Summary

Catching every cold and bug that comes along is rarely just bad luck. It usually points to something going on underneath. That might be how you’re sleeping, what your body is running low on, or how much background stress your immune system is already managing. This post looks at the root causes behind frequent infections, and the practical changes that let your body respond better.

Key takeaways

• Your immune system doesn’t get weaker in a simple way as you age. It becomes misdirected, busy with low grade inflammation but less able to respond to new infections.
• Sleeping fewer than six hours a night made people more than four times as likely to catch a cold after exposure. That held after accounting for age, stress and smoking.
• Around 70 to 80 per cent of your immune cells are based in your gut, so digestive health and immune resilience are directly connected.
• Zinc, vitamin D and iron all play essential roles in immune function, and a shortfall in any of them is common after 40.
• Herbs such as astragalus and echinacea work differently depending on whether you’re trying to prevent infections or recover from one.

Introduction

Some women get through winter picking up every cold, chest infection and stomach bug going, while the person sitting next to them stays well. It’s easy to put it down to bad luck, or to assume your immune system is simply not as strong as it once was. There’s usually a reason behind it, and often more than one.

The pattern of catching everything is your body telling you something, and the causes are almost always things you can do something about.

This post looks at what’s actually happening when your immune defences aren’t keeping up, and where to look first.

What your immune system normally does

Your immune system works in two layers. The first is your innate immunity, the one you’re born with. It’s your body’s fast response team. Cells called natural killer cells patrol your tissues and deal with threats as soon as they appear. Your mucosal barriers, the linings of your nose, throat and gut, act as a physical first line of defence.

The second layer is your adaptive immunity. This is the part that learns. When you catch a virus, your T cells and B cells remember it so they can respond more quickly next time. It’s how vaccines work too.

Both layers depend on good communication between cells. They also need the right nutrients for repair, and enough rest for the whole system to function well.

What changes as you get older

Immunosenescence: your immune system ages too

There’s a term for the way your immune system changes with age. Researchers call it immunosenescence. It doesn’t mean your immune system simply gets weaker. It means it becomes less precise.

Your thymus, the organ that trains new T cells, starts to shrink from your twenties onwards. By your fifties, it produces far fewer of the fresh, adaptable T cells your body needs to respond to new infections. The ones that remain tend to be older, more specialised cells. They’ve already committed to a particular threat, so they’re less flexible when something unfamiliar comes along.

Natural killer cell activity can also decline. These are the cells that respond fastest to viruses and bacteria. When their activity drops, you’re more likely to catch things, and recovery tends to take longer.

Oestrogen and immune function

For women, this process doesn’t happen gradually. The fall in oestrogen during and after menopause accelerates it. Oestrogen plays a direct role in supporting immune cell activity. Researchers have found that in postmenopausal women, CD4 T cells, B cells and natural killer cell activity all decline. Each of these is linked to oestrogen levels.

This is one reason many women notice they pick up more infections from their mid forties onwards. Nothing else in life has obviously changed, but their immune resilience has.

The inflammaging paradox

Your immune system isn’t simply doing less as you get older. In many ways it’s doing more, just not in ways that protect you.

As you get older, your body tends to produce more background inflammation. Researchers call this inflammaging: low grade, chronic inflammation that builds up even without any infection present. Your innate immune cells stay switched on, releasing inflammatory signals when there’s no threat to answer. A system that’s already busy in that way responds less well when a real infection arrives. Your defences haven’t gone down. They’re stretched, and pointing in the wrong direction.

That’s why so much of the standard advice about catching colds misses the point. It’s aimed at making your immune system stronger. If low grade inflammation is already overworking it, more stimulation isn’t what’s needed. Calming that background activity, so your immune system can do its real job, comes first. It’s also why the changes later in this post look the way they do.

You might also like my post:  What is Inflammaging

The root causes worth looking at

If you seem to catch everything, the explanation usually involves several of these at once. They overlap and feed into each other, which is part of what makes the pattern feel relentless.

Sleep

Sleep is probably the most underrated factor in immune resilience. During sleep, your body produces and releases cytokines, the signalling molecules that coordinate your immune response. It also carries out the repair and regeneration your immune cells depend on. Cut that short and the whole system runs behind.

The clearest evidence comes from a study in the journal Sleep. Researchers measured sleep with wrist sensors, then deliberately exposed people to a cold virus. Those sleeping fewer than six hours a night were more than four times as likely to develop a cold. The comparison was with people sleeping seven hours or more, and it held after accounting for age, stress, income, education and smoking. It doesn’t take weeks of poor sleep, either. A single night cut short, with people kept awake between 10pm and 3am, reduced natural killer cell activity the following day.

If you sleep lightly, wake in the night, or regularly get fewer than seven hours, that alone could explain a lot. It’s one of the most overlooked causes of frequent illness.

Chronic stress

Short bursts of stress prime your immune system for a while. Sustained stress, the kind that goes on for weeks or months, does the opposite. When cortisol stays high for that long, it suppresses T cell and B cell activity and disrupts the communication between immune cells.

Research has shown that chronic stress causes a measurable reduction in the ability of your immune cells to multiply and respond. This is part of why people going through prolonged difficult periods often find they pick up every bug going. Caring for a relative, financial pressure, or doing too much for too long can all contribute.

The stress doesn’t have to feel dramatic. Many women over 40 are managing work, family, ageing parents and broken sleep all at once. That adds up to a sustained cortisol load, even if no single part of it feels overwhelming.

You might also like my post:  Herbs for Resilience

Your gut

Around 70 to 80 per cent of your immune cells are based in and around your gut. The tissue lining your intestines contains a dense concentration of immune cells. These cells interact directly with the trillions of bacteria that make up your gut microbiome. Those bacteria train your immune system, producing signals that keep immune responses calibrated and appropriate.

Gut bacteria naturally become less diverse with age. That process is accelerated by antibiotics, processed food, and chronic stress. When diversity falls, your immune system loses some of its calibration. The mucosal barrier can become less effective too, which makes it easier for pathogens to get a foothold.

This is why digestive changes and frequent infections so often occur together. They’re part of the same picture.

Nutrient gaps

Several nutrients play a direct part in immune function, and a shortfall in each of them is common in women over 40.

Zinc is needed for the development and function of natural killer cells, T cells and B cells. The body holds very little in reserve, so it depends on what you eat each day. Older adults are prone to running short, through lower intake, poorer absorption and some medicines, and even a mild shortfall dulls the immune response.

Vitamin D supports both innate and adaptive immunity. In the UK, sunlight is too weak for your skin to make vitamin D for roughly six months of the year. Low levels are common as a result. A pooled analysis of 46 trials, covering more than 75,000 people, found that vitamin D supplements reduced acute respiratory infections. The clearest effect came from a daily dose of 400 to 1,000 IU.

Iron is another one to consider. Research on older women has found that iron deficiency is associated with impairments in both innate and cell mediated immunity. Iron is often overlooked as an immune nutrient, because it’s more commonly associated with energy and red blood cells. Its role in immune cell function is well established.

Herbs do a great deal here, and the skill is in matching the herb to the situation. A herb taken to prevent infections works differently from one taken during illness. Some are better suited to long term resilience, others to acute use.

Astragalus

Astragalus (Astragalus membranaceus) is the herb for women who seem to catch everything. In traditional Chinese medicine it’s a tonic for the immune system, taken over time to build resilience. It isn’t a herb for fighting an infection already under way, and it works best taken consistently over several weeks. A 2023 analysis of 19 clinical studies, covering more than 1,000 people, found two things. Astragalus lowered inflammatory signals in the blood, and it raised T cell numbers. The background noise quietens, and the immune system has room to respond.

Astragalus suits the woman who feels depleted and keeps picking things up. It’s less useful once you already have a cold and want to shorten it. It’s gentle enough for long term use, and it combines well with other adaptogens.

Echinacea

Echinacea is the most widely studied immune herb. The European Medicines Agency lists the fresh purpurea species for the short term prevention and treatment of the common cold. That listing rests on the trial evidence. A Cochrane review of 24 trials found a consistent trend towards fewer colds in people taking echinacea, of around 10 to 20 per cent. One large trial in the same review found it shortened a cold once it had started. The species matters. Echinacea purpurea has the strongest support for acute use. Echinacea angustifolia has traditionally been used more for prevention.

In practice, echinacea works best taken at the first signs of infection and continued for up to ten days. It’s less useful as a long term preventive on its own, which is where astragalus is the better fit.

Elderberry

Elderberry (Sambucus nigra) has been the country remedy for winter illness for as long as anyone has kept records. The trials back it up. In a trial of people with flu, those taking elderberry syrup recovered about four days sooner than those taking a placebo. In a trial of 312 air travellers, those taking elderberry who caught a cold spent less than half as many days with it as those on placebo. Their colds were milder too. The berries are rich in anthocyanins, the dark pigments, and that’s where much of the activity comes from.

One thing to be aware of: raw elderberries should not be eaten, including the berries. They need to be cooked first. Syrups, tinctures and properly prepared supplements are fine.

Mushrooms and beta glucans

Ordinary mushrooms contain beta glucans, compounds that can help to prime your innate immune cells. Shiitake, maitake and reishi have the most research behind them, but even everyday button mushrooms contain useful amounts. Cooking mushrooms increases the availability of these compounds. If you’d like to know more about this, there’s a full post on how to cook mushrooms for beta glucans.

If you take prescribed medicines, a herbalist who knows your case will choose the herbs that sit well alongside them.

You might also like my post:  The Best Way to Cook Mushrooms for Beta Glucans

The practical changes that matter most

Start with sleep

If you could change one thing, this would be it. Aim for seven to eight hours, and pay attention to consistency. Going to bed and waking at roughly the same time matters as much as the total hours. If you struggle with sleep, the post on perimenopause and sleep covers why this happens and what can help.

Reduce the background stress load

You don’t need to eliminate stress. That isn’t realistic. But, look for the areas where your nervous system is under sustained pressure and see whether any of them can be eased. Regular movement, breathing practices, time outside, and protecting your rest all bring cortisol down. The post on herbs for resilience covers adaptogens that can support your stress response over time.

Feed your gut

Your gut bacteria need fibre and diversity. Aim for a wide range of plant foods across the week, including vegetables, fruits, beans, lentils, whole grains, nuts and seeds. Fermented foods such as live yoghurt, sauerkraut and kefir can also help. The post on gut microbiome diversity after 40 goes into more detail about why diversity declines and what restores it.

Check your nutrient levels

If you’re catching everything, have your vitamin D level checked with a blood test. Zinc is harder to measure accurately, but pumpkin seeds, chickpeas, lentils, cashews and red meat are good sources. If your diet is limited, or you’ve been on a proton pump inhibitor for a long time, zinc intake may be lower than you realise. The post on zinc for gut health covers how zinc supports both immunity and your gut lining.

Check iron as well, especially if you’re also experiencing fatigue, hair thinning, or feeling breathless on exertion. The post on iron deficiency and hair loss in women covers the signs and what to look for.

Address the inflammation underneath

If low grade inflammation is part of what’s keeping your immune system busy, the foundations matter more than any single supplement. Foods that calm inflammation, good fats, plenty of fibre, and less processed food all lower the background noise. The post on what is inflammaging explains this in more detail.

When to take it further

If you’ve been catching frequent infections for more than a few months, it’s time to look at it properly. That’s especially true if you’re also noticing persistent fatigue, slow wound healing, or the same infection coming back. A consultation identifies what’s driving the pattern. It might be nutritional gaps, gut health, stress, or a combination. It also means the herbs and support are matched to your situation rather than chosen from a general list.

A medical herbalist can look at the whole picture, test where it’s useful, and put together a plan that fits what your body actually needs.