Ask the Doctor with Dr. Leslie Spry, MD, FACP
Dr. Spry, our resident doctor, answers your questions about sugar and its impact on the kidneys, as well as the kidney-heart connection.
Q: How does sugar intake impact healthy kidneys?
A: Sugar is not a problem to the kidneys unless the blood level of sugar gets too high. This commonly occurs in diabetes, both Type 1 and Type 2. Once the blood sugar gets higher than 180 milligrams per deciliter, then the kidney starts to spill sugar into the urine. The higher the blood sugar the more sugar that comes out in the urine. If your kidneys are normal, there is usually no problem. If you have diabetes, there is a problem.
Q: How can diabetes damage the kidneys?
A: The higher the blood sugar gets, the more that sugar gets attached to proteins in the body. Indeed, that is how we measure the damage that can be done by sugar in the body is by measuring a protein in the body to which the sugar attaches. We measure a protein know as Hemoglobin A1C (HgbA1C) in the blood and this gives us an estimate of the average blood sugar in the blood for the past 3 months. A normal HgbA1C is less than 6%. As the HgbA1C gets higher, the more damage is done to body proteins including the proteins of the kidney. Other abnormalities associated with diabetes, including high blood pressure and elevated cholesterol levels also contribute to damage of the blood vessel of the kidney and destroy the filters of the kidney.
Q: What is cardiovascular disease and how is it connected to kidney disease?
A: Cardiovascular disease includes damage to the heart and circulatory system, that includes all the blood vessels in your body. Every organ in your body has blood vessels including your kidney. Diseases such as diabetes, high blood pressure and arteriosclerosis (hardening of the arteries) cause heart damage and kidney damage. If one has heart disease, then it is likely that one also has kidney disease. If one has kidney disease, it is also likely that heart disease will also be present. The two diseases are risk factors for each other. Most of the time, you inherit the genetic predisposition to have one of these diseases, so if you have a family history of heart disease, kidney failure, diabetes or high blood pressure, you should also be tested for cardiovascular and kidney disease.