Vitamin C and uric acid. Across 13 studies, a majority found it lowers uric acid, but its reliability is still a puzzle.








This page about Vitamin C and uric acid was last reviewed or updated on 5 May 2015.

SUMMARY A 2013 study found that uric acid was not really lowered  by Vitamin C among gout sufferers. But a meta-analysis (a study of studies), in this case of 13 Vitamin C and uric acid studies, found that in 8 of the 13, uric acid was lowered by Vitamin C. In one, there was no change, and in 4 it rose. When Vitamin C was the only substance taken (9 of 13 studies) the average fall fell from - 0.35 mg/dL ( - 20.8 µmol) to - 0.54 mg/dL (- 32.08 µmol/L). These are useful reductions, but the participants were not gout patients.

A 2013 VITAMIN C AND URIC ACID STUDY WAS NOT ENCOURAGING

In May 2013 the latest study to enquire whether Vitamin C (ascorbic acid) lowers uric acid (1) found that it did not really reduce it and the study was among gout patients. Another conclusion was that in the tested patients who took Allopurinol plus Vitamin C, Vitamin C (ascorbic acid) did not help. (Although Allopurinol did lower uric acid in one group by a useful - 1.98 mg/dL on one measurement, which is more or less to be expected).

It was the first Vitamin C study that was specifically among only gout patients.

The dose was Vitamin C at 500 mg for 8 weeks; its level in blood plasma rose considerably; 500 mg is a modest dose.

But this 2013 study tested a small number - just 10 gout patients took only Vitamin C. There were 40 in all including those on Allopurinol and those who took both. What might explain this very small reduction could be the inability of this relatively small dose to increase kidney uric acid clearance. Moreover, some trialists were taking diuretics which can hinder uric acid excretion and probably overwhelm the Vitamin C effect; and some were on aspirin which can also inhibit it at low doses, (325 mg, or less, daily).

BETTER RESULTS IN A META-ANALYSIS OF VITAMIN C AND URIC ACID STUDIES

In contrast, the number of trialists analysed (analyzed) in a meta-analysis (a study of studies) of 13 Vitamin C and uric acid studies conducted from 1990 to 2009 amounted to 556 healthy (and some unhealthy) adults. (2) They were not gout sufferers although some had other ailments and some were in long term care. Many of these studies  had quite different design criteria, but the meta-analysis was able to conclude that a majority of them found that Vitamin C lowers uric acid.

The overall reduction figures quoted include those four studies where uric acid rose after Vitamin C intake, and include the magnitude of the rise. Here are the main conclusions :

  • At a median dose of 500 mg daily over 30 days Vitamin C lowered uric by an average of - 0.35 mg/dL (-20.8 µmol/L). 
  • Uric acid fell in 8 of 13 studies, rose in four and there was no change in one.
  • In trials where at least 500 mg of Vitamin C was taken, uric acid fell -0.59 mg/dL.
  • In trials where only Vitamin C was taken, it fell - 0.54 mg/dL.
  •  If one trial which tested both Vitamin C and low dose aspirin (in this case, 300 mg/day) is excluded, the combined uric acid fall rose from - 0.35 mg/dL to - 0.40 mg/dL. Low dose aspirin is thought to encourage uric acid retention thus reducing/negating any excretory effect of Vitamin C.
  • In sub group analysis, the researchers found that Vitamin C has more effect on uric acid when the starting level is higher, which it usually would be in gout patients.
  •  The biggest reduction was -2.52 mg/dL. And the lowest reduction was -0.20 mg/dL .
  • The amounts by which uric acid fell were bigger across the 13 studies than the amount by which it rose.
  • This meta-analysis also concluded the larger the daily dose (that is, a dose above 500 mg, say 1 or 2 grams), the greater the uric acid reduction.

VITAMIN C AND URIC ACID - MEGA DOSE STUDIES

So you might conclude that if considerably larger doses than 500 mg are taken, serum (blood) uric acid would invariably fall. But the results in mega dose studies have been mixed.

In one mega dose study not in the meta-analysis, (3) when 4 grams was given to 10 patients (5 of them had gout) the fractional clearance of uric acid increased considerably within 6 hours but the serum (blood) uric acid level did not fall. 

However, when just three patients took Vitamin C at 8 grams for 3-7 days serum uric acid fell - 1.2 mg/dL to - 3.1 mg/dl. These are good scores. They would be creditable reductions by drugs such as allopurinol, febuxostat or probenecid. Moreover, the patient with high uric acid got the best reduction.

In another mega dose study of Vitamin C, also not included in the meta-analysis, (4) an infusion of Vitamin C in 13 male trialists (8 had gout) resulted  in a considerable increase in  uric acid excretion in all of them. The gout patients did better than the non-gout patients.

On the other hand a third mega dose Vitamin C study (at 4 and 12 grams) among healthy patients – and again it was a small one - did not affect serum (blood) uric acid excretion. Nor its clearance by the kidneys.

Dr. Atkins’s gout protocol

At 4 grams you’re getting close to the Dr. Atkins’s (the Atkins diet) gout protocol level as published in his book Dr.Atkins’ Vita Nutrient Solution. That dose was 5 – 10 grams. Other nutrients too were in his gout protocol – details are in the book.

And in elderly patients, both moderate (200 mg) and high dose (2 grams) Vitamin C lowered uric acid in serum (blood) by a useful amount. (6)

Could it be that Vitamin C does not lower uric acid (UA) in gout patients as the 2013 study concluded, or only in healthy adults, or adults with other afflictions, as some had in the meta-analysis? Not according to the famous Dr.Atkins, who used high dose Vitamin C in his gout treatment.

And in the meta-analysis, when baseline (starting) uric acid was 4.85 mg/dL or higher, that is closer to the average of gout patients' uric acid, the uric acid reduction was greater: - 0.78mg/dL, more than double the pooled figure of 0.35 mg/dL and higher than assay variability (measurement error).  Moreover, in the mega dose studies above, more uric acid was excreted by some patients with gout. But these mega dose studies were also small ones.

Kidney impairment

If a gout sufferers’ kidneys have sub-optimal functioning it’s possible Vitamin C may not be able to encourage them to excrete more uric acid (UA), or its effect may be very small, or the dose needs to be higher.




Related articles you may enjoy

Another study, which used a Vitamin C rich beverage, orange juice, lowered uric acid by a broadly similar amount ( -0.71 mg/dL (men) and – 0.24 mg/dL (women) in just two weeks. Read about it here.

Go to our page about gout and Vitamin C   where a 500 mg dose lowered uric acid.

See our Vitamin C and uric acid page - what did a meta analysis (study of studies) of Vitamin C and uric acid studies say ?

What do the Vitamin C studies mean ? Read our conclusions





(1) Lisa K Stamp, John L O’Donnell, Christopher Frampton, Jill Drake, Mei Zhang, Peter T Chapman. Clinically insignificant effect of supplemental vitamin C on serum urate in patients with gout; a pilot randomised  controlled trial. Arthritis & Rheumatism, 2013; DOI: 10.1002/art.37925 (NB. Urate is uric acid).

(2) Stephen P. Juraschek, BA, Edgar R. Miller, III, MD, PhD, and Allan C. Gelber, MD, MPH, PhD Effect of Oral Vitamin C Supplementation on Serum Uric Acid: A Meta-analysis of Randomized Controlled Trials. Arthritis Care & Research. 2011 September; 63(9): 1295–1306. doi:  10.1002/acr.20519

(3) Abstract  Stein H.B, Hasan A, Fox I.H. Ascorbic acid-induced uricosuria. A consequency of megavitamin therapy. Ann Intern Med. 1976 Apr; 84 (4):385-8.

(4) Abstract Berger L, Gerson C.D, Yü T.F. The effect of ascorbic acid on uric acid excretion with a commentary on the renal handling of ascorbic acid. Am J Med. 1977 Jan; 62 (1):71-6.

(5) Mitch W.E, Johnson M.W, Kirshenbaum J.M, Lopez R.E. Effect of large oral doses of ascorbic acid on uric acid excretion by normal subjects. Clin Pharmacol Ther. 1981 Mar;29 3):318-21.

(6) Abstract Kyllästinen M.J, Elfving S.M, Gref C.G, Aro A. Vitamin C supplementation and common laboratory values in the elderly. Arch Gerontol Geriatr. 1990 May-Jun;10 (3):297-301.

(7) Hathcock J.N, Azzi A, Blumberg J, Bray T, Dickinson A, Frei B, Jialal I, Johnston C.S, Kelly F.J, Kraemer K, Packer L,  Parthasarathy S, Sies H, Traber M.G. Vitamins E and C are safe across a broad range of intakes. American  Journal of  Clinical Nutrition. 2005 Apr; 81(4):736-45.

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