Gout is a condition caused by elevated levels of uric acid in the body. If levels are high enough, uric acid can end up crystallising in one or more joint, which typically causes intense pain and inflammation. Gout quite often affects the ball of the foot (the major joint of the big toe), but the condition can affect any joint. Conventional medical treatment is centred on painkillers for attacks of gout, as well as drugs (e.g. allopurinol) that can lower uric acid levels by speeding its elimination from the body through the kidneys (known as having a ‘uricosuric’ affect).
However conventional drugs are apparently not the only agents which have a uricosuric effect. Previous studies have found, for instance, that vitamin C also does this [1-4]. And recently saw the publication of a study which assessed the relationship between vitamin C intake and risk of gout in almost 47,000 men [5]. All the men had no history of gout when they entered the study. Their intakes of vitamin C (via diet and supplements) were assessed every 4 years over a 20-year period.
Risk of gout was found to be lower in individuals with higher vitamin C intake. Compared to individuals with a total vitamin C intake of less than 250 mg per day, those with total intakes of 500-999 mg per day were at a 17 per cent reduced risk of gout. For intakes of 1000-1499 and 1500 or more mg per day, risk of gout was down by 34 and 45 per cent respectively.
The authors of this study also looked at the relationship between amounts of vitamin C ingested in supplement form only and risk of gout. Here again, higher supplemental levels were associated with a reduced risk of gout. Compared to those who did not supplement with vitamin C, those supplementing with 1000-1499 and 1500 mg or more of vitamin C per day were found to be at 34 and 45 per cent reduced risk of gout.
These results suggest that vitamin C, either from diet and/or supplements, is associated with a reduced risk of gout. This study is epidemiological in nature, and cannot be used to conclude that vitamin C reduced the risk of gout. However, the fact that vitamin C is known to be uricosuric does make a genuine protective effect likely.
Another piece of research which provides further supporting evidence for this is a randomised controlled trial in which individuals were treated with 500 mg of uric acid or placebo (inactive medication) over a 2-month period [6]. Vitamin C, compared to placebo, led to a statistically significant reduction in uric acid levels (the average fall in uric acid levels in this study was 0.5 mg/dL which is equivalent to about 30 micromols/litre).
Put together, these results suggest that vitamin C has real potential to help prevent gout. My tendency in practice is to use doses of about 2000 mg per day (as 1000 mg taken twice a day). Individuals who should consult their doctor before supplementing with vitamin C include those with the condition glucose-6-phosphate dehydrogenase deficiency, those suffering from conditions in which iron levels are elevated in the body such as haemosiderosis or haemochromatosis (vitamin C enhances iron absorption), and those with a history of kidney stones or kidney failure.
References:
1. Stein HB, et al Ascorbic acid-induced uricosuria: a consequency of megavitamin therapy. Ann Intern Med 1976;84:385-8
2. Sutton JL, et al Effect of large doses of ascorbic acid in man on some nitrogenous components of urine. Hum Nutr Appl Nutr 1983;37:136-40
3. Berger L, et al. The effect of ascorbic acid on uric acid excretion with a commentary on the renal handling of ascorbic acid. Am J Med 1977;62:71-6
4. Mitch WE, et al. Effect of large oral doses of ascorbic acid on uric acid excretion by normal subjects. Clin Pharmacol Ther 1981;29:318-21
5. Choi HK, et al. Vitamin C intake and the risk of gout in men: a prospective study. Arch Intern Med. 2009;169(5):502-7.
6. Huang HY, et al. The effects of vitamin C supplementation on serum concentrations of uric acid: results of a randomized controlled trial. Arthritis Rheum. 2005;52(6):1843-7
