Drink and drink a lot. Against kidney stones it is the golden recommendation. But are some waters better than others? Or, to be precise: are there waters that help to avoid the risk of stones more than others? We have been wondering about this topic for some time to understand how to optimize prevention: not just by drinking a lot, but by drinking well, and trying to understand what is best to avoid or what doesn’t make that much of a difference. This is apparently the case with alkaline waters: waters with a basic pH, considered by some to be useful for health, including kidney health, but which in reality would not help prevent the appearance of stones, according to a recent study. conducted in the United States.
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Alkaline water against stones: the study
This is what the team of researchers from the Urology Department of the University of California in Irvine (Colorado) states from pages of the Journal of Urology: alkaline waters – at least the ones they considered – would not be better than that of their taps in reducing the risk of stones, especially stones formed by uric acid and cystine.
However, the hypothesis that alkaline waters can help in the fight against stones is not entirely far-fetched, he tells Salute Giuseppe Grandalianodirector of the Nephrology Complex Operational Unit of Agostino Gemelli University Hospital IRCCS (among “Hospitals of excellence”): “It is in fact believed that waters rich in bicarbonates, producing alkalinisation, can prevent the formation of some stones favored by acidic environments, just like those of uric acid and cystine”.
The problem, however, is that the waters analyzed have a basic pH (between 8 and 10), but have a negligible content of alkaline substances, not enough to modify the acidity of the urine and thus influence the risk of stones, as he explains Roshan M. Patel, head of the study. It is easier to hypothesize that the beneficial role associated with these waters – the authors continue – is due to the fact that they taste better than tap water, and can therefore induce you to drink more, with all the benefits of the case.
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Is water rich or poor in calcium better?
Against the stones, in fact, the volume of water introduced and diuresis are undoubtedly the most important aspects, Grandaliano continues. Drinking a lot – at least two liters, preferably three in people at risk of stones – helps to dilute the urine, preventing the precipitation of the substances that make up the stones. “A high volume of fluids is valid as a general prevention strategy for everyone. But if this is the main rule, some precautions in choosing what to drink help to protect yourself further”.
Since most stones are made up of calcium, a widespread belief is that waters rich in this mineral are not recommended and that those that are low in it are preferable. “In reality, however, the stones are made up of calcium oxalate, where the problematic substance is precisely the oxalate, and calcium helps to reduce its absorption”. In fact, at the level of the intestine – summarizes a recent review on the topic – oxalate, combining with calcium, becomes insoluble and is expelled in the feces or is degraded by some bacteria, reducing the amount that can reach the plasma and therefore the kidneys. “For this reason, waters rich in calcium, which can also be those from the tap, are not to be avoided but are even recommended. And even better if taken close to meals, when oxalates are introduced, which are found in many foods: from chocolate with vegetables, dried fruit, tea”.
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Be careful with tea and carbonated drinks
Tea, therefore, should also be consumed in moderation in people at risk of stones. The same goes for carbonated drinks: “Many of these drinks are rich in fructose, which can ultimately promote the production of uric acid – continues the expert – Some, moreover, also provide high quantities of orthophosphoric acid, which facilitates acidification and the precipitation of low pH stones, such as uric acid or cystine stones.” The liquids that we introduce with the diet are not all the same, Grandaliano points out, and it is not the same thing to promote diuresis with water or other drinks.
What about low-sodium waters?
Finally the expert recalls how, in Mediterranean of the offers of mineral waters – even considering that the tap water is of average good quality – waters with reduced sodium content can also be helpful, as long as they are combined with a low-sodium diet. Because “most of the sodium we consume comes from food: drinking low-sodium water, if you introduce large quantities of sodium in your diet, is simply useless.”