Dietary management of kidney stones
18 Mar 2017 - 12:35
Our kidneys filter waste products from blood and add them to urine for removal. When the waste in urine does not dissolve completely, crystallisation occurs. Eventually crystals grow in size to form renal stones. Stones usually develop within the kidneys but can migrate down the urinary tract. They might even pass out in urine if sufficiently small in size.
Renal stones may be painless or can be associated with severe pain and urine outflow blockage when they are sufficiently large. Stones usually affect people between the ages of 20 and 40, men more often than women. In more than half of people, renal stones recur after one episode, if preventive measures are not taken.
Kidney stones are usually made up of more than one type of crystal. Identifying the predominant type of crystal in the stones (Stone analysis) helps in determining the cause for stone formation.
Different types of stones are:
1. Calcium stones: Composed of Calcium oxalate, and is the most common type. Oxalates are found in some fruits and vegetables like dark green vegetables, nuts, berries and chocolate.
2. Struvite stones: Found more inwomen and arise with frequent urinary tract infections.
3. Uric acid stones: a byproduct of protein metabolism, commonly seen with gout, and may result from hyperurecemia, fructose consumption and certain genetic conditions where uric acid production by the body is increased.
4. Cystine stones: Comprise a small percentage of kidney stones; these are the result of cystinuria, a hereditary disorder that causes kidneys to excrete massive amounts of certain amino acids.
Appearance of renal stones can be reduced and maybe even eliminated with adequate dietary and lifestyle changes. Diet Therapy is usually tailored to the type of stones involved and the patient’s dietary habits. Current general dietary recommendations are:-
1. Drink plenty of water. Total fluid intake per day must reflect as a daily urine output of about two liters. This keeps the urine sufficiently dilute enough to prevent crystallization and stone formation.Drink a cup of fluid (250mL) each hour during waking hours, and a glass of water before going to bed. Drink a glass of water if you wake up during the night.
2. Add 100ml of Lemon juice in daily intake as the citrate in them prevents stone formation. Reduce soft drinks to not more than one liter (4 glasses)per week, as the Phosphoric acid used in them predisposes to stone formation.
3. Daily calcium intake is to be maintained at 1,000–1,200 mg per day. Reduction in Calcium levels increases free oxalate levels. Include calcium in diet as a glass of calcium fortifiedmilk, a small cup (200ml) of yoghurt, or 2 slices of cheese.
4. High-sodium diet strigger kidney stones. Daily intake should not exceed 2.3gm. Buy fresh foods, or foods without salt. Most extra sodium come from processed foods which are best limited, e.g. soup, processed meat, sauces, gravy, crisps etc. Do not add salt at the table or in cooking.This is also good for your blood pressure and heart.
5. Reduce daily intake of animal proteins, such as meat, seafood, fish,chicken, eggs to a moderate serve (120-150g) daily (cooked) Eating too much animal protein, such as red meat, poultry, eggs, and seafood, boosts the level of uric acid and could lead to kidney stones. A daily protein take should be no bigger than a pack of playing cards.
6. Avoid supplements if you have a tendency to form stones, like Vitamin C (Ascorbate),Vitamin D supplements or cod liver oil.
7. Choose whole meal and wholegrainfoods which duce stone formation by reducing the calcium and oxalates that you absorb.
Most kidney stones will pass on out their own without medical intervention, but in some cases, such as if a stone blocks the flow of urine, damages kidney tissues, or is simply too large to pass on its own, more aggressive treatment may be needed.
There are several surgical techniques that can be used to treat kidney stones, but they are generally reserved for advanced cases.Your physician will best advice you on what is needed as per your condition.
Dr Deepak Chandramohan is an MBBS MD (Internal Med) Physician Internal Medicine, who works for Naseem Al Rabeeh Medical Center