13 replies to this topic

[cylon]

Surprised to find out that, according to recent studies,  1000mg per day is really too much and there are a few studies that link higher incidence of cataracts among women and kidney stones among men with long term high dosage(1000+mg day). This is from consumerlabs and also askdrweil's site. So I guess I will be taking 250mg, not 1000 daily unlessI'm coming down with a cold. Any suggestions for quality buffered brands?

 

[Dorian Grey]

I found some 500mg caplets (cheap drugstore brand) and cut them in half.  I take these custom 250mg half tabs 3 times a day, always on an empty stomach.  Taking low doses several times a day helps maintain stable blood levels and reduces GI side effects.  

 

Vitamin-C greatly increases absorption of dietary iron if taken with food, and for males this is not a good thing!  Males tend to accumulate iron with age and iron accumulation accelerates aging.  

Edited by synesthesia, 26 February 2015 - 02:45 AM.

[Kalliste]

Megadosing Vit C seems bad. Increases the risk of some cancers, decreases the effects of physical exercise. I've cut all Vit C pills and feel fine about the amount I get from apples, citrus fruits etc.

[Dorian Grey]

I've noticed if I don't supplement "some" Vitamin-C, my gums sometimes bleed when I brush my teeth...   A little C every day and not a drop.  I haven't seen any blood in the sink for years.  

 

C from dietary sources is great, but you really need to be sure you get adequate C every day for optimal health.  This doesn't happen for me unless I supplement.  

 

As always...  Low doses are best!  

[johnjuanb1]

Studies can be skewed both ways. I tend to be more a believer in higher doses of vitamin with 500mg per setting. I have no problem ingesting up to 3 grams per day for antioxidant and antiviral protection. I have heard mega dosing vitamin c intraveneously has been used in cancer tumor therapy with success.

[JohnDoe999]

Studies can be skewed both ways. I tend to be more a believer in higher doses of vitamin with 500mg per setting. I have no problem ingesting up to 3 grams per day for antioxidant and antiviral protection. I have heard mega dosing vitamin c intraveneously has been used in cancer tumor therapy with success.

 

I agree on this. The kidneystone danger of vitamin C is a myth. There is, as far as I know, no valid research that shows any connection. However, if you have suboptimal kidneys to begin with, THEN there is research showing a connection.

 

Vitamin C has intravenously been used with success for cancer. It then acts not as an antioxidant, but as a prooxidant. However; this prooxidant acitvity is beneficial in this context.

 

I normally take between 3000-5000 grams of vitamin C daily.Time relase.  Have been doing this for 20 years or something.

[Galaxyshock]

I normally take between 3000-5000 grams of vitamin C daily.Time relase.  Have been doing this for 20 years or something.

 

Now that I would say is too much hehe.

 

Anyway, I prefer to get vitamin C from berries and camu camu. Flavonoids like quercetin synergize to make it more bioavailable and stay in the system longer. It's cheaper to buy the synthetic stuff though, maybe taking it with meals works kinda similarly. But studies tend to show most of extra ascorbic acid is just peed out.

[cuprous]

I've noticed if I don't supplement "some" Vitamin-C, my gums sometimes bleed when I brush my teeth...   A little C every day and not a drop.  I haven't seen any blood in the sink for years.  

 

C from dietary sources is great, but you really need to be sure you get adequate C every day for optimal health.  This doesn't happen for me unless I supplement.  

 

As always...  Low doses are best!  

 

If I remember right, watercress was historically used to "bind the teeth."  It's also high in vitamin c!  

[osris]

In Defense of High-Dose Vitamin C: Challenging the Narrative on Megadosing Risks

 

By

 

ChatGPT

 

Vitamin C megadosing has long been a controversial subject. While some researchers and health authorities have raised caution flags over potential risks like kidney stones or diminished exercise benefits, a closer look at the broader scientific and historical context suggests that these concerns may be overstated—or at least not universally applicable. Let’s explore the case for high-dose vitamin C supplementation and question the growing trend of caution.

 

1. The Linus Pauling Legacy and Clinical Research

 

Two-time Nobel Laureate Linus Pauling strongly advocated for high doses of vitamin C, sometimes recommending several grams daily. Critics dismissed his claims as fringe science, but decades later, his views are getting a second look. Clinical trials in recent years, particularly in integrative oncology and infection management, have demonstrated that intravenous and oral high-dose vitamin C can offer tangible benefits—ranging from immunomodulation to enhanced collagen synthesis, and even potential cytotoxic effects on tumor cells via hydrogen peroxide production in the extracellular space.

 

2. Kidney Stones: A Misrepresented Risk

 

The kidney stone argument is often cited, especially in men. But the evidence is far from definitive:

 

• The Health Professionals Follow-Up Study showed a slight increase in stone formation at 1000 mg/day—but correlation is not causation.
• Many participants likely had other dietary risk factors (e.g., high animal protein or low hydration).
• Conversely, numerous case reports and trials show no such link, and the risk is virtually nonexistent in women.

 

Vitamin C’s conversion to oxalate does occur, but this effect may be modulated by magnesium, hydration, and citrate intake, factors rarely controlled for in studies.

 

3. Cataracts: Selective Concern

 

Yes, one Swedish study found an association between high-dose vitamin C and cataracts in women. But this finding:

 

• Was observational, not causal.
• Did not replicate strongly in other major studies like the Nurses’ Health Study.
• May have been confounded by preexisting oxidative stress, statin use, or smoking.

 

More importantly, vitamin C is highly concentrated in the aqueous humor of the eye, where it acts as a UV shield. Multiple studies actually suggest a protective effect against cataract formation.

 

4. Blunting Exercise Gains: Context Matters

 

The popular claim that antioxidants blunt exercise benefits is largely based on studies of untrained individuals undergoing short-term aerobic regimens. The doses used were often very high, combined with vitamin E, and the effect was mainly on insulin sensitivity—not endurance, strength, or mitochondrial gains in general.

 

For most people—especially older adults or those under oxidative stress—the antioxidant effect of vitamin C may help reduce DOMS (delayed onset muscle soreness) and improve recovery without hindering adaptation.

 

5. Why 1000 mg May Still Be Optimal for Some

 

• Absorption plateaus around 200–400 mg for single doses, but splitting doses (e.g., 500 mg twice daily) maintains plasma saturation better than food alone.
• Smokers, people with chronic illness, high-stress levels, and the elderly may all benefit from intakes above the RDA.
• Many modern diets, even those with fruits, fall short of optimal antioxidant intake to counter environmental and dietary pro-oxidants.

 

Conclusion: Reconsider the Retreat

 

While prudence is wise, the growing caution around 1000 mg/day of vitamin C lacks nuance. For many, this dose remains not just safe, but potentially beneficial—especially when combined with appropriate cofactors, hydration, and dietary balance. The fear of megadosing risks may be a case of throwing the antioxidant-rich baby out with the bathwater.

 

[pamojja]

There simply isn't any case study for kidney stones or cataracts without serious comorbidities. Therefore, the strong confounder of self-medication in observational studies.

 

On the other hand, I do have a more than 16 years case study of taking 25 g/d ascorbic acid myself.

 

 Screenshot 2025-04-17 112704.png   28.83KB   0 downloads

 

The first column with lighter and reddish coloration indicates major changes:

• 2009 diagnosis of PAD with painfree walking distance down to 300-400 meters.
• 2010-11 gradual improvement to 1 and 2 hours painfree walking.
• 2012 chronic bronchitis for the whole year. Thereby diminishing walking distance to below 1 hr again. After diagnosis of COPD stage 1, but asymptomatic since.
• 2015 remission of walking disability.
• 2018 remission of post-exertional malaise (otherwise the main symptom of ME/CFS)
• 2021 corona circumstances worsened walking distance partially again. Fluctuating.
• End of 2024, major joints alternatingly in strong pain. (3 months of ultra-sounds, x-ray or MRI only found a lesion in a meniscus. Self-diagnosis with experimental 200 mg/d of hydroxychloroquine indicates rather rheumatoid arthritis.

From which it's obvious, that highest ascorbic acid intake was always correlated with all major remissions, and worsening (due to self-mediating effect).

 

The worsening in 2021 wasn't as bad as the former walking-disability, and the arthritis pain ceased with increasing anti-inflammatory herbs again (similar to Giulano's 4-herb-synergy). A CKD stage 1 ceased after the first few years of high-dose vitamin C.

 

Though I had rare oxLDL lab tests only:

 

2012 -  66

2016 - 114

2018 - 117

2020 -  44

 

(20-179 ug/l normal, <60 optimal range)

 

..here too it seems to have to optimized with the erstwhile highest intake of 33 g/d for a whole year.

 

It's been the clinical experience of orthomolecular practitioners, that kidney-stones cease with higher intake of multiple grams per day. So the increased excretion of oxalate in acerbate users, might be even beneficial with high enough doses.

 

 

 

[osris]

Interesting. 

 

It's rare to see such a detailed personal history of using vitamin C 

 

It adds real-world support to the argument that vitamin C is both safe and beneficial, even at the very large dosages you have been taking.

 

And it supports the view that any risk lies not in high intake per se, but in unbalanced protocols or misinterpreted correlations. 

[pamojja]

.. in high intake per se, but in unbalanced protocols or misinterpreted correlations.

 

I should have added, beside comprehensive supplementation of nutrients and life-style changes, I did monitor progress (or regress) with as many laboratory markers possible to get. Which I consider very important, with many co-morbidities and high dose supplementation.

 

Vitamin-C greatly increases absorption of dietary iron if taken with food, and for males this is not a good thing!  Males tend to accumulate iron with age and iron accumulation accelerates aging.  

 

Though male, iron markers stayed on the low side, in my case. Ferritin, for example, in average at 75 ng/ml. The only ferritin test 2 years before supplementing was with a myopericarditis at 342.
 

[pamojja]

But studies tend to show most of extra ascorbic acid is just peed out.

 

Tested in studies up to 2,5 g only, and extrapolated for all higher doses.

 

There is however a sole observational study, where oncology patients took up to 20 g/d. With unexpected outcomes (emphasis added by me):

 

 

 

Journal of the New Zealand Medical Association, 23-August-2002, Vol 115 No 1160

Glycohaemoglobin and ascorbic acid

Copplestone et al1 (http://www.nzma.org....al/115-1157/25/) identified misleading glycohaemoglobin (GHb) results due to a haemoglobin variant (Hb D Punjab) and listed a number of other possible causes for such false results (ie, haemolytic anaemia, uraemia, lead poisoning, alcoholism, high-dose salicylates and hereditary persistence of foetal haemoglobin).

We have observed a significant "false" lowering of GHb in animals and humans supplementing ascorbic acid (AA) at multigram levels. Mice receiving ~7.5 mg/d (equivalent to > 10 g/day in a 70 kg human) exhibited no decrease in plasma glucose, but a 23% reduction in GHb.2 In humans, supplementation of AA for several months did not lower fasting plasma glucose.3,4 We studied 139 consecutive consenting non-diabetic patients in an oncology clinic. The patients had been encouraged as part of their treatment to supplement AA. Self-reported daily intake varied from 0 to 20 g/day. The plasma AA levels ranged from 11.4 to 517 µmol/L and correlated well with the reported intake. Regression analysis of their GHb and plasma AA values showed a statistically significant inverse association (eg, each 30 µmol/L increase in plasma AA concentration resulted in a decrease of 0.1 in GHb).

A 1 g oral dose of AA can raise plasma AA to 130 µmol/L within an hour and such doses at intervals of about two hours throughout the day can maintain ~230 µmol AA/L.5 Similar levels could also be achieved by use of sustained-release AA tablets. This AA concentration would induce an approximate 0.7 depression in GHb. The GHb assay used in our study, affinity chromatography, is not affected by the presence of AA.3 Thus, unlike the case with Hb D Punjab, our results were not caused by analytical method artifact. More likely, the decreased GHb associated with AA supplementation appears related to an in vivo inhibition of glycation by the elevated plasma AA levels, and not a decrease in average plasma glucose.3 If this is true, the effect has implications not only for interpretation of GHb but also for human ageing, in which glycation of proteins plays a prominent role in age-related degenerative changes.

A misleading GHb lowering of the magnitude we observed can be clinically significant. Current recommendations for diabetics suggest that GHb be maintained at 7, a level that is associated with acceptable control and decreased risk of complications; when GHb exceeds 8, re-evaluation of treatment is necessary.6 Moreover, relatively small increases in average blood sugar (ie, GHb) can accompany adverse reproductive effects. A difference in mean maternal GHb of 0.8 was found for women giving birth to infants without or with congenital malformations.7 In either of these circumstances, an underestimation of GHb could obscure the need for more aggressive intervention.

Vitamin usage is common in New Zealand and after multivitamins, AA is the most often consumed supplement.8 Moreover, diabetics are encouraged to supplement antioxidants, including AA. Thus, it seems prudent for primary care health providers to inquire regarding the AA intake of patients, especially diabetics, when using GHb for diagnosis or treatment monitoring.

Cheryl A Krone
Senior Research Scientist
John TA Ely
Director
Applied Research Institute
PO Box 1925
Palmerston North

References:

• Copplestone S, Mackay R, Brennan S. Normal glycated haemoglobin in a patient with poorly controlled diabetes mellitus and haemoglobin D Punjab: implications for assessment of control. NZ Med J 2002;115(1157). URL: http://www.nzma.org....al/115-1157/25/
• Krone CA, Ely JTA. Vitamin C and glycohemoglobin revisited. Clin Chem 2001;47(1):148.
• Davie SJ, Gould BJ, Yudkin JS. Effect of vitamin C on glycosylation of proteins. Diabetes 1992;41(2):167–73.
• Paolisso G, Balbi V, Bolpe C, et al. Metabolic benefits deriving from chronic vitamin C supplementation in aged non-insulin dependent diabetics. J Am Coll Nutr 1995; 14(4):387–392.
• Lewin S. Vitamin C: Its Molecular Biology and Medical Potential. New York: Academic Press; 1976.
• Kenealey T, Braatvedt G, Scragg R. Screening for type 2 diabetes in non-pregnant adults in New Zealand: practice recommendations. NZ Med J 2002;115(1152):194–6.
• Rosenn B, Miodovnik M, Dignan PS, et al. Minor congenital malformation in infants of insulin-dependent diabetic women: association with poor glycemic control. Obstet Gynecol 1990;76:745–9.
• Allen T, Thomson WM, Emmerton LM, Poulton R. Nutritional supplement use among 26-year-olds. N Z Med J 2000;113(1113):274–7.

[Dorian Grey]

Apparently, acids (ascorbic acid) can dissolve minerals and metals, which is often important & helpful, however there may be times when suddenly dissolving high levels of transition metals like iron and copper may have adverse effects via Fenton reaction and/or hydroxyl radicals generation.  

 

https://pmc.ncbi.nlm...les/PMC7285147/

 

Two Faces of Vitamin C—Antioxidative and Pro-Oxidative Agent

 

Apparently, this adverse oxidative stress becomes likely and perhaps only occurs when pre-existing elevation or disruption in normal physiological sequestration and regulation are present? 

 

The pro-oxidative activity of vitamin C depends mainly on the availability of Fe. Iron reduced by ascorbate to Fe2+ easily reacts with oxygen, which in the Fenton reaction leads to the formation of reactive oxygen species and H2O2 which in reaction with Fe2+ generates a highly reactive hydroxyl radical 

 

Base modifications, strand breaks or DNA adducts are the most common damage generated by ROS. The damaging factor is primarily the hydroxyl radical (●OH). Guanine (G) is the base that is easily oxidized, which causes 8-oxo-2-deoxyguanine (8-oxoGua) to be the most abundant DNA damage [87]. It is a mutagenic damage, because 8-oxoGua mispairs with adenine (A), which in the next replication cycle may generate a G to T transversion mutation

 

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Personally, I would want to make sure my ferritin was not at all elevated (triple digits) before I'd feel comfortable mega-dosing C. 

 

Concomitant chelation with IP6 (inositol hexaphosphate) might also be wise, particularly early on during initiation of high dose therapy.