Myth vs Fact: Does A High-Protein Diet Really Damage Your Kidneys?

Add as a preferred source on Google

Protein has become the default answer to almost every wellness question, from weight loss to type 2 diabetes. But a quieter question keeps surfacing alongside the high-protein diet: could all that protein be damaging your kidneys?

The answer depends on how much protein you eat, where it comes from, and your kidneys' baseline health.

Photo Credit: Chat GPT

We spoke to Dr Fathima Rejulin Konari, Consultant, Department of Nephrology, KIMSHEALTH, Thiruvananthapuram, who explained how much protein the body needs, when a diet turns high-protein, and who needs to be most careful.

How Much Protein Does The Body Really Need?

Dr Konari began with why protein matters at all.

"We all need protein in our diet every day. Protein builds muscle, helps you heal, fights infection, and keeps you healthy. Protein needs vary based on your age, sex and overall general health."

She then put a number on the basic requirement.

"The estimated average requirement for protein intake in human beings is 0.6 g of protein per kilogram of ideal body weight per day, which corresponds to the amount of protein required to combat the daily protein breakdown," she said.

For context, a review in Nutrients puts the recommended daily allowance for healthy adults at 0.83 g/kg a day.

When Does A Diet Become 'High-Protein'?

There is no single cut-off, but there is a range.

"Most definitions set a threshold between 1.2 and 2.0 g/kg per day. Hence, a diet above 1.5 g/kg protein could be considered a high-protein diet," Dr Konari explained.

That has not slowed its popularity. Yet the doctor cautioned that the trend carries a catch.

"Although high-protein diets continue to be popular for weight loss and type 2 diabetes, current studies suggest that a diet high in protein can affect your kidney function. This is possible in individuals with or without previous kidney disease."

Animal Or Plant: Where Your Protein Comes From

Photo Credit: Canva

The source matters as much as the amount, according to Dr Konari.

"Protein in the diet comes from both animal and plant sources. Animal sources of protein have all the essential amino acids (the building blocks of protein); however, they have a higher amount of fat, with fatty cuts of red meat, whole-milk dairy products and egg yolks being the highest in saturated fat, which is unhealthy for the heart and blood vessels."

Plant sources, she said, offer a different profile.

"Plant sources of protein include beans, lentils, nuts, peanut butter, seeds and whole grains. A plant-based diet can meet protein needs with careful planning by eating a variety of plant-based foods and is considered healthier."

Plant proteins also come with a bonus, she added: they are low in saturated fat and high in fibre.

How A High-Protein Diet Can Strain The Kidneys

So what exactly happens inside the body? Dr Konari pointed to two pathways.

"High dietary protein intake above 1.4 g/kg per day can produce a heavy acid load, which puts a huge stress on the kidney's filtration system, even if you have normal kidney function."

The second is uric acid.

"A diet rich in protein can also cause elevated uric acid levels, which can crystallise in the kidney tubules and cause kidney stones. This damage to the kidneys might or might not reflect in the blood creatinine levels."

Creatinine is a waste product that doctors measure to judge how well the kidneys are working. In other words, a normal result does not always rule out strain.

Who Needs To Be Most Careful

Photo Credit: Magnific

The risk is not spread evenly. Dr Konari said it weighs most heavily on those whose kidneys are already under pressure.

"Consumption of a high-protein diet becomes more relevant in patients who have underlying kidney disease or who have risk factors for developing kidney disease in the future, as in people with hypertension and diabetes. A heavy acid load leads to slow damage of the kidney's filtration barrier and can cause spillage of protein in urine."

Protein quality enters the picture here too.

The quality of dietary protein may also play a role in kidney health. Compared with protein from plant sources, animal protein has been shown to have an increased risk of worsening kidney function in people with kidney disease. Many studies suggest that limiting the amount of protein and including more plant-based foods in the diet may help slow the loss of kidney function.

International guidance leans the same way. The 2024 KDIGO guideline on chronic kidney disease (CKD) suggests 0.8 g/kg a day for adults with CKD stages G3 to G5 and advises against exceeding 1.3 g/kg a day when the disease is at risk of progressing. It also includes a practice point favouring plant-based over animal protein.

When Weight Loss Pushes Protein Too High

Crash plans built on protein and few carbohydrates deserve particular caution.

"We have to be careful when we go on a high-protein, low-carbohydrate diet to induce weight loss. A person with normal kidney function can handle up to 1.5-2 g/kg body weight protein in 24 hours," said Dr Konari.

Research on healthy adults has been reassuring at those levels. A meta-analysis in The Journal of Nutrition, which pooled trials of intakes from 1.5 g/kg a day, found no adverse effect on kidney function, measured by glomerular filtration rate (GFR), in healthy adults. GFR is a measure of how well the kidneys filter blood.

The picture changes at the end, she warned.

"When daily protein intake consistently reaches 2.0 to 3.5 g/kg/day (or higher, as often seen in bodybuilding diets), the kidneys are pushed into a state of chronic, intense workload, and this can lead to permanent damage to the kidneys."

Choosing Protein With Care

For those who still want to try it, Dr Konari.'s advice is to be selective.

"If you want to try a high-protein diet, it is important that you choose your protein with care. Stay away from processed meats. Pick nutrient-rich protein choices such as:"

• Soy protein
• Beans and other legumes such as lentils
• Nuts and seeds
• Fish
• Lean chicken with no skin
• Lean beef and pork
• Low-fat dairy products
• Egg whites

Bottomline

Dr Konari concluded, "Protein is not the enemy. The body needs it every day to build muscle, heal and fight infection. What matters is how much you eat, where it comes from and how healthy your kidneys already are. For anyone with hypertension, diabetes or kidney disease, a high-protein diet is worth discussing with a doctor before it becomes routine."

Disclaimer: The information provided in this article is for general informational and educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or a qualified healthcare provider with any questions you may have regarding a medical condition.