- Preventive Measures for Lithiasis
- Basic Instructions
- How does nutrition affect the risk for renal stone formation?
- What types of renal stones are there?
- Why is it important to identify the type of renal stones?
- How can a physician determine the type of a renal stone?
- How much fluid should we drink to prevent renal stone formation?
- Which liquids protect kidneys from stone formation?
- Which liquids should be avoided?
- How does salt consumption affect renal stone formation?
- How can we limit Sodium intake?
- How do animal proteins in our nutrition affect renal stone formation?
- How does Calcium in our nutrition affect renal stone formation?
- How do Oxalates in our nutrition affect renal stone formation?
- How can we reduce Oxalates in urine?
- Does alcohol affect renal stone formation?
- How do nutritional dupplements affect renal stone formation?
- Does body weight affect renal stone formation?
- Can a Dietician help in the prevention of renal stone formation?
Urine contains salts which, under specific conditions, take the shape of crystals that bind together and form stones (calculi). Stones can be formed either in kidneys (Renal Lithiasis) or in the bladder (Bladder Lithiasis). There are also cases in which a stone may move from the kidney to the ureter (tubule connecting each kidney with the bladder). The most common urinary stones are calcium-based stones: 1/3 of stones are made of Calcium Oxalate, while the other 1/3 are stone containing Calcium Oxalate in combination with Calcium Phosphate. The rest 1/3 are stones deriving from chronic urinary tract infections containing Magnesium Ammonium Phosphate (struvite stones) and Uric Acid (uric acid stones). Lastly, 2-3% are stones of purely genetic origin (cystine stones).
In general, urinary stone formation is favored by: a) insufficient hydration, b) urine stagnation due to obstruction of the kidney, ureter or bladder, c) urinary tract infections and d) genetic factors (in rare cases, e.g. in cystinuria).
- Water is the most powerful weapon against urolithiasis. Our daily water consumption should be least 3 liters, since the eliminated urine output should not be less than 2-2,5 liters/24hours.
- Specialized nutrition is a significant preventive measure for stone formation but is recommended only to those having already a lithiasis history. According to the stone composition, the diet is determined by an Expert Physician or Nutritionist/ Dietician.
- Cutting down on salt reduces the chances of calcium-based stone formation. Reduction of calcium intake is not recommended, for this may promote stone formation and induce osteoporosis.
- Meals with plenty of animal proteins, such as meat and eggs, increase the risk for the formation of uric acid and calcium-based stones.
Nutritional instructions for individuals with Urolithiasis history
Nutrition is one of the many factors probably contributing to stone formation in the kidneys. Other risk factors are heredity, body weight and low fluid intake. From the food consumed, the human body keeps what is necessary and beneficial to use, while a part of waste materials (debris) produced by metabolic processes (digestion) is transferred through blood to the kidneys and eliminated from the body with urine. Some of these substances may form crystals in the urinary tract. In some individuals, these crystals bind together and form stones (calculi). For those already having a lithiasis history, prevention is the top priority. Besides nutritional changes, there may be cases requiring also special pharmacotherapy, in order to avoid the risk of stone recurrence. The first step to prevent lithiasis is identifying the type/ composition of the stone/s.
- Calcium Oxalate stones (30%-35%): the most common type of stones. Some of the oxalates are produced by the body itself, while others are taken up with food intake. Oxalates are organic molecules contained in many vegetables, fruit and dried nuts.
- Calcium Phosphate stones (5%-10%): less common type of stones. The major risk factor for the formation of this stone type is the presence of alkaline urine.
- Magnesium Ammonium Phosphate or inflammatory stones (10%-15%). Major risk factor for the formation of this stone type is the presence of any kind of contamination in urinary tract (urinary infections, pyelonephritis). The primary preventive measure is keeping germs away from the urinary tract. Diet does not seem to affect the formation of this type of stones.
- Uric Acid stones (8%-10%). They are more likely to occur in individuals having persistently acidic urine, due to high consumption of animal proteins and purines [ =organic compound substances found in many different kinds of food, especially in organ meats (offal), fish and shellfish].
- Cystine stones (2%-3%). Cystine stones occur because of a rare genetic disorder allowing cystine -contained in proteins- to pass through kidneys to the urine and form crystals.
By knowing the chemical composition of the stone, the physician can determine the sorts of food that should be avoided and, if necessary, administer the proper pharmacotherapy. For example, limiting oxalate intake through nutrition can significantly help in preventing oxalate calcium stone formation but does nothing substantial for inhibiting uric acid stone formation. However, some nutritional recommendations are common for all types of stones. More specifically, drinking abundant water significantly contributes to preventing all kinds of urolithiasis.
If the patient manages to collect one of the stones discharged with urine, the physician can send it to the specialized laboratory for analysis. The same goes for stones that are removed surgically. The physician may also ask for further examinations to identify values of chemical substances, such as calcium, oxalates, magnesium and sodium in the blood and urine.
The amount of fluid a person should drink depends on the weather conditions and his/her activity level. Individuals with a lithiasis history should drink enough water and other liquids to produce at least 2-2,5 liters of water/day. People working in a warm environment need to drink more liquids to replace fluids lost through perspiration (sweat), especially in the summer. Water helps keeping urine diluted and washing away substances that form crystals in kidneys. Particularly when there is risk for cystine stone formation, a lot of water has to be consumed every day (even up to 4lts/24hrs), in order to dilute the cystine accumulated in urine.
Water offers cheap and calorie-free protection from renal stone formation. According to some studies, citrus drinks (e.g. lemon/ orange juice) prevent stone formation because they contain citrate, which prevents crystal formation. However, there are no large-scale studies confirming these findings. Although citrus drinks may protect individuals from oxalate calcium stone formation, they could be harmful for patients that form calcium phosphate stones. Coffee and tea can be added to the overall fluid intake of every person and have been found to reduce the risk for stone formation; yet, they contain oxalates and therefore are contra-indicated in patients who have a history of calcium oxalate stones. Moderate wine consumption and particularly beer consumption (due to its diuretic action) may also prevent stone formation.
Grapefruit juice and soft drinks, like coke, have been found to increase the risk for stone formation and should be avoided by individuals who tend to form calcium oxalate stones.
Although cranberry juice is often given to prevent urinary tract infection, it should be known that it contains many oxalates.
Salt consists of sodium and chloride. When eliminated from kidneys, sodium contained in salt causes the release of more calcium in the urine. High calcium concentrations in the urine bind with oxalates and phosphorus, and form stones. It is preferrable to reduce salt intake rather than calcium intake. The recommended Sodium daily dose is 2,4mg. Cutting down on salt is crucial for individuals who tend to form calcium oxalate or phosphate stones.
By learning the sodium content in various sorts of food, it is possible to control sodium intake. There are labels on foodstuff packages providing information about the sodium content. Some sorts of food happen to have such a high sodium content that even only one portion may provide a significant part of the recommended daily sodium dose.
Foodstuff containing high amounts of sodium includes:
- tinned vegetables and soups
- processed frozen food
- tinned meat
- typical "fast food" meals
Individuals trying to limit sodium intake should always check for ingredients containing "hidden sodium", such as:
- Monosodium Glutamate (MSG)
- Sodium Bicarbonate (baking soda)
- Baking Powder (containing Sodium Bicarbonate)
- Sodium Phosphate
- Sodium Alginate
- Sodium Nitrate
Meat, eggs and fish contain purines, which are eliminated from the body -in the form of uric acid- with urine. Foods rich in purines are meat organs/offal (e.g. liver) and shellfish. Individuals tending to form uric acid stones should limit meat consumption. Animal proteins may also increase the risk for calcium-based stone formation, for they increase calcium elimination and reduce citrate secretion in urine.
Calcium in nutrition does not increase the risk for oxalate calcium stone formation. Calcium in the digestive system binds to food oxalates, preventing those from reaching kidneys through blood and forming stones. Individuals tending to forming oxalate calcium stones should receive 800mg Calcium/day through their nutrition, not only to prevent stone formation in the kidneys but also to retain their bone density and avoid osteoporosis. A glass of skimmed milk contains 300mg Calcium. Other dairy products, such as yoghurt and cheese, are rich in Calcium. According to some studies, Calcium supplements increase the risk for oxalate Calcium stone formation. Researchers support that Calcium should be taken while reducing oxalate intake through nutrition, to prevent stone formation.
Some of the oxalates in urine are produced by the body. Also, some kind of food rich in oxalates may increase oxalate concentration in urine. Oxalates there bind with Calcium and form oxalate calcium stones.
Many sorts of food and drinks contain oxalates, but only a few of them have been proven to increase concentration of oxalates in the urine, such as:
- Dried nuts
- Soya products
Avoiding the above may help reducing oxalate concentration in urine. It is also necessary to consume food rich in Calcium, which reduce oxalates in urine. Calcium binds with oxalates in the intestine and they are all together eliminated from the body - with oxalates not being able to reach kidneys.
Athough alcohol consumption may increase purine production in the body, studies have demonstrated that individuals drinking excessive beer and wine are more likely to develop stones. Alchohol consumption should be limited to 1-2 glasses/day.
Nutritional supplements containing Vitamin C or D may favor stone formation. Inside the body, Vitamin C can be transformed into oxalates. Physicians recommend that Vitamin C should not exceed 500mg/day for those having urolithiasis history. Calcium supplements should be taken with meals, so that Calcium binds with oxalates contained in food. Individuals who are susceptible to stone formation should consult their physician or dietician before receiving high doses of vitamins or minerals.
Studies have shown that obesity favors the formation of uric acid and calcium-based stones in the kidneys. It is not known whether body loss on its own can reduce the risk for stone formation. However, the combination of body weight, healthy nutrition and physical exercise can surely reduce the risk for stone formation.
YES. As long as the physician completes the patient's screening and determines the cause and type of stones, the Dietician can substantially help by recommending a personal diet to reduce the risk for further stone recurrence. It would be better to ask for help from a Clinical Nutritionist specialized in Urolithiasis.