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How to prevent further kidney stones from forming:

Kidney stones are composed mainly of calcium, oxalate, phosphate and uric acid. These substances are formed in the body (oxalate and uric acid), or are derived from the food we eat (calcium, oxalate and phosphate).

When these substances are present above a certain concentration, they form crystals which join to form stones. Acidity of the urine promotes some of this activity.

Fluid intake:

The aim is to achieve a urine output of >2 litres a day, spread evenly over the day. This wi ll help keep the urine concentration below that needed for crystals to form.

Drink at least 10 glasses of fluid, 2 glasses every 4 hours during the day, and with meals. Have a glass of water before sleeping at night.

Water is the best fluid. If your drinking water is very hard, boil the water before drinking. Do not use water softeners (as they increase sodium content of the water)

Avoid strong tea, and any herbal teas which are tart.

Calcium intake:

Severe restriction is to be discouraged as it can increase oxalate absorption
Recommended intake: 800- 1000 mg of calcium over 3 meals.

Oxalate Intake:

Oxalate absorption varies. It is best to avoid foods high in oxalate

Salt intake:

High salt intake increases calcium excretion in urine.
Avoid cold cuts, pickles and prepared foods which tend to have a high salt content.
Do not add salt at the table.
Recommended intake: <3000 mg daily

Protein intake:

Animal protein increases uric acid production and acidity in kidney cells. The latter will increase

calcium and oxalate excretion by the kidneys, as well as decrease citrate excretion, all of which promote stone formation.

Avoid liver which is high in nucleic acids (which break down to uric acid).

Recommended intake: <100 g protein daily (3.5 oz).


Prepared by: DS Ooi 2005

Last updated on: November 1st, 2017