Vitamin C: Food sources, benefits, inadequacy and deficiency
Vitamin C: Food sources, benefits, inadequacy and deficiency
22 Aug 2019

Want to learn how to boost your immune system, reduce risk of cancer and have glowing skin? Vitamin C is one of the most powerful antioxidants that can achieve all of this, just by eating one orange each day. Read on to learn how vitamin C benefits you!

What is vitamin C?

Vitamin C, also known as ascorbic acid, is an essential nutrient that has many health benefits. It can be found in both naturally in foods as well as supplements. Some of the key functions vitamin C is involved in include wound healing, maintaining bones and teeth and synthesising collagen1.  

Unlike most animals, humans do not have the important enzyme used to create ascorbic acid from other nutrients.  This means, the body cannot store it, so it must be eaten in your diet each day. Vitamin C is water-soluble, meaning that any excess leaves the body in the urine for a dose of vitamin above 400mg. This is also why your urine might turn a bright colour after having a multivitamin!

Supplementation of vitamin C is usually used a an immune system booster to prevent common cold. Studies show that it can reduce the duration of illness by one day.12 It also provides protection against eye diseases, some cancers and aging.  

Why is it important?

Vitamin C benefits the body in many ways. As a powerful antioxidant, it can help boost the immune system by preventing the body against harmful cells known as free radicals1. Free radicals cause changes to cells and DNA, leading a state known as oxidative stress. Oxidative stress has been linked with a variety of illnesses including cancer.  

It is essential for synthesising the body’s tissues. Without it, the body is unable to create a protein known as collagen. This is an important protein for building and maintaining bones, joints, skin, blood vessels and the digestive tract.  

There is also evidence to suggest that vitamin C plays a role in chronic disease prevention.  

Cancer prevention:  Some studies suggest that a high intake of ascorbic acid can reduce the risk of some cancers2,3 and impair tumour growth.4 However, mixed results indicate that more research is needed in this area.  

Vision loss:  There is some evidence indicating that supplementation of 500mg per day may slow the progression of age-related eye loss and the loss of visual acuity.5

Blood pressure: Studied have shown that vitamin C may help to lower blood pressure in those with and without high blood pressure.6,7

Dementia: One study found that blood levels of vitamin C and beta-carotene are significantly lower in patients with mild dementia.8 This indicates that diet may play a role in the development of Alzheimer’s disease.8

Iron absorption: Ascorbic acid helps to convert the poorly absorbed non-haem iron into a form that is easier for the body to absorb.9 This is especially important for vegans and vegetarians, who only consume iron in the non-haem form.  

Cardiovascular disease: Current research indicates that vitamin C deficiency is associated with higher risk of mortality from heart disease.13 Vitamin C may also  improve blood vessel function and blood cholesterol levels.13

How much should you be having?

According to the Australian Nutrient Reference Values, the Recommended Dietary Intake (RDI) for vitamin C each day are as follows:

Who is at risk of deficiency?

Vitamin C deficiency is relatively rare in developed countries. Severe deficiency of vitamin C can cause scurvy, a condition causing fatigue, inflammation of the gums, pain in the fingers and toes, bleeding and oedema.1 Deficiency symptoms occur only if dietary intake falls below 7-8mg per day or less.1

High risk groups for low intake:

Vitamin C inadequacy can occur with all intakes that are below the RDI.

The following groups are at risk of obtaining insufficient vitamin C.

  • Smokers and passive smokers: Studies show that smokers have 40% lower blood levels of vitamin C than non-smokers.1
  • Limited food variety: Fruits and vegetables provide the highest content of ascorbic acid, however it is still found in smaller amounts in other foods. Those who have limited food variety may be at higher risk of inadequacy.
  • Medical conditions: Some individuals with medical conditions compromising the ability to absorb certain nutrients may be at higher risk. This may also be seen in patients with end-stage renal disease on dialysis.

Vitamin C rich foods:

Fruits and vegetables are the best sources of ascorbic acid. As it is water-soluble, cooking and prolonged storage can destroy it. To lessen the amount of vitamin C lost during cooking, it is recommended to steam or microwave these foods.

It is important to eat a wide variety of raw fruits and vegetables each day.  An easy way to ensure you are eating enough vitamin C is to aim for two pieces of fruit and five cups of vegetables each day. Just one orange each day meets over 100% of the RDI for all age group.

Meet your daily needs by:

  • Adding a piece of fruit to breakfast cereal.
  • Having a colourful salad for lunch.
  • Including steamed broccoli and Brussels sprouts with dinner.
  • Adding lemon juice to warm water.

Foods richest in vitamin C include:

Who should consider a supplement?

Dietary supplements, such as the Vitable vitamin C supplements are found in the form of ascorbic acid. This has the same absorption rate in the body as the ascorbic acid naturally found in foods. Supplements may be beneficial for those at risk of inadequacy, live in areas with limited fruit and vegetable supply or have restricted diets for medical or personal reasons.