A low-carb diet can offer a laundry list of health benefits, from weight loss to reducing blood pressure and balancing blood sugar. But as is true with any diet, there are always factors to consider in terms of overall health.
One risk factor that’s been associated with the ketogenic diet is kidney stones. Some claim that the amount of protein this diet contains is too much, while others blame mineral imbalances.
But is there any truth to these claims? While the ketogenic diet is certainly low-carb, it’s not necessarily high protein. And the window of time where mineral imbalance can occur is relatively short.
Let’s take a deeper dive into what kidney stones, are and if the ketogenic diet could be a cause for concern.
Kidney stones are made up of minerals and salts that have not been properly eliminated from your body. They typically start small but can grow larger in size, even filling the hollow structures of your kidneys.
It’s possible for these stones to stay in place and not cause any issues at all. However, if they travel down the tube between your kidney and bladder (the ureter), they can either be eliminated in your urine, or it can become lodged in your ureter.
If the latter happens, the kidneys stones may end up blocking the flow of urine from the kidney and causing pain. Passing a kidney stone can be quite painful, but it typically doesn’t cause permanent damage[*].
Common symptoms associated with kidney stones include [*]:
- Pain in the side and back, and below your ribs
- Pain while urinating
- Pain radiating from the lower abdomen to the groin
- Pink, red, or brown urine
- Nausea or vomiting
- Cloudy urine
- Foul-smelling urine
- Urinating more often or less often than usual
- Fever and chills (if there is an infection)
One of the essential tasks of your kidneys is to remove wastes and fluid from your blood to produce urine. However, if you have too much waste or you don’t have enough fluid, these wastes can build up and produce kidney stones[*].
Kidney stones can come from a few different sources:
Calcium stones are the most common type of kidney stone. Specifically, calcium oxalate stones. While it may sound intuitive that calcium stones could be prevented by taking in less calcium — it’s actually sodium that many healthcare practitioners advise to avoid.
Too much salt in the diet is a risk factor for calcium stones because as your kidneys are working to eliminate the sodium, they reabsorb less calcium. This means that less calcium is transferred from your urine back into your blood and is therefore stuck hanging around in your kidneys[*].
Uric acid is a waste product that your kidneys need to eliminate. If your urine is acidic due to diet or lifestyle factors, it makes it harder for these uric acid crystals to dissolve. Uric acid crystals can also form from eating a diet high in purines, which are found in animal proteins like beef, liver, chicken, pork, and eggs[*].
Struvite stones are a less common type of kidney stone and are related to chronic urinary tract infections (UTIs). Unlike uric acid stones, struvite stones are caused by urine that is too alkaline.
Struvite stones are most prevalent in people with poor bladder emptying or with long-term tubes in their kidneys. These issues can cause a build-up of bacteria which can lead to alkalinity in the urine[*].
Cystine stones are the least common type of kidney stone and are caused by a rare disorder called cystinuria. Cystinuria is an inherited disorder in which the sulfur-containing amino acid cystine leaks into your urine. The excess cystine in your urine can then lead to a buildup in the kidneys — causing kidney stones[*].
Depending on the type of kidney stone, there are lifestyle and diet factors that you can do to prevent them. The important part is to know which type of kidney stone you are trying to prevent, as they all have different causes and therefore require different preventative techniques.
There are several sources that claim that the ketogenic diet can cause kidney stones. Most sources claim that it’s the high protein content on the ketogenic diet that’s responsible for kidney stone formation. However, the ketogenic diet is not high protein — it’s high fat.
In an observational study of over 78,000 women, researchers examined the role of diet in the development of kidney stones. They found direct correlations to kidney stone development in women who were dehydrated, consuming too much sodium, or not consuming enough calcium.
They reported, however, that protein intake did not affect the likeliness of developing kidney stones[*].
On the other hand, an often-cited study conducted on 195 children following a ketogenic diet found that 13 children developed kidney stones. This accounts for 6% of the study population[*].
Oral supplementation of potassium citrate proved to be preventative for this group, hinting at the potential of mineral imbalance.
It’s possible that some unknown factor in the ketogenic diet led to stone formation. However, this percentage is actually closely in line with the lifetime incidence of kidney stones — which is 13% for men and 7% for women[*].
Regardless, there are several factors that could have contributed to the kidney stones in these children.
One important factor to keep in mind is hydration. As you’re transitioning into the ketogenic diet, you will lose some ketones in your urine. This is a natural process that takes place as your body gets used to running on ketones for fuel.
The problem, however, is that when you lose ketones, you’ll also lose some minerals along with them. Specifically, positively charged minerals like sodium. This is due to the fact that ketones carry a negative charge (anion), and therefore need to be extracted along with a positively charged compound (cation).
For most people, this shouldn’t cause an issue. However, it is another reason to make sure your hydration and electrolyte balance is on point while transitioning into keto.
Blood sugar levels are another factor that can contribute to the development of kidney stones (uric acid stone, specifically). This is especially true people with metabolic syndrome or diabetes.
If you are someone who is at risk for kidney stones, it’s important to keep an eye on your nutrient intake no matter what diet plan you’re following. Luckily, there are several natural things you can do to help prevent the formation of kidney stones.
The problem with kidney stones is that they tend to recur. In fact, about 50% of people that form one kidney stone will develop another within the next ten years.
Therefore, if you’ve had a kidney stone before taking steps for prevention should be a health priority for you[*]. Here are six natural ways to prevent kidney stones:
#1 Stay Hydrated
Not drinking enough water, or losing too much water can increase your risk for kidney stones. Fluids are needed to move minerals and wastes through your kidneys. If you are dehydrated, then your kidneys will hold on to too many minerals and stones could form.
In the same vein, overworking your body and producing too much sweat can also lead to inadequate fluid movement through your kidneys. If you tend to sweat a lot, go to hot yoga, saunas, or steam rooms, you’ll want to increase your water intake[*].
#2 Eat Less Sodium
A high sodium diet can be a trigger for calcium stones due to the effect that sodium has on calcium excretion and reabsorption.
When you consume excess sodium, your body also increases its urinary calcium. This causes more calcium to pass through the kidneys — increasing the risk for kidney stones.
One study even found dietary sodium intake to increase the risk of kidney stones 11-60%[*].
Current guidelines recommend limiting sodium intake to 2,300 mg a day. However, if sodium has contributed to kidney stone formation in your past, you may want to drop that number down to 1,500mg a day[*].
#3 Eat Fewer Oxalate-Rich Foods
Oxalates are referred to as “anti-nutrients” because they bind to other nutrients — mostly calcium and iron, and cause them to be eliminated. While most of this binding takes place in your colon, it’s possible for oxalates to bind to calcium in your kidneys as well.
For this reason, dietary oxalates may play a role in the development of calcium stones. Foods that contain high levels of oxalates will increase oxalate excretion in the kidneys. This, in turn, increases the risk of developing calcium-oxalate stones[*].
To prevent these calcium-oxalate stones from forming you can cut back on high oxalate foods. Some foods that are high in oxalates include:
- Cocoa powder
- Sweet potatoes
Although you may be tempted to eliminate these foods altogether, that may not be the answer. In fact, due to the binding nature of oxalates, they are likely to be bound and eliminated in your digestive tract as long as you consume them with other foods.
#4 Avoid Vitamin C Supplements
Oxalates can be found in a variety of foods as mentioned above. However, they can also be made in your body.
In fact, Vitamin C metabolism is one way that your body produces oxalates all by itself, and research shows that high-dose vitamin C therapy can lead to an increase in oxalate generation [*].
In a population-based study that took place over 11 years, researchers aimed to determine if vitamin C (ascorbic acid) supplementation would increase the incidence of kidney stones. Over 48,000 men aged 45 to 79 were recruited, and detailed diet and lifestyle information were recorded.
Over the 11-year time period, the researchers found a statistically significant correlation between kidney stones and vitamin C supplementation. With a two-fold increase in kidney stone risk for men who were supplementing with vitamin C.
It should be noted, however, that the level of vitamin C that correlated with kidney stones was 1000mg a day. What’s more, men taking multivitamins daily did not report statistically significant incidence of kidney stones[*].
#5 Manage Your Blood Sugar
People with metabolic syndrome and diabetes have an increased risk of uric acid kidney stones. This is due to a decreased ability to eliminate ammonium which causes your urine to become acidic.
It’s believed that insulin resistance is the culprit for this reduced ability to eliminate ammonium. Therefore, managing your blood sugar (especially if you have metabolic syndrome) could be an essential component in kidney stone prevention[*][*].
#6 Eat Enough Calcium-Rich Foods
Getting enough calcium in your diet is essential for the health of your bones, heart, muscles, and metabolism. This essential nutrient plays a role in almost every process in your body and provides a critical source of nourishment for your entire body[*].
When it comes to kidney stones, you may be thinking that avoiding calcium would be a good idea. Although that makes sense on paper — calcium intake can actually help prevent kidney stone formation.
When calcium is consumed along with oxalates, it binds with them and pulls them out of your body in your elimination. This helps prevent the buildup of oxalates in your body — especially in your kidneys[*][*].
There are plenty of keto-friendly foods that are also high in calcium. Below are some of the top high-calcium and keto-friendly foods:
- Cottage cheese
- Turnip greens
- Chinese cabbage
- Bok choy
If you’re prone to kidney stones keeping an eye on your diet is essential no matter what diet plan you follow. Whether for genetic reasons or if you’ve experienced kidney stones in the past, being aware of your person susceptibility is an essential part of prevention.
Consuming too much sodium can cause issues with kidney stones due to sodium’s effect on calcium excretion. At the same time, not eating enough calcium can contribute to kidney stones as calcium is essential for binding oxalates. And above all, hydration seems to play a key role in the prevention of kidney stones no matter what the cause.
As for protein, the jury is still out. Some sources say that a high protein diet can contribute to kidney stones, while others deny this claim.
Since the ketogenic diet focuses on low-carb, high-fat, moderate protein, it leaves the protein debate out of the equation.
However, when you’re transitioning into ketosis, dehydration may become an issue. In addition, with the initial loss of ketones in your urine, you may pull out excess minerals as well. For these reasons, it is always important to stay hydrated and to balance your electrolyte intake during the initial phase of ketosis.
If kidney stones have been a problem for you in the past, then working with a keto-informed functional medicine doctor or dietitian could be a good idea as well.