Diet can influence the formation and growth of kidney stones. However, contrary to popular belief, a diet low in oxalates is not always the right solution. Let’s dig deeper into the subject.
Kidney stones, also known as renal lithiasis, urinary lithiasis, urolithiasis or nephrolithiasis, are stones (or a compaction of crystals) that form in the kidneys or urinary tract (ureters and bladder) from minerals that have dissolved in the urine. Most of them (80%) spontaneously eliminate themselves by passing through the ducts of the urinary system. However, the ureters, which are tubes connecting the kidneys to the bladder, are very small ducts. A stone that is formed in the kidney that is in transit to the bladder can easily obstruct a ureter and thus cause severe pain.
Kidney stones can be the result of many factors including low fluid intake, an unbalanced diet, obesity, certain medications or supplements, genetic or metabolic diseases or urinary tract malformations. However, in many cases, there is no specific cause that can explain the formation of stones. There are different types of kidney stones, the most common being calcium oxalate stones (80% of cases). Other types of kidney stones include calcium phosphate, uric acid, struvite and cystine.
People with kidney stones are often told to follow a diet low in oxalates. However, this is not always the right solution. In fact, the changes to make to your diet vary according to the type of kidney stones that you have and their cause. For example, following a diet low in oxalates may help prevent the formation of calcium oxalate stones, but is not helpful for people who have uric acid stones. It is recommended to consult a urologist who can prescribe tests to evaluate your urinary and blood concentrations of various chemical compounds such as calcium, magnesium, sodium and oxalates in order to determine the best prevention strategy for your particular situation. A Registered Dietitian can then help you to adapt your diet according to your doctor’s recommendations.
Calcium binds to oxalates in the intestines, which can help increase the excretion of oxalates in the stools. Thus, a moderate intake of dairy products or substitutes (ex : calcium fortified plant based milk) may be beneficial to help prevent kidney stones. Talk to your doctor about how much calcium you should consume.
Drinking enough water helps to keep the urine well diluted and eliminates particles that can form stones. Not hydrating properly is the main cause of kidney stones. To increase your urine volume (the total amount of urine produced), it is recommended to drink about two liters of fluid a day, or more for those who are physically active or spend a lot of time in the heat. The presence of dark urine with a strong odor is a sign that you are not drinking enough fluid. With adequate hydration, urine will be pale and odorless. A doctor may ask you for a urine sample to determine more precisely how much liquid you should drink. All beverages (water, tea, coffee, juice, etc.) count in the total amount of fluid, but it is preferable to drink mostly water and avoid sugary drinks which are unhealthy. Your fluid intake should be distributed as evenly as possible throughout the day. If your urinary citrate level is low, it may be beneficial to drink lemon water. You can mix 60 ml (1/4 cup, 4 tbsp or 2 oz) of lemon or lime juice with your water twice a day.