Did your urologist tell you to follow a low protein diet? Or, perhaps you’ve read that protein is related to kidney stones. This is true! In susceptible people, too much protein can cause kidney stones.
Read on to learn more about how protein can cause kidney stones. And, what you can do about it!
What Is Protein?
Protein is an essential nutrient found in many different kinds of foods. Protein is made of amino acids, which are necessary for your body to function properly.
Protein is found in high amounts in foods like:
- Beef, pork & other red meats
- Fish & Shellfish
- Beans, Nuts & Seeds
One 3 ounce cooked portion of beef, chicken or fish has about 20 grams of protein. A 1/2 cup of beans has about 8 grams.
Protein is also found in vegetables and whole grains in smaller amounts. For example, 1 cup of raw broccoli has about 2 grams of protein. One slice of whole grain bread has about 4 grams.
How Does Too Much Protein Cause Kidney Stones?
Too Much Acid in Urine
Protein, especially from non-dairy animal foods like beef, chicken and fish, produce acid in your body during metabolism. Your kidneys get rid of extra acid in your urine. So, when you eat more protein, your urine will be more acidic. (1)
Fruits and vegetables produce alkali to help neutralize acid. (1) It is a balancing act. Your body absolutely needs some protein to function. But, it is important to eat plenty of fruits and vegetables to help balance acid produced from the protein you eat.
Potential Renal Acid Load (PRAL) is a common way to measure how much acid or alkali a food produces. Dietary patterns with a higher acid load are associated with kidney stones. (3) Learn more about PRAL and kidney health.
Bottom line: Too much non-dairy animal protein, especially without also eating plenty of fruits and vegetables, can increase urine acid and increase the risk of kidney stones in some people.
Lower Citrate in Urine
Eating too much protein can cause kidney stones by lowering urine citrate levels. (2)
Citrate is a powerful inhibitor of calcium kidney stones. It binds with calcium in urine, rendering that calcium unable to bind with other minerals to make a kidney stone. In fact, potassium citrate is a common medication prescribed to people with kidney stones. Potassium citrate can also be found in food.
Citrate is a source of alkali, and helps neutralize acid produced from protein in your diet. When you eat too much protein, extra acid is produced in your liver. To help neutralize that acid, your kidneys keep more citrate in your body, instead of getting rid of that citrate in urine. For kidney stone prevention, we want that citrate to end up in your urine so it can help prevent kidney stones.
Possible Higher Urine Oxalate
Even though animal protein foods do not have oxalate in them, they may increase urine oxalate levels. (6)
Your liver can make oxalate from protein. When you eat too much protein, your liver may be more likely to make oxalate. (7) That oxalate is eventually excreted in your urine, and is one possible reason why high protein diets are associated with kidney stones.
Liver production of oxalate is significant. It accounts for nearly 50% of urine oxalate. (7) This is one of the many reasons it is so important to look at all of the foods you eat for kidney stone prevention, not just those high in oxalate. A focus solely on a low oxalate diet is negligent and potentially dangerous. It restricts many foods shown to be beneficial for health and completely disregards the complex nature of oxalate balance and kidney stone formation.
Higher Urine Calcium
Note: High urine calcium does NOT mean you need a low calcium diet. In fact, a low calcium diet can make calcium kidney stones worse. (10) The relationship between kidney stones, urine calcium and dietary calcium is much more complex. Learn more about calcium and kidney stones.
Type of Protein & Kidney Stones
Protein is not created equal when it comes to kidney stone prevention. Usually, non-dairy animal protein is the culprit if protein is a concern for kidney stones.
Why so specific? Let’s break it down.
Non-Dairy Animal Protein & Kidney Stones
Non-dairy animal protein is specifically called out in the American Urological Association’s recommendations for kidney stones.
This is because animal protein produces more acid compared to protein from plant foods or dairy. (11) Non-dairy animal protein changes urine chemistry in ways that are generally negative for kidney stones such as higher acid and less citrate.
Sources of non-dairy animal protein are:
- Beef, pork & other red meats
- Fish & Seafood
- Game Meats
- Organ Meats
Dairy Protein & Kidney Stones
Dairy is an important source of calcium for people with calcium kidney stones. Eating enough calcium is critical for people with calcium oxalate kidney stones. Dietary calcium binds oxalate in the intestine, causing that oxalate to be excreted in stool, rather than getting absorbed and excreted in urine. (2)
Dairy does not produce the same amount of acid as other animal protein foods. In general, milk and yogurt are neutral in terms of acid load. Most cheese produces a small amount of acid. (11)
Most importantly, diets high in dairy are consistently linked with lower kidney stones. (13)
For these reasons, dairy protein is typically not restricted for kidney stones.
Plant Protein & Kidney Stones
Plant protein is a very good thing for kidney stones! Plant protein foods do not produce acid, so will not change urine chemistry negatively like non-dairy animal protein foods can. In fact, diets that include plenty of plant protein foods, like the Dietary Approaches to Stop Hypertension (DASH) and the Mediterranean Diet, are associated with fewer kidney stones. (14) (15)
Plant protein foods are:
Concerned about the oxalate content in these foods? Make sure you really need to follow a low oxalate diet (not everyone with calcium oxalate stones does!). Also, there are many lower oxalate beans and nuts & seeds!
Frequently Asked Questions
How Much Protein Can I Eat with Kidney Stones?
The amount of protein that is right for you depends on your body size, past medical history, lifestyle and kidney stone risk factors.
If your 24-hour urine test reveals that limiting protein could help prevent kidney stones, a good rule of thumb is to aim for 0.8-1.0 grams of protein per kilogram body weight per day.
For example, a person who weighs 175 pounds (79.5 kilograms) needs about 64-80 grams of protein per day.
This protein recommendation includes protein from all food sources. But, the focus should really be on reducing non-dairy animal protein. It can be helpful to focus on replacing non-dairy animal foods with more plant protein and dairy.
A Registered Dietitian is the best person to help you figure out how much and what type of protein is right for you. You may need more or less protein than the general recommendation.
Does Protein Powder Cause Kidney Stones?
Protein powder can cause kidney stones in susceptible people. As most people are already eating more protein than they need, extra protein from protein powder could easily bring your daily protein total above recommended levels. (16)
Protein adds up quickly. Most protein powder has about 20 grams of protein per scoop. In our above example, this is 27% of protein needed in an entire day. Added to protein from food you eat, protein powder can easily send you way above your daily protein goal. A small 3 ounce portion of chicken has about 20 grams of protein.
Protein powder can also have added sugar and sodium. These things can increase kidney stone risk further.
Does Whey Protein Cause Kidney Stones?
Whey protein powder could also cause kidney stones. Although whey protein is derived from dairy (cheese, to be specific!), it does not have as much calcium as dairy. So, it will not provide the same benefits for kidney stone prevention. Whey protein powder will likely be acid-producing due to its very high protein content, and relatively small amount of potassium, calcium and magnesium.
Just like protein powder in general, whey protein could cause kidney stones by adding excess protein to your diet.
Can Collagen Cause Kidney Stones?
Just like protein powder in general, collagen peptides could cause kidney stones. If collagen protein powder adds excess protein to your diet, it could increase kidney stone risk.
Can I Still Eat Meat?
Yes! A kidney stone diagnosis does not mean you have to be vegetarian. Although, eating a more plant forward diet can be hugely helpful for kidney stone prevention. (13)
If your 24-hour urine test reveals excess protein is a cause of kidney stones, the key is to eat the right amount of protein. If you enjoy meat, poultry, fish or seafood, you can absolutely eat them and still prevent kidney stones. You may just have to eat them in smaller portions, or eat them fewer times per day.
A Registered Dietitian can help you figure out how much meat is right for you!
How Do I Prevent Kidney Stones?
Protein is only a small piece of the puzzle for kidney stone prevention. For effective prevention, kidney stone nutrition must be personalized to your 24-hour urine test results. There is no one-size-fits-all “kidney stone diet”.
Can You Help Me? I’m confused.
Absolutely! Kidney stone nutrition is anything but straightforward. It is different for every single person, depending on your 24-hour urine test results. You do not have to do this alone.
I help people prevent kidney stones and feel confident in their food choices in Kidney Stone Nutrition School!