Diet plays a bigger role in kidney stone formation than many people realise. While factors such as genetics, hydration, and underlying medical conditions all contribute, what you eat and drink on a daily basis can significantly alter the chemical composition of your urine – and it is that composition that determines whether crystals form and eventually develop into stones.

Understanding which foods carry the most risk is one of the most effective steps you can take to protect yourself, particularly if you have already had a stone and are concerned about recurrence.

Why does food matter?

Kidney stones form when certain minerals and salts become so concentrated in the urine that they begin to crystallise. The kidneys are usually able to flush these substances out before they accumulate – but when urine is too concentrated, or when the balance of stone-promoting versus stone-preventing compounds tips the wrong way, crystals can start to cluster together.

Diet influences this balance directly. Certain foods raise the levels of calcium, oxalate, uric acid, or sodium in the urine, all of which can contribute to stone formation depending on the type of stone a person is prone to developing.

Understanding what kidney stones are made of is a useful starting point, since the dietary triggers vary depending on the stone type.

Foods that can contribute to kidney stones

High-oxalate foods

Oxalate is a naturally occurring compound found in many plant-based foods. In the gut, dietary oxalate normally binds to calcium and is excreted harmlessly in the stool. But when oxalate levels are high – or when there is insufficient dietary calcium to bind to it – free oxalate passes into the bloodstream and is filtered by the kidneys, where it can combine with calcium to form calcium oxalate stones, the most common type of kidney stone in the UK.

Foods particularly high in oxalate include:

• Spinach, Swiss chard, and beet greens
• Rhubarb
• Nuts and nut butters, particularly almonds and peanuts
• Dark chocolate and cocoa
• Sweet potatoes
• Soy products

This does not mean these foods need to be eliminated entirely – many are nutritious and beneficial in other ways. The key is moderation and, importantly, pairing them with adequate dietary calcium so that oxalate is bound before it reaches the kidneys.

Salty foods

Sodium is one of the most overlooked dietary contributors to kidney stones. A high-salt diet causes the kidneys to excrete more calcium into the urine – and excess urinary calcium is a major driver of stone formation. Sodium also reduces the kidneys’ ability to reabsorb calcium, compounding the problem.

Common high-sodium culprits include processed meats, ready meals, crisps, tinned soups, fast food, and many condiments and sauces. The NHS recommends no more than 6g of salt per day for adults, yet the average UK intake remains above this threshold. If you have a history of calcium stones, reducing your salt intake is one of the most impactful dietary changes you can make.

High-purine foods

Purines are compounds found predominantly in animal proteins. When the body breaks them down, they produce uric acid as a byproduct. If uric acid accumulates in the urine – particularly when urine is acidic and concentrated – it can crystallise to form uric acid stones.

Foods with a particularly high purine content include:

• Red meat and organ meats such as liver and kidney
• Game meats
• Oily fish such as sardines, anchovies, mackerel, and herring
• Shellfish, including prawns and scallops
• Meat-based gravies and stocks

Men who follow high-protein diets, or those who eat large quantities of these foods regularly, may be at greater risk. Moderating animal protein intake – rather than eliminating it entirely – and spreading consumption across the day can help keep uric acid levels more stable.

Sugary foods and drinks

Sugar – and fructose in particular – has been increasingly linked to kidney stone risk. Fructose raises the urinary excretion of calcium, oxalate, and uric acid all at once, making it a particularly problematic compound for those prone to stones. Sugary fizzy drinks are a notable concern, as many also contain phosphoric acid, which can lower urinary citrate – a compound that naturally inhibits stone formation.

Fruit juices, sweets, baked goods, and foods containing high-fructose corn syrup all warrant attention. Swapping fizzy drinks for water or diluted squash is one of the simplest and most beneficial changes for kidney stone prevention.

Excessive animal protein overall

Beyond purine-rich meats specifically, a generally high animal protein intake across all sources – including poultry and dairy – can promote stone formation by increasing urinary calcium and uric acid while reducing citrate levels. This does not mean avoiding protein, but rather being mindful of portion sizes and considering plant-based protein sources as part of a balanced diet.

A common misconception: calcium and kidney stones

Many people who have been told they have calcium oxalate stones mistakenly conclude that they should cut back on calcium-rich foods such as dairy. In fact, the opposite is generally true. Dietary calcium from food sources binds to oxalate in the gut, preventing it from reaching the kidneys in the first place.

What does carry risk is excessive calcium supplementation taken between meals, as this delivers calcium directly into the urine without the benefit of gut-level binding. If you take calcium supplements, it is worth discussing the timing and dosage with a specialist.

What about alcohol?

Alcohol contributes to dehydration, which concentrates the urine and raises the risk of crystal formation. Beer in particular contains purines, adding a further uric acid burden. While moderate alcohol consumption is not a major isolated risk factor, it compounds other dietary risks – especially when fluid intake is already low. If you are prone to kidney pain or have a history of stones, staying well hydrated is essential, and alcohol should be consumed in moderation.

Dietary changes that can help reduce risk

The good news is that dietary adjustments can meaningfully reduce the risk of stone formation. The most consistently supported measures are:

• Drinking more water. Aiming for two to three litres per day keeps urine dilute and reduces the concentration of stone-forming substances. Urine should be pale yellow – darker urine is a sign you need to drink more.
• Eating adequate dietary calcium. Rather than restricting calcium, ensure you are getting enough from food sources such as dairy, fortified plant milks, and leafy greens with lower oxalate content.
• Reducing salt and processed foods. Lowering sodium intake directly reduces urinary calcium excretion.
• Moderating animal protein. Spreading protein intake evenly and incorporating plant-based sources can lower uric acid levels.
• Limiting high-oxalate foods if you have previously had a calcium oxalate stone, particularly in large portions.

It is also worth noting that kidney stones can lead to further complications if left unmanaged, including recurrent urinary tract infections and kidney damage – so taking preventive steps is well worth the effort.

When to seek specialist advice

If you have already had a kidney stone, the risk of recurrence is real – around half of those affected will develop another within five to ten years. Knowing what the first signs of kidney stones look and feel like can help you seek prompt attention if symptoms return.

Dietary changes are an important part of prevention, but they work best alongside a proper clinical assessment. A specialist can analyse the composition of any stone you have passed, carry out urine and blood testing, and tailor preventive advice to your specific situation – rather than relying on general guidance alone.