Vitamin C is an essential nutrient that strengthens the immune system and acts as an antioxidant. In this post, you will discover what it does and which foods contain the highest amounts.
What is vitamin C?
Definition and characteristics
Vitamin C, also known as ascorbic acid, is an essential water-soluble vitamin that the body cannot synthesise itself, so it is needed in our daily diet. It acts as a powerful antioxidant, protecting cells from oxidative damage, participates in collagen synthesis and strengthens the immune system. It is sensitive to heat and light, meaning it can degrade during cooking or prolonged storage.
Functions in the body
Vitamin C stands out for its antioxidant action, protecting cells from oxidative damage. It is also essential for collagen synthesis: collagen is a protein that maintains the integrity of tissues such as skin, muscles, tendons and blood vessels. It also improves absorption of iron found in plant-based foods, helping prevent deficiencies.
It also participates in neurotransmitter synthesis, directly affecting mood, concentration and cognitive performance. It plays a key role in strengthening the immune system too, helping improve the body’s response to and recovery from infections.
Health benefits
Immune support
Vitamin C participates in the production and function of white blood cells, the cells responsible for defending the body against viruses and bacteria. It also maintains the integrity of epithelial barriers, such as skin and mucous membranes, acting as a first line of defence against pathogens.
Its antioxidant effect protects immune system cells from oxidative damage, improving their effectiveness. All this contributes to a more efficient immune response, reducing the duration and severity of common illnesses.
Collagen production
Vitamin C is essential for the production of collagen, a fundamental protein in connective tissue. Without enough vitamin C, collagen production is affected, potentially causing dry skin, premature wrinkles, muscle weakness and fragile joints. Adequate intake helps keep skin firmer and healthier, improves muscle and tendon flexibility, and strengthens bones and blood vessels. It also supports wound healing, facilitating recovery.
Iron absorption
Vitamin C improves the absorption of non-haem iron, found in plant foods such as pulses and spinach. Consuming this vitamin alongside plant-based iron sources converts the iron into a form that is more easily absorbed in the intestine.
This helps prevent iron-deficiency anaemia and supports energy and physical and mental performance.
Antioxidant properties
Vitamin C acts as an antioxidant, helping protect cells from oxidative damage caused by free radicals. These radicals are generated by factors such as stress, pollution and poor diet, and can disrupt cellular balance and accelerate processes such as ageing or fatigue.
By neutralising free radicals, vitamin C reduces oxidative stress and also preserves the health of tissues such as skin, muscles and blood vessels, improving recovery after exercise and helping prevent injuries.
This antioxidant action also plays a role in preventing chronic diseases associated with oxidative damage, such as cardiovascular and neurodegenerative diseases.
Vitamin C-rich foods
Citrus fruit
Citrus fruits such as oranges, lemons and grapefruit are known for their high vitamin C content. Including them in your daily diet is a way to ensure adequate intake of this vitamin.
Other fruit and vegetables
Alongside citrus fruits, other fruit and vegetables such as strawberries, kiwis, papayas, peppers and broccoli are also rich in vitamin C.
Recommended amounts and preparation
The recommended daily amount of vitamin C varies by age, sex and individual needs. In general, an intake of 75-90 mg/day is suggested for healthy adults. Eating fresh, raw foods such as fruit and vegetables is the best way to make the most of their vitamin C content, as it can be degraded by heat and light.
Deficiency: causes and symptoms
Common causes
Vitamin C deficiency can result from a diet lacking fresh fruit and vegetables, situations of high physiological demand such as pregnancy or breastfeeding, diseases affecting nutrient absorption, smoking, intense physical activity, or recovery periods after surgery or injuries.
Symptoms and consequences
A lack of vitamin C can cause fatigue, dry skin and swollen, bleeding gums, slow wound healing, joint pain and a reduced ability of the immune system to fight infections. In extreme cases, scurvy may develop, a serious disease associated with prolonged vitamin C deficiency.
Vitamin C supplements: when are they needed?
Intake recommendations
For most people, it is preferable to obtain vitamin C through a balanced diet rich in fruit and vegetables. However, supplements may be necessary in cases of diagnosed deficiency, reduced absorption, smoking or high physiological demand.
The doses used in these cases may range from 200 to 1000 mg per day. The safe upper limit for healthy adults can reach 2000 mg/day. However, above 1000 mg/day, no additional benefits have been demonstrated, and digestive discomfort may occur. To avoid this discomfort and improve absorption, it is recommended to divide the daily intake and take it with food.
Possible side effects
Vitamin C has low toxicity. However, consuming more than 2000 mg daily can cause side effects such as diarrhoea, nausea, abdominal cramps and other gastrointestinal disorders, because unabsorbed vitamin C in the digestive tract has an osmotic effect. In people with a history of kidney stones, sustained high supplement intake may increase the risk of oxalate formation.
