Certain foods raise your risk of kidney stones by increasing the concentration of oxalate, calcium, or uric acid in your urine. While there’s no single “top 10” list that all doctors agree on, the foods most consistently linked to stone formation fall into clear categories: high-oxalate plants, salty processed foods, excess animal protein, sugary drinks, and a few surprises like vitamin C supplements. Here’s what to know about each one and why it matters.
How Food Causes Kidney Stones
Most kidney stones are made of calcium oxalate. They form when your urine contains more crystal-forming substances than the fluid can dilute. The foods below contribute by flooding your urine with oxalate, pulling extra calcium into your urine, raising uric acid levels, or lowering your urine’s pH to a point where crystals form more easily. Not everyone who eats these foods will develop stones, but if you’ve already had one, your lifetime risk of a second stone is high, and diet is one of the most controllable factors.
1. Spinach
Spinach is one of the highest-oxalate foods you can eat. The NIDDK specifically names it as a food to avoid if you’ve had calcium oxalate stones. A single cooked serving can contain over 750 mg of oxalate, while a low-oxalate diet aims to keep total daily intake around 100 mg. That means one helping of spinach can blow past the entire day’s recommended limit several times over. Other leafy greens like kale and romaine are much lower in oxalate and work as substitutes.
2. Rhubarb
Rhubarb is another plant that concentrates oxalate in its stalks and leaves. It’s less commonly eaten than spinach, but people who bake with it regularly or drink rhubarb-based beverages can accumulate meaningful amounts. Like spinach, it’s on the NIDDK’s shortlist of foods to limit for stone prevention.
3. Nuts and Nut Products
Almonds, cashews, and other tree nuts are high in oxalate. Nut butters, nut flours used in low-carb baking, and trail mixes can add up fast. Peanuts deserve special mention. Though technically a legume, peanuts are high in oxalate and frequently consumed in large quantities as peanut butter. If you’ve had calcium oxalate stones, the NIDDK recommends limiting both tree nuts and peanuts.
4. Wheat Bran
Wheat bran rounds out the NIDDK’s list of high-oxalate foods to avoid. It shows up in bran cereals, bran muffins, and whole wheat products where the outer grain layer is concentrated. This doesn’t mean all whole grains are off-limits. Rice, oats, and corn are significantly lower in oxalate.
5. Red Meat and Organ Meats
High-purine animal proteins raise uric acid levels in your blood and urine, which promotes uric acid stones and can also encourage calcium oxalate stone formation. Beef, lamb, and especially organ meats like liver are among the richest purine sources. Research published in the Journal of Urology confirmed that consuming animal protein increases both serum and urinary uric acid in healthy people. Keeping portions moderate, roughly the size of a deck of cards per meal, is the standard advice for stone formers.
6. Fish and Shellfish
Fish has a higher purine content than beef or chicken, and this shows up directly in urine composition. In a metabolic comparison study, people eating fish produced significantly more urinary uric acid (741 mg per day) than those eating beef (638 mg) or chicken (641 mg). Sardines, anchovies, and shellfish are particularly high in purines. You don’t need to eliminate fish entirely, but if you’ve had uric acid stones, it’s worth paying attention to how much and how often you eat it.
7. Salty Processed Foods
Sodium is one of the most underappreciated drivers of kidney stones. When you eat excess salt, your kidneys excrete more calcium into your urine, and that extra calcium can bind with oxalate to form stones. The relationship is well quantified: for roughly every 2,300 mg increase in sodium intake, your body dumps an additional 40 mg of calcium into your urine. One study found that cutting sodium intake in half reduced urinary calcium excretion by about 45%.
The biggest sodium culprits are processed and packaged foods: deli meats, canned soups, frozen meals, chips, fast food, and soy sauce. These can easily push daily sodium past 4,000 or 5,000 mg when the general recommendation for stone prevention is closer to 2,300 mg or less.
8. Sugary Sodas and Sweetened Drinks
Sugar-sweetened sodas hit you with a double problem. The fructose in high-fructose corn syrup increases oxalate production and promotes insulin resistance, which lowers urinary pH and creates conditions favorable for uric acid stones. In one study, infusing roughly 35 grams of fructose increased urinary oxalate excretion by 60% compared to glucose. People in the highest category of fructose consumption had significantly greater kidney stone risk across multiple large studies.
Colas carry an additional risk because they contain phosphoric acid, which alters urine composition in ways that promote recurring stones. Even diet sodas still contain phosphoric acid and caffeine, both of which have been linked to stone risk. Water, unsweetened tea, and drinks with real citrus juice are consistently better choices.
9. High-Fructose Sweets and Candy
It’s not just soda. Any food heavy in fructose or high-fructose corn syrup can raise your stone risk through the same mechanisms. This includes candy, sweetened yogurts, flavored cereals, fruit-flavored snacks, and many condiments like ketchup and barbecue sauce. Fructose intake in the American diet increased roughly 2,000% over 30 years following the widespread introduction of high-fructose corn syrup. A high-fructose diet, especially when combined with low magnesium intake, also increases urinary calcium losses, adding another pathway to stone formation.
10. High-Dose Vitamin C Supplements
This one catches many people off guard. Your body converts vitamin C (ascorbic acid) into oxalate, and at supplemental doses, this conversion becomes significant enough to raise kidney stone risk. In a controlled study, taking 1,000 mg of vitamin C twice daily increased endogenous oxalate production by 39% and boosted oxalate absorption by 31% in 40% of participants, including people who had never had a stone before. The effect was strong enough to measurably raise the calculated risk index for calcium oxalate stones.
Getting vitamin C from food (oranges, bell peppers, strawberries) is not the same as taking mega-dose supplements. Food sources provide far lower amounts alongside other beneficial compounds. If you’ve had stones, most experts recommend staying well below 2,000 mg per day from supplements, and many suggest avoiding supplementation entirely unless medically necessary.
The Calcium Paradox
One of the most counterintuitive facts about kidney stones is that eating more dietary calcium can actually protect you. Calcium binds with oxalate in your digestive tract before it ever reaches your kidneys, so less oxalate ends up in your urine. The National Kidney Foundation specifically states that people with calcium kidney stones should not follow a low-calcium diet. The goal is 1,000 to 1,200 mg of calcium per day, ideally from food sources like dairy, eaten alongside meals that contain oxalate. Pairing a calcium source with a high-oxalate food is one of the simplest strategies for reducing oxalate absorption.
Foods That Help Prevent Stones
Citrate is a natural stone inhibitor. It binds with calcium in urine and prevents crystals from growing. Foods rich in citrate include lemons, oranges, grapefruit, kiwi, melons, tomatoes, and bell peppers. Adding lemon juice to your water is a practical, low-effort way to boost citrate intake throughout the day. Beyond specific foods, fluid intake matters enormously. Producing at least 2.5 liters of urine per day significantly dilutes stone-forming substances, and for most people that means drinking around 3 liters of fluid daily.