Additional information if you form calcium oxalate stones

Calcium is helpful for people that form calcium oxalate stones. This is because calcium from the food you eat can bind to oxalate in your gut, reducing the amount of oxalate absorbed by the body. 

Aim to have 3-4 of the following high calcium foods each day, and preferably around mealtimes (700-1200mg calcium per day): 

•  Milk: a third of a pint or 200ml).
• Cheese, including cream cheese: 1oz or 30g.
• Yoghurt: 1 individual size pot.

For healthier options, choose lower fat alternatives

If you use non-dairy alternatives, make sure the product contains 120mg calcium per 100g/ 100ml.

Eating plenty of fruits and vegetables is good for our health, and people that eat plenty of fruits and vegetables appear to have a lower risk of forming kidney stones. Fruits and vegetables may help to make your urine more alkaline (less acidic), and eating a diet that helps to make your urine more alkaline (less acidic) is beneficial because calcium oxalate stones are more likely to form in acidic urine.  

Aim to eat at least 5 portions of fruit and vegetables each day (this does not include potato). 

What is a portion?

• Fruit: what you can hold in your hand (like 2 Satsumas or 1 apple).
• Vegetable: 2-3 heaped tablespoons.
• Salad: the amount to fill a breakfast bowl. 

Eating a lot of animal protein can make your urine acidic, and acidic urine may increase your risk of forming calcium oxalate stones. 

Animal protein foods include: 

• Meat (like beef, lamb, pork, minced meat, ham, burgers, sausages)
• Poultry (like chicken, turkey)
• Fish (like cod, tinned tuna, prawns, fish fingers)
• Eggs and cheese.

Animal protein in cow’s milk and yoghurt has a lower acid load than the foods listed above and does not need to be limited unless eaten in large amounts (exceeding the 4 high calcium foods each day as mentioned earlier). 

Try to limit your portions of animal protein to healthy eating amounts, for example: 

• 60g/ 2oz at a snack meal (cold meat/1 large egg in a sandwich).
• 115g/4oz at a main meal. This amount is about the size of a packet of playing cards.

Plant based proteins do not make the urine acid like animal protein does. Many plant based proteins may help make the urine more alkaline. Here are some ideas to include more plant-based proteins:

• Use lentils and beans as the protein source for meals.
• Reduce meat portion and pad meals out with beans or pulses.
• Include meat free days in the week .

You should limit excessive amounts of high oxalate foods in your diet if you form calcium oxalate stones, especially if you have been found to have high levels of oxalate in your urine. Advising on oxalate is hard because not all foods have been tested. The amount of oxalate in a food can also vary depending on where and when it was grown, and how it has been prepared -for example, boiled potato without skin contains a lot less oxalate than a baked potato (oxalate comes out into the water when boiling). 

The below foods have been found to be high in oxalate, so reducing them in your diet (not eliminating them) may be helpful. 

Very high oxalate (more than 100mg per serving)

• Spinach (raw and cooked)
• Rhubarb *
• Rice bran *
• Roasted buckwheat groats 

High oxalate (50-100mg per serving)

• Haricot/navy beans (canned)
• Baked beans (canned)
• Almonds
• Cashews
• Bulgar wheat
• Quinoa
• Soy flour *
• Brown rice flour *
• Baked potato
• Baked sweet potato
• Beetroot
• Dark Chocolate
• Miso (soup) 
•  

Nutritional information taken from the arvard School of Public Health & University of Chicago How To Eat A Low Oxalate Diet | Kidney Stone Program 

If you know you are going to have something high or very high in oxalate, perhaps try and have something high in calcium at the same time. 

High dose vitamin C supplements (1000mg/d or more) have been linked with a higher risk of forming calcium oxalate stones. If you buy vitamins, do not take more than the reference nutrient intake (RNI) or dietary reference value (DRV). The label on the bottle will tell you what percentage of the RNI or DRV the vitamin will give you. Avoid any that will give you more than 100%. 

Overview | Renal and ureteric stones: assessment and management | Guidance | NICE

EAU Guidelines on Urolithiasis - Uroweb

Kidney Stones: Medical Management Guideline - American Urological Association