Kidney stones are a well-known potential side effect of the ketogenic diet. Research published in the Journal of Child Neurology found that among children following the ketogenic diet as a treatment for epilepsy, 13 of 195 subjects developed kidney stones. Children who received potassium citrate supplements in the study noted a decrease in the likelihood of kidney stones. It is important to talk to your healthcare professional about supplementation if you are concerned about kidney stones.
Eating a lot of animal foods on the ketogenic diet can lead to more acidic urine and an increased risk of kidney stones. This acidic state can also worsen the progression of chronic kidney disease. In addition, a review of multiple randomized controlled trials concluded that low-carb diets were more effective than low-fat diets in reducing blood pressure and other cardiovascular risk factors, at least over the course of 6 to 12 months. At Diet Doctor, we recommend that most people consume between 1.2 and 2.0 grams of protein per kilogram of desired body weight, which is a “moderate” or “adequate” protein intake.
A more recent meta-analysis of 12 RCTs found no evidence that low-carb diets are harmful to kidney health, even in people with type 2 diabetes. Even for those who don't follow a low-carb diet, evidence suggests that people who eat more protein do not increase the risk of kidney disease. The following observational study reported that those who consumed higher amounts of protein had a significantly lower risk of developing kidney disease. Most kidney stones are composed of calcium oxalate or calcium phosphate (80%).
The stones formed by uric acid and struvite constitute the remaining 9% and 10%, respectively. Very rarely, and usually only in families with genetic risk, stones are composed of cystine (~ 1%). In addition, it has been found that people who regularly form kidney stones have a higher risk of future high blood pressure, chronic kidney disease and end-stage renal failure. Kidney stones have been reported in children with epilepsy using special, highly restrictive versions of ketogenic diets, but potassium citrate supplementation may reduce the risk of kidney stones by five times.
In addition, a meta-analysis of clinical trials and observational studies reported a combined incidence of kidney stones of 5.6% after 4 years on a ketogenic diet. Compared to the incidence of kidney stones in the general population of 0.3% per year for men and 0.25% per year for women, it appears that ketogenic diets may increase the risk. However, the trials included in this meta-analysis mostly included studies that used a highly restrictive version of keto, so we must be careful when extrapolating these data to the general population. Certain contributing factors may increase the risk of kidney stones while on a ketogenic diet, especially if you have already had a kidney stone attack.
These factors include not drinking enough water, eating too many vegetables that are high in oxalate, taking high doses of vitamin C supplements, not getting enough calcium or magnesium, and following a diet that is very high in protein. Published research that actually demonstrates an improvement in kidney function is scarce. However, in a case report, an obese man with type 2 diabetes who switched to a low-carb diet that provided 80 to 90 grams of carbohydrates per day experienced a stabilization of his kidney function, which had been steadily declining over the previous six years. In addition, he was able to stop taking insulin after two weeks of dieting, reducing his body weight by 46 pounds (21 kg), lowering his blood sugar levels and lowering his HbA1c from 9.4% to 6.5%.
The authors concluded that man's stabilized renal function was probably due both to his improved blood sugar control and to the resolution of his obesity. In addition, a moderate to high protein intake against the background of more advanced kidney disease can accelerate the deterioration of kidney function; restricting protein is strongly recommended when the kidneys are significantly damaged. Reducing protein intake to the range of 0.6 to 0.8 grams per kilogram of body weight per day (about 40-50 grams per day), or less than half of what most people normally eat, can slow progression to end-stage renal failure, reduce protein in the urine, delay the onset of symptoms symptoms of renal failure and delaying the need for dialysis or transplantation. Excess protein in the diet has the potential to cause additional stress on the kidneys.
In simple terms, when you eat above a certain amount your kidneys have to work harder to process proteins which can cause small filters in your kidneys called glomeruli to become scarred; if these filters leave scars then your kidney function may decrease over time and your kidney disease may worsen. Very high levels of ketones make your blood more acidic and overload your kidneys as well as forcing them to excrete more sodium, calcium and potassium as well as filter out more by-products from protein metabolism which can lead to low blood pressure another function mediated by your kidneys. Medical News Today reports that one side effect from following a ketogenic diet is forming kidney stones; this is because your kidneys are working hard and being forced to process higher amounts of protein which can lead to additional loss fluid and electrolytes.