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This leaflet provides information on how to alter your diet to reduce your risk of kidney stones.
Kidney stones develop from tiny mineral deposits within the kidney, which then increase in size to form visible fragments. This happens when urine is very concentrated.
The majority of kidney stones are calcium-containing. These include calcium oxalate or calcium phosphate types.
You may be at higher risk of kidney stones if you have:
• A family history of kidney stones.
• Urinary tract abnormalities.
• Frequent urinary tract infections.
• Absorption problems e.g. gastric bypass, Crohn’s disease, intestinal resection.
• Gout.
• Obesity, diabetes, hypertension, metabolic syndrome.
Your diet and lifestyle can reduce the growth of kidney stones.
• Reduce the acidity and change the amount of stone forming substances in your urine by changing your diet.
• Increasing your urine volume to 2-3 litres a day.
• Promoting a healthy lifestyle to address obesity, diabetes and hypertension.
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Calcium oxalate stones are the most common type of kidney stone. Kidney stones are solid masses that form in the kidney when there are high levels of calcium, oxalate, cystine, or phosphate and too little liquid. There are different types of kidney stones. Your healthcare provider can test your stones to find what type you have. Calcium oxalate stones are caused by too much oxalate in the urine.
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Oxalate is a natural substance found in many foods. Waste products, such as oxalate, from your food travel through the bloodstream to the kidneys and are removed through urine. If there is too much waste and too little liquid in the urine, crystals can begin to form. These crystals may stick together and form a solid mass, called a kidney stone.
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Certain risk factors may cause your body to form calcium oxalate stones. These risk factors include:
• Dehydration from not drinking enough fluid
• A diet too high in:
-Protein
– Oxalate
– Sodium (salt)
– Sugar (like high fructose corn syrup)
• Obesity
• Medical conditions such as:
-Dent Disease (a rare genetic disorder that affects the kidneys)
– Hyperparathyroidism (a very high amount of parathyroid hormone in the blood that causes a loss of calcium, and high levels of oxalate)
• Digestive diseases and surgeries, such as:
– Inflammatory Bowel Disease (IBD):
▪ Ulcerative Colitis
▪ Crohn’s Disease
– Gastric bypass surgeryIt is important to know that kidney stones are more common if you have Inflammatory Bowel Disease (IBD). This affects your body’s ability to absorb fats properly. When fat is not absorbed the right way, the fat binds to calcium and leaves oxalate behind. The oxalate is then absorbed and taken to the kidney, where it can form stones.
Similarly, following gastric bypass surgery, your body absorbs less calcium from your digestive system. Because of this, higher levels of oxalate are found in the urinary tract. The build-up of oxalate can form crystals, which can form kidney stones.
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Drink enough fluids. The number one thing you can do is to drink enough fluids, especially water. Drinking enough fluids will thin out your urine and make it harder for chemicals to build up and form crystals. Your healthcare provider will look at your overall health, diet, and lifestyle and recommend the right amount of fluid you should have each day.
• Avoid eating too much protein. Eating too many animal proteins (such as poultry, beef, pork, fish) can cause stones to form.
• Eat less salt (sodium). A diet high in salt (sodium) causes calcium to build in your urine.
• Include the right amount of calcium in your diet. Calcium is a nutrient that is found in dairy products, such as yogurt, milk and cheese. Eating foods with calcium is a good way for oxalates to leave the body and not form stones. The best way to get calcium into your body is through the foods you eat Do not take a calcium supplement; calcium in the form of a supplement may raise your chances of forming new stones. Your healthcare provider will help you find the best way to include calcium in your diet.
• Eat less oxalate-rich foods. Limiting how many oxalate-rich foods you eat each day may help lower your chance of forming new stones. These are some foods you should limit because of their high oxalate levels:
o Nuts and nut butters
o Beans
o Rhubarb
o Beets
o Soy products
o Chocolate
o All Bran®
o Buckwheat flour
o Miso
o Tahini
o Sesame seeds
o Dark green vegetables, such as spinach
o Sweet Potatoes
o Berries
o Oranges
o Coffee
o Tea (black)
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The most important thing you can do to prevent the formation of stones is to increase the amount of fluid you are having. Passing urine regularly, including through the night, helps prevent stone formation.
Aim to drink at least two and a half to three litres of water a day.
Some fluids are better to drink than others:
• Adding lemon or lime juice to water increases citrate levels in your urine. This can reduce your risk of forming oxalate stones. Add 60ml of concentrated lemon or lime juice (or the juice of three to four lemons or limes) to one litre of water.
• Avoid carbonated and sugar-sweetened drinks, such as cola, orangeade, energy drinks and sparkling water. If choosing a carbonated drink; lemonade or diet lemonade with a higher percentage of lemon juice is a better option.
• Choose no added sugar squashes or cordials.
• Always add milk to tea and coffee if you have oxalate stones to help reduce oxalate being absorbed in your gut.
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Look at food labels when making decisions on which foods to buy. Remember, food labels may show the salt content per 100g and not always the salt content of the entire portion. Choose foods with more green coding and fewer with amber coding. Avoid foods with red coding.
Look at food labels when making decisions on which foods to buy. Remember, food labels may show the salt content per 100g and not always the salt content of the entire portion. Choose foods with more green coding and fewer with amber coding. Avoid foods with red coding.
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If you are overweight and would like to lose weight, below are some tips:
• Don’t mistake thirst for hunger – have a glass of water and wait 30 minutes before reassessing your hunger.
• Try sugar-free gum or sweets in between meals.
• Make sure meals are of a sensible size – you could try using a smaller plate.
• Try to limit snacks between meals. If you need a snack, choose lower calorie options like vegetable sticks, a piece of fruit or a handful of plain popcorn.
• Keep yourself occupied, boredom can lead you into the kitchen.
• Be as active as you can, to burn excess calories.
• For a 12-week diet and exercise plan, see the NHS website:
www.nhs.uk/Livewell/weight-loss-guide/Pages/losing-weight-getting-started.aspx
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Fruit and vegetables can help reduce stones forming, particularly if you have oxalate stones as they provide citrate which reduce the acidity of urine.
• Aim for at least five portions of fruit and vegetables per day.
• One portion = one medium-sized fruit, e.g. apple, banana; two small fruits, e.g. plum, satsumas or three tbsp of cooked vegetables.
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There is some evidence to suggest that a diet high in animal protein may cause stones to form. A vegetarian diet including dairy may have a protective effect. There is no need to stop eating meat but here are some ideas to reduce the amount of animal protein you eat and plant proteins you can replace it with:
• Limit meat and fish to no more than 200g (8oz) a day. Preferably spread throughout the day.
• Beans and lentils are good sources of vegetable protein. Use to replace some or all the meat in dishes e.g. lentils or reduced-salt baked beans in shepherd’s pie, beans in chilli con carne or lentils in stews and hot pots.
• Have less processed meats, such as bacon, sausages and ham.
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It is not recommended to go on a low calcium diet as this can cause more stones to form. This is because calcium binds to oxalate in the gut to reduce the amount of oxalate absorbed.
• A moderate calcium intake (700-1200mg/day) through food is recommended. You would achieve this by having three to four of the following a day:
– 200ml of milk – if choosing a plant milk such as soya, oat, almond or rice milk have those fortified with calcium
– 30g of cheese
– 120g of yoghurt
– 80g of tofu
– 60-100g of tinned fish with edible bones, such as sardines and pilchards.
• Choose lower fat varieties.
• The use of calcium supplements is not recommended, unless prescribed by your doctor.
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There is some uncertainty about how much oxalate the body absorbs from these foods but having an adequate calcium in your diet can help reduce absorption of oxalate from the diet. If you have been diagnosed with oxalate containing stones, you may wish to avoid the following high oxalate foods or to eat them in small amounts.
• beetroot
• black tea (always have tea with milk)
• cereals containing added wheat bran and/or nuts such as All Bran, Bran Flakes, Sultana Bran, Shredded Wheat, Weetabix, granola, muesli
• chocolate
• miso soup
• nuts (almonds are particularly high in oxalate)
• rhubarb
• Spinach.
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The best way to make sure you get enough vitamins and minerals is through a healthy, well-balanced diet.
Extra supplementation of vitamins and minerals may not be recommended. Always ask for advice from your doctor.
There is no evidence that supplementation of omega 3/DHA/EPA fish oils helps reduce the risk of kidney stone formation.