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Orthomolecular Medicine News Service, Dec 3, 2019

Vitamin C Supplementation Improves Chronic Kidney Disease

by Robert G. Smith and Andrew W. Saul

(OMNS December 3, 2019) Chronic kidney disease patients are habitually warned off of vitamin C supplementation. This is usually a mistake, as it is almost always based on a fear of oxalate kidney stone formation. Let's put that legend where it belongs. Yes, vitamin C does increase oxalate production. But that is not the same as producing a stone. Emanuel Cheraskin, MD, DMD, professor of Medicine at the University of Alabama, reports that vitamin C actually interferes with and blocks the union of calcium and oxalate, preventing a stone. This article will further consider ways that persons with chronic kidney disease can improve their health with intelligent use of supplements and diet.

Why kidneys are so important

The kidneys are a critical organ of the body because they cleanse the blood by removing waste products of the body derived from its metabolism. They are important for maintaining relatively constant levels of acidity, minerals such as sodium and potassium, and blood volume and pressure. The kidneys function by excreting all of the contents of blood except some large molecules and cells, and then re-absorbing all that are necessary for life, such as water, minerals, and small molecules such as amino acids and glucose. Chronic Kidney Disease (CKD) occurs when the kidneys progressively lose function and are gradually unable to cleanse the blood of waste products. When CKD worsens, it may be necessary for the individual to undergo dialysis, which is a method of artificially cleansing the blood.

As CKD progresses, the some of the products of normal metabolism can accumulate in the body's tissues, and in some cases may do so up to toxic levels. For example, one product of eating large amounts of meat is uric acid, which must be excreted to avoid toxic levels. Although the urate ion in blood plasma is a strong antioxidant, at high levels it can crystallize and cause kidney stones or gout in joints. Although uric acid kidney stones are not the most common, they and several other types of kidney stone can be managed by eating an excellent diet with adequate water intake [1,2]

What about oxalate?

Another product of metabolism is oxalate. This biochemical is found in many foods including spinach (100-200 mg oxalate per ounce of spinach), other dark green leafy vegetables such as kale, collards, and Swiss chard, rhubarb, and beets. [1,2] Tea and coffee are thought to be the largest source of oxalate in the diet of many people, up to 150-300 mg/day. Oxalate is also formed in much smaller quantities by the normal metabolism of ascorbate (vitamin C).

High levels of oxalate can cause a common variety of kidney stone because oxalate in the urine tends to precipitate with calcium to make crystals of calcium oxalate. The problem gets worse with inadequate liquid intake. But the typical amount of oxalate ingested in the diet is much more than would be generated by an ascorbate dose of 1000 mg/day.

Why have CKD patients been told to avoid vitamin C supplementation?

Vitamin C is needed but is often low in CKD and in dialysis patients. [4,5] But in previous decades (1950-1970) there was a problem with oxalate accumulation in tissues, likely because patients with CKD didn't always receive dialysis, and in dialysis patients sometimes the level of oxalate increases prior to their dialysis treatments. [4] Therefore, individuals with CKD were advised to avoid foods that contain oxalate and to avoid vitamin C. However, more recent dialysis treatments when done properly show no oxalate accumulation. [4]

Even at doses higher than 1000 mg/day, there is no credible evidence that vitamin C causes kidney stones or oxalate accumulation. [1-3] In fact, high doses of vitamin C tend to prevent precipitation of calcium oxalate, even when the oxalate originates in other dietary sources such as dark green leafy vegetables that contain high levels. [1,2] If some individuals have a problem with calcium oxalate kidney stones, calcium supplements should be completely avoided, and eating foods with a high calcium content minimized. Further, magnesium competes with calcium for binding to oxalate, and magnesium oxalate is much more soluble than calcium oxalate, which tends to prevent precipitation of calcium oxalate into stones. [6] Therefore adequate intake of magnesium, including magnesium supplements (in citrate, malate, or chloride form, 300-500 mg/day in divided doses), along with adequate water intake, can alleviate the tendency to make the most common form of kidney stone. [6]

Diet and supplement guidelines for chronic kidney disease patients

An excellent diet including lots of colorful vegetables, dark green leafy vegetables, fresh fruits, nuts, butter, moderate amounts of whole grains (whole wheat bread, brown rice, whole kernel corn meal) and meat and fish, avoiding sugar, along with adequate intake of liquids and supplements of essential nutrients that provide adequate doses of vitamins and minerals (B vitamins, vitamin C, D, E, and magnesium) will tend to prevent problems of oxalate precipitation and maintain good health [1-17]. Higher doses of vitamin D (3000-10,000 IU/day) than specified by current clinical practice are necessary for optimum health in CKD patients. [18,19] Dialysis patients may need to supplement with vitamins and minerals, including vitamin C, D, E, and magnesium to prevent deficiency and to lower the risk of oxalate accumulation. [4-8]

Individuals with CKD may be advised by their doctors to watch their diet carefully to avoid foods that cause high levels of biochemicals or minerals that cannot be removed by the kidneys or by dialysis treatments and might accumulate to toxic levels. However, vitamin C is not one of these foods, as it tends to prevent oxalate precipitation [1-3]. Further, dialysis patients are often deficient in vitamin C and may need supplements of vitamin C (2,000-6,000 mg/day in divided doses) to maintain a healthy level. [4,7-9] There is good evidence that in patients with CKD or renal failure, vitamins C and E, along with magnesium are helpful in preventing cardiovascular disease and other conditions related to or caused by renal insufficiency. [4-17]


1. Orthomolecular News Service (2013) What Really Causes Kidney Stones (And Why Vitamin C Does Not).

2. Saul A. (2019) Kidney Stones (Renal Calculi) and Their Relation to Diet.

3. Hickey S, Roberts H. (2005) Vitamin C does not cause kidney stones.

4. Raimann JG, Levin NW, Craig RG, Sirover W, Kotanko P, Handelman G. (2013) Is vitamin C intake too low in dialysis patients? Semin Dial. 2013 Jan-Feb;26(1):1-5. doi: 10.1111/sdi.12030. Epub 2012 Oct 29.

5. Roumeliotis S, Roumeliotis A, Dounousi E, Eleftheriadis T, Liakopoulos V. (2019) Dietary Antioxidant Supplements and Uric Acid in Chronic Kidney Disease: A Review. Nutrients. 11(8). pii: E1911.

6. Dean, C (2017) The Magnesium Miracle, Ballantine Books. ISBN-13: 978-0399594441

7. Case, HS (2018) Vitamin C Questions: Answered.

8. Orthomolecular News Service (2009) Vitamin C and Acidity: What Form is Best?

9. Smith RG (2017) Vitamin C Papers Hot off the Press.

10. Case HS (2017) Orthomolecular Nutrition for Everyone: Megavitamins and Your Best Health Ever. ISBN-13: 978-1681626574

11. Sabri MR, Tavana EN, Ahmadi A, Gheissari A. (2015) Effect of vitamin C on endothelial function of children with chronic renal failure: An experimental study. Adv Biomed Res. 2015 4:260.

12. Gillis K, Stevens KK, Bell E, Patel RK, Jardine AG, Morris STW, Schneider MP, Delles C, Mark PB. (2018) Ascorbic acid lowers central blood pressure and asymmetric dimethylarginine in chronic kidney disease. Clin Kidney J. 11:532-539.

13. Fiore DC, Fox CL. (2014) Urology and nephrology update: anemia of chronic kidney disease. FP Essent. 2014 Jan;416:22-5.

14. Sung CC, Hsu YC, Chen CC, Lin YF, Wu CC. (2013) Oxidative stress and nucleic acid oxidation in patients with chronic kidney disease. Oxid Med Cell Longev. 2013:301982.

15. Del Vecchio L, Locatelli F, Carini M. (2011) What we know about oxidative stress in patients with chronic kidney disease on dialysis--clinical effects, potential treatment, and prevention. Semin Dial. 24:56-64.

16. Dupont JJ, Farquhar WB, Townsend RR, Edwards DG. (1985) Ascorbic acid or L-arginine improves cutaneous microvascular function in chronic kidney disease. J Appl Physiol. 111:1561-1567.

17. Korish AA, Arafah MM. (2008) Catechin combined with vitamins C and E ameliorates insulin resistance (IR) and atherosclerotic changes in aged rats with chronic renal failure (CRF). Arch Gerontol Geriatr. 2008 Jan-Feb;46(1):25-39. Epub 2007 Apr 6.

18. Restrepo Valencia CA, Aguirre Arango JV. (2016) Vitamin D (25(OH)D) in patients with chronic kidney disease stages 2-5. Colomb Med (Cali). 47:160-166.

19. Strugnell SA, Sprague SM, Ashfaq A, Petkovich M, Bishop CW. (2019) Rationale for Raising Current Clinical Practice Guideline Target for Serum 25-Hydroxyvitamin D in Chronic Kidney Disease. Am J Nephrol. 49:284-293.

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