When we talk about chronic diseases, two of the most mentioned would be type 2 diabetes and cardiovascular diseases. However, there is another that does not receive much attention, which is strange, since 10% of the world's population suffers from it. That would be chronic kidney disease.
Living with kidney disease can be incredibly painful and complicated, and most people who do suffer from it eventually require dialysis or a kidney transplant to survive.
As with many chronic diseases, kidney disease can develop through diet. That is why we must be very careful with what we eat. There has long been an idea that protein can damage the kidneys. However, this is not the case, and healthy people should not worry about consuming protein. Sugar, on the other hand, can be the real enemy of your kidney health.
The function of your kidneys
The kidneys don't have a particularly impressive job. These filter waste from your blood and direct it into your urine to remove it from your body. If this function is not performed correctly, you will not be able to regulate the balance of salt and other electrolytes in your body, keep your blood at the correct pH or have a normal blood pressure.
This is extremely important, even if it is not something that people constantly pay attention to. When the kidney is working well, you hardly notice it, everything seems normal and even automatic. But if it doesn't work right, you're in big trouble. So, what is the role of diet in all of this?
Do proteins contribute to kidney disease?
Before we explore any other topic, let's tackle the old myth that protein is bad for the kidneys. The idea that protein causes kidney damage seems logical at first glance. When your body breaks down protein, it produces certain wastes in the process.
If these waste products remain in the blood, they are very dangerous, which is why the kidneys filter them into the urine. The more protein you eat, the harder your kidneys have to work to filter the by-products. The symptoms of chronic kidney disease and kidney failure are primarily caused by a lack of excretion of protein by-products.
All of that can make it seem like protein is somehow stressful on the kidneys, and that you could give your kidneys a break by eating a lower protein diet.
But for healthy people who don't have kidney disease, eating a high-protein diet shouldn't really harm the kidneys. Eat more protein; your kidney will adapt to the increased workload. A Cochrane review concluded the following: changes in kidney function from eating a high-protein diet are not a cause for concern.
There is some evidence that people who already have kidney disease may improve on a low-protein diet. For these people, their kidney function is already impaired and their kidneys may not be ready for the kind of adaptations needed by having a higher protein load.
But that doesn't mean that a low-protein diet prevents kidney disease in healthy people. I mean... there is a lot of evidence to suggest that people with an allergy to eggs can improve by avoiding consuming them, but that doesn't mean that everyone should avoid eggs for fear of developing an allergy.
If you already have kidney disease, see a doctor. It is very possible that the doctor will tell you to eat a low-protein diet or some other type of diet (there are all kinds of diets for the kidneys, depending specifically on your problem). But if you don't have kidney disease, rest assured that there is no evidence that eating protein will harm you.
Sugar is the real danger
Simply put, eating protein does not cause kidney disease or damage the kidneys in healthy people. But there is another potential enemy to consider here: sugar and refined carbohydrates. Sugar and refined carbohydrates damage the kidney indirectly, through diabetes and liver damage.
Diabetes and kidney disease
We will start with diabetes. If you already know something about diabetes, the term “diabetic nephropathy” may sound familiar; this is the fancy word for kidney failure caused by diabetes. Diabetic nephropathy is the most common cause of kidney failure in the US, and as rates of diabetes continue to rise, it will become increasingly common.
How does diabetic nephropathy work? To put it simply, high blood sugar levels caused by diabetes damage the blood vessels in the kidneys. This allows too much protein to pass into the kidneys, so they have to overwork. Ultimately, it prevents the kidneys from effectively filtering waste from the bloodstream.
Eating a diet high in sugar and refined carbohydrates is one of the quickest ways to cause high blood sugar and eventually type 2 diabetes. And this metabolic damage has a huge impact on kidney health.
Liver and kidney health
This is less well known, but still important. Recently, scientists have been investigating the connection between liver health and kidney health. If your liver isn't happy, your kidneys won't be happy either.
Patients with type 2 diabetes and non-alcoholic fatty liver disease are even more likely to develop chronic kidney disease than patients with only diabetes.
The same is true for patients with type 1 diabetes (genetic / autoimmune, also known as juvenile diabetes) and prediabetes. And not just with diabetes - non-diabetic people who have liver disease also have higher rates of developing chronic kidney disease.
· Liver disease can affect several enzymes that in turn affect kidney health.
· It can also affect the gut microbiome in ways that damage the kidney.
· Liver disease can dysregulate several hormonal functions that affect the kidney.
· Liver disease can lead to inflammatory problems that damage the kidney.
Simply put, if you want your kidneys to be healthy, you want your liver to be healthy first. And what do you have to avoid so that your liver is healthy? Fructose! This substance can be particularly dangerous for the kidneys, or at least it is in rats, and even in healthy rats.
Fructose could also be the reason why sugary sodas in particular are closely linked to the development of chronic kidney disease in humans (they are a great source of fructose). It is not like protein, which is harmless unless the kidneys already have previous problems. Fructose is dangerous even in the absence of pre-existing kidney disease.