"I had a kidney stone earlier this year and was advised to cut back on my consumption of tea as a result. I currently drink between one and two cups per day, which is a 50 per cent reduction. I have also seen articles where food such as spinach and rhubarb is thought to increase susceptibility to further stones. Could you update me on the latest thinking regarding diet and kidney stones?" - Kevin
Dr Sarah Jarvis says: "There are several different kinds of kidney stone, and the best diet changes to minimise the chance of recurrence depend on which type you have.
The most common kind of stone is a calcium oxalate stone. Oxalate is found in tea, as well as a wide variety of foods ranging from nuts and seeds to some fruit and vegetables (peanuts, sweet potatoes, spinach and beetroot are particularly high. So, I'm afraid, is chocolate). If you've been advised to reduce your intake of tea, you're likely to have an oxalate stone. However, because many foods containing oxalate are healthy, it may be appropriate for you to combine calcium and oxalate in the same meal rather than trying to cut your intake of oxalate too much. That's because the calcium and oxalate may bind to each other in your gut, rather than your kidneys. Dairy products are good sources of calcium
If you have a calcium stone, you don't need to reduce your calcium intake. Instead, reducing the sodium (salt) in your diet with cut the risk of developing further stones, because a high-sodium diet increases the amount of calcium you pass through your kidneys into your urine. As well as the obvious sources of salt, such as added salt on food and salty crisps and snacks, be aware of hidden sources of sodium in the diet. Many ready-prepared foods, including soups, pickles and savoury bread/biscuits, are high in salt. Restaurant and fast foods often have high levels of salt. It's worth getting to grips with food labels and if possible cooking foods yourself from scratch. Herbs and spices added to foods will often keep them tasty without the need for added salt. While you may find that food is tasteless with less salt, your taste buds will soon get used to lower levels.
Uric acid stones are also fairly common. High levels of uric acid are also implicated in gout, and foods high in purine can increase your risk of both. Marmite®, shellfish, liver and kidneys, along with sugary drinks, are your enemy here. You may also be advised to reduce the amount of protein in your diet, and this may reduce your risk of another stone whatever type you have.
Regardless of which kind of kidney stone you have, it is important to stay hydrated, and ideally you should drink more than the 'average' recommended fluid intake of 1.5 litres a day (for women) and 1.8 litres a day for men. It's worth aiming for in the region of 12 glasses of non-alcoholic fluid a day. Alcohol is a diuretic and can make you dehydrated, so it's best avoided as much as possible. In hot weather or if you have diarrhoea and vomiting, you should increase your fluid intake to make up for the fact that you are losing more fluid."