The biggest dietary enemies of kidney stones are high sodium, too much animal protein, oxalate-rich foods, and not drinking enough water. But several less obvious factors also raise your risk, including certain supplements, cola drinks, and even cutting back on calcium (which backfires for reasons most people don’t expect).
Not Drinking Enough Water
Dehydration is the single most consistent risk factor for kidney stones. When your urine is concentrated, the minerals that form stones have an easier time clumping together into crystals. The American Urological Association recommends producing at least 2.5 liters of urine per day, which generally means drinking about 3 liters (roughly 100 ounces) of fluid daily, though the exact amount depends on your size, activity level, and climate.
Heat exposure makes this worse. Steel workers exposed to temperatures above 45°C (113°F) were nine times more likely to develop kidney stones than coworkers at room temperature. Glass plant workers in the hottest sections of the facility had stone rates more than three times higher than those in cooler areas. You don’t need an industrial job for this to matter. Hot climates, outdoor work, intense exercise, and even long sauna sessions all increase fluid loss and concentrate your urine.
Too Much Salt
Sodium is one of the strongest dietary drivers of calcium stones, the most common type. When you eat more salt, your kidneys excrete more calcium into your urine, and that extra calcium can bind with oxalate or phosphate to form stones. Guidelines recommend keeping sodium below 2,300 mg per day if you’ve had calcium stones, with some expert groups suggesting a stricter cap of 2,000 mg.
Most of the sodium in a typical diet comes from processed and restaurant food, not the salt shaker. Canned soups, deli meats, frozen meals, soy sauce, and fast food are common culprits. Reading nutrition labels and cooking more at home are the most practical ways to cut back.
High-Oxalate Foods
Calcium oxalate stones account for roughly 80% of all kidney stones. Oxalate is a natural compound found in many plants, and when it reaches your kidneys in large amounts, it binds with calcium and crystallizes. The National Institute of Diabetes and Digestive and Kidney Diseases flags these as the highest-oxalate foods to limit if you’ve had this type of stone:
- Spinach
- Rhubarb
- Nuts and nut products
- Peanuts (technically a legume, but very high in oxalate)
- Wheat bran
Other notable sources include beets, sweet potatoes, chocolate, and black tea. You don’t need to eliminate all of these, especially if you’ve never had a calcium oxalate stone. But if you’re a repeat stone former, reducing the highest-oxalate items can meaningfully lower the oxalate concentration in your urine.
Too Much Animal Protein
Diets heavy in red meat, poultry, and fish affect stone risk through several mechanisms at once. Animal protein is rich in sulfur-containing amino acids that produce acid when metabolized. This acid load does three things: it pulls calcium out of your bones and into your urine, it lowers urinary pH (making the urine more acidic), and it reduces citrate, a natural stone inhibitor your kidneys normally excrete. In controlled studies, switching from a vegetarian diet to an animal protein-rich diet increased daily calcium excretion from about 103 mg to 150 mg, a jump of nearly 50%.
The acidic urine is especially problematic for uric acid stones. When urine pH drops, uric acid becomes less soluble and is more likely to crystallize. If you’ve had uric acid stones specifically, the National Kidney Foundation recommends cutting back on high-purine foods: red meat, organ meats (liver, kidney), sardines, anchovies, shellfish, meat-based gravies, and beer.
Cola and Sugary Drinks
Not all sodas carry equal risk. Cola beverages are acidified with phosphoric acid, while most non-cola sodas use citric acid. That distinction matters. Phosphoric acid promotes urinary changes that favor oxalate stone formation. In a randomized trial of men with kidney stones, those who continued drinking phosphoric acid-containing soft drinks had higher stone recurrence than those who switched to citric acid-based beverages.
Sugary drinks in general also contribute to stone risk by increasing calcium and oxalate excretion while reducing urine volume (since sugar can have a mild diuretic effect). Replacing soda with water or citrus-based drinks like lemonade is one of the simpler swaps you can make.
The Calcium Mistake
This one surprises most people: cutting calcium from your diet actually raises your risk of calcium oxalate stones. The reason is that dietary calcium binds with oxalate in your digestive tract, forming a complex that your body can’t absorb. That oxalate passes harmlessly through your stool instead of reaching your kidneys. When you eat too little calcium, more oxalate gets absorbed into your bloodstream and filtered through your kidneys, where it can crystallize.
This doesn’t mean you should take calcium supplements freely, though. Calcium from food is protective because it’s consumed alongside other nutrients and absorbed gradually. Calcium supplements, especially when taken between meals, don’t have the same oxalate-binding benefit and may actually raise stone risk in some people. The goal is to get adequate calcium from dairy, fortified foods, or leafy greens, ideally eaten at the same meals as oxalate-containing foods.
Vitamin C Supplements
Your body converts excess vitamin C into oxalate. At high doses, this becomes clinically meaningful: taking 2 grams of vitamin C daily increased urinary oxalate excretion by about 22% in a metabolic study. That’s a significant jump for anyone prone to calcium oxalate stones. The vitamin C you get from food (an orange has about 70 mg) isn’t a concern. The risk comes from megadose supplements, particularly those marketed at 1,000 mg or more per day.
Certain Medications
Several common medications can promote stone formation as a side effect. Topiramate and other carbonic anhydrase inhibitors (used for seizures and migraines) lower citrate levels and raise urine pH, creating conditions favorable for calcium phosphate stones. Loop diuretics increase calcium in the urine. Some antibiotics and antiviral medications can themselves crystallize in the urinary tract. If you’re a stone former taking any of these, it’s worth discussing your stone history with whoever prescribes your medication, since alternatives or preventive measures may be available.
Alcohol and Beer
Beer is a double problem for uric acid stones. It’s high in purines, which break down into uric acid, and alcohol in general is dehydrating. That combination of increased uric acid production and reduced urine volume is a reliable recipe for stones. Other alcoholic drinks are less purine-heavy than beer but still contribute to dehydration, especially in warm weather or when consumed without water alongside.