Sources of Vitamin C - citrus fruit sliced open

Vitamin C Benefits And Its Role In Immune System Health

Written by: Swisse Wellness
Swisse Wellness

We all know that vitamin C is important for immune health, which is why many of us reach for oranges when we feel a cold coming on. But there’s far more to this micronutrient than just citrus fruits. So, what is the science behind vitamin C? What foods is it found in? And how can it support the immune system? Here’s what you need to know.

What is vitamin C?

Vitamin C, also known as ascorbic acid, is an essential micronutrient that is important for a range of different processes within the body. Not only is vitamin C important for immune health, it also assists with wound healing, the repair and maintenance of cartilage, bones and teeth and the absorption of iron.

Vitamin C is water-soluble vitamin which means it dissolves in water and is not stored in the body. Unlike many animals, humans can’t make vitamin C within the body, which means we have to consume it from our diet or through supplementation[1]. Vitamin C is naturally present in many fruits and vegetables.

Benefits of vitamin C for a common cold 

In 2013, a scientific review was published that examined the effect of vitamin C on relieving the symptoms of the common cold[2]. The authors found that vitamin C supplementation had the effect of reducing the duration of common cold symptoms. Regular vitamin C intake (with most studies using 1000mg per day) was associated with a 14.2% reduction in cold duration in children and 7.7% reduction in adults.

Vitamin C deficiency results in an impaired immune system. In turn, a weakened immune system can lower vitamin C levels due to inflammation in the body and pressure on the metabolism. So, it’s important to make sure you’re getting plenty of vitamin C to support your health and wellbeing and immune function.

What does Vitamin C do for the rest of your body? 

Vitamin C is necessary for the growth and repair of all tissues in our body and needed for various functions, including:

  • Supporting the immune system;
  • Keeping the bones, teeth, connective tissue and bone cartilage strong and healthy;
  • Acting as an antioxidant which helps protect cells against the effects of free radicals;
  • Helping the body absorb iron from plant sources (non-heme iron); and
  • Producing collagen, a protein in the structure of the body essential for your muscles and skin.[3]

Does vitamin C give you energy?

Vitamin C has an important role to play in energy production. It helps our bodies convert the food and drink we consume into energy and absorb other vitamins, minerals and micronutrients [4].

What are the symptoms of low vitamin C?

The most common vitamin C deficiency symptoms are fatigue and – if the deficiency is severe – scurvy[5]. Some of the hallmarks of scurvy are bleeding gums, hair loss and poor wound healing [5].

How does vitamin C help to support the immune system?

Vitamin C plays an important role in supporting functions of both the innate (first line of defence, mechanisms that immediately attack foreign cells or block them from entering the body) and adaptive immune system (second line of defence, which develops over time after exposure to diseases or vaccinations) immune system[6].

Firstly, vitamin C supports epithelial barrier function. This barrier regulates nutrient absorption and also prevents the invasion of pathogenic bacteria (bacteria that can cause disease) in the body. Vitamin C also promotes the oxidant scavenging activity of the skin, which protects against environmental oxidative stress[7].

How to add more vitamin C into your diet

As vitamin C cannot be stored in the body for long, it’s important to eat an abundance of fresh fruits and vegetables to ensure your body has sufficient vitamin C levels.

The recommended dietary intake (RDI) of vitamin C for adults is 30mg per day. If you’re following the common advice of eating two servings of fruit and five servings of vegetables daily,[8] you’re on the right track to meeting your daily vitamin C target[9].

Which foods contain vitamin C

Most fruits and vegetables contain some vitamin C, but there are foods that have higher levels than others. Vitamin C-rich foods include:

  • Kiwifruit
  • Strawberries
  • Kakadu Plums (Australian native plum)
  • Capsicum, particularly red (which are ripened green capsicums)
  • Blackcurrants
  • Oranges, mandarins, lemons and other citrus fruit
  • Papaya
  • Guava
  • Tomatoes
  • Broccoli
  • Brussel sprouts
  • Kale and Spinach.

When it comes to enjoying a diet rich in vitamin C, how you cook your food plays a role too. To retain as much of the vitamin C content as possible, cooking methods that require shorter periods of time are your best bet such as stir-frying or steaming briefly. Even frozen vegetables can be a convenient way of boosting your daily vitamin C intake. There are so many delicious, vitamin C and nutrient-rich recipes for you to explore in our hub,. All of the recipes are written, tried, tested and loved by our in-house nutritionists and dietitians.

Can you have too much vitamin C?

While vitamin C has low toxicity and is therefore not believed to cause serious adverse effects at high doses, excessive intake may lead to complaints such as diarrhea, nausea and stomach cramps[1].  



  2. Hemilä H, Chalker E. Cochrane Database of Systematic Reviews 2013, Issue 1.
  4. Tardy AL, Pouteau E, Marquez D, Yilmaz C, Scholey A. Vitamins and Minerals for Energy, Fatigue and Cognition: A Narrative Review of the Biochemical and Clinical Evidence. Nutrients. 2020;12(1):228. Published 2020 Jan 16. doi:10.3390/nu12010228
  5. Harvard School of Public Health. The Nutrition Source: Vitamin C. Sourced 26 July 2023
  6. Carr AC, Maggini S. Nutrients 2017
  7. Carr AC, Maggini S. Nutrients 2017


Swisse Wellness

Swisse Wellness - Swisse Wellness

The copywriting team at Swisse Wellness plan, research and generate blog content with inputs from multiple teams across the business. With access to our industry-leading Science team, Product Development team, Customer Service team as well as informative Brand Managers, we have the contacts to deliver a well-rounded suite of blogs tailored to an array of wellness interests....