welcome back to Mayo Clinic radio I'm dr. tom chives and I'm Traci McCray a study was recently published in the american journal of kidney disease and it found that one-third of Americans with chronic kidney disease take at least one supplement and most do it without telling their doctor or talking to their doctor about it for people with kidney disease taking supplements can be especially concerning since they have a harder time filtering medications wastes and as excess fluids from the body here to discuss is the senior author of this study Mayo Clinic endocrinologist dr. Rosalina McCoy
welcome back to the program good to see you again thank you so much for having me yep nice to have you especially to talk about this what prompted you to do this study I think I work in our primary care clinic and so many of my patients have chronic kidney disease and I think I was struck with just how often people take multivitamin supplements wanting to improve their health often not even tell us about it because they assume it's safe and yet we don't know whether they are truly safe for people with kidney disease so
you said you a lot of people with kidney disease how many really and isn't it sort of seems unusual to me that that's the one organ where we've got to back up we do and unfortunately thing when people have kidney disease both kidneys tend to be affected you know about 15 percent of Americans have some degree of kidney disease now not all stages of kidney disease present to the degree that require modifications and medications or food so these people are at risk for worsening kidney functions but can still take supplements medications much like everyone else
as long as they're cautious but people we focus on in our study they have moderate or even advanced kidney disease now as this affects a lot of people in our cohort it's almost 16 million American adults have moderate or severe kidney disease okay exactly and these are the people who really should be concerned about the medications and supplements are that they are taking because they can damage their the kidney or because the kidneys which normally filter these supplements are working well enough to filter them and get them out of the system it's both when it
comes to medications or we have a lot more information about how medications affect or are metabolized by people's chronic kidney disease we're concerned about some medications being nephrotoxic so actively harming the kidneys and either causing acute kidney injury they can lead to hospitalization even or can gradually worsen kidney function you know ibuprofen for example is a notorious example of medications that worsen kidney function for other medications the they don't damage kidney disease kidney function but they can't either the medications themselves or their metabolites can't be filtered and they're those byproducts can be toxic now supplements
just because they're not given by prescription or they're not medications they're also active compounds and they affect our patients the same exact way so they can be damaging to the kidney or they can themselves or they are components or byproducts accumulate in the context of kidney disease you know class of many supplements we looked at which we call high risk defined by the National Kidney Foundation they're considered high risk because they contain potassium or phosphorus so and those minerals are to be used with caution and limited by people with kidney disease potassium and phosphorus and
which kind of supplements are those in what are the names of some supplements that would contain those so the most common but that we found was flaxseed so flaxseed is very high in phosphorus and it was one of the most common high risk supplements taken by people of all stages with kidney disease black sea mm-hmm you know what this is just really something to consider actually because what I was going to say was the number of patients who don't think that the over over-the-counter medication or the supplements they're taking is anything they even need to
bother or trouble they're in their healthcare provider with when you say flaxseed I consider that a food and I would never report that as a supplement that I'm taking and I think that's really the biggest message that we hope that our patients and you know my colleagues and clinicians take away from this is that I think everything that people consume whether it be prescription over-the-counter medication an herbal supplement or you know things that we add to our foods they are all potentially active and they all affect our health and we hope that they do it
in a positive way and with flaxseed there's a lot of benefits right there's protein phosphorus health is great for people without kidney disease there's healthy fatty acids so we take the all of these things to help our health but we have to recognize that in many situations the patients may be affected differently and chronic kidney disease is the most common example of that but certainly not the only one so in my practice I always make a point to ask people about any of herbal supplements vitamins additives - food mixes shakes you specify all of that
because that's all a dietary supplement how why is it that you that people take multivitamins and as many supplements as they do and are you convinced that there are any supplements out there that actually help people and improve people's health I think we all take supplements and vitamins to improve our health you know the word vitamins really suggests you know vitality health and we think more of a good thing is always better now the data it's a misconception that's absolutely a misconception because too much of a good thing can can hurt us with for most
healthy people taking multivitamins is not harmful because the amounts of vitamins and minerals are gonna add the recommended daily allowance even a little bit more but it's still safe for most people but that's not the case for people who can't filter them were excrete them like people with with kidney disease and very high doses of many vitamins and many minerals are potentially harmful and you said there's a pretty fair 15% I think you said of the population has got some form of kidney disease that's a pretty big number it is so kidney disease is very
common it's growing in prevalence because because of diabetes or why because of diabetes as we age the kidney disease in longer mm-hmm high blood pressure which is associated with obesity is one of the most common causes of kidney disease together with diabetes so as people are getting older and having multiple comorbidities the presence of kidney disease increases are there other you mentioned multivitamins you mentioned flaxseed are there other supplements out there or vitamins out there that people with kidney disease should definitely avoid so the unfortunately the data about what is safe for people with kidney
disease when it comes to supplements is very limited you know in contrast to medications which are closely regulated by the Food and Drug Administration supplements are not so we we don't know the National Kidney Foundation and I encourage everyone to go and even look up Google national kidney foundation and supplements has a list of the most common supplements that include potassium phosphorus and some other supplements which are harmful to kidney disease but those that list is definitely not exhaustive both because mostly because we just don't have the research we don't know it's such a black
box and the other problem is that you know we buy a multi a supplement and we look in the back on the nutritional information not everything that is important for our patients with kidney disease to know is on there and if it's not listed it doesn't mean that it's not there so when we look at flaxseed for example often they will not list how much phosphorus is in there if you google it and go to any of those nutritional websites it will tell you how much and what percent of the recommended daily allowance for people
without Kamiya disease it is but it's not on the bottle in the ingredients it will say flaxseed it's not going to tell you what else is in there how about if people with kidney disease just avoid multi vitamins and supplements so I think we don't want people to avoid things that may be helpful so people with moderate kidney disease so stage three they can take a simple multivitamin as long as they look through one of the nutritional information make sure there's nothing excessive in there and that they're not taking anything at the same time that
has more of the same thing so if they're eating you know if they're drinking a lot of milk for example and they take a multivitamin well the level of potassium and phosphorus can be too high people with more advanced kidney disease should not probably not take a regular multivitamin but there are multivitamins designed specifically for people with kidney disease and those do take into account and of the vitamin the minerals that should be avoided well I guess the bottom line is if you're taking supplements whether they're herbal or dietary it's important to talk to your
doctor especially for people who have kidney disease and you might also ask your doctor if any of those are doing you anything doctor Rosalina McCoy is an endocrinologist at Mayo Clinic thanks so much for being with us thank you so much
