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Question: I was surprised when my doctor told me to stop taking supplements because my kidney function was low. But after stopping the supplements, my kidney function returned to normal. Can taking a lot of supplements really damage the kidneys?
Answer: The effect of supplements on kidney health depends, in part, on an individual's underlying health issues, and which supplements are taken. However, there are reports of certain supplements causing kidney problems. A 2012 review of supplement-induced kidney dysfunction lists 15 herbs and supplements reported to have caused kidney problems, including chromium, creatine, licorice, willow bark, vitamin C and yohimbe (Gabardi, Clin J Am Soc Nephrol 2012).
Taking high doses of vitamin C (1 gram or more daily), for example, has been associated with an increased risk of kidney stones, especially in people with a history of kidney stones (see the Cautions section of the Vitamin C Review for more information). Supplementation with cranberry tablets may pose a similar risk in people with a history of kidney stones (Terris, Urology 2001).
In diabetes patients with advanced kidney disease, high daily doses of B vitamins (folate, B6 and B12) were found in one study to worsen kidney function and double the risk of heart attack stroke and death (see the Cautions section of the B Vitamins Reviewfor more information).
If you are on an immunosuppressive drug, taking very large amounts of turmeric/curcumin may lead to kidney damage -- possibly due to reduced metabolism of the drug).
The National Kidney Foundation advises people with kidney disease, people who are on dialysis, and people who have received a kidney transplant to avoid all herbal supplements, and provides a list of supplements that may be the most harmful. The foundation also warns that some minerals, like potassium, may be present in supplements in which you may not expect them, like turmeric rhizome, evening primrose, noni and garlic leaf can all contain potassium.
Heavy metal contamination from supplements is another potential cause of kidney problems (Gabardi, Clin J Am Soc Nephrol 2012). Long-term exposure to excessive cadmium (which accumulates in kidneys), for example, can cause irreversible kidney damage and may also weaken bones. ConsumerLab.com has reported surprisingly high concentrations of cadmium in some popular cocoa powders. To avoid unnecessary exposure, it's best to use supplements that have been tested by an independent testing organization, like ConsumerLab.com, to be sure that a supplement does not exceed heavy metal limits.