Vitamin C (ascorbic acid): uses and side effects

Vitamin C, or ascorbic acid, is an essential nutrient that the human body cannot synthesise. It plays a key role in immune function, collagen formation and protecting cells from free radicals.

Vitamin C at a glance

• Vitamin C, or ascorbic acid, is an essential nutrient that the human body cannot synthesise.
• It plays a key role in immune function, collagen formation, and protecting cells from free radicals.
• Adult women typically require 95 mg per day, while men need 110 mg.
• Healthy individuals can meet their needs by regularly consuming fruit and vegetables.
• In some cases, taking a vitamin C supplement may help prevent deficiencies.

What is Vitamin C?

Vitamin C is a water-soluble vitamin, also called ascorbic acid. The body neither produces nor stores this essential nutrient, making regular dietary intake necessary. Vitamin C is naturally present in many foods and can also be synthetically produced. Due to its antioxidant properties, it is often used as an additive to extend the shelf life of processed foods such as meats and sausages.

What are the benefits of vitamin C?

Vitamin C serves multiple functions in the body. It supports the immune system and protects cells from oxidative stress.

Additionally, vitamin C contributes to:

• normal collagen formation,
• normal psychological function,
• a properly functioning nervous system, and
• iron absorption.

Does vitamin C help with colds?

Many people believe that vitamin C can prevent and treat colds. However, the evidence on this is inconclusive. Studies do not consistently show a clear effect on reducing the risk, severity, or duration of cold symptoms.

Regular supplementation may provide some benefits for endurance athletes, such as marathon runners, but appears to have little to no effect for most other people.

Does vitamin C help fight cancer?

Experiments on cell cultures and mice suggest that high-dose vitamin C might help combat cancer. However, this theory has yet to be definitively proven in human studies. For instance, a 2022 study found that high-dose vitamin C had no impact on survival rates or tumour growth in bowel cancer patients.

How much vitamin C per day?

Vitamin C requirements depend on factors such as gender, age, and lifestyle. The German Nutrition Society (DGE) recommends the following daily intake levels:

• 95 mg for women aged 19 and over
• 110 mg for men aged 19 and over
• 90 mg for female teenagers aged 15 and over
• 105 mg for male teenagers aged 15 and over
• 20 to 85 mg for infants and children up to 15 years old

When is the daily requirement higher?

The daily requirement can be increased for various reasons.

• Pregnant women require 105 mg per day from the fourth month onwards, increasing to 125 mg per day during breastfeeding.
• Smokers need significantly more vitamin C, with recommendations of 135 mg per day for women and 155 mg per day for men.

How to meet daily vitamin C needs?

A well-balanced diet usually provides sufficient vitamin C. As this vitamin is found in many fruits and vegetables, vegans and vegetarians can easily meet their daily requirements. However, animal-based foods contain little to no vitamin C.

Which foods are highest in vitamin C?

Citrus fruits are widely recognised for their vitamin C content, but many other foods contain significantly higher amounts.

Here are some of the richest sources of vitamin C (content in mg per 100 g):

How should vitamin C-rich foods be stored and prepared?

Prolonged storage and cooking can lead to significant vitamin C loss in plant-based foods. To retain as much vitamin C as possible, they should be consumed soon after purchase and cooked for a minimal amount of time.

What causes vitamin C deficiency?

A prolonged lack of fruit and vegetables in the diet can eventually lead to vitamin C deficiency. However, due to the abundance of food in industrialised countries, this is now rare. The National Consumption Study II, conducted in Germany between 2005 and 2006, found that all age groups met or exceeded their recommended vitamin C intake.

Nonetheless, certain factors can increase the risk of deficiency, including:

• pregnancy
• smoking
• chronic gastrointestinal diseases
• inflammatory conditions
• cancer
• surgery
• alcohol abuse
• intense physical labour
• endurance sports

What are the symptoms of vitamin C deficiency?

A lack of ascorbic acid can lead to various non-specific symptoms, such as slow wound healing and increased susceptibility to infections.

Other potential symptoms include:

• joint pain
• muscle pain
• weight loss
• fatigue
• irritability
• weakness

What are the consequences of a persistent deficiency?

A severe deficiency can have serious long-term health consequences. Those affected develop scurvy, which causes changes in the connective tissue, bones and joints, as well as infections, bleeding and tooth loss, among other things. Without countermeasures, scurvy is even fatal.

In infants, a persistent deficiency triggers Moeller-Barlow disease. It manifests with symptoms similar to scurvy. In addition, Moeller-Barlow disease leads to severe disorders of bone formation and growth.

How is a vitamin C deficiency treated?

If a deficiency is suspected, determining the vitamin C status in the blood can be useful. Normal values are between 5 and 15 milligrams of ascorbic acid per litre. If the suspicion is confirmed, fresh vegetables and fruit as well as vitamin C supplements help to remedy the deficiency.

Is too much vitamin C dangerous?

Vitamin C has a very short half-life, and the body cannot store it. This means that any excess is simply excreted in the urine. It is almost impossible to overdose on vitamin C through diet alone. However, consuming very high doses in supplement form may occasionally cause mild side effects.

What is the safe upper limit for vitamin C intake?

According to the German Nutrition Society (DGE), a daily intake of up to 1 gram of vitamin C is considered safe. Temporary side effects, such as diarrhoea, usually occur only at doses of 3 to 4 grams per day.

The European Food Safety Authority (EFSA) has not set an official maximum daily intake for vitamin C due to its low toxicity and inconsistent data.

The German Federal Institute for Risk Assessment (BfR) recommends the following upper limits:

• 250 mg per day for vitamin C supplements
• 60 mg per 100 g in fortified foods
• 16 mg per 100 ml in beverages

Who is at risk of side effects from excessive vitamin C?

Although vitamin C is generally safe, certain individuals should avoid excessive intake:

• People prone to kidney stones: the German Association of Internists advises against taking 1 gram or more of vitamin C per day on a long-term basis.
• People with haemochromatosis (a condition causing excessive iron absorption) should limit their intake to a maximum of 500 mg per day, as vitamin C enhances iron absorption.

Should you take vitamin C every day?

Since the body does not store vitamin C, it is best to consume vitamin C-rich foods daily. If your lifestyle or a medical condition increases your vitamin C needs, taking a daily supplement may be beneficial.

Important to know

If you are not a medical specialist and have complaints, specific health conditions, or suspect deficiencies, please make sure to consult a doctor to discuss this.