KIDNEY STONES

WAYS TO PREVENT OR SLOW KIDNEY STONE FORMATION

Stone analysis is important to determine the chemical composition of the stone.
A urine collection over 24 hours is used to determine the chemical composition of the urine that is increasing the risk for kidney stone formation.  

General Principles.
For rational see below.  
(1) Dilute urine by drinking fluids.
(2) Increase citrate excretion in the urine.  
(3) Reduce acid in urine to prevent most kidney stones (NOTE: some stones form in alkaline urine)
(4) Reduce the chemical that is shown to be in high concentrations in the 24 hour urine collection.

Your doctor and / or nutritionist will discuss specific details with you based on results of blood and urine tests as well as stone composition analysis

**INCREASE FLUID INTAKE
This will dilute the urine and prevent precipitation of chemicals to form crystals and / or stones.

Volumes to drink and timing:
-Drink enough fluids to produce at least 2 liters of dilute urine a day.
-Drink throughout the day and before going to bed and whenever you wake up at night.
-One may need to drink more than 2 liters a day if there are other sources of fluid loss e.g.  sweat or diarrhea.
-A good estimate that the urine is dilute is when it is colorless or light yellow in color.

Types of fluids:
Drink
-Water is the safest drink to hydrate and reduce urine concentration. Some advocate to avoid certain bottled water brands if they have high sodium content.

-Non-sweetened juices help reduce risk of stone formation as they contain citrate which blocks stone formation.

-Orange juice contains potassium and citrate. Both have been shown to reduce risk of kidney stone formation. Avoid orange juice if kidney function is reduced to avoid high potassium levels in the blood. 

Do Not Drink
-Avoid drinking carbonated drinks as they were shown to increase the risk of kidney stone formation for the following reasons:
(1) They have a high sugar content that can promote stone formation
(2) They contain acid (e.g. phosphoric acid in dark colored drinks) that will acidify urine. The acid may also leach calcium out of the bones and cause thinning of bones. It may also irritate stomach lining and cause ulcer disease.

-Avoid alcoholic beverage. Some studies have shown alcohol to increase the risk of stone disease. 

No Harm Shown:
-Coffee and tea have a negligible effect on urinary oxalate excretion. Drinking tea and coffee (including decaffeinated) have been shown in some studies to lower risk of stone formation

-Cranberry juice effect on oxalate concentration and urine acidity has been variable in different studies. However there are no studies that show that cranberry juice can cause stone formation.

**ADEQUATE DIETARY CALCIUM INTAKE NOT calcium supplements.
-Avoid dietary calcium restrictions. Calcium in the diet binds to oxalate in the intestines and prevents its absorption and excretion in the urine. This way oxalate concentration will be low in the urine and will not be available to bind calcium to form stones.
-It is recommended to eat several servings of dairy or other calcium-rich foods to obtain calcium intake of 800 to 1000 mg daily.
-Calcium supplements, especially if they are taken without food, have been shown to slightly increase the risk of stone formation.

**AVOID HIGH ANIMAL PROTEIN INTAKE 
-High animal protein diet has been shown to increase the risk of stone formation.
-Metabolism of animal protein will increase acid production and excretion in the urine which will encourage formation of certain stones such as uric acid and calcium oxalate.
-High animal protein diet (particularly nondairy animal protein) will also reduce level of citrate in the urine which inhibits the formation of stones.  
-Dairy protein has been shown to reduce risk of stone disease by increasing urine citrate excretion and lowering urine oxalate excretion.
-High animal protein intake (dairy or non-dairy) increases urine calcium excretion.
-Of note, vegetable protein has no effect on stone formation.

**REDUCE SODIUM INTAKE to 100 mEq daily (2 gm sodium, 5 gm salt).
Calcium in the kidney follows sodium. If sodium intake is low, it will be absorbed in the kidney and returned back to the blood, and calcium will follow passively. This will reduce calcium concentration in the urine and hence risk of precipitation to form stones.

**INCREASE FRESH FRUITS AND VEGETABLE INTAKE
Fruits and vegetables contain potassium and citrate both of which were shown to reduce risk of kidney stone formation.
-High potassium intake will reduce acidity of the urine and may reduce excretion of calcium in the urine. High potassium diet has been shown to reduce risk of stone formation. Avoid high potassium intake if kidney function is reduced. 
-Fruits and vegetables especially citrus fruits also contain citrate, a known inhibitor of stone formation.
-Use juices with no added sugar since high sugar intake predispose to stone formation.

**REDUCE HIGH OXALATE CONTAINING FOOD especially if urine oxalate and/or calcium concentrations are high in calcium oxalate stone formers.
-Calcium oxalate stone formers may absorb a higher proportion of dietary oxalate.
-Foods that are very high in oxalate include nuts, beets, chocolate, spinach, and rhubarb.

**REDUCE HIGH URIC ACID CONCENTRATION IN THE URINE in uric acid stone formers or those with high uric acid concentration in the 24 hour urine test.
Uric acid may form a nidus for the formation of other stones.
-Uric acid is formed from purines. Some foods or beverages may promote uric acid formation
-Avoid organ meats (e.g. liver)
-Avoid shellfish, alcohol
-Avoid sugar sweetened beverages especially those with sucrose and high fructose corn syrup.
-Crash diets may increase uric acid levels in the urine.

**INCREASE PHYTATE INTAKE
-Phytates (bran, beans and legumes, etc.) have been shown to reduce risk of stone formation in the Nurses’ Health Study II.
-Calcium oxalate crystal formation is strongly inhibited by phytate under laboratory conditions.

**REDUCE SUGAR INTAKE, INCLUDING SUCROSE AND FRUCTOSE 
-Oral glucose load has been shown to increase urine calcium excretion.
-Higher fructose intake has been associated with higher risk of kidney stones.
-Higher insulin levels (caused by high sugar intake) may lead to higher urinary calcium excretion.  

**CHECK WITH YOUR DOCTOR BEFORE USING SUPPLEMENTS 
-Reduce vitamin C supplements especially in people who form oxalate stones. Vitamin C is metabolized into oxalate.
-Reduce vitamin D supplement especially in people who form calcium stones.
-Avoid fish liver oils as they may promote stone formation.
-B6 may help people who have high oxalate in the urine.

**MEDICATIONS may be prescribed by your doctor to reduce certain chemical concentration in the urine based on the 24 hour urine assessment.
Certain medications help reduce calcium or uric acid in the urine.
Other medications help increase citrate and alkalinity of the urine. 

 

OTHER SOURCES OF INFORMATION

      UpToDate: Kidney stones in adults (beyond the basics) 

      National Kidney Foundation: Kidney Stones 

      National Kidney Foundation: Crush Those Kidney Stones with Good Nutrition

      Harvard.edu: 5 steps for preventing kidney stones