The Gut–Immune Connection: Why Your Microbiome Matters More in Winter

Winter often brings a rise in colds, flu, a touch of COVID, but overall slower recovery and lower energy. While many people blame the weather alone, the gut actually plays a major role in how well the immune system responds at this time of year. The gut and immune system are closely linked, and the bugs living in your gut help shape how your body reacts to viruses, inflammation and stress.

For women living with PCOS, this connection is especially important. Gut health influences inflammation, metabolic balance, cravings, hormone regulation and resilience, all of which can feel more sensitive during winter.

How Gut Health Shapes Immunity

Around seventy per cent of the immune system sits in and around the gut. The gut lining acts as a physical barrier, while immune cells monitor what enters the body. A healthy microbiome helps regulate inflammation, supports nutrient production, and contributes to a calm, balanced immune response.

When the microbiome becomes disrupted, the immune system may overreact or become less efficient. This can mean slower recovery from viruses, greater sensitivity to seasonal changes and more fatigue.

Winter brings natural shifts that can challenge the gut. Less sunlight (so less vitamin D0, dietary changes, comfort eating, reduced movement, and increased stress all influence the gut microbial environment and may alter immune resilience.

Microbiome Diversity and Immune Defence

A diverse microbiome is linked with stronger immune defence, better metabolic balance, reduced inflammation and improved digestion. Lower diversity is associated with greater susceptibility to infections and inflammatory conditions.

Some beneficial bacteria can work to strengthen the gut barrier. When the barrier is strong, the immune system remains calm and balanced. When it becomes compromised, the immune system becomes more alert and inflammation can rise.

Women with PCOS often show lower microbial diversity and higher inflammation. This can contribute to fatigue, cravings, hormonal symptoms and reduced winter resilience.

Prebiotics and Probiotics Explained

Prebiotics are fibres that feed beneficial gut bacteria. They help increase diversity and support the production of short chain fatty acids that regulate inflammation. Examples include garlic, leeks, onions, asparagus, oats, flaxseed and green bananas.

Probiotics are live microorganisms found in fermented foods. They help introduce and maintain beneficial species. Examples include kefir, sauerkraut, kimchi, miso and live yoghurt.

Including even one or two sources of these foods daily can support a healthier microbiome.

Digestive Issues That Affect Immunity: Dysbiosis, SIBO and Reflux

Gut health is not simpply about what you eat. Digestive symptoms can also influence the immune system, inflammation and overall wellbeing. Winter often brings these issues to the surface because the body is under more seasonal stress.

Dysbiosis

Dysbiosis refers to an imbalance in gut bacteria in our microbiome. This may involve too few beneficial microbes, too many inflammatory species or microbial patterns that contribute to excess gas or digestive discomfort.

Signs can include bloating, irregular bowel movements – diarrhoea and/or constipation, fatigue after meals, sugar cravings and skin flare ups. Dysbiosis is associated with inflammation and can influence insulin sensitivity and hormonal balance.

SIBO (Small Intestinal Bacterial Overgrowth)

SIBO occurs when bacteria that belong in the large intestine migrate into the small intestine. This can interfere with digestion and nutrient absorption.

Common signs include bloating that worsens through the day, abdominal discomfort, diarrhoea or constipation, nausea and persistent food reactions. SIBO is often assessed through a breath test which measures hydrogen or methane gases produced by gut bacteria.

Reflux and Upper Digestive Issues

Reflux, heartburn and upper abdominal discomfort can also affect the gut–immune connection. These symptoms may relate to imbalanced gut bacteria, delayed stomach emptying, stress or certain trigger foods.

Reflux can reduce sleep quality and contribute to inflammation, both of which weaken immune resilience. Supporting digestion through balanced meals, eating slowly and avoiding late eating can help.

When Testing Can Help

Testing is not always required, but it can be helpful for people with ongoing digestive symptoms.

Comprehensive stool tests: These provide information on microbial diversity, beneficial and opportunistic bacteria, digestion and absorption markers, inflammation levels and yeast overgrowth.

Breath tests for SIBO: These measure hydrogen and methane gases produced after a specific carbohydrate substrate is ingested. This helps determine whether bacterial overgrowth may be contributing to symptoms.

These tools help build a clearer picture of what is happening in the gut and can guide more personalised nutrition and lifestyle strategies. If you are interested in any of this testing, please do get in touch.

Best Foods for a Winter Proof Gut

Focusing on gut friendly foods at this time of year supports both digestion and immunity.

• Fibre rich vegetables: Aim for a wide range including carrots, kale, leeks, beetroot, broccoli and Brussels sprouts.
• Fermented foods: Include kefir, live yoghurt, sauerkraut or kimchi a few times per week.
• Polyphenol rich foods: Berries, apples, olive oil, green tea, herbs and spices help modulate inflammation.
• Healthy fats: Omega 3 rich foods such as salmon, sardines, walnuts and flaxseed support immune balance.
• Protein: Protein helps stabilise blood sugar and supports immune cell function.

These foods help create a microbiome that is more resilient and better equipped to support your immune system through winter.

Bringing It All Together

Your gut plays a central role in how well your immune system copes during winter. A diverse and balanced microbiome supports a calmer immune response, steadier energy, healthier digestion and lower inflammation. Digestive issues such as dysbiosis, reflux or SIBO can place extra strain on the gut–immune axis which is why symptoms often feel more noticeable during colder months.

This connection matters even more for women with PCOS. Gut health influences inflammation, insulin sensitivity and hormone regulation, which means that an imbalanced microbiome can make PCOS symptoms feel stronger. Research shows that women with PCOS are more likely to experience dysbiosis and lower microbial diversity, and this can contribute to cravings, fatigue, irregular cycles and higher inflammatory markers. Supporting the gut is therefore not only helpful for immunity but also for managing the wider metabolic and hormonal picture of PCOS.

By focusing on simple, consistent changes such as increasing fibre, including fermented foods, supporting digestion and reducing ultra processed foods, you can strengthen your microbiome and support both immune and hormonal balance. Many women notice fewer flare ups, more stable energy and improved symptoms when they support their gut in this way.

If you feel run down every winter, struggle with digestion or suspect your microbiome needs more attention, this is an ideal time to start making changes. Or if you’d like to know more, why not get in touch?

Tired, Run-down and Inflamed? Is Inflammation Driving your PCOS?

What is inflammation?

Inflammation is the body’s natural defence mechanism. When you injure yourself or catch an infection, your immune system releases chemical messengers to repair tissue and fight off pathogens. This short-term, or acute inflammation, is essential for healing.

However, when the immune system stays slightly switched on over time, a state of chronic low-grade inflammation develops. It’s subtle, often without clear symptoms, but measurable in the body through elevated inflammatory markers such as C-reactive protein (CRP), interleukin-6 (IL-6), or tumour necrosis factor-alpha (TNF-α).

Unlike acute inflammation, this persistent “background” inflammation can quietly affect many systems, including metabolism, hormones, fertility, gut health, and immune resilience. In other words, even though you may not feel overtly unwell, your body may still be under a gentle but ongoing immune strain.

The link between PCOS and chronic low-grade inflammation

Many studies show that women with Polycystic Ovary Syndrome (PCOS) tend to have higher levels of inflammatory markers compared to women without PCOS. This suggests that inflammation is part of the underlying physiology of the condition rather than just a by-product.

Researchers describe PCOS as a metabolic–endocrine–immune disorder, where factors like insulin resistance, excess androgens, and oxidative stress contribute to immune activation. The picture is complex: insulin resistance can increase inflammation, while inflammation itself can worsen insulin resistance, creating a vicious cycle.

Obesity and central fat accumulation often amplify this process because adipose tissue releases inflammatory cytokines. However, even lean women with PCOS can show signs of immune dysregulation, suggesting that the inflammation is not simply weight-related.

This persistent low-level inflammation may also influence how the ovaries function, affect egg quality, and disrupt normal ovulation. For many clients, this explains why symptoms such as fatigue, sluggish recovery from illness, acne, and irregular cycles tend to flare during times of increased stress or poor immune health.

How inflammation affects hormones 

Inflammation has wide-reaching effects on hormone balance:

1. Hormone production and clearance.
Pro-inflammatory molecules can disrupt ovarian function, reducing the ability of follicles to mature properly and affecting ovulation. Chronic inflammation also alters the way hormones are processed in the liver, which can lead to higher circulating androgens.

2. Insulin resistance and androgen excess.
Inflammation reduces insulin sensitivity, which in turn raises insulin levels. Elevated insulin drives the ovaries to produce more androgens (such as testosterone), worsening typical PCOS symptoms like acne, hair growth, and irregular periods.

3. Egg quality and implantation.
Within the ovaries, inflammatory cytokines and oxidative stress can damage developing follicles and reduce oocyte quality. This can make conception more difficult and may increase miscarriage risk.

4. Metabolic and cardiovascular risk.
Long-term inflammation contributes to higher risk of metabolic syndrome, type 2 diabetes, and cardiovascular disease, all conditions that are more prevalent in women with PCOS.

When clients describe being “constantly run down” or “taking ages to recover from colds,” it may reflect immune system overactivity and low resilience driven by this chronic inflammatory state.

Signs of inflammation in PCOS

Low-grade inflammation often goes unnoticed because it doesn’t cause the typical redness, swelling, or pain associated with acute inflammation. Still, there are patterns and symptoms that suggest it may be at play:

• Feeling constantly tired or taking longer to recover from illness
• Frequent colds or infections
• Worsening PCOS symptoms in times of stress or fatigue
• Irregular cycles, acne, or oily skin that flare around winter or illness
• Raised inflammatory markers such as CRP or white blood cell count (if tested)
• Digestive issues or gut dysbiosis, which can contribute to immune imbalance

Feeling “drained and exhausted by December” can often reflect a combination of immune strain, nutrient depletion, and chronic inflammation.

Steps to reduce inflammation

While inflammation is part of the body’s natural defence, long-term low-grade inflammation can be influenced by lifestyle and nutrition. The goal isn’t to “switch it off”, but to bring the body back into balance.

1. Improve insulin sensitivity and body composition.
Because insulin resistance drives inflammation, improving metabolic health is key. Regular movement, strength training, balanced meals, and reducing visceral fat all help reduce inflammatory signals. See more details here.

2. Eat an anti-inflammatory diet.
A Mediterranean-style pattern, one rich in vegetables, herbs, olive oil, oily fish, nuts, seeds, legumes (if tolerated), and colourful plant foods, is linked with lower inflammatory markers. Reducing refined sugars and ultra-processed foods helps stabilise blood glucose and reduce oxidative stress.

3. Support gut health.
Around 70% of the immune system sits within the gut. A disrupted microbiome or increased intestinal permeability (“leaky gut”) can promote systemic inflammation. Include diverse fibres, fermented foods, and prebiotic vegetables while avoiding excessive alcohol or ultra-processed foods that irritate the gut lining. Or get in touch if you’d like to investigate the root cause of your gut issues.

4. Optimise key nutrients.
Certain nutrients have been shown to help regulate inflammation, including omega-3 fatty acids, vitamin D, magnesium, selenium, and antioxidants such as polyphenols. While these can come from food, clients may wish to discuss testing or supplementation with their practitioner.

5. Manage stress and prioritise rest.
Chronic stress keeps cortisol high and the immune system on alert. Techniques such as yoga, walking, breathwork, journalling, or meditation can help regulate the body’s stress response and reduce inflammatory signalling.

6. Focus on winter resilience.
During the colder months, clients often experience more colds and fatigue. I encourage them to maintain vitamin D levels, eat adequate protein, include immune-supportive foods like garlic, mushrooms, and zinc-rich seeds, and make space for recovery instead of pushing through fatigue.

7. Support hormone balance through the cycle.
Because inflammation can vary with hormonal changes, I recommend balanced meals with protein, fibre and healthy fats throughout the month. Regular sleep, exercise, and stress management help buffer the hormonal impact of inflammation.

Have a go at tracking your energy, mood, cycle regularity, and immune resilience over time to identify improvements and patterns.

And if you’re interested in working with one of our practitioners on your gut health, looking to see if that or food sensitivities or intolerances may be driving your symptoms, please get in touch. We offer a range of testing options that we can discuss further with you.

PCOS and Inflammation

While hormonal imbalances often take centre stage in discussions about PCOS, there's another crucial piece of the puzzle that deserves attention: inflammation. 

Inflammation often emerges as a silent contributor, exacerbating symptoms and affecting various bodily processes. While inflammation is the body's natural response to injury or illness, it is designed as an acute response. Perfect if you’ve cut your finger or been bitten by a gnat. However, when inflammation becomes chronic or dysregulated, it can wreak havoc on multiple systems, including those implicated in PCOS.

Symptoms of inflammation often overlap with common PCOS symptoms, making it crucial to recognize the potential link. Some tell-tale signs of inflammation driven PCOS include:

• Persistent Acne: Inflammation can contribute to the development of acne by increasing oil production and clogging pores, leading to recurring breakouts that many women with PCOS experience.
• Unexplained Weight Gain: Chronic inflammation can disrupt hormonal signalling pathways, potentially leading to unexplained weight gain or difficulty in shedding weight.
• Elevated Androgen Levels: Inflammation may stimulate the ovaries to produce more androgens, exacerbating the hormonal imbalances inherent in PCOS.
• Insulin Resistance: Inflammation interferes with insulin signalling, a hallmark of PCOS. The resulting insulin resistance can further fuel inflammation, creating a vicious cycle.
• Mood Fluctuations: Inflammation can affect neurotransmitter function, potentially contributing to mood swings, anxiety, and depression – all of which are prevalent in PCOS.

How *Exactly* does Inflammation Fuel PCOS

Inflammation affects PCOS by involving various pathways, each impacting the other in a complex web of cause and effect:

• Hormonal Havoc: Chronic inflammation can disrupt the intricate balance of hormones implicated in PCOS, potentially exacerbating the hormonal rollercoaster experienced by those with the condition.
• Oxidative Stress: Inflammation triggers oxidative stress, a process wherein the body's antioxidant defences are overwhelmed by harmful molecules called free radicals. Oxidative stress can further damage cells and exacerbate PCOS symptoms.
• Insulin Resistance Intensified: Inflammation can amplify insulin resistance by disrupting the delicate signaling processes that govern how cells respond to this critical hormone.
• Disrupted Ovulation: Inflammation can disturb the ovulatory process, contributing to irregular menstrual cycles and fertility challenges common in PCOS.

Managing Inflammation in PCOS

Recognizing inflammation as a driver of PCOS symptoms opens the door to a more holistic and comprehensive approach to management. Implementing strategies to quench inflammation can help alleviate symptoms and promote overall wellbeing. 

Consider these steps:

A Nutrient-dense Diet: Focus on an anti-inflammatory diet rich in whole, unprocessed foods, abundant in antioxidants, omega-3 fatty acids, and fibre.

Regular Exercise: Engage in regular physical activity, which can help mitigate inflammation and improve insulin sensitivity.

Stress Management: Chronic stress contributes to inflammation. Prioritize stress-reduction techniques like mindfulness, meditation, and deep breathing.

Sleep Quality: Aim for adequate, restorative sleep, as sleep deprivation can exacerbate inflammation.

Supplement Support: Certain supplements have ingredients with potent anti-inflammatory properties and can be beneficial for individuals with PCOS.

However, getting to the root cause of the inflammation can be one of the best steps you can take. Looking at gut health, food sensitivities and intolerances, and ways to lose weight can help decrease your inflammatory load.  Want to know more? Why not book a call and discuss what’s going on with you – just click here to book.