E-Kidney | February 2013

Sugar and Your Kidneys

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Mary Poppins once declared, “A spoonful of sugar helps the medicine go down.” In some cases sugar is used to mask unpleasant tastes, and yet it can be found on the ingredient lists of sweet and sour foods alike. Take one quick look at the food labels on common grocery items and it becomes rather obvious that Americans consume large quantities of sugar.

What exactly is sugar?

There are a quite a few different types of sugars and each has a distinct sweet flavor. Sugar serves as an energy source for the body. Various types include “fructose”, “glucose” and “sucrose.” Each of these sugars is processed by the body a little differently.

Fresh and prepared foods often contain natural sugars and/or processed sweeteners. In moderation, natural sugars can be good for you, but consuming too much table sugar or too many processed sugars or sweeteners can lead to health problems such as weight gain, diabetes and obesity.

How does sugar affect the kidneys?

Sugar is not a problem for the kidneys unless the blood sugar level gets too high. This commonly occurs in both Type 1 and Type 2 diabetes. Once the blood sugar level gets higher than 180 mg/dl, the kidneys start to spill sugar into the urine. The higher the blood sugar, the more sugar comes out in the urine. If your kidneys are normal, this usually isn’t a problem, but if you have diabetes, too much sugar can cause kidney damage.

A common blood test used to detect diabetes and monitor blood sugar levels over time involves the Hemoglobin A1C (HgbA1C) protein. The higher the blood sugar gets, the more sugar gets attached to this protein. Determining the levels of hemoglobin A1C helps to give an estimate of the average sugar level in the blood for the past 3 months and provides an indication of how much damage the sugar may be causing in the body, including to the kidneys. A normal HgbA1C is less than 6% for someone who doesn’t have diabetes. As the HgbA1C gets higher, more damage is done.

Uncontrolled diabetes can damage the blood vessels of the kidney and destroy the kidney’s filters. At this point the kidneys can no longer do their job effectively. When the blood vessels in the kidneys are injured, the kidneys can’t clean the blood properly, resulting in more water and salt being retained and waste materials building up in the blood.