Kidney Stones Nutrition & Dietetics Department What Are Kidney Stones? Kidney stones can be caused by a high concentration of crystals in the urine. These include oxalate and urate, which can also be found in normal urine. They do not normally cause problems when present in low levels, but can form crystals and predispose to stone formation at higher concentrations. These stones in the kidney may travel down the urinary tract and can cause pain or blood in the urine. Smaller stones may be passed out; but larger stones can obstruct urinary flow, and may then require further treatment or procedures. Your doctor will advise on the appropriate treatment you require. The common types of kidney stones are: calcium oxalate or calcium phosphate.
Other types of stones include: struvite stones, uric acid stones and cystine stones. What Are The Symptoms? Symptoms of kidney stones may include: • Severe flank pain • Pain on urination, in the lower abdomen or groin • Pink, red or brown urine • Cloudy or foul smelling urine • Persistent urge to urinate • Fever and chills, if infection is present However, some urinary stones may not cause any symptoms at all.
Lifestyle Factors The following lifestyle factors increase your risk of kidney stones: • Inadequate fluid intake • Excessive intake of protein and sodium • Being obese (BMI >23) The following dietary recommendations may reduce the risk of kidney stone formation. Stay well hydrated Drink 2-3L (8-12 cups) of fluid daily to ensure good urine output and prevent accumulation of minerals in the kidney. You are recommended to take fluids with higher citric content, and to minimise intake of carbonated drinks. If weight is of concern, limit the intake of all higher calorie drinks. Examples of drinks with high citric content include:
Lemonade
Orange juice
Choose foods lower in sodium Consume fresh food and limit your processed or preserved food intake. Examples of these types of food are:
Fresh food
Processed or preserved food
Consume a moderate amount of protein Limit your protein intake to 2-3 servings a day. Examples of 1 serving are:
90g Fish / poultry / meat (palm size)
2 glasses of milk
170g of beancurd
5 medium prawns
120g of cooked beans / lentils
Consume adequate calcium Calcium from food does not increase the risk of kidney stones, and individuals should opt for calcium-rich foods instead of supplements. Do not intentionally reduce dietary calcium intake as an inadequate amount of calcium will also result in deficiency conditions such as osteoporosis. The table below shows the recommended calcium intake for normal healthy persons: Category mg/d 10 – 18 years old 1000 19 – 50 years old 800 51 years and above 1000 Pregnant and lactating 1000
It is recommended to have 1 serving of a high-calcium dairy product daily. Examples of 1 serving are:
200ml milk
200g yoghurt
1 slice of cheese
170g of beancurd
Reduce foods high in oxalate Reducing the intake of oxalate-rich foods can reduce the chance of stone formation. Examples are:
Beetroot
Figs
Nuts & seeds
Chocolate products
Spinach
Caffeinated drinks
Yishun Health is a network of medical institutions and health facilities in the north of Singapore, under the National Healthcare Group. Admiralty Medical Centre • (65) 6807 8000 • www.admiraltymedicalcentre.com.sg Khoo Teck Puat Hospital • (65) 6555 8000 • www.ktph.com.sg Yishun Community Hospital • (65) 6807 8800 • www.yishuncommunityhospital.com.sg The information is correct at the time of printing and subject to revision without further notice.
URO.PE.06.1020