Vitamin C

Vitamin C : Vitamin C is a water-soluble vitamin sensitive to heat and light playing an important role in the metabolism of humans and many other mammals. Chemically speaking, it is theL-ascorbic acid, one of the stereoisomers of ascorbic acid, and its salts, the ascorbates. The most common are sodium ascorbate and calcium ascorbate.
We are talking about ascorbic acid or L-(+)-ascorbic acid, therefore dextrorotatory, with CAS number 50-81-7 and it is the only one authorized to bear the name “Vitamin C”. Levorotatory ascorbic acid (D-(–)-ascorbic acid) does not have sufficient vitamin effect.
Action in humans: Vitamin C is an enzymatic cofactor involved in a certain number of physiological reactions (hydroxylation). It is required in the synthesis of collagen and red blood cells and contributes to the immune system. It also plays a role in iron metabolism as a promoter of its absorption; its use is therefore not recommended in patients with iron overload and particularly hemochromatosis. In oxidized form (dehydroascorbic acid), it crosses the blood-brain barrier to access the brain and several organs with a high concentration of vitamin C. Skeletal muscles respond quickly to taking vitamin C, but also lose it quickly if the vitamin intake is insufficient. This is a antioxidant, a molecule capable of countering the harmful action of oxidants such as radicals. For this purpose, D-ascorbic acid is also used which, unlike L-ascorbic acid, does not have vitamin activity.
Ascorbic acid is an enzymatic cofactor widely distributed in mammals. It is used in the synthesis of collagen. It is also a powerful reducing agent capable of rapidly eliminating a certain number of reactive oxygen derivatives. Given that ascorbate exhibits these important functions, it may be surprising that the synthetic capacity of this molecule has not always been conserved throughout evolution. In fact, anthropoid primates (including humans), Cavia porcellus (guinea pigs), teleost fish, most bats, and some passeriform birds have all independently lost the ability to synthesize vitamin C in the kidneys or liver. . In all cases where genomic analysis was performed on an ascorbic acid auxotroph, the origin of the change was found to be the result of loss of function mutations in the gene that encodes L-Gulono-?-lactone oxidase, the enzyme that catalyzes the final step of the ascorbic acid pathway.
Conservation: Very fragile in solution, it is destroyed in contact with air (by oxidation) or under exposure to light (by ultraviolet action) and heat accelerates these processes. Cooking food gradually destroys vitamin C, so short cooking at low temperatures is necessary to preserve it.
Synthesis: While most mammals are capable of synthesizing it in their liver or kidneys (so it is not a vitamin for them), the majority of primates (including humans), the guinea pig and some birds and fish are incapable of doing so. This would be the result of a genetic mutation, which occurred 40 million years ago, blocking the transformation of glucose en ascorbic acid. Animals lacking this capacity to synthesize vitamin C must therefore obtain it from their diet.
Several hypotheses have been formulated to explain the loss, in the ancestor of humans and great apes, of the capacity to produce vitamin C. Richard J. Johnson, a specialist in cardiovascular diseases, and blood uric acid human (another genetic error practically characteristic of large primates, including humans), suggests that uric acid and the lack of vitamin C, two pro-inflammatory factors, would have granted an evolutionary advantage by promoting the retention of fats (effect recognized for oxidative stress and inflammation), useful during the famines of the late Eocene and middle Miocene, contemporary with these genetic mutations.
Recommended intakes
Recommended daily allowance
European recommendations recommend a daily intake of 75 mg for a woman and 90 mg for a man. For example, an orange provides on average 53 mg of vitamin C (40 to 80 mg per 100 g).
In France, the AFSSA recommends a daily intake of 110 mg for an adult aged 20 to 60. People who are more exposed to the harmful effects of oxidants, such as smokers, have increased needs for vitamin C (125 mg according to the Higher Hygiene Council of Belgium). Some scientists, proponents of Orthomolecular Medicine, have argued that the recommended nutritional intakes should be at least 6 mg, or even 000 mg. These theories are rejected by the medical and scientific community, whose current studies prove that this intuition has been proven false.
In free-ranging primates, nutritional analyzes show a daily consumption of 2 to 000 mg per day8 for primates of a weight comparable (chimpanzees) or slightly greater (gorillas) to that of humans. We recommend 000 mg of vitamin C per kilogram of weight for all primates in captivity, or, for an average weight chimpanzee (18 kg), 25 mg per day.
NAC (new companion animals) veterinarians recommend 20 mg of vitamin C for guinea pigs whose weight can vary between 500g and 1,7Kg, and 30 to 60 mg for pregnant females.
We therefore see that the recommended intakes (per kg of body mass) by nutritionists are significantly lower for humans than for other species which require them.
Deficiency: A significant deficiency of vitamin C, very rare, causes scurvy when the intake is less than 10 mg per day. More discreet hypovitaminoses are very widespread and result in asthenia, weight loss, headaches, bone pain, greater susceptibility to infections and sometimes bleeding problems.
History
– In the 5th century BC. BC, Aristotle already knew the symptoms of scurvy.
– In 1227, Gilbert de Aquila recommended that sailors take on board stocks of fresh fruits and vegetables to prevent scurvy.
– It was only in the 1795th century that it was discovered that eating lemons prevented this disease. Scottish doctor James Lind conducted what is considered the first scientific trial: after forming six groups, each made up of two scorbutic sailors, he administered a different substance to each group, their nutrition being otherwise identical. These substances were: cider, sulfuric acid, vinegar, a concoction of herbs and spices, sea water and oranges and lemons. Only the last group quickly recovered from scurvy. The use of preserved foods developed by Nicolas Appert in XNUMX, retaining vitamin C, definitively resolved the problem for the navy.
– In 1919, Jack Cecil Drummond understood that the antiscorbutic factor was one of these new essential nutrients which were neither sugary, nor fatty, nor proteinaceous, like the substances “fat-soluble A”, “water-soluble B” already known (discovered in rats), he first called it “water-soluble C”, then recommended calling it vitamin C, a less “cumbersome” name.
– In 1928, Albert Szent-Gyorgyi wanted to understand the differences in biological oxidation between animals whose adrenal glands had been removed and others with their adrenal glands. He noticed that the adrenal cortex was highly concentrated in a very reducing substance (antioxidant). He also observed that additions of pressed plant juice to peroxidation reactions of hydrogen peroxide by peroxidases inhibited the oxidation reaction, he concluded that the plants also contained a strong antioxidant element which diverted water oxygenated. He then isolated the same reducing agent in the adrenal cortex, in oranges and in cabbages. He named it “hexuronic acid” because of its 6 carbons and 6 oxygens; he then immediately made the parallel with the famous vitamin C, which was also known to be an antioxidant106. But it was not until 1931 that he identified it as vitamin C, along with WA Waugh and Charles Glen King. Szent-Gyorgyi decided to abandon the name hexuronic acid for the name ascorbic acid (contraction of anti-scorbutic); he won the Nobel Prize in Physiology or Medicine in 1937.
– This molecule was synthesized in 1933 by Tadeusz Reichstein then in 1934 by Walter Norman Haworth who received the Nobel Prize in Chemistry in 1937 for this discovery.
Production: The annual global production of L-ascorbic acid is 80 tonnes, half of which is used in the pharmaceutical and parapharmaceutical industries, 000% in the food industry as a preservative (E25, E300, E301), 302% in the manufacture of beverages, the remainder being used for animal nutrition.
In plants, the synthesis of vitamin C takes place in all the cells of the plant (see below the list of foods with the highest concentrations of vitamin C). In several regions of the world, particularly in Europe where its consumption is significant, potatoes, despite a very moderate average content, are the main source of vitamin C in the average diet. In 1992, it represented 15 to 20% of the average daily intake in the United Kingdom.
In animals that are capable of it, the synthesis takes place mainly in the liver, but all the other cells have the capacity, which however remains very limited.

Miscellaneous: Vitamin C is part of the list of essential medicines of theWorld Health Organizationé (list updated in April 2013).

Sources and content of Vitamin C:

The contents below are average values ​​which can vary significantly depending on the varieties of the fruits and Team vegetables indicated.