Supporting Your Immune System Naturally This Winter

As the temperature drops and winter settles in, it’s common to see an increase in colds, flus, lingering coughs, fatigue, and general “run down” feelings. While winter bugs are often considered inevitable, the good news is that there are many practical and evidence-informed ways to strengthen and support your immune system naturally during the colder months.

Immunity is not built overnight.

It is influenced daily by sleep, stress, nutrition, movement, gut health, sunlight exposure, and overall lifestyle habits. Rather than relying on a single “immune booster,” the most effective approach is committing to create a strong foundation that helps your body stay resilient all season long.

Prioritise Nutrient-Dense Whole Foods

Your immune system requires a wide range of nutrients to function optimally.

Winter is the perfect time to focus on warming, nourishing meals rich in vitamins, minerals, antioxidants, and protein.

Key immune-supportive foods include:

• Citrus fruits, kiwifruit, apple, berries, capsicum, and broccoli for vitamin C.  A favourite recipe of mine is to slice and dice apples – add a squeeze of lemon and good helping of cinnamon and ginger and slowly simmer with a bit of water on the stove till soft. I then like to stir through organic berries and leave to sit till they have warmed through too. So delicious as a quick breakfast or snack topped with seeds, muesli and yoghurt of choice.
• Pumpkin seeds, seafood, legumes, and organ, poultry and red meat for zinc
• Garlic, onions, ginger, thyme, oregano and turmeric for their anti-inflammatory and antimicrobial properties. Try a finely sliced ginger, squeezed and honey lemon tea or simmer thyme leaves. Both a great options for congestion and niggly coughs.
• Bone broth and slow-cooked soups for gut and immune support. One of the best investments for the winter months is a slow cooker. Load it with your favourite vegetables and/or meat in the morning with a variety of spices and herbs and you’ll come home to the ultimate nourishing fast food for dinner.
• Oily fish such as salmon and sardines for omega-3 fatty acids
• Fermented foods like yoghurt, kefir, sauerkraut, and kimchi to support gut health. A small amounts regularly is the best way to go.
• Aim to “eat the rainbow” with a variety of colourful local and seasonal fruits and vegetables to maximise antioxidant intake.

Support Gut Health

Did you know roughly 70–80% of the body's immune cells are located in the intestinal tract? A healthy gut microbiome plays a major role in regulating immune responses and inflammation.

Ways to support gut health include:

• Eating fibre-rich foods daily
• Including fermented foods regularly
• Reducing excess sugar and ultra-processed foods
• Staying hydrated
• Managing stress levels

If needed, a quality probiotic supplement may also be beneficial during winter, it is particularly important after antibiotic use.

Don’t Underestimate Sleep

Sleep is one of the most powerful immune-supportive tools available. During sleep, the body repairs tissues, regulates inflammation, and produces immune cells that help fight infections.

Research shows that insufficient sleep can reduce immune function and increase susceptibility to viral illness.

We should all aim for approximately 7–9 hours of quality sleep per night. Helpful strategies include:

• Maintaining a regular bedtime
• Limiting screens before bed
• Reducing caffeine late in the day
• Keeping bedrooms cool and dark

Vitamin D Matters

Vitamin D plays a critical role in immune regulation. During winter, reduced sunlight exposure can contribute to lower vitamin D levels, especially in colder regions or for people spending most of their time indoors.

Low vitamin D levels are associated with increased susceptibility to respiratory infections and a higher likelihood of experiencing seasonal affective disorder (low mood during the winter months).

If you experience immune challenges over winter or are prone to low mood, I highly recommend getting a baseline Vitamin D blood test. With clients I typically target an optimal 25-hydroxyvitamin D blood level between 100–150 nmol/L (40–60 ng/mL). This is a lot higher than the standard conventional cutoff of 50 nmol/L, but is required if you are aiming to improve immune function, reduce inflammation, and optimize bone health.

Egg yolks, beef liver and oily fish are note-worthy food sources of Vitamin D and a fun fact: Certain mushrooms (like maitake, shiitake, and portobello) naturally produce Vitamin D2 when exposed to UV light. You can even place store-bought mushrooms in midday sunlight for 15 minutes before cooking to boost their vitamin D. Sunbathed mushrooms on the menu anyone?!

Manage Stress and Nervous System Load

Chronic stress suppresses immune function over time by increasing cortisol and inflammatory burden within the body.

Simple but effective stress-management tools that can be included year-round:

• Breathwork, prayer or meditation
• Endorphin boosting exercise – team sports, snow sports, meet a mate for a walk and talk
• Social connection
• Master the beautiful ‘No’ - Take time to rest, feet up by the fire, a night in with board games. 
• Spend time in nature
• Sauna/Cold plunge - So many fun opportunities for this around now with all the pop-up saunas by the lakes and sea. A great chance to connect with a new community and have some epic conversations while you sweat it out.

Even 10–15 minutes per day of intentional downtime can positively influence immune resilience. Remember you don’t have to do it all. Choose a couple of things you genuinely enjoy or feel the benefit of and commit to that!

Consider Evidence-Based Supplements

While supplements are not a substitute for healthy lifestyle foundations, there are some that may help support immunity during winter when used appropriately.

Researched backed options include:

• Vitamin D
• Vitamin C
• Zinc
• Probiotics
• Medicinal mushrooms such as reishi or turkey tail

It’s important to choose quality products that are free from fillers and come in forms that the body can utilise. Seek professional advice where needed, particularly if pregnant, taking medications, or managing health conditions.

Hydration Still Counts in Winter

People often drink less water during colder months, yet hydration remains essential for immune health, circulation, and mucosal barriers that help defend against viruses.

If you are working in a home or office that has a roaring fire or heat pump on for most of the day or having regular sauna sessions adding Circl Hydrate+ to your water will support optimal hydration.

Warm herbal teas, broths, and soups also help maintain hydration while providing additional nutrients and comfort.

The Circl’s Team Philosophy

Supporting immunity in winter is less about “quick fixes” and more about consistent daily habits that help your body stay balanced, nourished, and resilient.

Simple actions — quality sleep, nourishing foods, stress management, movement, hydration, and targeted nutritional support — can collectively make a significant difference to how you feel throughout the colder months.

Your immune system works hard for you every day. Winter is the perfect time to return the favour.

References

1. Calder PC. Nutrition, immunity and COVID-19. BMJ Nutrition, Prevention & Health. 2020.
2. Gombart AF, Pierre A, Maggini S. A review of micronutrients and the immune system. Nutrients. 2020.
3. Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk. Physiological Reviews. 2019.
4. Martens PJ et al. Vitamin D’s effect on immune function. Nutrients. 2020.
5. Mak JWY et al. Probiotics and the immune response. Nutrients. 2020.
6. Childs CE et al. Diet and immune function. Nutrients. 2019.