1. Fluids
It is important to drink plenty of fluid, especially in the summer months or when in a warm climate. You should aim to drink enough fluid to produce two litres of urine per day. This usually means drinking two and a half litres of fluid each day. The type of fluid does not really matter although excessive amounts of milk and tea should be avoided as these contain calcium and a stone forming substance called oxalate.  It is particularly important to keep well hydrated at night when urine is normally most concentrated. It is advisable to drink fluids before bedtime and once during the night to prevent the urine becoming too concentrated.

Alcohol, when taken in moderation, is safe in people who form stones. The recommended guidelines are 14 units per week for women and 21 units per week for men (1 unit=125ml glass of wine, half pint of beer or lager, or a single shot of spirits).

3. Sodium
Sodium is a salt found in many foods. The kidney eliminates excess sodium from the body alongside calcium; therefore high sodium diets increase the sodium and calcium levels in the urine. This can predispose to stone formation. It is recommended that patients known to form stones should follow a low sodium diet. This can be achieved by avoiding foods rich in salt, for example, crisps, smoked and tinned foods and instead choosing “low salt” varieties. Salt should not be added to foods during cooking or at the table.

For more information, visit:
http://www.bpassoc.org.uk/information/lifestyle/salt.htm

4. Calcium
In the past, doctors commonly recommended that people with a history of kidney stones restrict calcium intake. More recent studies suggest that this is not advisable and may even be dangerous. Dietary calcium restriction may contribute to the risk of osteoporosis as well as increasing the absorption of oxalate (see paragraph on oxalate stones). Patients who have been shown to have abnormally high calcium concentrations in the blood will require further investigation to find the cause to allow treatment. Unless told otherwise, you should take normal healthy amounts of calcium rich foods in your diet, for example, cheese and milk.

5. Protein
High protein diets may be associated with stone formation. Proteins increase urinary calcium, oxalate and uric acid excretion by making the urine more acidic. It is recommended that patients known to be stone formers should not eat excessive amounts of animal proteins, for example red meat, eggs and cheese. In general, eat more vegetables as vegetable proteins tend to make the urine less acid.

6. Fibre
Fibre is well known to be good for your health. It reduces the absorption of calcium from the gut and so decreases the amount in urine. It can be found in many fruits, vegetables, whole-wheat bread and high fibre cereals. High fibre diets are thought to decrease the risk of urinary tract stone formation.

1. Oxalate Stones
Three quarters of stones contain a substance called oxalate. If your stone contains oxalate, you should avoid foods containing high levels, for example, beetroot, chocolate and cocoa, carbonated drinks, grapefruit, almonds, peanuts, beans, spinach, strawberries and rhubarb.

2. Cystine Stones
It is essential to ensure a high fluid and low salt intake in the presence of a cystine stone. You may be given tablets, for example, penicillamine to prevent stone formation.

3. Uric Acid Stones
Again it is essential to ensure a high fluid intake with these stones as dehydration pays a large part in their formation. Patients with stones containing uric acid should eat less meat, fish and poultry. You may also be asked to make your urine less acidic using tablets. In some cases, your doctor may prescribe a drug called allopurinol to control the level of uric acid in the blood or urine.

4. Triple Phosphate or “Struvite” Stones
These stones are associated with chronic bacterial infections. They are only seen in a small proportion of patients, about 6%. In these patients the urine needs to be kept free of infection and this may require long term antibiotics.

• High fluid intake
• High fibre diet
• Low sodium diet
• Low oxalate diet
• Low animal protein diet
• Normal calcium intake unless specifically told otherwise

Buck, AC (1997). The treatment of renal colic and the medical and dietary management of urolithiasis. Current Opinion in Urology 7: 226-230.

Curhan GC, Willett WC, Rimm EB, Stampfer MJ (1993). A Prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. New England Journal of Medicine 328: 833–8.

Hughes J, Norman RW (1992). Diet and calcium stones. Canadian Medical Association Journal 146: 137–43 [review].

Massey LK, Whiting SJ (1995). Dietary salt, urinary calcium, and kidney stone risk. Nutritional Review 131–9 [review].

Menon M, Resnick MI (2002, Eighth edition). Campbell’s Urology, Edited by Walsh, Retik, Vaughan and Wein. London: Saunders pp 3277-3280.

Parivar F, Low RK, Stoller ML (1996). The influence of diet on urinary stone disease. Journal of Urology 155: 432-440

Saklayen MG (1997). Medical Management of Nephrolithiasis. Medical Clinics of North America 81(3): 785-799.

Shah PJR (1980). Unprocessed bran and its effect on urinary calcium excretion in idiopathic hypercalciuria. British Medical Journal 281: 426.

Marshall RW, Cochran M, Hodgkinson A (1972). Relationship between calcium and oxalic acid intake in the diet and their excretion in the urine of normal and renal-stone forming subjects. Clinical Scientist 43: 91–9.