During the summer, many of us enjoy a good glass of lemonade (or lemon juice) to cool off. And in fact, many doctors recommend it to prevent calcium oxalate kidney stones.
But is lemonade really good for your kidney stones? The answer is, it depends. Read on to learn more.
How does lemonade affect calcium oxalate kidney stones?
A liter of lemonade is usually made with water, 5 lemons, and 100g of sugar. You have the recipe!
Now, if we want to understand how lemonade affects the formation or prevention of kidney stones, we need to understand how each of its ingredients impacts them. Let's look at them one by one.
Water
Drinking water increases urine volume. By increasing urine volume, urinary supersaturation and the probability of stone formation are also reduced. In fact, some clinical studies conclude that with every 200 ml of water (1 glass), this probability is reduced by almost 13%.
Lemon
Lemon has two compounds that affect kidney stones: citric acid and vitamin C.
- The citric acid in lemon is converted into citrate in the body. This citrate binds to calcium in the urine, reducing the amount of calcium available to bind to oxalate and form calcium oxalate stones.
Approximately 30% of a lemon's weight is extracted as lemon juice. And of this juice, approximately 6% is citric acid. Considering that each lemon weighs approximately 100g, we can extract 100 x 30% x 6% = 1.8g of citric acid per lemon.
Therefore, in one liter of lemonade made with 5 lemons, we would ingest 5 x 1.8 = 9g of citric acid. Unfortunately, only a few milligrams of citrate from these 9g of ingested citric acid will reach the urine, with little capacity to bind to calcium and prevent kidney stones.
A recent published study (Doizi, et al., 2018) demonstrates that citric acid consumption does not significantly increase citrate in the urine.
- On the other hand, the vitamin C in lemon is converted into oxalate in the body. Every 100g of lemon provides about 50mg of vitamin C.
Therefore, 1 liter of lemonade made from 5 lemons would provide 250mg of vitamin C.
Another famous study (Ferraro, Curhan, Gambaro, & Taylor, 2016) demonstrates that consuming more than 750mg of vitamin C significantly increases the risk of forming kidney stones. Therefore, be careful with consuming 3 liters of lemonade, as excessive vitamin C can be counterproductive.
Sugar
In general, excessive sugar is not good for your health. In a patient who forms kidney stones, excess sugar increases calcium levels in the urine and reduces urine volume. That is, it significantly worsens the situation. This post (Coe, s.f.) from the University of Chicago explains it very well.
In conclusion
Drinking lemonade in moderation is good because it helps us to ingest water, which increases urine volume and reduces the probability of forming stones. But in excess, it can be counterproductive due to its high amount of vitamin C (which increases oxalate in the urine) and sugar (which increases calcium in the urine), favoring the formation of calcium oxalate stones. And the supposed effect attributed to the citric acid in lemon for preventing calcium oxalate stones is not significant.
If you want to drink a refreshing lemonade in summer, do not drink more than 3 liters a day and reduce the amount of sugar you use to sweeten it. And make sure to keep your pH in the appropriate range.
What if I have other types of stones?
Well, it also depends.
The citric acid in lemon also has the ability to raise the pH of the urine. Therefore, it can be beneficial for preventing uric acid stones (which form at a low urinary pH), but counterproductive if you have infectious stones (which form at a high pH).
References
Coe, F. (n.d.). Sugar: The End of Our Love Affair. Retrieved July 30, 2022, from https://kidneystones.uchicago.edu/sugar-end-love-affair/
Doizi, S., Poindexter, J. R., Pearle, M. S., Blanco, F., More, O. W., Sakhaee, K., & Maalouf, N. M. (2018). Impact of Potassium Citrate vs. Citric Acid on Urinary Stone Risk in Calcium Phosphate Stone Formers. J. Urol.
Ferraro, P. M., Curhan, G. C., Gambaro, G., & Taylor, E. N. (2016). Total, Dietary and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. Am J Kidney Dis.
