To maintain balance in the human body – so that we neither lose nor gain weight, can work, and have enough energy – a minimum of 0.6 grams of protein per kilogram of body weight is necessary. If we consume less than that, the body will begin to break down muscles. For example, a person weighing 70 kilograms needs to eat at least 40-45 grams of protein per day, says nephrologist Dr. András Tislér. However, the professor from the Department of Internal Medicine and Oncology at Semmelweis University adds that the international recommendation for protein intake is 0.8 grams per kilogram of body weight per day. For the previous example of a 70-kilogram person, this would mean 50-60 grams.
In Western societies, people consume more protein than necessary on a daily basis: A typical diet includes approximately 1-1.2 grams of protein per kilogram of body weight, partly from animal and partly from plant sources.
In other words, if you eat protein-enriched foods or protein powders as dietary supplements, these will increase your intake even further, to around 2 grams per kilogram of body weight, which is higher than necessary, the university professor points out.
He adds that, in healthy individuals, a slightly increased protein intake will not have any adverse health effects. This is because proteins are broken down into amino acids in the intestinal tract, which are then absorbed and used as building blocks for the body to produce its own proteins. This is a cyclical process: Proteins break down after a certain period of time, and the decomposition products of amino acids are removed by the kidneys in the form of nitrogenous substances, primarily urea. However, in chronic kidney disease, the kidneys are unable to excrete these substances, resulting in elevated urea levels in the blood.
The physiological effect of increased protein intake and thus amino acid absorption is that it intensifies the work of the small filters in the kidneys: If the body has received a lot of protein, it perceives that it needs to excrete more urea, so it starts working even harder. Amino acids therefore place an increased excretory workload on the kidneys. – Dr. András Tislér
In other words, if someone eats a lot of protein, it puts extra strain on the kidneys because it constantly forces the kidney filters to work harder than they can handle, but after a while, this response starts to damage the kidneys, explains the professor.
He adds that in people with healthy kidney function, a daily protein intake of 120-130 grams is not expected to cause kidney damage in the long term, but patients with chronic kidney disease are advised to reduce their protein intake to below 0.8 grams per kilogram of body weight, the nephrologist points out.
However, athletes and bodybuilders consume extreme amounts of protein, primarily through a diet rich in protein (e.g., chicken breast and eggs) and through protein powders. For them, daily protein intake can be as high as 3-4 grams per kilogram of body weight, amounting to over 200-300 grams total. The higher the intake, the greater the burden on the kidney filters.
“It often happens that those who focus so intensely on bodybuilding use not only protein as a dietary supplement, but also other substances such as creatine, vitamin complexes, or even anabolic steroids and sometimes diuretics, which together increase the risk of developing kidney disease,” warns Dr. András Tislér.
Certain life stages require higher protein intake
There are certain stages in life when our bodies need increased protein intake, such as infancy, pregnancy, or over the age of 65. In infancy, protein needs can be as high as 1.4 grams per kilogram of body weight, but at this stage, babies get the right amount from breastmilk or breastmilk substitutes. During pregnancy, protein need increases by about 10 grams per day in the second trimester and by an average of 20 grams in the third trimester. Over the age of 65, due to the natural decrease in muscle mass and changes in protein utilization, you should aim for an intake of 1 gram per kilogram of body weight. It is important to take into account your current protein intake, as excessive consumption may mean that it is not necessary to increase the amount even in these conditions, emphasizes Bernadett Dudás-Batu. The dietitian at Semmelweis University points out that protein supplements are only necessary if the recommended intake cannot be achieved through food alone. However, before starting to take supplements, it is advisable to consult a dietitian to determine the appropriate quantity and quality for your individual needs. If you have a chronic illness or are pregnant, it is essential to consult your doctor, too.
Orsolya Dávid
Translation: Judit Szabados-Dőtsch
Photos by Boglárka Zellei – Semmelweis University; cover: iStock.com/nortonrsx
