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Thread: Toxic Levels of Vitamins

  1. #1
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    Default Toxic Levels of Vitamins

    We've probably all heard about the recent studies on overdoing it with Vitamin E. I remember not so very long ago how it was touted as harmless in high doses.

    Are there any well done studies out there about such things as toxic levels for Vitamin C? I've just started taking 3,000 mg per day.

    How much is too much, do you think? And how long before any possible problem would manifest itself?

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    My understanding is that Vit C is safe at high doses. I get the impression it's a fairly well studied vitamin. The biggest problem with high doses of Vit C is that many people will get a side effect of upset tummy and/or the runs, so obviously it's best to keep the dose at a level where that doesn't happen.

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    there are two categories of vitamines, one are water soluble (like vit.c) and others fat soluble (vit.e).

    i think water soluble vitamins are those you can't overdose...

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    I did a little research, for what it's worth. Don't know the quality of the studies. Seems there's always something harmful to be found, doesn't it? Just as long as we know what we could be getting into--knowledge is power, they say:


    Oral administration of pharmacological doses of Vitamins C The antioxidant diet decreased the frequency of litters, litter size, total number of offspring born and survival of male pups to weaning. The strategy of supplementing the diet with antioxidant vitamins to prevent the age associated decrease in reproductive potential should not be implemented in human beings until a safe and efficient diet is designed.
    - Theriogenology 2002 Mar 15;57(5):1539-50 -- Oral administration of pharmacological doses of vitamins C and E reduces reproductive fitness and impairs the ovarian and uterine functions of female mice. -- Tarin JJ, Perez-Albala S, Pertusa JF, Cano A.

    It may be wise to avoid vitamin c in large doses if you have kidney problems.
    - J Am Soc Nephrol 1999 Apr;10(4):840-5 -- Intake of vitamins B6 and C and the risk of kidney stones in women. -- Curhan GC, Willett WC, Speizer FE, Stampfer MJ.

    Long-term or high-dosage consumption of vitamin C may play a role in calcium oxalate kidney stone formation. High percentage metabolic conversion of ascorbate to oxalate in this subject caused relative hyperoxaluria and crystalluria, the latter manifesting itself as haematuria. Clinicians need to be alerted to the potential dangers of large dose ingestion of vitamin C in some individuals.
    - Eur J Clin Invest 1998 Sep;28(9):695-700 -- Relative hyperoxaluria, crystalluria and haematuria after megadose ingestion of vitamin C. -- Auer BL, Auer D, Rodgers AL.

    Iron overload could promote the generation of free radicals and result in deleterious cellular damages. A physiological increase of oxidative stress has been observed in pregnancy. A routine iron supplement, especially a combined iron and vitamin C supplementation, without biological justifications could therefore aggravate this oxidative risk. These data show that pharmalogical doses of iron, associated with high vitamin C intakes, can result in uncontrolled lipid peroxidation.
    - Biol Trace Elem Res 2001 Nov;83(2):103-10 -- Increased lipid peroxidation in pregnant women after iron and vitamin C supplementation. -- Lachili B, Hininger I, Faure H, Arnaud J, Richard MJ, Favier A, Roussel AM.

    Use caution with high doses as 1 g or more of vitamin C may have adverse consequences in some people, including diarrhea.
    - JAMA 1999 Apr 21;281(15):1415-23 -- Criteria and recommendations for vitamin C intake. -- Levine M, Rumsey SC, Daruwala R, Park JB, Wang Y.

    This study confirms that a high ascorbic acid intake is antagonistic to copper status and may increase iron absorption.
    - Am J Clin Nutr 1983 Apr;37(4):553-6 -- Influence of ascorbic acid supplementation on copper status in young adult men. -- Finley EB, Cerklewski FL.

    High doses may interfere with prescription medications.

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    hi everyone-my friend just told me that doses over 250 mg of vitamin c daily can have negative effects on the heart- he said it is in the medical journals. i will try to find the studies and post them but wondered if anyone else heard this.....................................Lin

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    From what I understand it's almost impossible to overdose on water-soluble vitamins. It's the fat-soluble vitamins like A and D that you have to watch out for.
    KNOWLEDGE = POWER

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    steve-i think it was more about the dose being dangerous to the heart-even if it is excreted fast. this is shocking to me since i have always taken way more then that.......................Lin

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    Quote Originally Posted by newattitude
    steve-i think it was more about the dose being dangerous to the heart-even if it is excreted fast. this is shocking to me since i have always taken way more then that.......................Lin
    I wish you'd share the source of that shocking information. Here's a relevant abstract from PubMed:

    A robust database shows that dietary supplements of vitamins E and C are safe for the general population. Because these nutrients supply antioxidant and other functions for homeostasis and protection against free radical damage, supplementation has been intensively studied. Because of perceived benefits, many persons consume quantities of vitamins E and C well above the recommended dietary allowances. As safety guidance, tolerable upper intake levels have been established by the Food and Nutrition Board, Institute of Medicine, at 1000 mg for vitamin E and 2000 mg for vitamin C in adults. Many clinical trials with these vitamins have involved subjects with various diseases, and no consistent pattern of adverse effects has occurred at any intake. Numerous studies of vitamin C supplementation have provided no pattern of evidence to support concerns about safety other than occasional gastrointestinal upset or mild diarrhea resulting from the osmotic effects of unabsorbed quantities of vitamin C. Evidence of bleeding effects and other potential adverse effects of high vitamin E intakes in humans is not convincing. Evidence of adverse effects of vitamin C that result from its effects on iron absorption and metabolism has not been confirmed in clinical trials. Thus, we conclude from clinical trial evidence that vitamin E supplements appear safe for most adults in amounts </=1600 IU (1073 mg RRR-alpha-tocopherol or the molar equivalent of its esters) and that vitamin C supplements of </=2000 mg/d are safe for most adults.
    KNOWLEDGE = POWER

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