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What is vitamin C? The essential antioxidant for energy & immunity

Vitamin C, or L-ascorbic acid, is an essential water soluble nutrient that is naturally found in some plant foods. It's essential because, unlike most plants and animals, humans can’t produce it. It’s also a water-soluble vitamin, which means your body can't store it and you need to get a constant supply from your diet!

Vitamin C benefits

Vitamin C is widely recognised as a powerful antioxidant and for its role in supporting the immune system. It's also involved in many other processes and pathways in your body. Some of its main roles include: 

Vitamin C as an antioxidant

One of vitamin C’s many immune-supporting roles is as an antioxidant (1). This means it's able to mop up free radicals, which cause oxidative stress and inflammation in your body.

Oxidative stress is an imbalance of antioxidants and free radicals in the body. High levels of oxidative stress can be found in multiple organs, including the heart, pancreas, kidneys, brain and lungs, and if not kept in check, can cause damage. 

Free radicals are chemicals in your body that have been oxidised, i.e. have lost an electron. Electrons like to be in pairs, so this makes them unstable and highly reactive, oxidising everything they come into contact with. They scavenge your body to find other electrons to steal so they can become a pair and stabilise. 

Free radicals are naturally produced in your cells and pose a constant threat to your body. They are generated by processes like the metabolism of oxygen and food, exercise and exposure to environmental toxins and pollutants like cigarette smoke, chemicals, air pollution, radiation, etc. 

Antioxidants, such as vitamin C, donate some of their electrons to free radicals without turning into free radicals themselves. This neutralises free radicals, acting as a natural ‘off’ switch, and reduces oxidative stress. In other words, they come in to ‘clean up the mess’ that has been left behind from your natural bodily processes of metabolism, energy production and detoxification.

Vitamin C’s antioxidant power also protects all of your cell structures, including proteins, lipids, DNA, RNA, mitochondria and cell membranes, from oxidising damage and gives your whole body a natural line of defence. If these free radicals build up in high amounts, it can damage cells and cause premature ageing and inflammation (2).

Vitamin C and the immune system

Vitamin C also plays an important role in immunity. It's needed for the production and modulation of immune cells that help protect your body from invading pathogens, and supports a number of other cellular functions of both the innate and adaptive immune systems (3)

Vitamin C and collagen formation

Vitamin C is required for the formation of collagen in your body (4). Collagen is the glue that holds your body together and contributes to the maintenance of healthy blood vessels, skin, bones, cartilage, gums and teeth of which collagen is a vital structural component.  

Vitamin C and energy production 

Vitamin C is involved in the synthesis of L-carnitine (5), which supports energy metabolism and helps reduce fatigue and tiredness. It's also a vital nutrient for your adrenal glands, which are responsible for regulating your body’s stress response. In cases of chronic stress, your adrenal hormones can become imbalanced, leading to fatigue. Vitamin C can help reduce the overall burden and energy demands of stress on your body through its role in reducing oxidative stress. 

Vitamin C and cognition

Vitamin C supports the normal functioning of your nervous system. It plays a role in the production of norepinephrine, our ‘get up and go’ or ‘fight or flight’ neurotransmitter, and dopamine and serotonin, important neurotransmitters that support your mood and motivation (6). It also protects your brain cells from the harmful effects of oxidative stress via its antioxidant activities. 

Vitamin C and iron absorption

Vitamin C helps to increase the absorption of plant sources of iron (non-heme iron) (7).

Vitamin C and heart health

Vitamin C also may support the heart. A 2008 meta-analysis of 13 randomised controlled trials showed that supplementing with 500mg of vitamin C daily significantly reduced levels of LDL cholesterol and triglycerides (8).

Vitamin C deficiency & depletion 

Many foods contain vitamin C, but due to the effects of modern day living, we're finding ourselves not getting nearly the amount we need to meet our individual needs. The environmental toxins and air pollution we're exposed to in the home and outdoors, life’s increased demands that leave us in a constant state of stress, and chronic diseases are some factors that increase our need for vitamin C. The food we eat is also not of the same quality that it used to be, meaning that our nutrient requirements are always increasing, and this includes for vitamin C.

Factors that leave us much more prone to low vitamin C levels include: 

  • Poor diet: Alcohol, refined sugar, caffeine and processed foods. These can cause high urinary excretion of vitamin C or high production of free radicals, which increases our need for antioxidants
  • Toxins: Environmental pollutants, cosmetics, domestic products and smoking cause high levels of oxidative stress in the body and an increased need for antioxidants
  • Chronic illness (i.e. diabetes, autoimmune conditions): Produces high levels of free radicals and oxidative stress as well as lowers the body’s immune defences
  • Stress: Vitamin C is needed to produce stress hormones, so the higher levels of stress we have, the higher our need for vitamin C 
  • Acute illness: Lowers the body’s defences and increases demands
  • Medications: Aspirin and other non-steroidal anti-inflammatory drugs
  • Nutrient decline in foods due to soil depletion, intensive farming and long food storage
  • Iron deficiency

    Vitamin C deficiency & depletion

    Signs and symptoms of vitamin C deficiency develop after a few weeks to months of vitamin C depletion. Severe vitamin C deficiency, although very rare these days, can lead to the development of a condition known as scurvy, which is related to defects in connective tissues and collagen.

    Early signs & symptoms of vitamin C deficiency

    In early stages of vitamin C deficiency, usually seen within a few weeks to one month of inadequate intake, non specific symptoms include physical and mental fatigue, weakness, lethargy, irritability, weight loss, recurrent infections, poor wound healing, and mild muscle and joint aches and pains. 

    Later signs & symptoms: Scurvy

    Symptoms of scurvy, related to defects in connective tissues, develop after 8 to 12 weeks of irregular or inadequate intake. Signs and symptoms can include chronic inflammation and weak blood vessels (due to decreased collagen production). Weak blood vessels can lead to easy bruising, excessive bleeding, swollen and bleeding gums, loose teeth, coiled hair, and broken facial capillaries (spider veins). Other signs and symptoms include anaemia, muscle and joint pain, bone pain, mood changes, and depression.

    Vitamin C sources 

    As a water soluble vitamin, vitamin C doesnt stay in your body very long. In most cases, it's excreted within 24 hours. This means that it's absolutely necessary to get your vitamin C from external dietary sources or supplementation on a daily basis. 

    Vitamin C-rich foods

    Vitamin C is present to some degree in most fruits and vegetables, however, some types of fresh produce have more vitamin C than others. Contrary to popular belief, many fruits and vegetables contain more vitamin C than oranges and other citrus fruits.

    Foods that contain the most vitamin C include: papaya, bell peppers, guava, Brussels sprouts, broccoli, oranges, strawberries, kiwi, pineapple and cantaloupe melon. 

    These foods are best eaten raw and soon after preparation as cooking and exposure to oxygen can reduce the vitamin C content by about 25%.

    Vitamin C supplements

    Although it is possible to get enough vitamin C from foods, our modern lifestyles make it difficult to consume the amount of fresh fruit and vegetables we need to prevent depletion. If you are very physically active, under high amounts of stress or even just exposed to outside air pollution on a daily basis, your body’s needs for vitamin C increase.

    One of the easiest ways to ensure you are getting enough vitamin C to support all your body’s systems that require it is through supplementation. 


    1. Free radicals, antioxidants in disease and health

    2. Vitamin C as an antioxidant

    3. Vitamin C and immune function

    4. Vitamin C-squalene bioconjugate promotes epidermal thickening and collagen production in human skin

    5. Effects of vitamin C on health

    6. Synthetic or food-derived vitamin C--are they equally bioavailable?

    7. Interaction of vitamin C and iron

    8. Vitamin C supplementation lowers serum low-density lipoprotein cholesterol and triglycerides

    9. Vitamin C and risk of death from stroke and coronary heart disease in cohort of elderly people




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