Vitamin C

Ascorbic acid is the chemical name of vitamin C, a water-soluble, easily oxidized vitamin. The official name according to IUPAC rules is (R)-5-[(S)-1,2-dihydroxyethyl]-3,4-dihydroxy-5H-furan-2-one. Vitamin-C is a hexuronic acid. The pKS value is 4.2, and the solubility in water (20°C) is 333 g/l. The molar mass is 176.13 g/mol. The E-number of ascorbic acid, as found in food ingredient lists, is E 300. The chemical formula is C6H8O6. The melting point is 190-192 °C. A boiling point cannot be given, since the substance decomposes already above the melting point. There are 4 different stereoisomeric forms of ascorbic acid, which exhibit optical activity because the 4th and 5th C atoms are each a center of asymmetry...:

• L-ascorbic acid (also 2,3-endiol-L-gluconic acid-γ-lactone, (R)-5-[(S)-1,2-dihydroxyethyl]-3,4-dihydroxy-5H-furan-2-one).
• D-ascorbic acid
• L-isoascorbic acid
• D-isoascorbic acid

The molecules L- and D-ascorbic acid behave like image and mirror image of each other; they are enantiomers, as are L- and D-isoascorbic acid. L-ascorbic acid and D-isoascorbic acid as well as D-ascorbic acid and L-isoascorbic acid are epimers, they each differ in the configuration of only one C atom. Vitamin C is the generic name for all compounds that have the same biological effect as L-ascorbic acid. D-ascorbic acid and L-isoascorbic acid are biologically inactive, and D-isoascorbic acid exhibits little biological activity. Dehydro-L-ascorbic acid belongs to the group of vitamin C compounds, as it is reduced to L-ascorbic acid in the body.

Meaning

Vitamin C is a radical scavenger and has an antioxidant effect (reducing agent). It is an important cofactor in the hydroxylation reaction and thus controls the body's own production of collagen. In addition, it plays an important role in the formation of amino acids. Because of its reducing property, it is also occasionally used as a developing substance in photographic developers and is also used as an antioxidant in food production. The biosynthesis of this vitamin is possible for most organisms via glucose metabolism. Only humans, guinea pigs, primates and some birds and fish cannot produce the vitamin themselves. The storage capacity of the vitamin in humans is very low, so this substance must be supplied permanently.

Ascorbic acid is sensitive to light, air, water and heat. However, it is stable to oxygen in fruit juices with a pH value below six. However, vitamin C is not very stable, so significant losses occur even during storage. Blanching and freezing greatly reduces vitamin loss. This is why frozen goods often have more vitamin C than fresh goods that have been in the refrigerator for some time. During prolonged cooking, the water-soluble vitamin is also flushed out of the food or inactivated, as is the case when the food is reheated, kept warm or soaked.

Occurrence

In food, vitamin C is found mainly in fruits, vegetables and green tea, but its content decreases with the preparation methods of cooking, drying or soaking. Citrus fruits such as oranges, lemons and grapefruits contain a lot of vitamin C. Kale has the highest vitamin C content of all cabbages (105 mg/100 g edible matter).

In cabbage vegetables ascorbic acid is bound in the form of ascorbigens A and B. When the vegetables are cooked, the molecules break down into L-ascorbic acid and indole, so that they can contain more vitamin C when cooked than when raw. However, cooking for too long will partially destroy the vitamin. Red cabbage, white cabbage/sauerkraut are also sources of vitamin C (50 mg, 45 mg and 20 mg/100 g, respectively). The highest natural vitamin C concentrations have been found in camu camu and acerola cherries. Sea buckthorn also provides high concentrations of vitamin C.

• Pear 5
• Peach 10
• Banana 11
• Culture apple 12
• Avocado 13
• Pineapple 20
• Blueberry 22
• Orange (orange) 50
• Lemon 53
• Strawberry 61
• Mountain ash fruit 98
• Kiwi 100
• Blackcurrant 189
• Sea buckthorn berry 450
• Rosehip 1250
• Acerola cherry 1700
• Camu-Camu 2000

Deficiency symptoms (hypovitaminosis)

Albert Szent Györgyi, a Hungarian scientist, identified vitamin C as an effective substance against scurvy in 1933. However, vitamin C is fully effective only in the presence of a flavanol known as vitamin C2. Neither substance alone can cure scurvy, but in combination they are effective even in small amounts.

Only a few vertebrates, including primates, pigs and guinea pigs, are not capable of biosynthesizing ascorbic acid from glucuronic acid; they lack L-gluconolactone oxidase. Since the human body cannot produce vitamin C itself, the requirement must be met through the diet or with dietary supplements. Deficiency symptoms lead to scurvy in the long term. They can occur in the case of malnutrition and deficiencies such as incorrect diets and alcoholism, or in the case of increased requirements (pregnancy, smoking).

Only L(+)-ascorbic acid has biological activity. The strongly acidic character is due to the hydroxyl group on the C3 atom (pKs = 4.2). Deprotonated, it gives a resonance-stabilized anion. The other enolic OH group has no acidic properties (pKs = 11.8). Due to its antioxidant effect, it protects other very important metabolites such as glutathione (cell division control = cancer "protection") from oxidation.

Overdose (hypervitaminosis)

It is true that no hypervitaminoses are known for vitamin C as for vitamin A, for example, since the body excretes an excess of ascorbic acid again. However, it has been found that in very high doses it can destroy vitamin B12.

High single doses (5-10 g) may cause temporary insomnia (similar to caffeine) and diarrhea.

Infant scurvy occurs when very large amounts of vitamin C are ingested during pregnancy. Excretion of excess ascorbic acid occurs via its own channel proteins in the kidney. At high concentrations, these are increased, which also occurs in the embryo. After birth, the infant therefore excretes too much vitamin C, which is no longer replaced by the normal amount in the baby food.

Nature reported in 1998 that high doses of vitamin C can cause damage to genetic material.

Task / Function

The name ascorbic acid is derived from the disease scurvy, which can be prevented and cured by ascorbic acid. With niacin and vitamin B6, vitamin C controls the production of L-carnitine, which is needed for fat burning in the muscles. Furthermore, it favors iron absorption in the small intestine. It participates in collagen synthesis and in the formation of steroid hormones, as well as in the metabolism of phenylalanine, tyrosine, folic acid and iron. Vitamin C is a powerful antioxidant and has cortisol-lowering effects.

Vitamin C is also used to treat colds. However, a meta-analysis of 55 studies shows that, contrary to popular belief, vitamin C cannot prevent colds. At most, vitamin C appears to have a mild preventive effect in people who - like some extreme athletes - are exposed to intense physical exertion or extreme cold. At least there is evidence that the duration of a cold can be slightly reduced by the vitamin (R. Douglas & H. Hemilä: PLoS Medicine, vol. 2, no. 6, p. e168, 2005).

Vitamin C is easily destroyed by storage and cooking. In cabbage and kale the vitamin is stored in a precursor (ascorbigen), the formation here is favored by cooking.

Potential health benefits of vitamin C supplementation.

Vitamin C could reduce the risk of chronic diseases

Vitamin C is a powerful antioxidant that can strengthen the body's natural defenses (1). Antioxidants are molecules that can promote and improve the function of the immune system. They do this by protecting the body's cells from harmful molecules called free radicals.

When free radicals accumulate in the body, they can promote a condition known as oxidative stress, which is associated with many chronic diseases (2). Studies have shown that consuming more vitamin C can increase the body's antioxidant levels by up to 30%. This helps the body's natural defenses fight inflammation (3, 4).

Summary: Vitamin C is a powerful antioxidant that can increase the body's levels of anitioxidants, helping to reduce the risk of chronic diseases such as heart disease.

Vitamin C could help control high blood pressure

About one-third of the population of the Western world suffers from high blood pressure. High blood pressure increases the risk of heart disease, which is the leading cause of death worldwide. Studies have shown that vitamin C can help lower blood pressure in people who suffer from hypertension.

A study conducted with animals found that taking a vitamin C supplement helped relax the blood vessels that carry blood away from the heart, which helped lower blood pressure (5).

A meta-analysis of 29 human studies found that taking a vitamin C supplement in healthy adults lowered systolic blood pressure (the upper value) by an average of 3.8 mmHg and diastolic blood pressure (the lower value) by an average of 1.5 mmHg.

In adults with high blood pressure, vitamin C was able to reduce systolic blood pressure by an average of 4.9 mmHg and diastolic blood pressure by an average of 1.7 mmHg (6). However, although these results are promising, the long-term effects of vitamin C on blood pressure are not yet known.

Summary: Scientific research has found that vitamin C can lower blood pressure in both healthy people and people with high blood pressure.

Vitamin C could reduce the risk of heart disease

Heart disease is the leading cause of death worldwide. Many factors including high blood pressure, high blood triglyceride levels, high levels of "bad" LDL cholesterol and low levels of good HDL cholesterol can increase the risk of heart disease. Vitamin C may help reduce these risk factors, resulting in a lower risk of heart disease.

A meta-analysis of 9 studies with a total of 293,172 participants concluded that after 10 years, those who consumed at least 700 mg of vitamin C daily had a 25% lower risk of heart disease compared with those who did not use vitamin C supplements (7).

Interestingly, another analysis of 15 studies found that consuming vitamin C in the form of food - rather than supplements - was associated with a lower risk of heart disease.

However, the researchers were not sure whether the people who ate foods rich in vitamin C did not also follow a healthier lifestyle than those who used a supplement. Thus, it remains unclear whether the observed difference was attributable to vitamin or other aspects of diet (8).

Another analysis of 13 studies looked at the effects of taking at least 500 mg of vitamin C per day on risk factors for heart disease such as blood cholesterol levels and triglyceride levels. This analysis found that taking a vitamin C supplement significantly lowered levels of LDL bad cholesterol by 7.9 mg/dl and blood triglyceride levels by 20.1 mg/dl (9).

In short, an intake of at least 500 mg of vitamin C appears to be able to reduce the risk of heart disease. However, if one is already following a diet rich in vitamin C, then additional vitamin C supplements are unlikely to provide any additional heart health benefits.

Summary: Vitamin C supplements are associated with a lower risk of heart disease. They may reduce risk factors for heart disease including LDL cholesterol levels and triglyceride levels.

Vitamin C could reduce uric acid levels in the blood and help prevent gout attacks

Gout is a type of arthritis that affects about 4% of adults in the Western world (10). Gout is exceptionally painful and involves inflammation of the joints - especially the joints of the big toe. People who suffer from gout experience swelling and sudden, severe attacks of pain (11).

Symptoms of gout occur when there is too much uric acid in the blood. Uric acid is a waste product produced by the body itself. At high levels, uric acid can crystallize and be deposited in the joints.

Interestingly, several studies have shown that vitamin C may help reduce uric acid levels in the blood and thereby protect against gout attacks. For example, a study of 1,387 men showed that those who consumed the most vitamin C had significantly lower uric acid blood levels than those who consumed the least vitamin C (12).

Another study followed 46,994 healthy men over a 20-year period to determine if vitamin C intake was associated with the development of gout. This study concluded that people who took a vitamin C supplement had a 44% lower risk of gout (13).

In addition, an analysis of 13 studies found that taking a vitamin C supplement for 30 days significantly reduced blood uric acid levels compared with a placebo (14).

However, even though there appears to be a strong association between vitamin C intake and uric acid levels, more studies are needed to further investigate the effects of vitamin C on gout.

Summary: Foods rich in vitamin C are associated with reduced blood uric acid levels and a lower risk of gout.

Vitamin C helps prevent iron deficiency

Iron is an important nutrient that has a variety of functions in the body. It is essential for the production of red blood cells and the transport of oxygen through the body. Vitamin C supplements can help improve the absorption of iron from food. Vitamin C helps convert certain types of iron, such as plant-based iron compounds that are poorly absorbed by the body, into forms of iron that are more easily absorbed (15). This is particularly useful for people on a non-meat diet, as meat is one of the primary dietary sources of iron.

In fact, consumption of 100 mg of vitamin C can improve iron absorption by 67% (16). As a result, vitamin C may help reduce the risk of anemia in people who are susceptible to iron deficiency.

In one study, 65 children with mild iron deficiency anemia were given a vitamin C supplement. The researchers found that the vitamin C supplement alone helped control the anemia in these children (17).

If one suffers from low iron levels, then eating more vitamin C rich foods or taking a vitamin C supplement could help improve iron blood levels.

Summary: Vitamin C may increase the absorption of poorly absorbable iron such as iron from plant sources and reduce the risk of iron deficiency.

Vitamin C can improve the function of the immune system

One of the main reasons many people take vitamin C supplements is to improve immune function, as vitamin C is involved in many aspects of the immune system. First of all, vitamin C helps stimulate the production of white blood cells, also known as lymphocytes and phagocytes, which help protect the body from infection (18).

Second, vitamin C helps these white blood cells function more effectively while protecting them from potentially harmful molecules such as free radicals. Third, vitamin C is an essential part of the skin's defense system. It is actively transported to the skin, where it can act as an antioxidant and help strengthen the skin barrier (19). In addition, studies have shown that vitamin C can accelerate wound healing (20, 21).

In addition, low vitamin C levels are associated with a more severe course of disease. For example, it has been shown that people who develop pneumonia have lower vitamin C levels and that vitamin C supplements can accelerate healing (22, 23).

Summary: Vitamin C improves immune system function by helping white blood cells function more effectively, by strengthening the skin's defense system, and by helping wounds heal faster.

Vitamin C may protect memory and thinking ability with age

Dementia is a broad term used to describe symptoms of poor thinking ability and memory. It affects over 35 million people and typically occurs in older adults. Studies suggest that oxidative stress and inflammation in the brain, spinal cord, and nerves may increase the risk of dementia (24). Vitamin C is a potent antioxidant. Low levels of this vitamin are associated with impaired thinking ability and poorer memory performance (25, 26).

In addition, several studies have shown that people suffering from dementia have lower blood levels of vitamin C (27, 28). Furthermore, it has been shown that a higher vitamin C intake in the form of food or supplements during aging has a protective effect on thinking ability and memory (29, 30, 31).

Vitamin C supplements could help against conditions such as dementia if people do not get enough vitamin C from their diet. However, more human studies are needed to fully understand the effects of vitamin C on nervous system health (32).

Abstract: Low vitamin C levels have been associated with an increased risk of disorders of thinking ability and memory such as dementia, while it has also been shown that high vitamin C intake via food and supplements may have a protective effect.

Vitamin C and cancer

Vitamin C is produced by most living organisms themselves. Exceptions are humans, monkeys, guinea pigs and some species of fish and birds. According to current knowledge, vitamin C prevents the degeneration of healthy cells into cancer cells and their spread. Some studies even show a reversal of the degeneration process to healthy cells. Vitamin C appears to act directly on cancer-causing substances by inactivating them, or it protects the delicate DNA of the cell nucleus. Deficiency symptoms lead to weakening of the connective tissue. Inhibiting tumors requires not only an intact immune system but also firm connective tissue. This makes it more difficult for the tumor to penetrate the vessels and thus metastasize.

Vitamin C strengthens both cellular immune defenses by activating lymphocytes and macrophages and hormonal defenses because it increases serum concentrations of immunoglobulins. Some studies show a consistent association between low plasma levels of vitamin C and increased incidence of certain cancers. Thus, a good vitamin C supply probably contributes to the fact that certain types of tumors occur with a lower frequency.

The chemist Linus Pauling was of the opinion that high doses of vitamin C not only prevent cancer, but may even cure it. However, the Linus Pauling Institute of Science and Medicine, which he founded, has since moved away from massive doses of vitamin C again.

The connection between the (under)supply of vitamin C and the development of cancer has not yet been clearly clarified in medicine.

Additive in food production

Ascorbic acid is added to many food products as an antioxidant or reddening aid under the number E 300. The addition of ascorbic acid to flours is said to increase the gas retention capacity and the volume of the doughs. This can be explained by the formation of additional disulfide bridges between the gluten strands of the dough.

Demand

In large parts of the world, the supply of vitamin C is generally good; the daily requirement of an adult is 100 mg according to the recommendation of the German Nutrition Society. But even much higher amounts (up to 5000 mg) are considered safe. Excess amounts are excreted by the body through the urine.

Demand in sport

The requirement of the competitive athlete is higher - simply because of greater losses through sweat. My recommendation is to take 1000-5000mg a day several times a day with meals. Based on empirical data, especially supported by positive reports of many athletes, such high dosages can be recommended especially for hard training athletes. Athletes experience reduced susceptibility to infection, better recovery, and faster healing of injuries when vitamin C is taken in the gram range. It is best to take vitamin C, especially in weight training, 1g each in the morning, before and after training, and before bedtime.

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