An Immunologist’s guide to supporting autumn-winter immune resilience

There is a point each autumn when I notice that the season has changed before I have quite caught up with it. The mornings are darker, porridge becomes more appealing, and getting outside takes a little more preparation. Yet my very modern schedule rarely makes the same adjustment. Our biology is seasonal. Our lives increasingly aren’t.

I’m Dr Jenna Macciochi, and in addition to being Ancient + Brave’s Director of Science and Innovation, I’m a qualified immunologist and author of three books on the immune system. My work explores how the ways we eat, move, rest and live shape immune health. I also teach breathwork, bringing that understanding into everyday practice.

When I talk about immune resilience, I mean the ability to respond appropriately to a challenge, regulate that response and recover afterwards. Staying well over winter means considering the light we see, the food we have time to prepare, the people we share space with and the recovery our days allow. 

This guide is an invitation to build a few thoughtful winter wellness habits as the season changes. Within it, I’ll walk you through how the transition to autumn and winter impacts immune health and share my tips for supporting your immune resilience through the cold weather months, exploring everything from sleep and sunlight to the role that seasonal products can play in keeping you well.

How does cold weather affect our immune system?

We tend to talk about “cold and flu season” as though winter simply makes our immune system weaker. But that isn’t really what happens. 

Immunity never exists in isolation: there is the host, the pathogen and the environment, and the relationship between all three changes with the seasons. 

Crucially, it's not just the viruses and the world around us that change. As autumn begins and light, temperature, and humidity start to shift, we change too, with thousands of our genes shifting with the seasonal cues (1). 

Behavioural changes: We move indoors, close the windows and spend more time in close contact with other people, creating more opportunity for viruses to move from one person to the next.

Physical changes: As temperatures fall and the air becomes cooler and drier, it can affect the mucus and tiny hair-like cilia lining our nose and airways, part of our first line of defence working to trap and clear the things we breathe in (2, 3).

Winter can therefore change both the environment a virus encounters and the environment of our own respiratory tract. At the same time, many of the viruses that cause winter respiratory infections can survive and spread more easily. More about that in the next section.

Which viruses circulate more in autumn and winter?

If you’re wondering “Why do I get more sick in winter?”, you’re not alone. 

While influenza, respiratory syncytial virus and the rhinoviruses responsible for the common cold tend to be more common in winter, viruses don't know what month it is. 

Each have their own seasonal patterns of circulation, shaped by an interplay between the virus itself, our behaviour and the changing temperature and humidity of the seasons (2). 

They respond to the conditions they find themselves in. And winter creates particularly favourable conditions for many of the respiratory viruses that make us ill. 

Crucially, not every winter looks the same. The 2026 virus season is particularly interesting to Immunologists because we are heading into autumn with an unusually strong El Niño developing, which is expected to influence temperature and rainfall patterns around the world (4). 

Here in the UK, the Met Office is currently predicting an increased likelihood of a warmer, wetter autumn and a more unsettled start to winter 2026. Exactly what that means for our winter virus season remains to be seen, but it is a useful reminder that “cold and flu season” isn't fixed. The environmental conditions in which viruses circulate change from year to year.

Why prepare your immune system for winter? 

I'm often asked, “How can I boost my immune system?” and the truth is, immune resilience is not as nuanced as that.

Your immune system does more than fight colds. And it doesn't just switch on for flu season. As an immunologist, I see it as your wellness system, touching every part of your wellbeing. It’s working all the time: surveying, responding, repairing and maintaining the barriers that separate us from the outside world.

A resilient immune system is hinged on: 

+ Nutritional resources to build and maintain immune cells

+ Intact physical barriers

+ Recovery and sleep

+ Regular movement

This is why I don't particularly like the idea of waiting until you feel the first tickle in your throat before suddenly trying to “boost” your immune system.

Instead, I advocate ongoing immune support that enables your defences to mount an appropriate inflammatory response when needed and regulate and resolve that response afterwards.

This is especially important when the conditions in which our immune system is being asked to work change.

In winter we spend less time outdoors, move differently, sleep differently and have fewer opportunities to make vitamin D through our skin. 

Daylight hours shorten too, and one of the most powerful signals to our biology begins to change: light. 

Light helps set our body clock, which influences sleep, hormones and the timing and regulation of immune activity (5). Making room for daylight and a regular rhythm can be a useful way to care for ourselves as the season changes.

Taken together, it's easy to see how our immune response can benefit from extra support in winter.

When should you start preparing your immune system for winter? 

It is easy to think about immune health only when we feel a cold coming on. But there is value in adapting our everyday practices before then. The changing season is a useful cue to check in with yourself. What helps you feel well? What tends to become harder as the days shorten?

Start with something manageable: reviewing your vitamin D intake, making a few meals for the freezer or finding a regular opportunity to get outside despite the weather in ways you enjoy. Small practices are easier to return to when life gets busy.

How to prepare your immune system for autumn and winter 

So far we’ve explored how preparing for winter is less about trying to build “stronger defences” and more about giving your immune system the resources and conditions it needs to adapt well to a different season. 

In the next section, I’ll walk you through some of my favourite ways to help prepare the immune system for winter.

Diet and nutrition

There is something rather lovely about the way our food changes with the seasons. As the temperature drops, we naturally return to warming bowls of porridge, soups and stews, root vegetables, squashes, brassicas, beans, nuts and seeds. 

When we look at the nutritional properties of these seasonal foods, it's like nature designed them with autumn and winter in mind. Not to mention, seasonal dishes can bring comfort during winter months, as well as nourishment.

Here’s how I nourish my body on a typical autumn or winter day: 

BREAKFAST

There’s something comforting about a warm bowl on a dark morning, and I love adding plenty of toppings. Nuts and seeds bring texture, fibre and extra nutrients, while whole milk, yoghurt and a scoop of True Collagen, topped with nut butter, this helps make it a more protein-rich breakfast. 

Protein provides the building blocks our bodies use to make immune cells and antibodies (6). Oats also provide beta-glucans, a type of soluble fibre that helps feed our gut microbes. These microbes and our immune system are in constant conversation.

I sometimes stir a sachet of True Biome into my porridge once it has cooled, adding prebiotic fibre and a postbiotic. Around 70% of your immune cells reside in your gut, a reminder that gut health and immune health are deeply intertwined, making caring for your gut bugs an unsung hero of winter immune support.

LUNCH

Later in the day, soups and stews make it easy to bring variety to the table: carrots, pumpkin and squash, dark leafy greens, beans, lentils, herbs and spices. They’re forgiving meals too, making good use of whatever is in the fridge or cupboard.

At lunchtime, I often reach for a warm bowl of homemade vegetable soup. Carrots and pumpkin provide beta-carotene, which the body can convert into vitamin A, a nutrient that helps maintain our protective barriers and normal immune function (6). 

A slice of multi-seeded bread alongside adds a little more fibre and makes it a satisfying meal.

DINNER 

As the evenings draw in, I love a slow-cooked stew with root vegetables, beans or lentils and a flavourful chicken stock. Garlic, turmeric and other herbs and spices add depth of flavour and nutrient variety. Making enough for another day is also a small kindness to my future self.

Rather than looking for one heroic “immune food”, think diversity and overall diet pattern. Different foods supply different fibres, plant compounds, vitamins and minerals, while protein-rich foods provide the building blocks our immune system needs (6). There is no single food that does it all. The foundation is eating enough, eating well and finding meals you enjoy returning to.

More ways to support the immune system in winter

Vitamins and supplements: What matters most in winter

I'm often asked: “What are the best supplements and vitamins to help prepare the immune system for the cold seasons?”

When it comes to immune health, my foundations are the everyday things: nourishing meals, movement, sleep and time to recover. Supplements have a place alongside these, particularly when they help meet a need that food or our circumstances may leave unfulfilled.

Vitamin D is a good example of how those needs change with the seasons. It contributes to the normal function of the immune system and plays an important role in helping the body fend off infections more effectively (6). 

Sunlight is our main source, but unfortunately in a UK winter, UVB levels are not strong enough for the skin to synthesise enough vitamin D from sunlight alone. 

That’s why, in the UK, all adults and children over the age of one are advised to consider a daily supplement of 10 micrograms (400 IU) of vitamin D through autumn and winter by the NHS (7, 8) and is why I usually point people to consider their vitamin D levels, especially if they are in one of the groups that the NHS considers vulnerable to vitamin D deficiency.

At Ancient + Brave, we created True D3+K2. Offering a simple way to support vitamin D intake year-round, it pairs  50μg (2,000 IU) of vegan vitamin D3 with 50μg of vitamin K2 as MK-7. 

Before its launch, we invited 756 members of our Inner Circle customer community to participate in a survey (9) that explored awareness of why and how we should support our vitamin D through winter. 81% were aged 45+. 75% primarily worked or spent their daytime indoors, fitting the profile most likely to need extra support. 

Yet, while the majority of respondents (65.9%) were aware of the government guidance around vitamin D supplementation, only  59% said that they take vitamin D daily or nearly every day through winter, with just 1 in 6 confident in how much vitamin D they may need, showing the difference between knowing what’s good for us and actually doing it.

That’s why we chose to offer True D3+K2 in a three-pack set, a supplement you’ll return to.  The refreshing peppermint and rosemary help enormously with that, providing a daily cue that transforms supplementation into a ritual you commit to day after day.

Beyond vitamin D, I also take omega-3s, paying attention to my intake across food and supplements. These choices sit within the bigger picture of how I nourish myself; they are one part of caring for my health.

Exercise and Nature

Movement is woven into how I look after myself. It supports mood, long-term health and the way our immune system works (10).

Winter can make getting outside feel like more of an undertaking. But I often find that the walk I nearly talked myself out of gives me something I needed: a little daylight, a change of perspective and some space between one responsibility and the next. Spending time in nature has also been associated with reduced markers of stress (11).

Despite the short days and moody weather, try to keep being curious about the different ways you can stay active, whether that’s incorporating gentle movement like yoga or brisk walks or trying a new hobby with a friend.  A winter routine can look different to summer and have room for both effort and gentleness.

Sleep and stress

Modern life demands a lot of us. Work, family and the invisible mental load of keeping everything going can follow us into the evening and take their toll, even when we wouldn’t describe ourselves as particularly stressed.

Sleep and our immune system are closely connected (12). Giving ourselves opportunities to rest and recover helps support that relationship. 

Our sleep may change with the seasons too, so being mindful about supporting your rest and recovery is important. A study of people attending a sleep clinic found that some aspects of sleep differed between summer and winter, with winter requiring more REM sleep, the deep sleep our brains rely on to feel focused and emotionally balanced (12). 

For me, the useful invitation is to notice how rested I feel and make room for recovery where I can. As the busy festive season gathers pace, I find grounding rituals particularly useful: small, familiar moments that help me notice how I’m feeling.  A short walk before the day begins. A warm drink without my phone. My daily breathwork practice gives me that pause. A few minutes of a comfortable, quiet moment observing the breath between finishing work and stepping into family life can be just the tonic. 

Sometimes I notice I’ve been holding tension all day. Other times I realise I need food, an earlier night or fewer things in the diary. Often it's just the pause I need to swap hats between work and motherhood

Caring for your health is also recognising that you have already done enough for today by asking for help or declining one more commitment.  

In the evening, a simple ritual helps create a sense of closure: dimming the lights, putting work away and doing something familiar that signals the day is ending. If True NightCap is part of your routine, it can sit within that wider moment of care.

Closing thoughts

Winter changes both our daily lives and the conditions in which we encounter viruses. As the season shifts, it’s a useful moment to consider what we need to feel nourished, supported and able to recover.

Our immune system needs energy and nutrients to do its work. But it also needs a feeling of joy, connection and a sense of belonging.  In practice, that might mean a warming meal shared with someone we love, a walk in daylight with a friend or an evening ritual that helps us put the day down. 

More immune activity is not always better. Timing, coordination and knowing when to stop matter too.

There will still be colds, busy weeks and nights when sleep is hard to come by. Getting ill doesn’t mean you’ve failed to look after yourself. Even with supportive habits, infections happen. My hope is that this guide simply helps you find a few ways to care for yourself that feel both comforting and possible within your life. And if you're looking for where to start, our Immune Support ritual finder can help you find what fits.

References

1. Dopico XC, Evangelou M, Ferreira RC, et al. Widespread seasonal gene expression reveals annual differences in human immunity and physiology. Nat Commun. 2015;6:7000. https://doi.org/10.1038/ncomms8000

2. Moriyama M, Hugentobler WJ, Iwasaki A. Seasonality of respiratory viral infections. Annu Rev Virol. 2020;7:83–101. https://doi.org/10.1146/annurev-virology-012420-022445

3. Foxman EF, Storer JA, Fitzgerald ME, et al. Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. PNAS. 2015;112(3):827–32. https://doi.org/10.1073/pnas.1411030112

4. Met Office. What does the latest long-range forecast tell us and what role could El Niño play this autumn? 11 September 2026. https://www.metoffice.gov.uk/blog/2026/what-does-the-latest-long-range-forecast-tell-us-and-what-role-could-el-nio-play-this-autumn

5.  Scheiermann C, Gibbs J, Ince L, Loudon A. Clocking in to immunity.Nat Rev Immunol. 2018;18(7):423–37. https://doi.org/10.1038/s41577-018-0008-4

6. Great Britain Nutrition and Health Claims Register. Department of Health and Social Care. https://www.gov.uk/government/publications/great-britain-nutrition-and-health-claims-nhc-register

7. NHS. Vitamin D. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/ 

8. Scientific Advisory Committee on Nutrition. Vitamin D and Health. London: TSO, 2016. https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report

9. Ancient + Brave. Inner Community Vitamin D Awareness Survey, September 2026

10. Nieman DC, Wentz LM. The compelling link between physical activity and the body's defense system. J Sport Health Sci. 2019;8(3):201–17. https://doi.org/10.1016/j.jshs.2018.09.009

11. Twohig-Bennett C, Jones A. The health benefits of the great outdoors: a systematic review and meta-analysis of greenspace exposure and health outcomes. Environ Res. 2018;166:628–37. https://doi.org/10.1016/j.envres.2018.06.030

12. Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiol Rev. 2019;99(3):1325–80. https://doi.org/10.1152/physrev.00010.2018

13.  Seidler A, Weihrich KS, Bes F, et al. Seasonality of human sleep: polysomnographic data of a neuropsychiatric sleep clinic. Front Neurosci. 2023;17:1105233. https://doi.org/10.3389/fnins.2023.1105233