What is ascorbic acid?
Ascorbic acid, known as vitamin C, is a water-soluble organic compound with the formula C6H8O6. The main sources of vitamin C are citrus and other fruits, as well as the growing ends (buds and shoots) of several plants.
The vitamin is often added as an antioxidant to food. E number of ascorbic acid is E300.
The name ascorbic acid is derived from a (not) and scorbus, a word that has been corrupted to scurvy. Ascorbic acid is an acid that occurs scurvy. Of ascorbic acid derivative salts are referred to as ascorbates.
History
In the 18th century it became known that lemon juice was a particularly effective means for the prevention of scurvy. Initially it was thought that prevented the acid of the lemon scurvy. Doctors or quacks of that time gave some vinegar scurvy which did not help. From the end of the 19th century had to find the so-called "anti-scurvy factor". Various types of fruits and vegetables were examined for the degree to which they were able to prevent scurvy. Meanwhile, it was also known that substances that could prevent scurvy had reducing properties. Since 1920, it was known that prevent oxidants in the adrenal glands. In 1928, Albert Szent-Györgyi did research on substances that counteract these effects: reducing materials. In addition, he discovered a substance he gave the name hexoruninezuur. Szent-Györgyi indicated that this substance appeared to be identical to the reducing agent in lemon juice. This substance was already longer known by the names of vitamin C and anti-scurvy factor. However, it then had no idea what the chemical structure of this substance yet. In 1932 were particularly Tillmans and Hirsch who had evidence that the substance of Szent-Györgyi, the hexoruninezuur, sometimes could be vitamin C. In 1933 it became known that the substance of Szent-Györgyi was found to be identical to vitamin C / anti-scurvy factor, and the name hexoruninezuur was replaced by ascorbic acid.
The American doctor Frederick R. Klenner In mid 20th century promoted vitamin C as a medicine to apply in many diseases by increasing the dose significantly. Tens of grams of vitamin C per day administered through injections was no exception. However, it has never been shown that this would decrease the risk of for instance common cold or other viral infections. The investigations of Klenner not meet the test of modern methodological criticism.
Biochemistry
Vitamin C comes in two forms, both present in a variety of biological tissues and food, namely, L-ascorbic acid and L-dehydroascorbic acid. These forms can, through redox chemistry, via an intermediate form, merge into each other.
Strictly speaking, these three substances should be defined separately taken. In practice, the terms, vitamin C ascorbic acid are used as synonyms.
A stereo-isomer of ascorbic acid is erythorbic acid. This compound is also known under the name of iso-ascorbic acid.
Endo synthesis
Plants and most vertebrate animals are able to make their own vitamin C. Humans, apes, bats (tropics), guinea pigs, fish bone and certain songbirds are the exceptions among the vertebrates, which can not make vitamin C itself to. This is caused by a defect in the gulonolacton oxidase gene (gulo-gene), the last of a series of five genes that provide for the enzymes that convert glucose to ascorbic acid. Animal species can not make the enzyme L-gulonolacton oxidase making the final step in the synthesis of vitamin C can not occur. In such cases, enter ascorbic acid through diet. For the human and animal species, vitamin C is therefore a so-called essential nutrient.
Features
- Required for the synthesis of collagen, the most common building material of the human body
- Muscle Metabolism
- Strengthens the absorption of iron in the intestine
- Synthetic hormones
- Functions as a coenzyme in over 800 different biochemical reactions in the body including hydroxylation.
- Immune System
Resources
Natural resources
The yellow or red pepper is in proportion a great source of vitamin C in vegetables and fruits, this is the kiwi (see table below). A paprika contains twice as much vitamin C per 100 grams as a kiwi, but they eat more quickly than 100 grams 100 grams kiwi paprika, which is often incorporated in a (main) meal. The orange contains proportionally much less vitamin C. squeezed orange contains about as much vitamin C as an orange eaten.
Ingestion
In general, vitamin C from fruits and vegetables is well absorbed by the body. Vitamin C from cooked broccoli, orange juice, fruit and synthetic vitamin C (as it occurs in a vitamin or dietary supplement), have the same bioavailability (equally well absorbed by the body). A dose (synthetic) vitamin C in the form of pill-up to 180 mg (more than needed daily), for at least 80% absorbed by the body. The importance of flavonoids in the absorption of vitamin C is not sufficiently proven. The vitamin C content in a single piece of fruit or vegetable is very different: the amount of vitamin C in oranges from the same plantation varies from orange. Storing and editing (cooking etc.) of food affects the amount of vitamin C. For example, vitamin C from raw broccoli contained 20% less than that of boiled broccoli.
The intake (as a dietary supplement) to a maximum of a few grams of vitamin C, leads to the same amount of vitamin C in the blood, as 200-300 mg of vitamin C originating from food. That means swallowing a few grams (or less) of vitamin C per day is meaningless if one eats enough fruits and vegetables. There are those who feel benefit to have at higher concentrations of vitamin C in the blood, for example, for the prevention of a cold. However, to achieve this it is necessary to very much swallowing, because the body is very efficient in the removal of vitamin C. The effectiveness of such mega doses is, moreover, not shown, and may also have side effects such as diarrhea.
Symptoms Scurvy
Symptoms of scurvy include swelling and bleeding of the gums, petechiae, especially on lower legs, weakness, stiff and aching limbs and internal bleeding. There is no mention of a specific stomach disorder. Untreated scurvy is long term lethal.
Studies in healthy volunteers have shown that vitamin C deficiency can occur in less than a month. Subclinical vitamin C deficiencies are common is more common than often assumed.
Clinical applications
Vitamin C and colds
A Cochrane review of studies on the effect of vitamin C as a prevention against colds and for the treatment of the symptoms of colds yielded the following conclusions: Amounts up to 2 grams per day gave a minimal reduction of the likelihood of a cold, about 5%, which was just statistically significant at 11,000 patients. In a subgroup who did heavy physical labor (Marines on exercise in the snow), there was a clinically significant effect, a reduction of about 50%. At thirty trials with 9676 patients together was a slight reduction of 8% in the duration of colds by, among children some more, 13%. Again, this was statistically significant. Treatment with vitamin C after the first cold symptoms had already occurred (7 studies, more than 3000 common cold episodes) gave no significant difference seen with placebo on either the symptoms or for the duration of the common cold. The researchers conducted the review did conclude that "The use of megadoses of vitamin C to prevent colds due to lack of effect in the general population is not justified", but that "to justify it is with people that have to deliver brief intense efforts and / or in a cold environment. " Proponents then throw against the effect only at still larger doses would be noticeable; but then again it is virtually impossible to do it by the double-blind study of apparent side effects begin to occur in the gastro-intestinal tract.
Vitamin C and cancer
Prevention
A Cochrane review on the effect of various antioxidants (such as vitamin C: four studies of high quality) showed no effect of antioxidants on the incidence of cancers of the gastro-intestinal tract to. There were even indications that the mortality may increase.
Therapy
Vitamin C use in cancer therapy began publishing in 1978, Linus Pauling and Ewan Cameron in the influential journal Proceedings of the National Academy of Sciences of the United States of America. They found that administration of 10 grams of vitamin C per day (the first 10 days was administered parenterally) improved the survival of terminally ill cancer patients in 100 compared to 100 non-treated patients. The study was criticized because of the study design (non-randomized control group not comparable). Shortly thereafter, two studies were published which did meet the scientific requirements and in which no effect of vitamin C was found in cancer. Since then, people undergoing chemotherapy and / or radiation advised to take supplements containing vitamin C.
For orally administered vitamin C is that conclusion has not changed. But vitamin C parenterally (by injection or infusion) is administered and that much higher tissue concentrations can be achieved than has ever been possible with oral administration, scientists concluded that the resolute rejection of vitamin C in cancer therapy should be reconsidered.
In high concentrations, vitamin C appears to be toxic to cancer cells (in tissue). Mega doses vitamin C to generate hydrogen peroxide, which selectively kills some cancer cells without affecting the normal healthy cells. Vitamin C deficiency shows the prognosis of cancer patients clearly deteriorate.
French scientists demonstrated in February 2009 that vitamin C - in very high doses, administered parenterally (via injection), was able to slow the growth of cancer and to control. In mice with cancer was injected vitamin C. The vitamin had no nasty side effects on animals, the survival time of the animals surged tumor growth was stopped and put the formation of metastases completely blocked. A similar result was already found in mice, as well as in in vitro studies.
Following a number of publications which, in individual cases, parenterally administered vitamin C had beneficial effects in cancer therapy published in 2007, researchers from the Kwan Dong University in South Korea a study in which vitamin C, both parenterally and orally administered, the quality of life of terminally signifcant cancer patients appeared to improve. Meanwhile, there are other published case descriptions of patients whose tumor disappeared completely as a result of parent-administered real, high doses of vitamin C.
Research by the Consumers' Association in 2005 at the difference between organic and conventional vegetables showed 10 out of 14 examined vegetables (both organic and conventional) more than 60% contain less vitamin C than old foods indicate tables, but they are still used.
Too much vitamin C
Examples of the toxicity of vitamin C are rare. Most people tolerate a few grams per day without problems. Doses of from about 10 grams to give rise to the occurrence of diarrhea. In rare cases, organ damage can occur. By iron overload occur kidney stones, or other serious adverse events occurred. In most of these cases, the affected patients had an underlying illness. It seems that the body has a protective mechanism against high doses of vitamin C: At doses of 200 milligrams or more, is that their inclusion is greatly reduced by the body. It is also true that excessive amounts of vitamin C that have ended up in the blood, are excreted in the urine efficiently. About the safety of vitamin C administered intravenously is much less known.
Rebound effect
When suddenly stopped after the daily use of very high doses of vitamin C (many grams), it can be called "rebound effect" occur. This phenomenon implies that people who prolonged high doses of vitamin C swallow suddenly start showing symptoms of vitamin C deficiency. This can be explained in that ascorbate-dependent enzyme reactions proceed for another 24 to 48 hours after the intake of vitamin C is stopped, whereby vitamin C is replenished which is not consumed.