Can Soda Cause Kidney Stones?

Yes, soda can cause kidney stones. The connection is real and backed by solid research. The main culprits are the high sugar content, especially from fructose, and the phosphoric acid found in many dark colas. These substances change the chemistry of your urine in ways that make stone formation more likely. But the story is more specific than a simple “soda is bad” warning — different types of soda affect your kidneys differently.

How Does Soda Lead to Kidney Stones?

Soda affects your kidneys through several pathways. The most direct link is through sugar. Many sodas contain high fructose corn syrup. Your liver processes fructose differently than other sugars. When you drink a lot of fructose, your body produces more uric acid. Uric acid can form crystals in your kidneys. Those crystals can grow into stones.

The second pathway involves oxalate. Some sodas, especially iced tea, are high in oxalates. Oxalates bind with calcium in your urine. When this happens, calcium oxalate crystals form. This is the most common type of kidney stone, accounting for about 80% of all cases according to the National Kidney Foundation.

The third pathway is dehydration. Soda is a diuretic. It makes you urinate more. If you drink soda instead of water throughout the day, you are likely less hydrated than you should be. Concentrated urine is a perfect environment for stone formation. When your urine volume drops, minerals and salts have a higher chance of sticking together and forming stones.

Does Can Soda Cause Kidney Stones Differently Than Other Drinks?

Yes. Not all sodas are equal when it comes to kidney stone risk. The research shows clear differences.

Colas are the worst offenders. They contain phosphoric acid. This acid makes your blood more acidic. To neutralize that acid, your body pulls calcium from your bones. That extra calcium ends up in your urine. More calcium in urine means a higher risk of calcium stones.

Clear sodas like Sprite or 7-Up do not contain phosphoric acid. They use citric acid instead. Some evidence suggests citric acid may actually help prevent certain types of stones. Citric acid binds with calcium in urine and stops crystals from forming. But these sodas still have high sugar content, which raises uric acid levels.

Diet sodas are a mixed bag. They remove the sugar, which helps with uric acid stones. But diet colas still contain phosphoric acid. The artificial sweeteners do not seem to affect stone risk directly, though research is still limited on long-term effects.

Here is a quick comparison of how different sodas affect stone risk:

What Does the Research Actually Show?

A large study published in the Clinical Journal of the American Society of Nephrology tracked over 190,000 people for more than eight years. The researchers found that people who drank one or more sugar-sweetened sodas per day had a 23% higher risk of developing kidney stones compared to those who drank less than one per week.

The same study found that other sugary drinks like fruit punch and lemonade also increased risk. But the link was strongest for soda. The researchers controlled for other factors like age, weight, and overall diet. The soda effect remained significant.

Another study specifically looked at cola consumption. It found that people who drank cola daily had a significantly higher calcium level in their urine. Calcium excretion increased by about 10-15% in regular cola drinkers. That is enough to push some people over the threshold for stone formation.

Some people report that drinking soda helps them feel less thirsty and keeps them hydrated. This is misleading. Soda provides fluid, but the sugar and acid content offset the hydration benefit. A 2015 study in the American Journal of Physiology found that high sugar intake actually reduces the kidneys’ ability to concentrate urine. This means you lose more water than you gain from the soda itself.

What Are the Practical Steps to Lower Your Risk?

The most effective step is simple — drink more water. The National Kidney Foundation recommends at least eight glasses of water per day. If you have had a kidney stone before, aim for ten to twelve glasses. Water dilutes your urine and lowers the concentration of stone-forming substances.

If you drink soda regularly, do not try to quit cold turkey if that is unrealistic. Gradual reduction works better for most people. Replace one soda per day with water for a week. Then replace a second. Over a month, you can cut your intake significantly without feeling deprived.

When you do drink soda, choose clear sodas with citric acid over colas. Even better, choose diet versions to eliminate the fructose issue. But remember — diet sodas still have phosphoric acid if they are colas. The safest choice among sodas is a diet clear soda like diet Sprite or diet 7-Up.

Here are specific things to avoid if you are concerned about kidney stones:

• Drinking soda on an empty stomach — the sugar and acid hit your system faster
• Using soda as your main source of hydration during exercise or hot weather
• Mixing soda with alcohol — both are dehydrating and increase uric acid
• Drinking dark colas with high-oxalate foods like spinach or nuts
• Ignoring how much soda you actually drink — most people underestimate by 2-3 times

What About Other Ingredients in Soda?

Caffeine gets a lot of attention, but the evidence is mixed. Caffeine is a mild diuretic. In moderate amounts, it does not significantly dehydrate you. The British Journal of Nutrition published a review showing that caffeine’s diuretic effect is minimal in people who consume it regularly. Your body adapts.

The bigger concern with caffeine is how it affects calcium. Caffeine causes a small increase in calcium loss through urine. For most people, this is not enough to cause stones. But if you already have high calcium in your urine, caffeine could push you over the edge.

Artificial colors and preservatives have not been shown to cause kidney stones directly. Some people worry about high fructose corn syrup specifically. The concern is valid — fructose is the main driver of uric acid stones. But the sugar in soda is the problem, not the specific type. Regular sugar, honey, and agave all have similar effects on uric acid production.

Phosphoric acid deserves special attention. It is found almost exclusively in colas. This ingredient is what makes colas more harmful for kidney stones than other sodas. The phosphoric acid changes your body’s acid-base balance. Your kidneys have to work harder to maintain the right pH. Over time, this can lead to chronic low-grade acidosis, which promotes stone formation.

Common Misconceptions About Soda and Kidney Stones

Some people believe that only dark sodas cause kidney stones. This is not true. Clear sodas with high sugar content still increase uric acid stones. The risk is lower than with colas, but it is not zero.

Another myth is that drinking soda with meals is fine because food buffers the acid. Research does not support this. The phosphoric acid and fructose affect your urine chemistry regardless of when you drink them. Food may slow absorption slightly, but the overall effect on stone risk remains.

Some people think that if they have never had a kidney stone, they do not need to worry. This is a mistake. Kidney stones often develop silently over years. The first symptom for many people is sudden severe pain when a stone passes. By that point, the stone has been growing for months or years. Prevention matters before symptoms appear.

There is also a belief that diet soda is completely safe for kidneys. As mentioned earlier, diet colas still contain phosphoric acid. A study in the Journal of the American Society of Nephrology found that diet cola consumption was associated with a higher risk of kidney function decline over time. The effect was smaller than with regular soda, but it was still present.