Employee & Community Health

Kidney disease and vitamins/supplements may not mix

10/21/2019 by Dr. Rozalina McCoy

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Chronic kidney disease (CKD) affects an estimated 37 million people in the U.S., about one in seven adults. Most people with CKD don't even know they have it, including 90% of people with moderate CKD and 37% of people with advanced CKD. 

For a wide variety of reasons, but most often to support their overall health and wellness, many Americans turn to dietary or herbal/botanical supplements. Garlic, fish oil, turmeric, multivitamins, flaxseed, vitamin D all find their way into Americans' medicine cabinets to fill the gaps in nutrition, boost energy or relieve aches and pains. While dietary and herbal supplements are generally considered safe, they may not be for individuals with CKD. 

Some of these supplements contain potassium or phosphorous — minerals that can be harmful to people with impaired kidney function. Other supplement ingredients also can be harmful to people with CKD. These individuals have a harder time filtering medications, wastes, and excess fluids from their body, so it's especially important for them to know about the safety or risks of any supplements they're taking. 

Despite potential safety concerns, more than one-third of the 15.7 million Americans with moderate or advanced CKD use dietary or herbal supplements, according to new research conducted by a group of Mayo Clinic colleagues. Many Americans decide to take supplements on their own and not because of a doctor's recommendation. 

Supplements, in many ways, are an unknown. They aren't regulated by the FDA the same way as prescription medications, may not be completely labeled, or can interact with each other or other prescription medications. For example: 

  • 16% of study participants took flaxseed oil, the most commonly used high-risk supplement that contains phosphorus, but it's not listed on the nutrition label. 
  • One tablespoon of whole flaxseeds has about 62 mg of phosphorus — 7% of the daily recommended value for those without CKD, but the safe limit is likely much lower for people with CKD. 
  • Flaxseed and flaxseed oil also may interact with blood-thinning and blood pressure drugs and may decrease absorption of any oral drug. 

More study is needed to dig deeper into the use of supplements and risk for those with CKD. In the meantime, if you've been diagnosed with CKD, you should have a periodic review of your medications and various supplements with your health care provider or pharmacist. Also, be sure to check with them before starting to take a dietary or herbal supplement. 

You can read more about the study in the American Journal of Kidney Disease. This research was funded by the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery

Dr. Rozalina McCoy is an endocrinologist and primary care physician in Employee and Community Health's (ECH) Division of Community Internal Medicine (CIM). she specializes in the management of type 1 and type 2 diabetes, osteoporosis and thyroid disorders. Dr. McCoy also is a health services researcher who is passionate about improving the care of patients with diabetes, reducing their burden of treatment and hypoglycemia, and ensuring access and affordability of evidence-based medical care.