Kidney stones affect an estimated 11% of men and 6% of women in the United States. These hard deposits that can form inside the kidneys can be caused by many factors, including a high-protein diet.
Understanding the link between high-protein diets and kidney stones can help you make the right nutrition choices—especially if you meet risk factors for kidney stones.
What Causes Kidney Stones?
Kidney stones develop when high levels of calcium, oxalate, and phosphorus stay in the urine to form calcified stones. These minerals are already present in urine and do not cause problems when their levels are low. However, if you lack enough fluid in your urine to dilute these minerals (such as due to lack of water intake), hard deposits can form known as kidney stones.
What Is the Link Between Protein and Kidney Stones?
There are many types of kidney stones, but the type of kidney stones linked to high-protein diets are known as uric acid stones.
Uric acid is the byproduct of a natural chemical compound called purine. Purine is naturally found in red meats, organ meats, and shellfish. When you eat foods with purine, your body breaks it down into uric acid. Uric acid then leaves your body in urine.
If your purine intake is high, your body will produce more uric acid. Your kidneys will then need to work harder at expelling uric acid from the body. A high concentration of uric acid promotes the formation of kidney stones, especially when it is not well diluted in your urine.
If you eat a diet high in foods that contain purine, you may be at greater risk of developing kidney stones.
Which High-Protein Foods Can Cause Kidney Stones?
The only high-protein foods linked to kidney stones are those with high levels of purine. Other foods that are high in protein, like Greek yogurt, eggs, nuts, and seeds, contain low levels of purine and are generally safe to eat in moderation if your goal is to prevent kidney stones.
High-protein foods to avoid if you want to prevent kidney stones include:
- Red meats, including bison, venison, and beef
- Organ meats, including liver, tongue, and sweetbreads
- Shellfish, including shrimp, crabs, and lobster
- Sardines
- Anchovies
- Meat-based sauces and gravies
If you are diagnosed with kidney stones, ask your doctor about the type of kidney stones you have and find out whether restricting certain high-protein foods is necessary.
Other types of kidney stones—such as calcium stones—are driven by foods that contain high amounts of another naturally occurring compound called oxalates. If you have calcium stones, you should focus more on restricting high-oxalate foods such as spinach, peanuts, and chocolate.
How Much Protein Can I Eat With Kidney Stones?
The amount of protein you can safely eat if you have kidney stones will depend on the protein source. High-purine foods should be avoided or consumed in very small amounts. In general, you should aim to eat no more than 80 g of protein per day if you have kidney stones.
The best thing you can do is consult your doctor. Your doctor can talk to you in greater detail about nutrition and diet and may even refer you to a nutritionist or dietitian who can work with you to create a healthy meal plan for kidney stones.
Tips and Diet Recommendations For Kidney Stones
You can take many other diet-related steps to treat and/or prevent kidney stones, including:
- Drinking more water. Water helps dilute the crystal-like substances in your urine that can lead to the formation of kidney stones. Consider squeezing citrus fruits like lemons or oranges into your water because they can help prevent stones from forming. Aim to drink around two to three quarts of water per day.
- Reducing your salt intake. Eating too much salt can increase the amount of calcium in your urine, which in turn, can increase your risk of developing calcium stones.
- Using calcium supplements with caution. Calcium supplements have been linked to the formation of kidney stones. However, you may be able to avoid this risk if you take your supplements with meals. Your doctor can talk to you in more detail about calcium supplements and kidney stones.
- Avoiding high doses of vitamin C supplements. Taking at least 1,000 mg of vitamin C a day could lead to higher amounts of oxalate in your body. Limit yourself to the recommended amount of 60 mg of vitamin C a day.
Make an appointment with your doctor right away if you have symptoms of kidney stones or if you think a high-protein diet is putting you at risk. Symptoms of kidney stones include pain while urinating, cloudy urine, and sharp pains in your back, lower abdomen, or groin. Your doctor can perform an examination and discuss your available treatment options.
Resource Links
- “Definition & Facts for Kidney Stones” via National Institutes of Health
- “Symptoms & Causes of Kidney Stones” via National Institutes of Health
- “Kidney Stone Diet Plan and Prevention” via National Kidney Foundation
- “High protein diet brings risk of kidney stones” via National Institutes of Health
- “Protein Restriction Guidelines for Kidney Stone Formers” via University of Michigan Health System
- “5 steps for preventing kidney stones” via Harvard Health Publishing