Some people go through a whole winter without catching anything. Others pick up every cold going round the office. That difference isn’t luck, and it isn’t a constitution you either have or don’t.

It mostly reflects how well supported your immune system is, day to day.

This is a practical guide to supporting yours. It covers what to eat and which herbs are worth using. It also covers the daily habits that matter more than any supplement.

Why “boost” isn’t quite the right word

Boost is the word most of us think of, so it’s the one I’ve used here. It’s worth knowing what it means in practice, though.

An immune system running at full tilt all the time isn’t a healthy one. That’s closer to what happens in allergy and in autoimmune conditions.

What you want is a system that responds fast when it needs to. Then settles again once the work is done.

So the aim isn’t more immune activity. What’s needed is better regulated immune activity. Everything below works towards that.

What happens when you catch a cold

When a virus reaches your nose or throat, it’s your innate immunity that responds first. Cells in the lining spot the problem and release signals calling for help. Blood vessels widen, fluid moves in, and white blood cells arrive.

That’s what gives you the sore throat and the runny nose. The discomfort is your defences working, not the virus alone.

Over the following days, your adaptive immunity learns the pattern. It makes antibodies matched to that particular virus. Next time you meet it, the response is faster. Sometimes it’s fast enough that you never feel unwell at all.

Why winter makes this harder

Winter does stack the odds against you, and there’s now a decent explanation why.

Researchers measured what happens inside the nose in cold air. After a short spell outside, the temperature inside the nose dropped by roughly five to six degrees.

It’s the cooling that matters, and more than you might think. Cells lining your nose release billions of tiny sacs that neutralise viruses in mucus. But, in the cold, that release fell by nearly 42 per cent.

A scarf over your nose and mouth keeps a pocket of warmer air in that space. It’s a small thing that helps more than you might expect.

Indoor air is the other half of the problem. Heated rooms are dry, and dry air helps respiratory viruses survive and spread. It also dries your airways, which weakens a physical barrier. Putting some moisture back into the air helps.

Food first: what to put on your plate

Food is like daily training for the immune system. There’s no single perfect immune food, and no supplement replaces this part.

Build your meals around plants, protein and good fats. A simple pattern is half the plate colourful vegetables, a quarter protein, a quarter whole grains or starchy veg.

Protein supplies the raw material for immune cells and for repair. Colour brings a spread of vitamins and plant compounds. Orange vegetables support vitamin A, which keeps airway linings healthy. Berries, red onions and pomegranate add flavonoids that help calm excess inflammation. Greens and kiwi bring vitamin C and folate.

Think of vitamins A, D, E and K as your slow-release reserves. Vitamin C and the B group vitamins need topping up regularly. And, food variety across the week beats perfection on any one day.

Easy swaps

Have oats instead of sugary cereal. Try beans added to soups and stews. Use extra virgin olive oil in dressings rather than other oils. Have nuts and seeds to hand for snacks or toppings, if they suit you.

Small changes made most days count for more than one immaculate meal.

The balance of fats in your diet also affects how easily inflammation settles down. I’ve written about the omega-3 to omega-6 ratio separately.

Your gut does more immune work than you’d think

Most of your immune cells are found close to your digestive tract. That tissue is called gut associated lymphoid tissue, or GALT. Cells from this tissue sample what you eat and what your gut bacteria produce.

The fibre you eat feeds those bacteria. They ferment it into short-chain fatty acids, which help to regulate immune tone. That’s much of the reason fibre intake appears in immune research at all.

Prebiotic foods include onions, leeks, garlic, oats, beans, lentils and bananas. Fermented foods add live microbes: live yoghurt, kefir, sauerkraut and kimchi.

Researchers call the link between gut bacteria and airway immunity the gut-lung axis.

Shiitake mushrooms and beta-glucans

Shiitake mushrooms have been part of Chinese, Japanese and Korean cooking for centuries. They’ve been valued for supporting health for around two thousand years. Modern research now gives us a reasonable idea of why.

What’s in them

Shiitake are a good source of B vitamins and selenium. They also contain polysaccharides, and that’s the interesting part.

These polysaccharides are chains of glucose molecules linked together. Our digestive enzymes can’t break those links. So they behave as a form of dietary fibre, travelling largely intact to the colon.

The best studied group are the beta-glucans. Lentinan is the one you’ll see named most often.

How they reach the immune system

This is where the GALT comes in. Immune cells in the gut lining recognise these polysaccharides and respond to them.

Your gut bacteria also ferment them. The products of that fermentation appear to matter too.

So the effect isn’t mysterious. It’s a fibre that your gut immune tissue happens to take a great deal of interest in.

What the human research shows

Most mushroom research uses isolated extracts in a laboratory. Food studies in people are rarer, which makes one trial worth knowing about.

Fifty-two healthy adults ate 5 or 10 grams of dried shiitake daily for four weeks. Researchers measured immune markers before and after.

Proliferation of gamma delta T cells rose by around 60 per cent. Natural killer T cells doubled. Secretory IgA in saliva went up, which matters because that antibody guards mucous membranes. C-reactive protein, a marker of inflammation, came down.

It’s worth being clear about what that actually shows. Immune markers improved under controlled conditions. The trial didn’t count infections, so it can’t tell us that eating shiitake means fewer colds.

It’s supportive evidence, not proof of prevention.

You might also like my post: Mushroom Coffees: A Herbalist’s Guide to What’s Inside 

How to use them

Fresh shiitake are in most larger supermarkets now. Cook them as you would any mushroom.

Dried shiitake keep for months. Soak them for thirty to sixty minutes, then remove the stalk, which stays tough. Use them as you would fresh.

The trial dose was 5 to 10 grams of dried mushrooms a day. That’s a modest amount, and it’s an easy habit rather than a course of treatment.

Cooking method affects how available the beta-glucans are. I’ve covered the best way to cook mushrooms for beta-glucans in its own post.

Safety

Don’t eat shiitake mushrooms raw. Some people develop a distinctive rash after raw or undercooked shiitake, known as shiitake dermatitis. Cooking the mushrooms prevents it.

Avoid shiitake if you have a known mushroom allergy. Otherwise they’re a food, and they suit long-term daily use.

Ordinary mushrooms come up in other research too. I’ve written about mushrooms and dementia risk separately.

Sleep, stress and movement

These three things do more for you than most supplements, and they cost you nothing.

Sleep is when immune messaging resets and repair can become the priority. Try to aim for a consistent sleep window, that gives you seven to nine hours in bed. A simple wind-down can help a lot: a warm drink, dimmed lights, screens off, and some breathing techniques, such as simple slowed breathing, or box breathing.

Long-running stress dampens useful immune activity over time. Short, regular practice helps more than the occasional long session. Ten minutes walking, a few minutes of paced breathing, time outdoors, prayer or meditation all count.

Movement improves immune surveillance. Brisk walking on most days helps distribute immune cells around the body. Moderate and regular beats occasional and punishing.

Herbs through the cold season

Herbs fall into two groups here. Some are used across the season as background support. Others are used at the first sign of illness. Consider this educational in nature rather than a herbal prescription.

Astragalus, through the season

Astragalus root is used across autumn and winter as background support. In traditional use, slices are used in cooking, so it goes into broths, or it is taken as a decoction of the sliced root.

Research suggests its polysaccharides can increase antibody production and support certain immune signalling pathways. Human evidence for preventing everyday colds is limited. So I’d describe it as a seasonal builder for the people it suits, not a guarantee of fewer infections.

How to use it: a few slices of dried root in slow-cooked soups. A capsule, decoction or tincture works too.

Who it suits: people wanting background support alongside food and lifestyle. Avoid it in pregnancy and breastfeeding. Avoid it if you take immunosuppressant medication, as it may work against them. If you live with an autoimmune condition, get personalised advice first.

Elderberry, at the first signs

Elderberry syrup is simple to make at home. Taken early, it may shorten how long a cold lasts and ease how rough it feels.

The evidence supports it as something you take once ill, rather than as prevention. Start within the first 48 hours if you can.

Use cooked preparations or a commercial syrup only. Raw parts of the plant, including the berries, can cause side effects.

Andrographis, at the first signs

Andrographis is a strongly bitter herb used for acute upper respiratory illness. Trials report reduced severity and faster recovery when it’s started promptly.

It isn’t suitable in pregnancy. There are rare reports of severe allergic reactions. Avoid it if you have a strong allergy history, unless you have tailored advice.

I’ve written a fuller guide to using andrographis for colds and flu.

Echinacea

Echinacea results are mixed. Species, plant part and product quality all differ between trials.

Reviews suggest a small preventive effect, or a modest reduction in duration, for some preparations. Other trials find nothing.

If you use it, use it at the first hint of illness, in short runs. Choose a product that states the species and the part used. A good echinacea should tingle on the tongue. You won’t taste that from a capsule, so a tincture or tablet tells you more.

You might also like my post: Do Herbal Remedies Actually Work?

Supplements worth considering

Vitamin D

Vitamin D behaves more like a hormone than a vitamin. Low levels are common through a UK winter.

The evidence here has moved, and it’s worth knowing how. A 2021 review of 37 trials found a small protective effect against respiratory infections. An updated review published in 2025 added six more trials, including one very large one. The size of the effect barely changed. But the range of uncertainty around it now includes no benefit at all.

What has held up is that regular modest dosing works better than occasional large doses. Testing is what lets you choose a dose that fits you.

I’ve written more on vitamin D in a UK winter.

Practical note: typical winter maintenance in adults sits between 400 and 1,000 IU daily. Adjust to your blood test result and your diet. Speak to your GP first if you take thiazide diuretics, digoxin or long-term steroids.

Zinc

Zinc won’t stop you catching a cold. But, taken early, it may shorten one.

The evidence is contested, and I’d rather you knew that. A large 2024 review concluded the evidence was too uncertain for firm recommendations. It found colds shortened by around two days, but with wide uncertainty around that figure.

Other researchers reanalysed the lozenge trials from that review and found a clearer effect in adults. They put the shortening at around a third.

The disagreement is mostly about which trials belong in the pool. Where both sides agree: any benefit is for treatment rather than prevention, and lozenges matter more than tablets.

If you use them, start within 24 hours of the first scratchy throat. The trials showing benefit used at least 75 mg of elemental zinc daily, split through the day. Let each lozenge dissolve slowly. Avoid formulas containing citric acid, which binds zinc.

Practical note: at this dose zinc often leaves a metallic taste and can cause mild nausea. Keep it’s use short, just for the cold itself. It can interfere with some antibiotics, so separate them by at least two hours.

Vitamin C

Research shows that routine high-dose vitamin C doesn’t prevent colds in most people. That’s a myth that has proved hard to dislodge.

But, regular intake can slightly shorten how long your cold lasts. Starting it after an illness begins gives mixed results.

Some well-chosen foods can cover most people’s needs. If you do supplement, studies have used 1 to 2 grams daily. More than that tends to upset the gut without adding benefit.

Probiotics

Probiotic effects are strain-specific, so reading the label on the supplement matters.

A 2022 review found that probiotics reduced the chance of getting at least one upper respiratory infection. Episodes were a little shorter too. But, the evidence was rated as low quality, so treat it as possibly beneficial.

Lactobacillus and Bifidobacterium strains are the best studied. Food sources still count. Live yoghurt and kefir might be your simplest daily options.

Putting it together

Start with the foundations and only add what you need.

Daily foundations. Plants and protein at each meal. A regular sleep window. Stress care as a daily act rather than as a someday plan. Movement on most days. A bowl of nourishing soup, a brisk walk and a regular bedtime probably go further than most supplements.

Seasonal support. Check your vitamin D levels with a test and top up with regular modest dosing if needed. Build your gut health with fibre and fermented foods. Add shiitake to your cooking through the week. Astragalus can work in the background over the colder months, if it suits you.

At the first signs. Act early. Zinc lozenges, elderberry syrup, and andrographis where it’s appropriate. Rest, fluids and warm broths still matter more than people expect.

Sensible care

Herbs and nutrients can interact with medicines. Zinc can interact with some antibiotics. And, vitamin D with digoxin or thiazides. Don’t use Astragalus with immunosuppressants. And, be careful with Andrographis where there’s a strong allergy history.

Pregnancy and breastfeeding need particular care. And, if you live with an autoimmune condition, some herbs that stimulate immune activity won’t be suitable for you.

Infections that keep returning are worth looking into properly rather than managing alone. Cold sores that come back repeatedly are one example.

If an illness drags on, or if you’re worried, it’s best to consult a healthcare professional.