Protein is essential for muscle growth – but how does it affect the kidneys? Here’s what science says.
Most of us now understand that a high-protein diet plays a central role in muscle growth, maintaining muscle mass, and overall health. As we get older, we benefit even more from an adequate intake of protein sources to prevent muscle loss. However, one question keeps coming up: can too much protein harm the kidneys?
A 2018 meta-analysis published in the Journal of Nutrition by the American Society for Nutrition tackled this very topic, comparing studies on protein intake and its effects on kidney function in healthy adults. The researchers aimed to find out whether increased protein intake actually poses a risk for kidney disease, or if such assumptions are outdated myths.
The Role of Protein in Our Diet
Before diving into the study results, let’s first address why protein is such a crucial part of our diet. Protein is an essential nutrient, composed of amino acids that act as building blocks for tissues, muscles, hormones, and immune cells. A high-protein diet not only supports muscle growth and recovery after exercise but also helps regulate body weight, as protein has a satiating effect. To consume enough protein, many people turn to high-protein foods or supplements like protein powder and protein shakes.
Athletes and active individuals often focus on a high protein intake, aiming for around 1.5 to 2 g of protein per kg of body weight per day. This amount is now widely recommended by experts such as nutritionists, even though it greatly exceeds the German Nutrition Society's (DGE) minimum recommendation of 0.8 g per kg of body weight. Naturally, this raises questions about how a higher protein intake might affect our body, and specifically kidney function, over the long term.
The Study Overview: Is Protein Harmful to the Kidneys?
The analysis from Canada included 28 studies with 1,385 participants to compare the effects of low, normal, and high protein intake (from both animal and plant sources) in healthy adults. The "glomerular filtration rate" (GFR) – a key parameter for assessing kidney function – was measured as the endpoint. The GFR indicates how effectively the kidneys filter blood and eliminate waste products such as albumin and urea.
The analysis showed that in healthy individuals, a high-protein diet led to a slight increase in GFR, without negatively impacting kidney function. The observed increase in filtration rate is simply a natural adaptation of the body to higher protein intake, and does not necessarily mean the kidneys are under strain – they are simply performing their normal function. For comparison: during pregnancy, GFR also increases – by around 65%!
What Do These Findings Mean for Nutrition Advice?
The findings of this meta-analysis provide reassurance for anyone looking to follow a high-protein diet. For people without existing chronic kidney disease, an increased protein intake does not harm the kidneys. So, we can enjoy our protein intake without concern – as long as it’s part of a balanced diet and with adequate fluid intake.
However, for those with chronic kidney disease, protein intake should be adjusted in consultation with a doctor or dietitian, as the kidneys in these cases are more sensitive to high protein intake.
Long-Term Effects and Conclusions
In summary, a high protein intake is safe for healthy individuals and has no adverse effects on kidney function. The study emphasises that even long-term high protein intake does not have significant negative effects on kidney disease markers such as the glomerular filtration rate. Those on a high-protein diet can therefore rest easy: a high-protein diet does not harm the kidneys.
Getting enough protein for one’s health and muscle growth brings positive effects without endangering kidney health. Protein-rich foods or protein shakes like our WAM Protein can be a convenient way to meet protein needs and help you achieve your fitness goals.
Sources
[1] Devries MC, Sithamparapillai A, Brimble KS, Banfield L, Morton RW, Phillips SM. Changes in Kidney Function Do Not Differ between Healthy Adults Consuming Higher- Compared with Lower- or Normal-Protein Diets: A Systematic Review and Meta-Analysis. J Nutr. 2018 Nov 1;148(11):1760-1775.
