Every year on March 22, World Water Day highlights the importance of this resource, which is essential to human life. From a medical perspective, water is much more than just a comforting liquid—it is central to virtually all of the body’s physiological functions, from the kidneys to the brain, including thermoregulation, nutrient transport, and the elimination of metabolic waste. Yet mild chronic dehydration is one of the most common and least recognized health problems among the adult population in Quebec.
Kidney stones—also known as urinary lithiasis or «kidney stones»—are one of the conditions most directly linked to insufficient hydration. Their prevalence has doubled over the past thirty years in North America, and today affects approximately % of the Canadian adult population at some point in their lives. Understanding the mechanisms of kidney stones, actual water needs, and prevention strategies can significantly reduce this risk.
The Fundamental Role of Water in the Body
Water accounts for about 60 % of body weight in adults—more in men and muscular individuals, less in people with a higher proportion of adipose tissue. It plays a role in regulating body temperature through sweating, transporting nutrients and oxygen to cells, eliminating metabolic waste through the kidneys and intestines, lubricating joints and mucous membranes, facilitating enzymatic chemical reactions, and maintaining blood volume and blood pressure.
The kidneys filter about 180 liters of blood per day to produce an average of 1.5 to 2 liters of urine. To perform this task efficiently and sufficiently dilute substances that could crystallize, they require an adequate water supply. Even mild chronic dehydration—a loss of just 1 to 2 % of body weight in water—is enough to impair cognitive function, increase the concentration of substances in the urine, and increase the risk of stone formation.
Kidney stones: mechanisms, types and risk factors
Kidney stones form when certain substances dissolved in the urine—calcium, oxalate, urate, phosphate, and cystine—become too concentrated and precipitate as crystals that gradually clump together. The most common type is a calcium stone—calcium oxalate or calcium phosphate—accounting for about 80 % of cases. Uric acid stones account for about 10 % and are closely linked to a diet high in animal protein and to certain conditions such as gout. Struvite stones are often associated with recurrent urinary tract infections, and cystine stones with a rare genetic condition.
The main risk factors for urinary stones include low water intake—the number one and most modifiable factor—a diet high in salt and animal protein, excessive intake of dietary oxalate in predisposed individuals, a family or personal history of stones, certain medical conditions such as hyperparathyroidism, inflammatory bowel disease, and obesity, as well as certain medications and high-dose supplements such as vitamin C or calcium tablets.
Hydration and Kidney Stone Prevention: How Much Water Should You Drink?
The main goal of staying hydrated to prevent kidney stones is to achieve a urine output of more than 2 to 2.5 liters per day—which generally requires a total fluid intake of 2.5 to 3 liters per day, depending on individual fluid losses (sweating, weather conditions, and physical activity). A practical indicator of hydration is urine color: pale, lemon-yellow urine indicates good hydration, while dark yellow or amber urine signals relative dehydration. The goal is to maintain clear urine throughout the day.
It is best to spread out your water intake throughout the day rather than drinking large amounts in a short period of time. Drinking a glass of water when you wake up, before each meal, and before bed is a simple strategy. Fluid needs increase during physical activity, in hot weather or at high altitudes, and during episodes of fever, diarrhea, or vomiting. People who have previously had a kidney stone have a 50 % recurrence rate at 5 years—strict hydration is the most effective preventive measure to reduce this risk.
Nutrition and Hydration: Beyond Plain Water
Water intake doesn’t come solely from beverages: about 20 % of our daily hydration comes from food, particularly fruits and vegetables with high water content—cucumbers, lettuce, tomatoes, strawberries, cantaloupe, and watermelon—all of which contain more than 90 % water. Soups, herbal teas, and other caffeine-free beverages also contribute to hydration. Coffee and tea, despite their mild diuretic effect, contribute positively to overall fluid balance when consumed in moderation.
To prevent calcium stones, a diet low in sodium—since salt promotes the excretion of calcium in the urine—and moderate in animal protein is recommended. Contrary to popular belief, it is generally not necessary to drastically reduce foods rich in dietary calcium—the calcium in dairy products binds to oxalate in the digestive tract before it is absorbed, thereby reducing oxaluria. It is calcium supplements taken between meals that may increase the risk of stones in certain individuals.
Chronic dehydration: consequences far beyond the kidneys
Mild chronic dehydration—which is insufficient to trigger the sensation of thirst in many adults, especially older adults whose thirst mechanism is less sensitive—has measurable effects on numerous bodily functions. Cognitively, dehydration of 1 to 2 % reduces concentration, short-term memory, and psychomotor performance. Digestively, insufficient hydration contributes to constipation. Cardiovascularly, it increases blood viscosity and the risk of thrombosis. Urinary-tract-wise, it increases the risk of urinary tract infections and kidney stones. Skin-wise, it accelerates skin aging and reduces skin elasticity.
Frequently Asked Questions About Hydration and Kidney Stones in Quebec
Is a renal colic attack really as painful as people say?
Yes—renal colic is described by most patients who have experienced it as one of the most intense pains of their lives, often compared to the pain of childbirth. It is caused by a kidney stone moving through the ureter, the narrow tube that connects the kidney to the bladder. The contractions of the ureter as it tries to expel the stone cause colicky pain—intense waves of pain—typically in the flank, radiating to the lower abdomen and groin. It is often accompanied by nausea, vomiting, and restlessness. It is a medical emergency requiring rapid pain relief and evaluation.
Are kidney stones always treated surgically?
No. The vast majority of small stones—less than 5 millimeters—pass on their own with adequate hydration, sometimes aided by alpha-blocker medications that relax the muscles of the ureter. Stones measuring 5 to 10 millimeters may also pass on their own but require closer monitoring. Larger stones or those causing an obstruction, an infection, or intractable pain require treatment—extracorporeal shock wave lithotripsy, laser ureteroscopy, or surgery, depending on the stone’s location and composition.
Can you tell if you have kidney stones without symptoms?
Yes. Many kidney stones are discovered incidentally during an ultrasound or CT scan performed for another reason, even though the person has never had any symptoms. As long as a kidney stone remains in the kidney without obstructing the flow of urine, it can be asymptomatic for years. A kidney stone becomes symptomatic when it begins to move into the ureter. An imaging test—a renal ultrasound—may be ordered during a medical visit if you have risk factors or a family history of kidney stones.
Should I stop eating spinach if I've had a kidney stone?
Not necessarily—and not always. Spinach is high in oxalate, which can contribute to the formation of calcium oxalate stones in people with hyperoxaluria or a genetic predisposition. However, dietary recommendations depend on the type of stone identified by analysis and each patient’s urinary metabolic profile. For most people, a varied diet and adequate hydration are more important than strictly avoiding certain foods. A medical consultation that includes a metabolic workup provides personalized recommendations rather than generic restrictions that might be unnecessary or counterproductive.
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