Vitamin C and immunity are an iconic duo - and vitamin C is the ultimate ally when it comes to keeping your immune system fighting fit. This essential nutrient plays a key role in protecting your body against illness and keeping you feeling your best year-round. But how does it actually work, and what’s the best way to ensure you’re getting enough? Is diet alone going to cut it when it comes to keeping colds and flu at bay? Let’s explore the answers to these questions and more as we learn how vitamin C works and the best ways to maximise its benefits.
How Vitamin C Boosts Your Immune System
Vitamin C is a powerful antioxidant that helps support the body’s natural defences. Here’s how it works:
- Enhances White Blood Cells – It helps stimulate the production and function of white blood cells, your body’s first line of defence against infections.1
- Fights Free Radicals – As an antioxidant, vitamin C neutralises harmful free radicals that can weaken the immune system.
- Supports Skin Barrier Function – Your skin is an important part of your immune defence. Vitamin C strengthens this protective barrier, supporting the fight against the invasion of harmful pathogens. 2
- Boosts Iron Absorption – Iron is critical for immune function and energy production – adequate vitamin C is required to enhance its absorption, ensuring your body makes the most of these nutrients when consumed either in food or as a supplement.
Why Vitamin C is Essential During Cold and Flu Season
Research shows that vitamin C can help reduce the severity and duration of cold and flu symptoms.3 Here’s why taking an immune health supplement rich in vitamin C during winter months can be beneficial:
- Shortens Recovery Time – Studies suggest regular vitamin C intake can help you bounce back faster from colds and flu.
- Reduces Symptom Severity – Supplementing with vitamin C can lessen symptoms such as congestion and coughs, particularly when paired with vitamin C and zinc.4
- Bridges Dietary Gaps – Many people don’t get enough Vitamin C from diet alone, especially during colder months when fresh fruits and vegetables may be less available.
Top Vitamin C-Rich Foods for Immune Health
Adequate vitamin C intake can be achieved through a balanced diet of colourful fresh fruits and vegetables. Here are some of the best vitamin C sources:
- Citrus fruits – Oranges, lemons, limes, and grapefruits
- Berries – Strawberries, blueberries, and raspberries
- Peppers – Red and yellow bell peppers contain more Vitamin C than oranges!
- Leafy greens – Spinach, kale, broccoli, and bok choy
- Tomatoes – Fresh and sun-dried varieties are excellent sources
- Kiwifruit – Packed full of fibre and antioxidants, including plenty of vitamin C
- Pineapple & Mango – These tropical favourites are high in vitamin C and beta-carotene (pro-vitamin A) for an added immune-boosting effect.
How to Maximise Vitamin C Absorption
To get the most out of your vitamin C intake, consider these tips:
- Pair with Zinc & Vitamin D – If you’re looking for a supplement, consider one that also contains zinc and vitamin D. Together, these enhance immune support.
- Take It at the Right Time – Vitamin C is water-soluble, meaning it’s best taken in smaller doses throughout the day rather than all at once.
- Eat Fresh Fruits & Veggies – Cooking can deplete sensitive antioxidants, including vitamin C, so opt for raw or lightly steamed options.
- Stay Hydrated – Water helps transport nutrients such as vitamin C throughout the body.
Recommended Vitamin C Supplement Dosage
Ensuring you’re getting the right amount of vitamin C is key:
- Adults: 45-90 mg per day (higher doses of 200–500 mg may provide additional benefits during cold and flu season)
- Children: 25-40 mg per day, depending on age
- Upper Limit: While vitamin C is generally safe up to 1,000mg, higher doses (over 2,000 mg daily) can cause digestive issues such as diarrhoea.5
Signs of Vitamin C Deficiency
If you’re not getting enough vitamin C, your immune system and overall health may suffer. Watch out for these signs:
- Frequent colds or infections
- Slow wound healing
- Fatigue and low energy
- Bleeding gums or frequent bruising
- Dry, rough skin
- Low iron (which requires vitamin C for absorption)
Are High Doses of Vitamin C Safe?
Vitamin C is generally well-tolerated, but extremely high doses may cause:
- Upset stomach or diarrhoea
- Kidney stone formation (in people prone to kidney issues)
- Iron overload if taken with high doses of iron supplements
To stay on the safe side, stick to recommended daily doses unless advised otherwise by a healthcare professional.
Vitamin C is a simple yet powerful way to keep your immune system in top shape. Whether through diet or supplements, ensuring you get enough vitamin C can help your body fight off infections, recover faster, and stay energised. For an extra immune boost, consider pairing your vitamin C supplement with zinc and Vitamin D, and make sure you're incorporating plenty of vitamin C-rich foods into your daily routine.
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This article was written by Sophia Power, a Clinical Nutritionist.
References:
- Linus Pauling Institute. Vitamin C. Reviewed December 2018, accessed February 2025 from https://lpi.oregonstate.edu/mic/vitamins/vitamin-C
- Pullar JM., et al. The roles of vitamin C in skin health. Nutrients, 2017;9(8):866.
- Hemilia H., et al. Vitamin C reduces the severity of common colds: a meta-analysis. BMC Health, 2023; 23(1):2468.
- Abioye AI., et al. Effect of micronutrient supplements on influenza and other respiratory tract infections among adults: a systematic review and meta-analysis. BMJ, 2021;6(1).
- NHMRC. Vitamin C. Accessed February 2025 from https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/vitamin-c