Diet and fluids with kidney stones

Anyone who has had a kidney stone once rarely wants to go through it again. Without a change in habits, however, stones often come back – and the most powerful tool against this is in your own hands: what and how much you drink and eat every day.

Many popular tips, though, are outdated or downright harmful: cutting out calcium, drinking beer, banning whole food groups. Below is what modern urology recommends and what Dr Penev discusses with his patients in Plovdiv and Karlovo. The rules depend on the type of stone, so the general advice is fine-tuned after an examination and analysis; for the condition itself, read the article on kidney stones.

Fluids: the first and most important rule

Dilute urine is the best protection against crystals. The aim is roughly 2.5–3 litres of fluid a day, so that you pass at least 2–2.5 litres of pale, almost colourless urine. Spread your drinking evenly – a glass every hour or two, including in the evening, because urine is most concentrated at night. In hot weather, during sport, in the sauna or with physical work you need more; in a Plovdiv summer a bottle of water should always be within reach.

Water is the basis; unsweetened herbal and fruit teas are also fine. Limit sweetened fizzy drinks, especially colas, and large amounts of strong black tea.

Why beer is not the answer

The myth that beer “flushes out stones” dies hard. Alcohol increases urine output for a short time but then dehydrates you, and beer is rich in purines, which raise uric acid – itself a cause of stones. During renal colic, beer does not help; it only blunts your judgement about when to seek help.

Less salt and moderate amounts of meat

Salt is a bigger culprit than calcium. The more sodium you take in, the more calcium your kidneys flush out into the urine. Aim for less than 5 grams of salt a day – about one teaspoon, including the hidden salt in cured meats and sausages, cheeses, pickles, crisps, ready-made sauces and bread.

Animal protein – meat, sausages, fish, eggs – makes the urine more acidic, raises the uric acid and calcium in it and reduces protective citrate. You do not need to become a vegetarian: moderate portions are enough, no more than one portion of meat or fish a day, plus some meat-free days. High-protein weight-loss diets are risky if you have stones.

Do not cut out calcium

This is the most common mistake. Calcium from food binds to oxalates while they are still in the gut, so they do not reach the urine; on a low-calcium diet more oxalate is absorbed and stones become more frequent. That is why dairy products in normal amounts – yoghurt, cheese, milk – stay on the menu, preferably with your main meals. Calcium supplements in tablet form are a different matter – take them only after medical advice and always with food.

Oxalates: moderation, not a ban

If your stones are calcium oxalate stones and tests show raised oxalate in your urine, cut down on the richest sources: spinach, sorrel, rhubarb, beetroot, nuts (especially almonds and cashews), cocoa and chocolate, wheat bran, soya products and strong black tea. Other vegetables and fruit are not restricted, and it is a good idea to combine oxalate-rich foods with a dairy product in the same meal. Avoid high-dose vitamin C tablets – the excess is turned into oxalate.

Citrus fruit, vegetables and weight

Citrate is the natural “brake” on crystal formation, and its most accessible source is lemon: the juice of half to one lemon, diluted in a glass of water, several times a day. Oranges and most fruit and vegetables also help – they are rich in potassium, magnesium and citrate. Keep a healthy weight and stay active: being overweight, diabetes and metabolic syndrome make the urine more acidic and increase the risk, especially of uric acid stones.

Different stones – different rules

• Calcium oxalate (the most common): everything described so far.
• Uric acid: limit red meat, offal, seafood and alcohol, especially beer; lose weight. These stones can often be dissolved with medicines that make the urine more alkaline, under a urologist’s supervision.
• Calcium phosphate: the advice is individual, because making the urine too alkaline is harmful here; a cause is also looked for, such as a disorder of the parathyroid glands.
• Infection (struvite) stones: diet plays a secondary role; what is decisive is removing the stone completely and treating the infection.
• Cystine (rare, inherited): more than 3.5 litres of fluid a day, little salt and animal protein, and specific medicines.

Stone analysis and when to see a urologist

The advice works best when you know what kind of stone you are dealing with. So pass urine through a sieve during an attack and keep the stone or the fragments after a procedure – their composition is tested in a laboratory. For recurring stones, stones in childhood or a family history, Dr Penev may also order a metabolic work-up of the blood and a 24-hour urine collection and draw up a personal plan, sometimes including medication. A kidney stone consultation with an ultrasound also shows whether the new rules are working.

Diet is prevention, not treatment for an acute problem. If you have severe pain in the lower back, a temperature, vomiting or are passing no urine, go to an emergency department straight away or call 112 (the European emergency number); what to do at such a moment is explained in our first-aid advice for renal colic.

More water, less salt and meat, calcium from food, citrate from lemons and moderation with oxalates – these are the rules that help most people with stones. Book an appointment with Dr Penev in Plovdiv or Karlovo to turn the general advice into a personal prevention plan.