Dietary treatment for kidney stones
Kidney stones occur when the urine is saturated with waste products that can crystallize into stones or when the chemicals that normally inhibit this crystallization process are absent. The most common type of stone contains calcium with either phosphate or oxalate. Some kidney stones contain uric acid, and these are more common in people with gout.
The goal of nutritional treatment is to eliminate the diet-related risk factors for stone formation and to prevent the further growth of existing kidney stones.
The importance of fluids
First, and most importantly, a regular intake of plenty of fluids is essential for people with stones. This will dilute the urine, thus reducing the concentration of stone-forming substances in the urine. It is also very important to drink plenty of extra fluid in hot weather and when on holiday in a hot climate. Water is the best choice for maintaining fluid levels.
On the other hand, a moderate intake of alcohol, coffee, and tea may help reduce the risk of kidney stone formation, presumably, to the diuretics effect of the caffeine in these beverages. A daily intake of 3-3.5 liters (about 5-6 pints) of fluids is recommended.
Maintain calcium intake
Most calcium stones are not, in fact, attributable to a diet high in calcium-rich food. It is important to maintain a moderate calcium intake if you suffer from kidney stones. This is because a low intake may promote the formation of calcium oxalate stones. A calcium intake of approximately 600-800mg per day is recommended for people with kidney stones.
Cut out high oxalate foods
A reduction in dietary intake of foods containing high levels of oxalate is important for susceptible people, since this is an important factor in the formation of calcium oxalate stones. Vitamin C supplements should also be avoided by people at risk of kidney stones since this vitamin can break down to oxalate, which is excreted in the kidney.
Restrict animal protein
A high intake of animal protein is acidic and increases the excretion of urinary calcium. In addition, the binding effect of sulphate in dietary protein decreases kidney calcium reabsorption. Therefore, it is recommended that people with kidney stones should limit their intake of animal proteins from meat, fish, poultry, and eggs to 60-70g per day.
Reduce sodium intake
A high intake of sodium increases calcium excretion, which can result in an increase in calcium-containing crystals in the urine. A reduction of high-sodium foods is therefore recommended, with an intake of no more than 2-4g per day.
High-sodium foods include most canned, processed, and packed foods. Check the labels, any food that has a sodium content greater than 400mg per serving is considered to be high in sodium.
It is also advisable for people with kidney stones to reduce their intake of simple sugars and products made from refined flour (such as white bread, cakes, and biscuits), in favor of whole-grain foods, such as wholemeal bread and pasta and brown rice, which are high in complex carbohydrates as well as eating more fruits and vegetables.