Vitamin C: functions, foods, deficiency and supplements

Find out all about vitamin C, including what it does, how much you need, where to find it, and who might need to supplement their diet.

What is vitamin C?

Vitamin C is an essential vitamin, necessary for the healthy functioning of the body.¹ Also known as ascorbic acid, vitamin C is a water-soluble vitamin; our bodies don’t store it, so we have to get enough from our diets every day.² 

The benefits of vitamin C and its roles include:

• An antioxidant – it helps protects cells against damage from free-radicals (oxidation), which has been linked to chronic disease³
• Enzyme support- maintaining a healthy nervous system by supporting enzymes that process messages between neurons in the brain⁴
• Collagen co-creator - contributing to the production of collagen for tendons and ligaments, skin, cornea, bones, blood vessels and cartilage⁵
• Iron enabler - helping the body to absorb non-heme iron from plant sources⁶
• Defender – vitamin C supports our immune system, which helps to defend us from illnesses
• Healthy ageing advocate – as it can help us to produce collagen, vitamin C can help to preserve skin elasticity, which is key for healthy looking skin
• Healing helper – this antioxidant helps to heal wounds and form scar tissue, amongst other physiological function

Vitamin C is found in lots of fruits and vegetables, especially citrus fruits and juices, dark green leafy veg, peppers and berries.⁷

Vitamin C deficiency is rare but can lead to scurvy, which causes symptoms such as fatigue and swollen, bleeding gums.⁸

Summary

• Vitamin C supports multiple body functions, from supporting bones, joints and skin, to helping absorb non-heme iron from plant foods

Facts about vitamin C

Lots of animals can produce their own vitamin C, except humans, other primates and guinea pigs!

Vitamin C was first discovered in 1747 when James Lind trialed 6 different treatments for sailors suffering with scurvy. Only oranges and lemons were found to be effective.¹⁰

Taking vitamin C doesn’t appear to prevent colds and flu but taking vitamin C before the illness sets in could help reduce the duration.

What does vitamin C do in the body?

We’ve already briefly discussed what vitamin C is and what it does, but let’s go into more detail.

The function of vitamin C in the body include:^11,12

1. Healthy skin

The main job our skin has is to protect our insides from any external dangers, e.g. UV rays, harmful particles, etc.

Two of the main compounds that helps us to do this are collagen and antioxidants – and vitamin C helps to make both!

Our bodies need vitamin C to make collagen, which provides both strength and structure for skin. That’s why it’s often referred to as our skin’s scaffolding.

However, several factors contribute to declining collagen production, like:

• Getting older
• Smoking
• UV light exposure

Making sure you’re getting enough vitamin C through your diet can help to slow down this decline in collagen production.

Vitamin C also contains antioxidants that help to protect the skin from UV damage (it shouldn’t replace sun protection though!)¹³

Handpicked content: 10 best vitamins for healthy skin

2. Normal blood vessels

One of the organs most affected by vitamin C are our blood vessels, which also help to distribute it throughout our bodies.

Vitamin C has been seen to help support the cells that line the walls of blood vessels as well as form their basement membrane (helps to send and receive signals).

3. Maintaining normal blood vessels

Our blood vessels also help to distribute vitamin C and other nutrients throughout our body, so they make quite the harmonious pair!¹⁴

4. Heart health

Vitamin C could help look after your heart.

As mentioned in the section above, vitamin C helps us to maintain normal blood vessels, which are connected to normal heart function.

Observational studies have shown that being deficient in vitamin C can increase the risk of cardiovascular disease and mortality.¹⁵

5. Bone support

The connection between bone health and vitamin C was first discovered when maritime explorers with scurvy complained about severe bone pain.

Vitamin C helps our bodies to develop and maintain healthy bones by aiding collagen production.

A lack of vitamin C can lead to increased risk of bone fracture, impaired bone growth and difficulty healing damaged bones.¹⁶

6. Healthy joints and cartilage

Some other parts of the body that rely on healthy collagen levels are our joints and cartilage.

Vitamin C aids collagen production, which helps to keep joints and cartilage healthy and supported.¹⁷

7. Supporting immune function

You’ve probably been told that vitamin C can help when you have a cold or flu infection, which is true! However, there is no evidence that it can prevent these illnesses, instead, it is said to help reduce the duration of them instead.

Vitamin C helps keep our immune system functioning normally in general, too, especially during and after intense exercise.

One of the ways it does this is by strengthening the skin to keep pathogens out and reduce oxidative stress.

Being deficient in vitamin C can result in impaired immunity and higher susceptibility to infections.¹⁸

8. Normal physiological function

Vitamin C plays an important role in many physiological processes, like helping to heal wounds, form scar tissue and maintain dental health.¹⁹

9. Normal nervous system function

Our nervous system is a complex network of cells and neurons from the brain and spinal cord to various body parts.

Vitamin C can be found inside the neurons in our central nervous system. In fact, these neurons contain some of the richest concentrations in human body tissues.²⁰

A recent review of 50 studies on vitamin C and cognitive function found a significant relationship between the two.

The studies showed that those who had good cognitive health had higher blood concentrations of vitamin C than those who were cognitively impaired.²¹

10. Improved absorption of iron from plant sources

Vegetarians and vegans listen up: you need vitamin C to absorb iron from plant foods.

Iron is the most abundant metal in the human body; adults need around 3-4g of iron a day and it must be obtained via the diet.

There are two main types of iron:

• Heme iron: the most common type of iron found in red meat, poultry and fish
• Non-heme iron: found in plan foods

Heme iron is generally well-absorbed, whereas non-heme iron is slightly more difficult, especially if you are lacking in vitamin C.

Vitamin C helps our bodies absorb iron from plant sources like citrus fruits and green leafy vegetables.

Summary

• Vitamin C benefits include maintaining healthy skin, bones, blood vessels, heart function, joints, immune function and is even linked to better mental health

Dosage of Vitamin C

Wondering how much vitamin C you should be taking? Read on to find out.

How much vitamin C do you need a day?

Women and men need 80mg of vitamin C every day.²² That’s the same as half an orange.²³ Vitamin C is water soluble so it can’t be stored in the body.

This means you need to replace it from your diet every day.²⁴

How much vitamin C do children need?

1-10 years – 30mg of vitamin C a day

11-14 years – 35mg a day

15 years and older – 40mg a day²⁵

Vitamin C foods

It’s not just oranges that pack in the vitamin C you know!

Which foods are the best sources of vitamin C?

Foods high in vitamin C include:²⁶

• Red and green peppers
• Brussels sprouts
• Oranges and orange juice
• Mango
• Papaya
• Grapefruit
• Pineapple
• Other citrus fruits
• Kiwi fruits
• Strawberries
• Raspberries
• Blueberries
• Cranberries
• Melon (especially cantaloupe)
• Cauliflower
• Spinach
• Broccoli
• Cabbage
• Kale
• Other dark green leafy vegetables
• Tomatoes
• Potatoes
• Green peas

Other sources of Vitamin C

• Juices with vitamin C
• Tinned fruits and vegetables

Vitamin C deficiency

Vitamin C deficiency in the UK is extremely rare, as people usually get enough from their diet.

What are the symptoms of a vitamin C deficiency?

A vitamin C deficiency can lead to scurvy after as little as one month.

If you don’t get your daily dose of vitamin C and become deficient, symptoms could include:²⁷

• Skin bruising
• Inflamed, bleeding gums
• Fatigue
• Low energy
• Depression
• Irritability
• Joint pain

People with low levels of vitamin C can also develop iron-deficiency anaemia.¹⁷

People at risk of scurvy include those whose diets lack fruits and veg, perhaps because of illness, alcohol abuse or smoking: it reduces how much vitamin C is absorbed by the body, increasing your need for the nutrient.²⁸

How much vitamin C is too much?

Is too much vitamin C bad for you? It could be.

High doses of vitamin C may lead to diarrhoea, nausea, vomiting and stomach cramps. It can also cause headaches and insomnia.²⁹

Best vitamin C supplements

There are a few different types of vitamin C supplements you can take if you choose to take one, like:

• Vitamin C tablets/capsules

And if you don’t like tablets or struggle to take them:

• Vitamin C drink sachets
• Vitamin C effervescent tablets
• Vitamin C powder
• Vitamin C oral sprays

Kids may prefer to take vitamin C gummies.

Wondering which is best for you? Have a read of our article on 11 of the best vitamin C supplements. 

When should I take vitamin C supplements?

You should be able to get all the vitamin C you need from a balanced diet. But there are some people who should pay particular attention to their vitamin C intake, like:

Smokers and passive ‘smokers’

Studies have shown time and time again that smokers tend to have lower vitamin C levels than nonsmokers.

In fact, the institute of occupational medicine (IOM) recommends that smokers need 35mg more vitamin C per day than nonsmokers.

Babies fed boiled or evaporated milk

Most infants in developed countries are fed infant formula or breastmilk, both of which contain adequate amounts of vitamin C. However, if you feed babies evaporated or boiled milk, this can cause vitamin C deficiency.

Those with limited diets

If you don’t eat many fruits, vegetables or other sources of vitamin C, you may want to consider taking a vitamin C supplement.

Vegans and vegetarians

Although many vegan and vegetarian diets probably contain a lot of fruit and vegetables, if you’re not a fan, it’s even more essential to maintain healthy levels of vitamin C.

This is because vitamin C is essential for helping our bodies to absorb iron from plant foods.³⁰

Should children take vitamin C supplements?

The NHS says children under the age of five may not get enough vitamins A and C. So, the government recommends all children aged between six months and five years old take a daily multivitamin containing vitamin C.³¹

Do women need to take a vitamin C supplement during pregnancy?

There is no specific need, as you should be able to get all the vitamin C you need from a healthy, balanced diet.³²

What are the potential benefits of taking a vitamin C supplement?

Most people should be able to get enough vitamin C from a healthy balanced diet full of fresh fruit and vegetables.

However, a 2018 study discovered that taking extra vitamin C could help shorten the length of the common cold.³³

The final say

• Vitamin C is essential for many bodily functions
• Our bodies can’t make it, so you need to make sure you get enough every day through your diet or supplementation
• You can find vitamin C in a wide variety of plant foods, including citrus fruits and green leafy vegetables
• Vitamin C deficiency is rare, but can result in serious conditions like anemia and scurvy if not treated

Last updated: 1 July 2021