Vitamin C megadosage and its Adverse effects

Vitamin C megadose is the term used to describe intake or injection of vitamin C (ascorbic acid) far in excess of the current U.S. recommended dietary allowance of 90 mg per day and often well in excess of the tolerable 2,000 mg per day intake limit.There is no scientific evidence that high doses of vitamin C help cure or prevent cancer, the common cold, or some other illnesses.Historical advocates of vitamin C megadose include Linus Pauling,who won the Nobel Prize in Chemistry in 1954. According to Pauling, since humans lack a functional form of L-gulonolactone oxidase, an enzyme necessary for the manufacture of vitamin C, which is functional in most other mammals plants insects, and other life forms, humans have developed many adaptations to cope with relative inadequacy.He argues that these adaptations ultimately shorten lifespan,but that this could be reversed or mitigated by supplementing humans with hypothetical amounts of vitamin C,which is produced in the body if the enzyme is working properly.

Alternative medicine advocates, including Matthias Rath and Patrick Holford, claim that high doses of vitamin C have preventive and therapeutic effects on diseases such as cancer and AIDS,but available scientific evidence does not support these claims.Some trials have shown some benefit when used in combination with other treatments,but this does not mean that high-dose vitamin C has any therapeutic effect on its own.

Side effects

Although sometimes considered non-toxic, ingestion of vitamin C actually has known side effects, and it has been suggested that intravenous administration should require a "medical setting and a trained professional".For example, genetic disorders that result in insufficient levels of glucose-6-phosphate dehydrogenase (G6PD) can lead to hemolytic anemia in patients treated with intravenous vitamin C.The G6PD defect test is a common laboratory test.Because oxalate is produced during the metabolism of vitamin C, intravenous ascorbic acid can cause hyperoxaluria.Taking vitamin C may also acidify the urine and may promote the precipitation of kidney stones or medications in the urine.

While vitamin C is well tolerated at doses well above those recommended by government organizations, doses above 3 grams per day may have adverse effects.A common "threshold" side effect of large doses is diarrhea.Other possible side effects include increased oxalate excretion and nephrolithiasis, increased uric acid excretion, systemic regulation ("rebound scurvy"), pre-oxidation, iron overload, decreased vitamin B12 and copper absorption, increased oxygen demand, and Tooth erosion when chewing vitamin C tablets.In addition, a case was noted in which a woman who underwent a kidney transplant and was subsequently given high doses of vitamin C died shortly thereafter due to calcium oxalate deposits that damaged her new kidneys.Her doctors concluded that high-dose vitamin C regimens should be avoided in patients with kidney failure.

Overdose

As mentioned earlier, vitamin C generally exhibits low toxicity.LD50 (the dose that kills 50% of the population) is generally considered to be 11,900 mg (11.9 g) per kg in rat populations.The American Association of Poison Control Centers reports zero deaths from vitamin C poisoning.