Stone, Diet, and Evidence?
Now that you have been diagnosed with kidney stones you must be inundated with all sorts of advice regarding the kind of diet that you should take. Although well-meaning, most of such advice may not be correct. We have compiled a few facts which are backed by scientific evidence to guide you in your dietary restrictions.
About taking milk and dairy products?
Stopping intake of milk may actually increase the chances of stone formation! Kidney stones are most commonly formed of calcium oxalate. A fall in calcium levels in the intestine leads to increased availability of oxalate which can be absorbed. This leads to increased oxalate in the urine and subsequent increase of calcium oxalate stone formation in the urine. Therefore, if you have been assiduously avoiding milk and dairy products, start taking some milk or curd! Calcium tablets, if prescribed by other doctors, should not be taken on an empty stomach, when there is no food with oxalate in the intestine. Then there will be an increase in calcium absorption which can predispose to stone formation. So calcium tablets should be taken with food.
About taking spinach?
Spinach is supposed to have high oxalate content. Spinach means different leaves for different people. Patients are often told to avoid spinach completely. Studies have shown a very small effect on stone prevention with low oxalate diets. Intake of spinach, in the usual quantity in an Indian diet is unlikely to have an effect on stone formation.
Can we eat tomatoes?
There are no studies to prove that tomatoes increase the risk of stone formation. In fact, what we do know is that fresh tomato juice is a rich source of citrate! Intake can therefore only be beneficial. The belief that seeds from tomatoes form a nucleus for stone formation is a classic case of grandmother`s medicine. Free and home-made, but of little value!
What about eating meat?
Animal proteins are known to reduce citrate and increase calcium in the urine. Citrate protects against stone formation. Thus, urinary changes after an animal protein intake predispose to stone formation. Short term dietary protein restriction has been proven to improve the urinary milieu.
It is a good idea for non-vegetarians to limit their dietary intake to not more than 0.8-1.0 g/kg/day.
Can I take carbonated soft drinks?
Phosphoric acid in colas and the high sugar content in most carbonated drinks can lead to stone formation. It is best to avoid these completely.
How much water to be consumed?
Stones are nothing but a conglomeration of tiny crystals. These crystals start forming when the water in the urine can no longer hold the crystals in solution. The simplest and the most decisively proven intervention to prevent stone recurrence is to stay well hydrated. The question is how much water is enough? It is recommended that you drink enough water to maintain a urine output of 2 liters/day.
What about lemonade juice?
Citric juices are a natural choice for preventing recurrent stone disease as consumption will increase fluid as well as citrate intake. Citrate in orange is complexed mainly by potassium, whereas citrate in lemon juice, with high citric acid content, is accompanied by protons, hence not conferring the alkalinizing load that orange juice provides. These Protons in lemon juice reduce its effectiveness in preventing stone disease. Orange juice has a more beneficial effect. (9, 10) Having said that, the consuming the fruit is better than consuming its juice.
Here is a summary of what we believe is sound advice for stone formers:
All stone formers should follow some common sense preventive measures. The main focus of these is normalization of dietary habits and lifestyle risks. A common sense approach to diet should be taken, i.e. a mixed balanced diet with contributions from all food groups, but without any excesses. Drink enough fluids to ensure a urine output of 2 Liters/day. Intake may vary depending on whether you work in an air-conditioned office or in a farm land laboring under the hot sun. Another important point to be kept in mind is that water intake must be distributed throughout the day. There is little point in drinking one liter at a go and then allowing oneself to get dehydrated during the rest of the day. It has been our experience that individuals keeping religious fasts are prone to recurrent stones. Fasting, in essence, dehydrates the body and results in concentrated urine. Such a situation is ripe for stone crystals to deposit in the urine. Once this process is triggered it progresses slowly but surely to formation of a stone. Therefore fasting is to be given up if you are a stone former. What you drink is also important. pH neutral beverages are recommended. Adequate water intake is the one most important measure in prevention of stones. If you desire to add fruit juices, orange juice is more beneficial than lemonade. Juice will have reduced fiber content compared to the fruit and added sugar in the juice will have a negative effect as it increases calorie which increases the calcium content in the urine. Cold drinks must be avoided completely. Fortunately or unfortunately (depending on your perspective) beer consumption does not help in stone passage or in prevention of recurrence.
A diet rich in vegetable fiber is good for stone formers. Generous portions of fruits, vegetable and fiber are beneficial. Salt intake restriction to 4-5 grams/ day is recommended. However the ubiquity of salt in a typical Indian diet makes it impractical to try to limit salt. Junk food with its high calorie and salt content must be avoided. You do not need to convert to vegetarianism if you are non-vegetarian but limit your intake to one or two pieces of chicken, mutton or fish in a day. Even if you eat meat once a week you still need to restrict intake during each meal as sudden changes in urine parameters after intake of large amounts of animal protein can result in crystal formation as well as crystal growth.
In patients who are obese, weight loss does help to reduce the chances of stone recurrence. Adequate physical activity with a balancing of excessive fluid loss to maintain hydration is recommended.
If you notice, these steps are no different from what is commonly followed by anyone who leads what we call a healthy lifestyle. Therefore eat sensibly, drink enough water and exercise in moderation. It will keep your heart and muscles healthy and, at the same time, prevent the stone stork from giving you a visit!