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Craig G. Hurwitz, M.D.

diet & kidney health

There is no doubt that our diet is one of the most important aspects of maintaining our health whether or not we have any active health issues such as kidney disease. With that said, it may be one of the things you speak the least about with your doctor. It's extremely hard in today's world to eat healthy without significant effort. Our busy lives tend to invade time for food preparation and therefore time-wise, fast food seems to fill that gap for many. A poor diet plays a role in developing or accelerating illnesses and also plays a major role in medications just not working. Therefore, taking stock of your diet and gaining some insight into what you are consuming can have some remarkable benefits such as improved health and well being as well as less medications and cost savings. 


In patients with kidney disease there are a number of key elements of the diet that require much more careful consideration. These include the following:

  1. Sodium

  2. Potassium

  3. Phosphorous

  4. Protein

I will discuss each of these topics briefly as they pertain to patients with kidney disease. 

  • Sodium

  • Potassium

  • Phosphorus

  • Protein

 

We all know and love sodium. In fact, before salt was sprinkled on your favorite vegetables it was a religious offering in Egypt and a major currency for trade in ancient times. Sodium (or Na) is in table salt, occurs naturally in many foods and is also used as a preservative. It's important to proper function of every cell in our body. However it is not as carefully regulated, which means our kidneys allow us to retain excess salt and therefore water even when they function normally. A healthy person on a high sodium diet will gain weight. A very high sodium diet can lead to increasing blood pressure, which in turn can lead to heart disease, kidney disease and even stroke. In a patient with poor heart function just one very salty meal can tip the heart function over leading to congestive heart failure. In the setting of kidney disease salt regulation is faulty or absent. Therefore carefully monitoring sodium intake is required to avoid significant swelling, heart failure and high blood pressure.


Your doctor may have you on a diuretic or "water pill", which really should be considered a "salt removal" pill. Examples are hydrochlorothiazide (in patients with fairly normal kidney function) or furosemide, which are the most common. These medications work by impairing the kidney's ability to retain salt. However, they do not work if you are ingesting excess salt. I often see patients on a diuretic who complain "it's not working". They have persistent swelling and are "peeing all the time". It's like trying to drain a barrel when someone is adding more fluid to it quicker than it can drain.
Current dietary recommendations for daily sodium intake are less than 2300 mg and are the same for patients with or without kidney disease. Importantly you need to read labels when you buy prepared foods and also consider the serving sizes. If it's 250 mg per serving and there are 8 servings in a bag of  chips, finishing off the bag is a problem. It takes time to get used to a low sodium diet but you begin to appreciate the natural taste of foods. Avoid processed foods or canned foods. Try replacing the salt shaker with Mrs. Dash or another salt substitute. 


It's not easy to eat a sodium restricted diet and it takes some work. However, once you get your "menu" down it's easier and the payoff is worth it. 

 

Most of us are not as aware of potassium.  No one really talks about potassium much outside of the 'kidney world'.  However, this is one of the most important minerals to monitor in your diet if you have kidney disease.  Even with some cases of mild kidney disease the ability of the kidneys to clear potassium out of the blood is impaired leading to high levels of potassium in the blood, which can be dangerous and lead to abnormal heart rhythms and even death. It's serious and doctors worry when we see a high potassium level in the blood.  It's one of those critical labs that can prompt us to call a patient and send them directly to the ER for emergency evaluation.


Potassium is responsible for what I call our "human voltage".  That's right, every cell in our body is charged like a battery and potassium is the ion that does it.  Therefore, a potassium level that is either too high or too low throws off the voltage leading to symptoms that may feel like someone pulled out your battery.  Profound weakness, cramping or nausea may be experienced. 


So you can see that watching your potassium intake is critical.  Trying to keep potassium intake below 2000 mg is a goal. Foods to watch out for include prunes, oranges, apricots, raisins and dried fruits.  Potatoes, tomatoes, nuts, peanut butter, bananas and beans are also high in potassium.  Here is a link to the National Kidney Foundation's low potassium diet.  

 

Phosphorous is another mineral that you may not have heard of but is just as important as the others above although not quite in the same way.  We are now learning that problems with phosphorous balance are playing a major role in much of the heart and vascular disease we are seeing in patients with kidney disease over the years.  Even in healthy individuals it looks like abnormally elevated phosphorous levels are potential risk factors for cardiovascular disease.  Furthermore, there are fairly high levels of phosphorous in most foods, but considerably higher in dairy products, bran, nuts and chocolate.


In the setting of kidney disease phosphorus levels can get very high even in mild chronic kidney disease, seriously increasing the risk of vascular disease.  In advanced kidney disease while dialysis helps "replace" some aspects of lost kidney function , it is not easy to remove all of the phosphorus ingested with intermittent treatments.  So how do we handle this?  There are two major methods to handling high phosphorus levels.  The first is limiting phosphorus intake to the best of one's ability.  however, this is not always enough.  The second component is to add a medicine called a "phosphate binder".  This medicine is taken with each meal (at the start or during the meal).  Just like it sounds, it "binds up" or mops up dietary phosphorus in the stomach and then is excreted through the bowels.  You do not absorb this medicine.  These medications need to be taken often with each meal and some people require as much as 10 to 15 of these tablets daily to control their phosphorus. 

 

Controlling phosphorus is a challenge.  It mostly depends on patient compliance with a strict diet and binder regimen.  It often takes quite a bit of work coordinating with your doctor and kidney nutritionist to optimize these numbers but the payoff is huge.

 

When it comes to protein, there are a lot of mixed messages. Of course proteins are important for growth and repair of our body tissues. However, a high animal protein diet may have some negative impact as well. There is plenty of protein in non-meat sources, which may be a healthier alternative. Animal proteins break down into urea, which is a nitrogen based waste product that is cleared from our blood through the kidneys. With kidney disease the urea level rises and can be associated with symptoms.

 

Much of the kidney literature supports the intake of "high quality" proteins (from animal products, fish, poultry and dairy products) over "low quality" proteins found in non meat sources such as grains, vegetables and fruits. However, I'm changing my stance here. Firstly, there is growing evidence that a plant based diet has major benefits to our blood vessels and reducing our risk of heart disease. Furthermore, there is evidence that a higher animal protein diet (and low carb diet - often used for more rapid weight loss) can increase cardiovascular events (see study from British Medical Journal in 2012). Based on the current data overall I think a modified version of these diets is reasonable. While there is likely some benefit to the Vegan approach, this may not be realistic for most. We all certainly have a connection to food and letting go of all meat products may not be your lifestyle decision. However, reducing signifcantly your animal protein intake, oil intake and dairy intake and increasing your intake of plant based foods is likely to improve your overall health. This holds for patients with and without kidney disease.

 

This debate over protein sources and health are ongoing and quite heated. The meat lobby in our country is strong and darn it that meat just tastes soo good! Much smaller portions is likely the balance point.

 

For more details on the benefits of a Plant Based Diet read the update on our website summarized by Dr. Harvey I Hurwitz.