How to Prevent Kidney Stone Recurrence

More than 1 in 10 people will experience kidney stones in their lifetimes, most commonly between the ages of 30 and 60. The most common type (and the focus of this article) are calcium oxalate stones, which account for about 80% of cases. Kidney stones have a high rate of recurrence, with about half of those who experience kidney stones having another attack within 5 years. Fortunately, lifestyle changes can be very effective at reducing risk of stone formation.

  • Drink more water. If you are dehydrated, there is a much higher risk of crystals forming in your urine, eventually becoming stones. It is generally recommended that persons susceptible to kidney stones aim for 3 litres of fluid daily.

  • Consume more calcium. Since they are called “calcium oxalate” stones, many people restrict calcium intake for fear of increasing the risk. In reality, the opposite is true. The problem with calcium is when there are high levels in the urine, and this is not caused by ingested dietary calcium. In fact, calcium from food binds oxalates in the intestines, and the two are then eliminated with the stools. This way, oxalates are prevented from reaching the blood and eventually urine. It is particularly important to consume calcium with oxalate-containing foods (more on this later). On the other hand, calcium supplements are generally advised against, as these may increase urine calcium levels.

  • Reduce salt intake. In order for the kidneys to remove salt from the blood (through the urine), they must also excrete calcium in the urine. And as mentioned previously, high levels of calcium in the urine is something we should avoid.

  • Limit non-dairy animal protein. Diary should be included for reasons stated previously, however, other animal proteins (meat, fish, poultry) should be limited. This is due to the fact that when the body is digesting and metabolising these proteins, it produces acid which is excreted in the urine. To balance this acid, the kidneys will excrete calcium as a buffer. In addition, very high intakes of protein can increase endogenous production of oxalate in the liver.

  • Increase fruit and vegetables. High intakes of fruits and vegetables have consistently been associated with a lower risk of stones. A possible reason is that these contain a substance called citrate, which can inhibit stone formation in the urine. Citrus fruits, in particular, contain high levels of citrate.

  • Limit added sugar. Although the reasons are not fully understood, high intakes of added sugars (e.g. from sugary beverages) have been associated with a higher risk of stones.

  • Avoid vitamin C supplements. The liver can make oxalates from vitamin C, and in fact vitamin C supplements have been shown to be a primary contributor of oxalates in the urine. Note that vitamin C from foods should not be limited because as stated earlier, higher intakes of fruits and vegetables are actually associated with lower risk.

  • Limit dietary oxalates. Oxalates are found in a range of foods, and a high intake of oxalates from the diet is known to increase oxalate levels in the urine, making stones more likely to form. There are no official cut-offs for the quantities of oxalate that should be consumed, and generally, complicated oxalate calculations are not needed. Avoiding, or greatly limiting, the foods highest in oxalate tends to be enough: these include spinach, almonds, beets, raspberries, and potatoes. Note that this recommendation is only for persons who have experienced kidney stones in the past. One needs to also be careful with supplements and nutritional powders since these may contain extracts of high oxalate vegetables.

Published by Manuel Attard

Manuel Attard Registered Dietitian & Nutritionist

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