Why Protein is Not Bad for Your Kidneys
Since Doctor Atkins popularized the Low Carb Way of Eating, detractors and critics have continuously proclaimed, "Yer gonna kill yer kidneys!". This has been a particularly thorny criticism to refute because of the biology involved, so most of us have had to counter by pointing out the fact that no patient or adherent who started with healthy kidney function has ever sustained kidney damage through a ketogenic diet. This statement is true enough, but not exactly conclusive.
Where did the idea come from in the first place? It came from the very real association between ketones in urine and kidney damage suffered by diabetics. When a diabetic is in the more severe stages of the disease, his blood sugar is grossly elevated, his metabolism is vastly compromised, large amounts of aceto-acetic acid are found in his urine, and sure enough, there is frequently severe or even fatal kidney damage. The reasonable mind associates the presence of ketones in the urine with kidney damage; and the reasonable mind is wrong. To understand why, we must (briefly) examine how the kidney does its job.
The kidney is a size-exclusion filter (just what it sounds like). A small filtering unit called a glomerulus (about 6 million of them per kidney) is fed a stream of blood. Small molecules such as glucose, salts, urea, and ketones, along with all sorts of other (small) waste products, are filtered out of the blood through small pores and drained off to the bladder. The issue is a good bit more complicated than I am presenting here, but the principal is real. Small stuff is filtered out through these pores, while larger molecules are retained in the blood stream. When all is normal, an excess of protein is not harmful in any way. Proteins are *big* molecules, and will not fit through the pores. When a person's blood glucose levels are grossly elevated, many bad things happen; one of which is the formation of gluco-protein complexes in the blood. Glucose has a slight positive molecular charge, and the pores are negatively charged, so glucose will fit though and flow through the pores in the glomerulus. If that glucose molecule is dragging a protein with it, the protein end of the complex gets stuck in the pore. Blood pressure behind the protein will quite frequently shove the protein through the pore, physically damaging the pore in the process. Multiply this scene by several million times, and severe kidney damage is the result.
What does this mean? The protein did the damage, right? Yes, but it would not have done that damage if it weren't stuck to the glucose molecule. And the gluco-protein complex would not have formed if blood glucose levels were normal or near normal. The conclusion then, is obvious. If you are concerned about your kidneys, monitor your blood glucose levels. Many stores sell blood glucose monitors at reasonable prices. It's a small price to pay for something which can tell you exactly what is happening in your body, and just maybe save your life. And no, you don't have to be diabetic to buy one.
So now you know what to say when someone says, "yer gonna kill yer kidneys eating all that protein!" You can tell them that is a bunch of baloney; the sugars and starches kill the kidneys, not the protein.
Copyright © 2002, By Walter Dees. Used with Permission.