Vitamin C (= ascorbic acid) can shorten the duration of cold symptoms if it is taken regularly before the illness in the correct dose. This seems to be especially true for athletes and older people (1) (2). However, it should be noted that a single study provides very preliminary evidence, so even if it finds some benefit, further studies will be needed to confirm this before treatment with the product can be recommended (3) (4) (5) (6). Vitamin C in food is sensitive to storage and processing and it is easily oxidised by heat/light and exposure to metal ions (e.g. a copper pot), thereby losing its physiological effectiveness (7). An average loss of 30% is reported when foods containing vitamin C are kept warm and processed. In food it is mostly present as L-ascorbic acid and it is either chemically bound in the food or is freely available in a food supplement.
Effect and dosage of vitamin C / ascorbic acid
Vitamin C is an antioxidant, which means that this water-soluble micronutrient is considered a free radical scavenger. In this way they help ward off diseases and counteract oxidative stress. This is associated with the aging process and diseases, which in turn means that vitamin C can counteract these factors. In industry, ascorbic acid can also play an important role as a technical aid, as it is used, for example, to counteract atmospheric oxygen. A practical example is the spreading of lemon juice on a cut fruit to prevent the oxidation process (7). Other positive properties at physiological level (7): -Improvement of iron absorption -Improved formation of connective tissue (wound healing, scar healing) -Cofactor in the formation of hormones and neurotransmitters (dopamine, noradrenaline, cortisone) -Cofactor in carnitine formation (fatty acid transport in the body) The consumption of antibiotics, antidiabetics, cortisone or aspirin leads to an increased excretion of vitamin C, which may result in an increased need. Smokers have higher metabolic losses and lower blood vitamin C concentrations than non-smokers (9).
For healthy adults, a dosage of 95mg (women) and 105mg (men) vitamin C per day is a guideline according to the DGE (Deutsche Gesellschaft für Ernährung) (8).
Food with high vitamin C content
Foods with a high vitamin C content include peppers, currants, parsley, citrus fruits, cabbage, spinach, kale and tomatoes. The vitamin C content of a particular food varies depending on the time of harvest, transport, duration and type of storage and kitchen preparation. During the processing of foodstuffs, vitamin C may be lost through the influence of oxygen, high temperatures or because of its solubility in water (9).
Possible Side Effects
According to current research, a dose of up to 1000mg vitamin C per day is unproblematic. At doses of 3000-4000mg per day, symptoms such as diarrhoea or problems in the gastrointestinal tract have been observed in the past. People with kidney problems, a predisposition to urinary or kidney stones or with disorders in the utilization of food iron should be careful when consuming ascorbic acid (8)(9). However, the ADI (Acceptable Daily Intake) of 1000mg should be unproblematic even in people with previous illnesses.
Vitamin C can help strengthen your immune system. If it is possible, you should cover your vitamin C needs through fruits and vegetables. Dietary supplements can also be a solution if the quality of these is guaranteed.
My Vitamin C recommendation
References: (1) https://www.ncbi.nlm.nih.gov/pubmed/30069463 (2 ) https://www.ncbi.nlm.nih.gov/pubmed/27855744 (3 ) https://www.ncbi.nlm.nih.gov/pubmed/23440782 (4 ) https://www.ncbi.nlm.nih.gov/pubmed/23440782 (5 ) https://www.ncbi.nlm.nih.gov/pubmed/28353648 (6 ) https://www.ncbi.nlm.nih.gov/pubmed/29099763 (7) ELMADFA I (2009): Dietetics. 2nd edition. Stuttgart. Eumen Ulmer publishing house. S.144-145 (8). https://www.dge.de/wissenschaft/referenzwerte/vitamin-c/ (9 ) https://www.dge.de/wissenschaft/referenzwerte/vitamin-c/