Alcohol is a fluid that has a diuretic affect allowing the kidneys to produce more urine. This may be helpful in preventing stones. Individuals who drink a beer a day had a 41 % lower chance of developing kidney stones while wine drinkers had a 33 % lower chance of developing stones [1]. Other studies demonstrated that for each 8 oz. serving of wine decreased the risk for stone formation by 39–59 % [3, 4].

The potent diuretic effects of excess alcohol can lead towards potential dehydration. Dehydration produces more concentrated urine, and increases the risk of stones if adequate consumption of other fluids is not maintained. In addition, certain alcoholic beverages, especially beer and grain alcohol are high in purines that may increase the risk of stones, particularly uric acid stones.

The association of coffee and tea intake with risk for stone formation appears to be less controversial, with findings of an inverse association with risk [1, 3, 4]. A recent study indicated that caffeinated Coffee leads to a 26 % lower risk, decaffeinated coffee leads to a 16 % lower risk and tea an 11 % lower risk of stone formation [1].

Coffee and tea are sources of caffeine and increased diuresis. Excessive consumptions of these liquids can lead towards dehydration and may increase the risk of stone formation.

Although further research is required, evidence indicates that cola consumption significantly increases urinary calcium [5] and oxalate excretion [6]. Patients who avoid colas and other phosphoric acid–containing beverages have been found to have a 15 % lower rate of stone recurrence than those who continue to consume these beverages [7]. A recent study comparing sugar-sweetened soda and artificially sweetened soda demonstrated a 23 % higher risk and a trend to lower risk, respectively, suggesting the higher fructose content in the cola, which is known to increase urinary calcium, oxalate and uric acid, will increase the risk of stones [1].

Soda should not be the major source of your fluid intake to achieve your daily goal for hydration. Soda may provide you with appropriate volume, but it also has some negative effects. Caffeinated sodas act as a diuretic and can reduce your ability to achieve an adequate balance of fluid. In addition, soda also contains phosphoric acid. This can reduce the amount of citrate in your urine, which is necessary to prevent new stone formation. The more citrate you lose in your urine, the greater risk you have for generating new stones.

In summary, the key to avoiding kidney stones is moderation of your hydration. The occasional glass of wine, beer, soda, coffee or tea won’t mean you are going to start producing stones, but you should balance your alcohol intake with plenty of hydrating substances like water, decaffeinated tea and diluted juices. Remember, not all fluids are the same!

The amount of fluids you drink is not always equal to the volume of urine eliminated. Some fluids may be eliminated by sweat, loose bowel movements and even by breathing. This is what we refer to as indispensable water losses. Therefore, when we drink, we need to compensate for these losses. Previously, we stated that you want to produce at least 2 l of urine per/day. Even as a “couch potato”, with minimal energy expenditure, additional fluids are required to compensate for these losses.

There are multiple factors that determine an individual’s requirement for fluids. When a patient exercises, the sweat that is produced is fluid that would have normally been eliminated as urine. Therefore, this fluid loss needs to be replaced. Likewise, patients with irritable bowel, such as Ulcerative Colitis, Crohn’s Disease, Diverticulitis; and surgical treatment of the gastrointestinal tract, such as bowel resection, gastric bypass, can result in significant water losses. These patients need to replenish these losses too. Finally, if you live or work in a hot and dry environment or in the summer months spending time outside when you perspire, additional and adequate fluid consumption is paramount (see Chap. 9 for additional information on risk factors of stones).