Vitamin C

It is a water-soluble vitamin also known as L-ascorbic acid or ascorbate. Due to the absence of enzymatic activity of L-gulonolactone oxidase, humans, primates and some other species of animals cannot synthesize it themselves, so it must be constantly introduced into the body through diet.

Vitamin C plays an important role in

  • the functioning of the immune system, as well as during and after intense physical activity
  • the formation of collagen for the normal functioning of blood vessels, bones, cartilage, gums, skin, and teeth.
  • contributes to the release of energy during metabolism
  • contributes to the functioning of the nervous system
  • contributes to normal psychological functioning
  • protects cells from oxidative stress
  • helps reduce fatigue and exhaustion
  • contributes to the restoration of the reduced form of vitamin E
  • increases iron absorption

 In 2013, EFSA (European Food Safety Authority) set recommended dietary allowances for vitamin C.  This is 90 mg/day for an adult male and 80 mg/day for an adult female. In pregnant women, vitamin C is actively transferred from mother to fetus, so the recommended need for vitamin C is higher (105 mg/day), as well as in breastfeeding mothers, as vitamin C is excreted in milk (155 mg/day).

In doing so, we need to know that daily vitamin C needs vary between individuals. Increased needs for vitamin C are in intense physical activity (heavy physical work, competitive sports), in long-term mental and emotional stress, in alcohol and drug addiction, in some chronic diseases such as diabetes or chronic kidney disease, and infections, as well as in the elderly who are malnourished due to chewing problems or are constantly taking medication. Increased intake is also recommended for smokers.

The best source of vitamin C is vegetables and fruits, and a smaller source for omnivores is also the meat of internal organs, e.g. kidney and liver. Plants synthesize ascorbate from sugars such as glucose, fructose, mannose, and galactose. Most seeds do not contain ascorbic acid, it begins to be synthesized only during germination – today we can often encounter a variety of germs, which in addition to vitamin C also have improved nutritional value. We wrote about sprouts in the introduction at lunch with kale and aubergines with couscous. Some plants accumulate vitamin C in very high concentrations and are therefore a very good source of this vitamin.

However, the recommended intake of vitamin C does not need to be achieved every day, it is enough that the needs for the vitamin are covered within one week. Intake should be carried out evenly and not in sparse, large doses, as absorption decreases with increasing intake. When 180 mg of vitamin C is ingested per day, the absorption efficiency is 80-90% high, but it drops significantly if the intake is increased above 1 g / day (50%) and the remaining vitamin C is excreted from the body.

A good source of vitamin C is mainly foods that we eat raw, as part of the vitamin is destroyed or washed away by cooking, as well as by prolonged storage. Vitamin C is well soluble in water and poorly stable at elevated temperatures. Losses from cooking in water are greater if the food is boiled in it for a long time. The vitamin content can be maintained by rapid methods of heating with little water, e.g. steaming.

To meet the recommended daily requirement of vitamin C, we can eat e.g. 63g red peppers, 86g cabbage, 140g strawberries, 150g oranges, 220g cabbage, or 280g spinach.

The table lists some foods that are richest in vitamin C (USDA base)


Vitamin C content per 100g of food (mg)

Recommended Dietary Allowances (RDA) in %

Red pepper



Brussels sprouts





































Here are some suggestions for meals from our recipe collection that were very rich in vitamin C.

What about over-intake?

It is generally accepted that excessive nutrient intake over a long period can be harmful and lead to adverse health effects. However, the risks are higher in chronic patients and those who may not be aware of the increased sensitivity due to their minor abnormalities in the functioning of the metabolic system.

EFSA has not set a maximum allowable daily intake of vitamin C. It could be said that all existing data indicate very low toxicity of vitamin C, but it is important to know that despite the widespread use of high doses of vitamin C, a small number of controlled studies have been conducted to systematically investigate adverse health effects. No adverse effects were observed in 12 healthy volunteers who received a daily dose of 500 mg of vitamin C for eight weeks. However, doses greater than 1 g of vitamin C per day may cause acute gastrointestinal symptoms such as diarrhea, nausea, abdominal cramps, and other digestive disorders, mainly due to the osmotic effect of unabsorbed amounts of the vitamin in the gastrointestinal tract.

Vitamin C deficiency is reflected in various signs of a syndrome called scurvy. This occurs in adults 60 to 90 days after stopping vitamin C, and some signs are visible after 30 days. Signs of the disease first appear in the mesenchymal tissue. Due to the reduced rate of collagen synthesis, wound healing is prolonged, bleeding occurs in the skin, mucous membranes, internal organs, and muscles, and collagen structures in bone, cartilage, teeth, and connective tissue weaken.

The first records of signs of the then-unknown scurvy are recorded as early as Ancient Egypt and Ancient Greece, in the time of Hippocrates. Scurvy, however, later hit sailors the hardest, who spent a long time on ships and did not eat fruit and vegetables during that time. It was not until the 18th century that Scottish Captain James Lind discovered that the consumption of citrus fruits prevented scurvy.