Many people think of the kidneys as simple filters and instinctively assume that the “better” they filter, the healthier they are. But what happens when the kidneys work too fast and with excessive intensity?
In this talk, we discuss how what appears to be good kidney function can actually reflect overload, reduced oxygen supply, and, over time, even permanent damage. We also look at the role of high blood pressure, salt and fluid intake, diet, and modern lifestyle factors—connections that are rarely addressed in routine clinical conversations. If you want to understand why a “nice-looking” lab value can be misleading on its own, it’s worth reading on—or watching the full video.
The content of the video in written form
Hello, this is Dr. Zsom.
They are patients, well, we stated before that the kidney is a complex organ, not just a filter. Yet today, we are mainly going to focus on the filtering capacity of the kidney. Why is that? Well, it turns out that the filtering capacity of the kidney correlates very closely with something that is very important, and that is the excessive function, the exhaust, and the subsequent exhaustion of the kidney.
So when is it that the kidney is functioning too well, too much? Well, let’s imagine that we have a filter right here, and that filtration process is going to be dependent on the pressure that the filter is seeing. Now, if we increase this pressure, then the filtration process is gonna be faster, right? So the same thing happens in the kidney. There is this little small blood vessel, okay, and this is the glomerulus, the filtering unit of the kidney. And so what happens is that if the pressure here is very high, then the kidney is going to filter, all of a sudden, too much, too fast, okay.
So what happens is that the kidney is trying to protect itself against this pressure, and what happens is that the kidney is capable of keeping its filtration, by various compensatory mechanisms, relatively stable over a range of blood pressure. However, if the blood pressure is greater than a given number, then this defense is overwhelmed, okay, and the kidney is gonna work very hard. Now, the problem is that even this not 100 percent effective defense mechanism is going to be less effective if you have vascular disease. So for instance, if you have diabetes, you have hypertension, or any kind of disease that affects blood vessels, then you’re gonna see that this protective mechanism is not going to be perfect and the more your pressure, the more your filtration, okay. So what’s going to happen is that the filtration capacity is going to be a function of the actual pressure that the filtering unit of the kidney sees, and the same thing happens with arterial hypertension, in other words, the high blood pressure.
So here’s what happens: you have a high blood pressure result like this, okay, and blood pressure too rapidly affects filtration. So filtration is going to be too fast, excessive. And if you maintain the state of affairs for decades, then what’s going to happen is that the kidney is just going to tire out. Why is that? Because filtration is a highly oxygen-demanding process, okay, and sooner or later the oxygen supply just simply cannot keep up with the demand. And so what happens is that there’s going to be hypoxia, so low oxygen concentration in the kidneys, and certain poisons will then—reactive oxygen species, etc.—accumulate in the kidney, and that’s going to hurt the integrity of the cells that participate in the filtration. And because of that, you’re going to have damaged cells, scarring, and then gradually the filtering unit is not going to function that well anymore, and scarring and deficient function is going to mean that not only the filtration will be affected but all functions of the kidney—in other words, you have a true chronic kidney disease here.
So one of the very important factors that can accelerate kidney function is hypervolemia. Now, whenever we talk about hypervolemia, we think about too much fluid in the body and that, of course, causes high blood pressure. But when you have hypervolemia, so too much fluid in the body, it is generally not just water, you see. The human body does not contain pure water; it is a solvent and it has a lot of things that are very important that are dissolved in this water. And one of the many things that is very closely regulated that is in water is salt, okay. So the non-cell part of the blood is called plasma, and the plasma contains about 90 grams for each one liter of water, okay. So this is about as much as Baltic Sea water, okay. So blood does not contain simply water, but it contains a lot of solutes, and one of the most important and most tightly regulated of these solutes is salt, sodium salt. Since salt and the salt-to-water ratio, otherwise known as sodium concentration, is very closely regulated, therefore hypervolemia is directly related to salt intake, okay. So salt always draws water; water comes with salt. The two things are inseparable, okay.
So here’s what happens: if you eat salt, you are going to be thirsty, you know, unless you are very old, unless you are very sick, unless you do not have access to water because of whatever reason—you have disability or whatever. So you will be thirsty and you will drink water depending on how much salt you ate, okay. Now, so there is a common misconception here and even a misnomer; okay, we call hypervolemia “hyper hydration,” a state of affairs where the human body contains a lot of fluids, and we concentrate on fluids. But this fluid is not water, okay; this fluid is salt and water, okay. So “high fluids” really mean high water and salt, and this works both ways. So in other words, when you have hypervolemia, that means that you have high water and salt in the body.
Now, to explain what exactly happens when you have hypervolemia, we need to look at a hose, okay. So a hose is made out of a flexible material, okay, and so the more fluid is inside the hose, the more there is going to be tension in the wall, okay. Now the same is happening in the blood vessels, except the fact that this fluid is not just water, it’s salt and water. So the more salt and water you have inside your blood vessels, the more tension is going to be created by excessive fluid. But that is even more important in situations when you have various blood vessel problems such as vascular disease due to hypertension, due to diabetes, or simply old age, because then the wall is less flexible, more rigid, okay. So the more volume you have, the more blood pressure you have; the higher blood pressure you have. So salt draws water through thirst with only a few exceptions, right, like we talked about, okay. And so what happens is that when you have too much fluid, then sooner or later the blood vessels, because of the tension inside the vessel walls, are going to be damaged, you develop high blood pressure, and this high blood pressure then is going to translate into what—excessive function of the kidney.
Now when we talk about fluids helping, okay, improving kidney function, then first of all, we always talk about salt and water, not just water. Second, it is situations when you have hypovolemia, so you start off by decreased kidney function due to inadequate amounts of salt and water in your body, such as what happens in diarrhea, vomiting, profuse sweating because of excess heat, or you have an infectious disease and you sweat a lot, okay. So in these situations, then, of course, fluids—that means salt and water—are going to be very, very helpful restoring the kidney function, okay. But when you are not dehydrated, and this is a misnomer—dehydrated means you don’t have enough salt and water, okay—then if you then drink a lot of fluid, okay, a process called iatrogenic polydipsia (so doctor-induced too much drinking), then what you are going to have is that you are not gonna change your kidney function, okay. Or if you eat a lot of salt, then you are gonna overwork your kidneys, okay. And whenever you have either kidney disease or heart disease already, and if you drink too much, that’s gonna hurt your heart and your kidney. So pushing fluids is useful when you are at risk for dehydration, okay, but when you have a normal amount of salt and water in your body and you push too much fluids, while then either you just push water in, in which case nothing much is gonna happen, or you push salt and water in, in which case you are gonna have kidney disease on the long run. And if you already have kidney disease and/or heart disease, then you are gonna just hurt that process even more.
So let’s talk about for a minute of what happens when you just drink too much water without salt. So if you drink too much water without salt, that’s not going to change your filtration capacity, that’s not gonna overwork your kidneys. What is happening—but it’s also not going to help your kidneys—it’s just it doesn’t do anything. The thing that it does, however, is that what’s going to happen is that your kidney is going to be very dilute all the time, okay, because the kidney just dumps unnecessary water, okay, through a mechanism by which the small water channels in the kidney are permanently open. But in this case, the problem is that you start losing the concentrating capacity of the kidney; so if you don’t drink too much water anymore, you just can’t concentrate your urine, okay. You lose that capacity, but the filtering capacity of the kidney is not going to be affected, okay. And here we come to a very interesting concept, okay: more urine does not equal more filtration, okay; it’s just that simply the excessive water is dumped, and so the water volume inside the urine is more, but the filtration is the same, okay.
So here is an example to what happens if you eat too much salt, okay. And so this is a personal experience that I had in Shreveport, when candidates were getting a transplantation came to me and said, “Well, we have this family member or this friend and we want to give one of our kidneys to this person because he or she is on dialysis.” And so they were convinced that they were very healthy and their kidneys were perfect, okay. So what happened was, as it turned out, that they really every single day they went to the steakhouse, they ate a lot of protein. And so here’s what I found: well, you are healthy, okay, fine, but it’s protocol to check your kidney function, and we are checking your kidney function not by simple labs but by sophisticated methods measuring filtration. And so what we found that in a lot of these healthy people, okay, they were hyperfiltering, okay, so their filtration was excessive, and with that they started having protein in the urine, okay. So remember the little mouse in the previous lecture, okay, who for another reason—metabolic syndrome—had too much filtration and therefore had protein in the urine. Well, the same thing is happening now because of excessive protein and salt, okay.
So let’s investigate that a little bit. So if you eat too much animal-based protein and if, on the top of that, you also eat a lot of salt—and remember that one of the most ancient preservatives in human history is salt, okay—then what’s going to happen is that both the protein, which increases pressure in the small vessels in the kidney and therefore in the filtration unit of the kidney, and salt, which increases blood pressure by inducing hypervolemia and also affects the microbiome (the gut bacteria flora) and the blood vessel walls, okay, inducing inflammation in blood vessel walls—so what happens is that they have an additive effect. So animal protein and salt have an additive effect increasing filtration, destroying the capacity of the kidney protecting it against the effects of high blood pressure and increasing the pressure inside small blood vessels inside the kidney, okay. So what happens is that you are—your kidney is running a marathon all the time for years and years and years. And so both animal protein and salt increase filtration and lead to protein in the urine, okay, when consumed in excess. And what happens is that on the long run, and you have additive effects of organic acids and a lot of other things, sooner or later your kidney—the kidney tissue, the kidney cells, okay—is going to be affected by this.
So here is the dream food for kidney disease, okay. So what happens is you have corn syrup which causes metabolic syndrome—we remember the little mouse, right? We have trans fats which is very good for storage, in other words, for industrial food production; okay, it‘s very good that you have fats that are solid on, you know, common room temperature. So what happens is that they put a lot of hydrogen into these fats so that they are solid, so that they are easy to store and transport, okay. But these cause blood vessel damage, okay. You have salt which causes dysbiosis, in other words, changes in the gut flora, and vascular inflammation, so inflammation in the small blood vessels. You have an animal protein with increased kidney pressure; small arteries in the kidneys have increased pressure because of animal protein. And you have phosphate, organic acids, preservatives, coloring agents and others. So you have highly processed industrial food in this—so what happens is kidney disease, you guessed.
So here is something that was published in a very prestigious internal medicine journal more than 15 years ago, and so the idea is that for hundreds of thousands of years, okay, people used to eat a more plant-based diet with more potassium, less salt, less animal and heavy grain protein, less acid, less fat. They have more exercise, they had less caloric intake and more fiber, okay, and basically they eat fresh, fresh food. So these ancient humans had very low blood pressure, very low cholesterol, and no proteinuria. So the modern man—and this process definitely accelerated in the last 40-50 years, okay, but this is a process that happened already about 10,000 years ago, okay—changed their diet. Okay, so modern humans eat more animal-based protein, more wheat-based protein, okay, more salt, too much, too much calories, mass-produced industrial sugars, refined sugars, industrial chemicals. They’re congested in small urban areas with a lot of stress, okay. And so what’s gonna happen? Normal blood pressure is already high for what the humans are really used to for hundreds of thousands of years, okay. They have normal cholesterol, which is really high, especially triglycerides, for what people were used to, and they often have proteinuria, especially if they eat too much, okay.
So here’s what happens: what happens is that there are certain things that we know are associated with chronic kidney disease, okay: salt intake, less potassium intake, animal-based protein, fats, organic acids, etc., okay. And so therefore sudden changes cause an acceleration in a process that ultimately results in kidney failure, and we are talking about true kidney disease here, not just temporary changes in lab results. So hyperfiltration, excessive work by the kidney, results in—of course we’re talking about years and decades of exposure—high pressure inside the small kidney blood vessels and that causes stretch and that causes ultimately scarring, okay. Scarring is blue on a kidney biopsy specimen here and it’s white on the ultrasound. And so what this means is that there’s true damage to kidney cells, and when there’s chronic damage to kidney cells, their function—and I’m talking about all functions of the kidneys—sooner or later, okay, it goes lower and lower and lower, and you have a chronic process called chronic kidney disease, okay. Generally it makes up the few situations like diabetes. This results in shrinking of the kidneys, so you have shrunk small kidneys and you have the decline of all functions of the kidneys, and this eventually causes need for renal replacement therapy: dialysis or transplantation.
So the next time we are going to talk about what happens when the kidney filters less and what that means in kidney disease and in the absence of kidney disease. But here we are talking about kidney disease which is really often caused by initial hyperfiltration—so excessive work of the kidney—and it is often characterized by the appearance of proteinuria, so protein in the urine, okay, and that’s why we always should screen for protein. But more on that later. So for now, thank you for your attention and goodbye for now.
