covering several bases at once rather focusing on specific nutrients individually. Iron, folate, the B vitamins and vitamin A all play their own supporting roles in normal immune function, and gaps in any of them are more common than people assume, particularly for anyone eating a restricted, low-variety, or calorie-controlled diet.

OneVit Complete Multivitamin is formulated to cover vitamin C, D and zinc alongside these other nutrients in one daily dose, which is a solid starting point if you're looking for general nutritional support and coverage.

The gut-immune connection: what about probiotics?

This is an area where the science is actively discovering new findings. Somewhere between 70 and 80% of the body's immune cells are located in and around the gut, and researchers increasingly understand the gut microbiome as having effects on immune activity well beyond digestion.6

However, it's important to note that this is a developing area of research and more data needs to be collected before a clear and official link between probiotics and immune function can be confidently declared. This doesn't discount any existing clinical data or anecdotal evidence into probiotics and their effect on immune function. Many people are choosing to take a product like OneVit Probiotics Complex as part of a broader strategy around gut health, particularly around travel or dietary changes.

You can read more about the gut-immune relationship in our gut health guide.

Mushroom complex and beta-glucans: what the research says

Medicinal mushrooms - reishi, shiitake, maitake and similar varieties - contain compounds called beta-glucans that have been studied for their effects on immune cell activity. Early human trials have shown some promising signals. One small randomised trial of reishi-derived beta-glucan reported changes in certain immune cell populations compared with placebo, and laboratory research has documented how beta-glucans interact with immune receptors in the gut wall.7

That said, this remains an emerging field. Reviews of the human trial data consistently note that studies are small and mechanisms aren't fully mapped yet.7,8 We think that's worth saying plainly rather than glossing over, because it's the difference between "interesting area of ongoing research" and "proven benefit."

OneVit Mushroom Complex combines several mushroom varieties for people who want to explore this area, positioned as a complement to the nutrients with firmer evidence above rather than a replacement for them.

When to take immune support vitamins

For most people in the UK, the single highest-value change is the vitamin D supplement recommended by the NHS every autumn and winter, since this addresses a genuine, near-universal seasonal shortfall rather than a hypothetical one.1 Vitamin C and a general multivitamin are reasonable additions if your diet is inconsistent, you're recovering from illness, or you're travelling somewhere with limited access to fresh food. Our guide to building a supplement routine covers timing and absorption in more depth if you're starting from scratch.

If you're getting frequent infections, feel persistently run down, or are concerned about a specific deficiency, that's a conversation for your GP rather than something to self-diagnose through supplementation. Vitamins support normal immune function - they aren't a substitute for medical assessment when something feels genuinely off.

Frequently Asked Questionsl

What are the best vitamins for immune system support? Vitamin D and vitamin C have the clearest evidence for supporting normal immune function, alongside zinc. A well-formulated multivitamin is a practical way to cover all three plus supporting nutrients like iron and folate.

Can vitamins actually prevent colds? Not reliably. Vitamin C hasn't been shown to reduce how often the general population catches colds, though it modestly shortens their duration. Vitamin D supplementation has shown a protective effect against respiratory infections generally, particularly in people who were deficient to begin with.

Do I need a vitamin D supplement all year round? The NHS recommends everyone in the UK consider a 10-microgram vitamin D supplement between October and early March, when sunlight isn't strong enough to make enough naturally. Some people - including those with limited sun exposure or darker skin - are advised to take it year-round.

Is it worth taking probiotics for immunity? The gut is home to a large share of the body's immune cells, which is why the area is actively researched. There is clinical evidence to support probiotics' immune function and gut health benefits, but more widespread studies need to be conducted to confidently claim them. Take this context into account if you're considering one.

Do mushroom supplements really support the immune system? Some early human research on mushroom-derived beta-glucans is promising, but the evidence base is still small and more data on the immune benefits for mushroom extracts needs it to be collected. Treat it as an area worth watching rather than a settled benefit.

Can you take too much vitamin C or vitamin D? Both have recommended upper limits, and taking significantly more than the recommended dose doesn't improve on the benefits described above. Stick to the dose on the label, and speak to a pharmacist if you're combining multiple supplements that might overlap.

Should I take these all together? There's no issue combining vitamin D, vitamin C and a general multivitamin, though it's worth checking labels to avoid unnecessary duplication, particularly with fat-soluble vitamins like D, which the body stores rather than excretes.

References

  1. NHS. Vitamin D. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
  2. O'Connor C, Glatt D, White L, Revuelta Iniesta R. Knowledge, Attitudes and Perceptions towards Vitamin D in a UK Adult Population: A Cross-Sectional Study. Int J Environ Res Public Health. 2018;15(11):2387. https://doi.org/10.3390/ijerph15112387
  3. 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. https://doi.org/10.1136/bmj.i6583
  4. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;(1):CD000980. https://doi.org/10.1002/14651858.CD000980.pub4
  5. Scientific Advisory Committee on Nutrition. SACN vitamin D and health report. GOV.UK. https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report
  6. 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. https://doi.org/10.3390/nu13030886
  7. Cerletti C, Esposito S, Iacoviello L. Edible mushrooms and beta-glucans: impact on human health. Nutrients. 2021;13(7):2195. https://doi.org/10.3390/nu13072195
  8. GOV.UK. Great Britain nutrition and health claims (NHC) register. https://www.gov.uk/guidance/great-britain-nutrition-and-health-claims-nhc-register

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.

Subscribe to our newsletter for similar articles & knowledge on supplements