Does a high-protein diet really damage your kidneys?

Author: Zeng Yan, Associate Researcher, Chinese Center for Disease Control and Prevention

Reviewer: Fu Rui, Chief Physician, Beijing Century Altar Hospital, Capital Medical University

In recent years, high-protein diets have been very popular among young people, especially in the ketogenic diet and fitness. However, at the same time, there are news reports that some people have found kidney damage after excessive consumption of protein-rich foods or protein powder. So, does a high-protein diet really damage kidney health? How should we treat protein?

Before answering this question, you need to patiently understand a few issues.

What exactly is protein and why do we recommend supplementing it?

Protein is a biological macromolecule with a certain spatial structure formed by amino acids forming polypeptide bonds through "dehydration condensation" and folding. As the "big brother" among the seven nutrients, it is not only the core component of the body's tissues and cells, but also plays an irreplaceable role in the body's various physiological functions. It can be understood that everyone cannot do without the nourishment of protein every day from coming into this world, getting married and having children, to leaving this world peacefully. But the protein mentioned here is not just the protein powder in bottles and jars, but more of it comes from daily meals such as meat, eggs, and milk.

What is a high-protein diet and what are its benefits? Can this eating pattern really cause kidney disease?

The so-called "high-protein diet" refers to a diet that adds protein-rich foods to a basic diet. In recent years, as people pay more and more attention to fitness and weight loss, high-protein diets have become more and more popular, especially among young people. High-protein diets account for a relatively high proportion and were even once touted as "the most preferred, healthiest and safest diet in the 21st century."

In addition, many people believe that a high-protein diet is the same as the increase in the proportion of high-quality protein intake advocated in the Dietary Guidelines for Chinese Residents (2022). Is this really the case? In fact, this understanding is wrong. The latter recommends that the proportion of high-quality protein foods, such as poultry, eggs and milk, should be appropriately increased under the premise that the total energy and protein intake account for a relatively fixed proportion of total energy. Generally speaking, the Dietary Guidelines for Chinese Residents (2022) recommends that adults also consume 280 to 525 grams of poultry meat per week. A high-protein diet is different. It aims to increase the absolute total amount of protein intake, including the proportion of protein intake to total energy. Even in some ketogenic diet concepts, the proportion of protein in the total daily energy intake is as high as 20% to 25%. This helps to enhance immunity, accelerate metabolism, and promote calcium absorption and utilization. However, in real life, many people add protein powder to their daily diet and take it for a long time because they are worried about insufficient protein intake or for the purpose of fitness and weight loss, or eat a lot of high-protein foods such as beef, chicken, and eggs. These practices have clearly exceeded the scope of a reasonable diet.

Figure 1 Copyright image, no permission to reprint

So, does a high-protein diet really cause kidney disease?

Although there is no direct evidence to show that there is a causal relationship between excessive protein in the diet and kidney disease, more and more studies suggest that the risk is high. An epidemiological survey conducted by the Harvard School of Public Health in the United States believes that a high-protein diet is good for heart health, but it also points out that the higher the better.

Researchers from Leiden University in the Netherlands selected patients with stable myocardial infarction and collected their dietary data through a dietary questionnaire. They found that those with higher daily protein intake had a glomerular filtration rate that decreased twice as fast as those with lower daily protein intake [1]. Related research in South Korea [2] found that protein intake may be an independent risk factor for renal hyperfiltration, which accelerates the deterioration of renal function. Excessive protein intake can cause a sharp increase in glomerular blood flow and glomerular filtration pressure. If this condition persists for a long time, it can lead to chronic damage to the glomeruli, fibrosis, and mesangial cell proliferation. These studies suggest from different perspectives that excessive protein intake may pose a health risk to the kidneys, and people with underlying diseases need to be more careful.

In daily life, especially for patients with underlying kidney diseases, how can they supplement protein to be healthier?

According to the 2023 edition of the Dietary Reference Intake of Chinese Residents issued by the Chinese Nutrition Society, daily protein intake should account for 10% to 20% of total calories. Among them, for adults under 65 years old, it is recommended that men should consume 65 grams of protein per day and women should consume 55 grams of protein per day; for the elderly aged 65 and above, it is recommended that men consume 72 grams of protein per day and women consume 62 grams of protein per day; for those with diabetes, especially those with abnormal renal function, they should supplement according to the doctor's advice. For example, according to the Health Industry Standard of the People's Republic of China "Dietary Guidelines for Patients with Chronic Kidney Disease" (WS/T557-2017), the daily protein intake of patients with stage 1 and stage 2 chronic kidney disease should be 0.8 to 1.0 grams per kilogram of body weight, and patients with stage 3 and stage 4 chronic kidney disease should be determined according to specific circumstances.

Figure 2 Copyright image, no permission to reprint

A reasonable diet is still the primary source of protein, such as meat, eggs, milk, etc., and it should be diversified. For the elderly and other special groups with severe protein deficiency, protein powder and other supplements can be appropriately selected, but they need to follow the doctor's advice.

In addition to excessive protein intake, some dietary patterns also pose certain health risks, such as a single dietary structure, low-carbohydrate, low-fat and other patterns. Compared with a balanced diet, these dietary patterns have a simple food structure and incomplete nutrient supply, which can easily lead to nutrient deficiencies in the human body. Taking a low-carbohydrate diet as an example, Professor Li Duo's team found that this dietary pattern is not only not conducive to weight control, but also causes an increase in the levels of various inflammatory factors in plasma. In addition, there are studies that believe that a low-carbohydrate diet may shorten a person's life expectancy.

In short, any nutrient supplement needs to follow the principle of appropriateness, just like a "double-edged sword". Nutrient deficiency can lead to malnutrition, and excessive intake can also cause harm. Therefore, it is recommended that everyone eat a diversified diet and "eat" healthily.

References

[1]Kevin Esmeijer, Johanna M Geleijnse, Johan W de Fijter, et al. Dietary protein intake and kidney function decline after myocardial infarction: the Alpha Omega Cohort[J]. Nephrol Dial Transplant, 2020, 35(1): 106-115.

[2]Jong Hyun Jhee, Youn Kyung Kee, Seohyun Park, et al. High-protein diet with renal hyperfiltration is associated with rapid decline rate of renal function: a community-based prospective cohort study[J]. Nephrol Dial Transplant, 2020, 35(1): 98-106.