What would most of us do without a good hot cup of coffee in the morning? At least, for many of us who work at Devicare, it would be difficult to start the day without that extra boost of energy that caffeine provides.
Coffee is one of the most popular beverages in the world, with over 166 million 60 kg bags sold in 2021 according to Statista, which is 10 million tons! And its consumption continues to grow. But is coffee good for kidney stones? Read on to find out.
Can coffee cause kidney stones?
Coffee increases calcium excretion in urine. And that's why there are many myths that say consuming coffee can cause kidney stones. However, to date, no direct relationship has been established between coffee consumption and kidney stone formation. In fact, quite the opposite is true. There are numerous studies [1], [2], [3] that conclude that coffee is associated with a lower risk of stone formation.
So, can coffee prevent kidney stone formation?
It seems so.
In an interesting study published in the American Journal of Clinical Nutrition in 2014, Dr. Pietro Manuel Ferraro and his colleagues [1] wanted to verify this. They analyzed the coffee consumption habits of 217,883 patients. They concluded that patients who drank more coffee had up to a 30% lower risk of forming kidney stones. These results have recently been confirmed by another group of researchers in China in a population of 30,176 patients [2].
What is the reason for this preventive effect?
It is not yet known why coffee has a preventive effect on kidney stone formation. Even less so when it has been shown to increase the amount of calcium in the urine. It seems contradictory.
Some researchers believe that the substance that has this preventive effect is caffeine. Caffeine is a chemical compound present in coffee that was discovered in 1819 and has a powerful stimulating activity on the central nervous system, causing that extra energy we get from drinking a cup of coffee.
To analyze the renal effects of caffeine, researchers Massey and Wise [4] conducted a biochemical study in 1992. They found that a dose of 5.91 mg/kg of caffeine (equivalent to 4 cups of coffee in an adult) increased urinary calcium excretion by up to 78%. This is an enormous amount, and that's why the myth of coffee causing kidney stones makes some sense. But in the same study, the authors also saw that with the same dose of caffeine, urine volume increased by 23% and urinary magnesium by 45%, both preventive effects.
Later, other biochemical studies also showed that caffeine consumption reduced the amount of oxalate and uric acid in the urine, as well as the risk of urinary crystallization.
Therefore, it seems that caffeine could indeed be the substance that prevents kidney stone formation.
What about decaffeinated coffee?
Oops! Well, it also seems to have a preventive effect.
In Dr. Ferraro's same study, it was observed that patients who consumed decaffeinated coffee also had a lower risk of forming kidney stones. But how is this possible if decaffeinated coffee does not contain caffeine?
Here, some might think... "Well, that's not true, decaffeinated coffee also contains caffeine and that's why it can also prevent stone formation." Yes and no. It is true that there is no system to 100% eliminate caffeine from coffee, but international regulations require manufacturers to label "decaffeinated" only if they reduce the initial caffeine by more than 97%. Therefore, we can assume that decaffeinated coffee practically has no caffeine. In fact, a cup of decaffeinated coffee contains only 2 mg of caffeine versus the 100 mg found in a cup of regular coffee.
So, if it's not caffeine, what prevents kidney stone formation in decaffeinated coffee? This is still an unanswered question. Some researchers believe it may be magnesium, others believe it may be other antioxidant substances such as polyphenols, and the Devicare scientific team believes it may be other substances from the same family as caffeine, such as theophylline or theobromine, which would be present in decaffeinated coffee.
Specifically, theobromine is a substance that we have studied extensively in our laboratory in collaboration with the University of the Balearic Islands, and which we have shown to have the ability to bind to uric acid and inhibit its crystallization. Theobromine is a methylxanthine (like caffeine) that comes from cocoa. And it is very possible that, along with caffeine and theophylline, they are the main culprits of this preventive effect. In any case, further research is needed to confirm this hypothesis.
Can coffee help me pass kidney stones?
As we have seen in the studies mentioned, coffee has a diuretic effect, just like tea or beer. This means that it increases urine production in the patient. Therefore, if you have a stone smaller than 5 mm in the ureter, the increased urine caused by coffee could facilitate its expulsion.
So, should I increase my daily coffee consumption?
Definitely not.
Although studies associate coffee, caffeine, and theobromine with a lower risk of kidney stone formation and a higher likelihood of passing small stones, excessive coffee consumption can be detrimental to your health.
The European Food Safety Authority recommends a consumption of up to 400 mg/day of coffee in healthy adults (equivalent to 4 cups of coffee a day). Beyond these amounts, coffee can cause side effects such as headaches, insomnia, nervousness, irritability, arrhythmias, and muscle tremors. And according to some studies, prolonged consumption of more than 9 cups of coffee a day has been associated with bladder cancer.
In summary
Have your cup of coffee in the morning to start your day with energy. And keep drinking it throughout the day if you need to. After all, coffee prevents kidney stone formation. But always do it in moderation to avoid possible side effects. And if you can, combine it with some decaf.
In any case, if you really want to prevent uric acid stone formation, remember that water is still your best option in combination with the concentrated theobromine present in Lit-Control pH Up.
References
[1] P. M. Ferraro, E. N. Taylor, G. Gambaro y G. C. Curhan, «Caffeine intake and the risk of kidney stones,» American Journal of Clinical Nutrition, 2014.
[2] J. Geng, Y. Qiu, Z. Kang, Y. Li, J. Li, R. Liao, Z. Qin, Q. Yang y B. Su, «The association between caffeine intake and the risk of kidney stones: A population-based study,» Frontiers in Nutrition, 2022.
[3] S. Yuan y S. C. Larsson, «Coffee and Caffeine Consumption and Risk of Kidney Stones: A Mendelian Randomization Study,» American Journal of Kidney Disease, 2021.
[4] L. K. Massey y K. J. Wise, «Impact of gender and age on urinary water and mineral excretion responses to acute caffeine doses.,» Nutrition Research, 1992.
