The ketogenic diet, characterized by high fat, moderate protein, and very low carbohydrate intake, has gained popularity for weight loss and as a treatment for certain medical conditions like epilepsy. While it offers potential benefits, it also presents several risks, including the development of kidney stones. This article delves into the research surrounding kidney stones and the ketogenic diet, exploring the potential mechanisms, incidence, and preventative measures.
Introduction to the Ketogenic Diet
The ketogenic diet, around since the 1920s as a treatment for epilepsy, typically reduces carbohydrate intake to less than 50 grams per day while increasing fat and moderately increasing protein consumption. This metabolic shift leads to the production of ketone bodies, which the body uses for energy instead of glucose. While touted for quick weight loss and other health benefits, the diet's strictness and potential side effects warrant careful consideration. Some find its regimented nature appealing, as it removes the need for calorie counting. However, adherence can be challenging due to side effects, social isolation, and cravings.
Potential Dangers and Side Effects of the Ketogenic Diet
The ketogenic diet has many potential benefits and side effects, with 11 of its potential dangers, which any beginner considering the approach needs to know:
Serious Muscle Loss: Research suggests that individuals on the ketogenic diet may experience muscle loss, even with resistance training, potentially due to the reduced effectiveness of protein for muscle building without carbohydrates. Loss of muscle mass can decrease functional strength and heighten the risk of falls.
Stress on the Kidneys and Kidney Stones: Kidney stones are a well-noted potential side effect of the ketogenic diet, with one past research observing that among children following the keto diet as a treatment for epilepsy, 13 out of 195 subjects developed kidney stones. High intake of animal proteins makes your urine more acidic and increases calcium and uric acid levels. This combination makes you more susceptible to kidney stones, while high uric acid can increase your risk of gout. The ketogenic diet can be dangerous for people with kidney disease, as people with kidney disease often need to consume a low-protein diet, which may not align with the type of keto you’re following.
Read also: Managing Stage 3 Kidney Disease with Diet
Low Blood Sugar Risk for People with Diabetes: While a keto diet may help control HbA1C levels, the diet may also cause episodes of hypoglycemia, which is a dangerous drop in blood sugar. Whole grains are off-limits on the ketogenic diet.
Yo-Yo Dieting: Sticking with such a restrictive diet long-term can be difficult, however, and leave you open to weight re-gain, and the cycle of yo-yo dieting. Chronic yo-yo dieting appears to increase abdominal fat accumulation and diabetes risk.
Dehydration and Electrolyte Loss: The brain’s favorite fuel is glucose, which is most easily created from carbohydrates. In very low carb diets, the brain has to adjust to using ketones from digested fats for energy. To add to this discomfort, your kidneys release more electrolytes as insulin levels fall. The result is the keto flu, which can cause constipation, nausea, headache, fatigue, irritability, cramps, and other symptoms.
Nutrient Deficiencies: When carbohydrate intake is low, fiber consumption tends to be low, too. Another possible nutrient deficiency: potassium, a mineral important for both electrolyte balance and blood pressure control.
Bowel Problems: "Many of the richest sources of fiber, like beans, fruit, and whole grains, are restricted on the ketogenic diet,” says Clark. As a result, ketogenic eaters miss out on the benefits of a fiber-rich diet, such as regular laxation and microbiome support. Indeed, in a long-term study, constipation was noted as a very common side effect in children who were put on ketogenic diets for epilepsy treatment. In addition to constipation, diarrhea can crop up as a side effect of the keto diet - especially in the first few weeks.
Read also: A Review of the Mediterranean Diet in Kidney Disease
Bad Breath: Considered a symptom of the keto flu, your breath on this diet often smells fruity at first.
Menstrual Changes: Periods may become irregular or completely stop on the keto diet because of drops in gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone, estrogen, and progesterone.
Low Blood Sodium: When you start the keto diet, you lose sodium and other electrolytes in the urine due to reductions in insulin.
High Cholesterol and Increased Heart Disease Risk: The ketogenic diet doesn’t put a cap on saturated fat, which has been associated with adverse health effects.
Kidney Stones: A Significant Concern on the Ketogenic Diet
Kidney stones represent a notable risk for individuals adhering to a ketogenic diet. These stones are solid masses formed from crystals that separate from urine and build up on the inner surfaces of the kidneys. Research indicates a higher incidence of kidney stones in individuals following a ketogenic diet compared to the general population.
Read also: Nutrition and stage 2 CKD
Incidence and Prevalence
A meta-analysis of 36 studies involving 2795 patients on ketogenic diets revealed an estimated pooled incidence of kidney stones of 5.9% over a mean follow-up time of 3.7 years. This incidence was observed to be approximately 5.8% in children and 7.9% in adults. The incidence of nephrolithiasis in the general population is reported at 0.3% per year in men and 0.25% per year in women.
Types of Kidney Stones Associated with Ketogenic Diets
The composition of kidney stones in individuals on ketogenic diets varies. Uric acid stones are the most prevalent, accounting for approximately 48.7% of cases, followed by calcium-based stones (calcium oxalate/calcium phosphate) at 36.5%, and mixed uric acid and calcium-based stones at 27.8%. This contrasts with the general population, where calcium oxalate stones are the most common.
Mechanisms Contributing to Kidney Stone Formation
Several factors associated with the ketogenic diet contribute to the increased risk of kidney stone formation:
Hypercalciuria: Chronic metabolic acidosis, a common occurrence on ketogenic diets, decreases calcium reabsorption in the renal tubules, leading to increased urinary calcium excretion.
Hypocitraturia: Acidosis induces the proximal tubules to increase citrate absorption and decrease its excretion. Citrate normally binds urine calcium, lowering its concentration and inhibiting calcium crystallization.
Low Urine pH: Chronic acidosis persistently causes low urinary pH, which facilitates uric acid crystal formation due to lowered uric acid solubility.
Increased Uric Acid Load: The digestion of animal protein produces a transient acidic environment, which results in a lower urine pH, promoting the precipitation of uric stones.
Studies on Ketogenic Diet and Kidney Health
In 2019, studies in animal models of autosomal dominant polycystic kidney disease (ADPKD) showed the extremely positive effects of a ketogenic diet. This finding attracted a lot of attention among nephrologists, scientists, and patients. The change in diet inhibited both cyst growth and the loss of kidney function. A great scientific success. However, until now, data in humans or from clinical studies was lacking. Recently published in the renowned Cell Reports Medicine, the KETO-ADPKD study addressed this issue.
The ketogenic diet leads to a metabolic change in which ketone bodies are formed as a metabolic product, hence the name. In a nutshell, in order to achieve this metabolic shift, the amount of carbohydrates (i.e. sugar) is significantly reduced and the amount of fat in the diet is greatly increased. The bottom line? Yes. This diet was indeed feasible over the three-month period studied. On the ketogenic diet, the kidney volume decreased. However, this difference was not statistically significant. In contrast, kidney function increased over the course of the three months on a ketogenic diet. This result was statistically significant, so we assume there was a real effect. However, KETO-ADPKD only studied the diet for three months.
The only side effect reported more frequently by participants were symptoms of the so-called “keto flu.” This is a well-known phenomenon. In the first few days of the dietary change, participants experienced symptoms similar to an infection, such as headaches or tiredness. These symptoms can also appear in those not affected by ADPKD starting a ketogenic diet. In addition, some patients showed an increase in cholesterol levels (blood lipid levels). Whether this has negative consequences under a ketogenic diet, will need clarification. The duration of KETO-ADPKD was certainly still too short to make a statement about kidney stones. In other studies on ketogenic diets in patients not affected by ADPKD, they occurred more frequently.
In our sample, patients on long-term ketogenic diets showed low bone mineral density, with a significant portion experiencing fractures and kidney stones. In light of this case report, we recommend regularly monitoring the urine Ca/Cr ratio with ultrasonography for further development of renal stones in patients following the ketogenic diet.
Preventative Measures and Management Strategies
To mitigate the risk of kidney stone formation on a ketogenic diet, several preventative measures and management strategies can be implemented:
Fluid Liberalization: Maximizing fluid intake helps to dilute urine and reduce the concentration of minerals that can form stones.
Urine Alkalization with Potassium Citrate: Oral potassium citrate increases urine pH and solubilizes calcium, thereby decreasing the concentration of free calcium available to crystallize.
Dietary Modifications: Switching from animal proteins to plant-based proteins may result in lower uric acid excretion, potentially reducing uric acid stone formation.
Avoidance of Initial Fasting Phase: Modification of the diet regimen to allow small, frequent meals might help decrease gastrointestinal side effects and avoid volume depletion.
Monitoring Urine Chemistry: Periodic urine chemistry analyses to measure the calcium to creatinine ratio, calcium, citrate, and oxalate can help identify patients at risk for kidney stone formation.
Professional Consultation: All patients should discuss dietary changes with the physician and dietician, as the answer depends on a wholistic view of their health and disease state.