Foods To Avoid
General advice across different types of stones is to reduce sodium intake, in table salt and processed foods, and limit animal protein in your diet, particularly in the case of uric acid stones. Also avoid foods high in oxalates if you have calcium oxalate stones. Get tested to identify the type of stones you are likely to develop and modify your diet accordingly.
Obscure, painful, and potentially life-threatening, kidney stones affect 1 in 10 people at some point or the other during their lifetime. The most awful thing about kidney stones, besides the blatant pain, is that they threaten to come back – the incidence of recurrence being a whopping 70%.
You need not live in fear anymore. With a little caution and simple dietary changes, you can set aside the anxiousness of recurring stones. If you have kidney stones or you’ve had them in the past, here’s what you can do.
How To Prevent Kidney Stones
When there is too much calcium, oxalate, or phosphorous in the urine, they can combine and crystallize to form calcium oxalate or calcium phosphate kidney stones. Even too much uric acid in urine can settle to form uric acid stones. Your diet can greatly influence the urinary levels of these substances and is well within your control.
The basic strategy to discourage stone formation is to lower the urinary levels of sodium, oxalate, uric acid, and calcium and increase urinary citrate.1 Citrate stops crystals from growing into stones.
Foods To Avoid If You Have Kidney Stones
Knowing the exact nature of your stones, present or past, can help you decide exactly which foods you need to avoid. For instance, steering clear of oxalate-rich foods can help a person with calcium oxalate stones but will do nothing for a person who has uric acid stones.
Some dietary recommendations are consistent across different types of stones, such as drinking more fluids. Others are more specific.2
|Type of Stone||Sub-type||Causes||Dietary Intake Advice (Elimination)|
|High calcium and high oxalate excretion
High urine calcium and alkaline urine
|Reduce sodium, animal protein, and oxalate-rich foods (rhubarb, nuts. wheat bran)
Reduce sodium and animal protein (meat, eggs, and fish)
|Uric acid stones
|Uric acid alone
Uric acid and calcium
|Highly acidic urine because of high levels of uric acid; often caused by purines found in meats, fish, and shellfish||Limit animal protein (meat, eggs, and fish)|
(more common in women)
|–||Genetics; the amino acid cystine leaks into kidneys and form stones.||–|
Note: For those who have calcium phosphate stones, it may help to refrain from orange and lemon juice.3 They acidify the urine, undesirable in the case of these stones. Cranberry juice, on the other hand, may help alkalinize the urine.
1. Oxalate-Rich Foods
This is actually a no-brainer once you know that oxalate is very often one half of a kidney stone. By avoiding foods rich in oxalate, you are decreasing the availability of the raw material required to form the most common stones. This, however, is effective only for those who have calcium oxalate stones.
Avoiding the following will help:4
- Apricots, figs, rhubarb, kiwi fruit, strawberries
- Artichoke, green and wax beans, beets, raw red cabbage, celery, chives, eggplant, endive, leeks, okra, green peppers, rutabagas, summer squash, parsley, white corn
- Dark leafy greens: Swiss chard, beet greens, mustard greens, Dandelion greens, spinach, kale, collards, escarole, arugula
- Potatoes, sweet potatoes, tomato paste ( Do Tomato Seeds Cause Kidney Stones?)
- Beans: baked, black, white, great northern, navy, pink
Nuts and seeds:
- Almonds, cashews, peanuts, peanut butter, pecans, sesame seeds, sunflower seeds, poppy seeds
- Grits, barley, cornmeal, buckwheat, lentil & potato soup
- Whole wheat products: bread, pasta, tortilla, wheat germ, wheat bran and bran cereal, cream of wheat, shredded wheat
Drink no more than 2-3 cups of tea or coffee a day. They carry moderate amounts of oxalate.
- Chocolate beverages
- Tea, instant coffee, colas, carob ice cream
Chocolate, soy products, black olives, pepper (more than 1 tsp/day), turmeric, draft beer
2. Sodium-Rich Foods
Sodium provokes the kidneys to excrete more calcium in the urine. High concentrations of calcium can form salts with oxalate or phosphorus, leading to kidney stones. Sodium also lowers stone-fighting citrate levels in urine.5
The fact that urinary calcium levels mirror dietary sodium levels can be used to our advantage. Limit your daily sodium intake to less than 2 gm per day.6
A huge 75% of our sodium intake is from processed foods. Before consuming packaged foods, check the Percent Daily Value (%DV) for sodium on the Nutrition Facts label. Sodium equal to or less than 5% is fine, anything higher than 20% is a complete no-no.7
Avoid the following:
- Table salt (sodium chloride)
- Fast foods
- Processed, canned, and packaged foods
- Foods with these labels – sodium bicarbonate (baking soda), baking powder, disodium phosphate, monosodium glutamate (MSG), sodium alginate, sodium nitrate, sodium nitrite
3. Animal Proteins And Other Purine Sources
Purines are natural compounds found in the body, even in our DNA, and in many foods. They can be broken down into uric acid by our body. So, if we ingest too much purine, urine concentrations of uric acid will spike. Urinary uric acid can settle and form kidney stones.
Animal protein sets the odds in favor of stone formation, lowering citrate excretion and increasing calcium and uric acid excretion. Individuals with a history of recurring kidney stones should limit their daily animal protein intake to 80 gm.8 It is better to avoid:9
- Meat: Beef, chicken, pork, lamb, duck, and so on (particularly organ meat and sweetbreads)
- Seafood: Anchovies, crab, fish roes, herring, mackerel, sardines, shrimps, whitebait
- Other sources: Eggs, dairy products (milk and cheese), yeast and extracts, beer, asparagus, cauliflower, mushrooms, beans and peas, spinach
Control Your Diet To Fight Obesity And Diabetes
You may wonder what obesity and diabetes have to do with stones formed in the kidneys. Here are the connections:
- Insulin resistance, a common cause of diabetes, can reduce citrate and increase calcium in urine – both risk factors for kidney stones.10
- A higher body mass index (BMI), as in the case of obese individuals, has been linked to greater oxalate excretion – another risk factor for stones.
So, weight loss driven by a healthy diet not dependent on animal protein and effective management of diabetes may be able to better prevent kidney stones.
Not All Fluids Are Good For Kidney Stones
The most effective advice anyone could give to avoid kidney stones is to fill up on fluids. Drinking 2.5–3 liters of fluids per day to increase urine volume can work wonders.11 However, the kind of fluid matters, too. For instance, coffee and beer decrease the risk of non-oxalate stones but increase the risk of calcium oxalate stones. Lemon juice with a high citrate concentration can decrease risks of stones other than calcium phosphate stones while they are detrimental to those with calcium phosphate stones. Similarly, grapefruit juice seems to increase the risk of stones in general for reasons unknown.
A good starting point would be to get blood or urine tests done to identify the kind of stones you have or may develop. Some people who are able to catch small stones as they pass out in urine can send the stones to the lab for testing as well.
The very thought of developing kidney stones or of them recurring is painfully discomforting. Take control of your health and do what is in your kidney’s best interests, even if that means making a few food sacrifices.
References [ + ]
|1, 11.||↑||Finkielstein, Vadim A., and David S. Goldfarb. “Strategies for preventing calcium oxalate stones.” Canadian Medical Association Journal 174, no. 10 (2006): 1407-1409.|
|2.||↑||Diet for Kidney Stone Prevention. National Institute of Diabetes and Digestive and Kidney Diseases. National Institutes of Health.|
|3, 5, 9.||↑||Diet and Lifestyle Advice for the Prevention of Kidney Stones. Guy’s and St. Thomas’ NHS Foundation Trust.|
|4.||↑||Foods and Beverages High in Oxalates. Digestive Health Center. University of Virginia.|
|6, 8, 10.||↑||Finkielstein, Vadim A., and David S. Goldfarb. “Strategies for preventing calcium oxalate stones.” Canadian Medical Association Journal 174, no. 10 (2006): 1407-1409.|
|7.||↑||Eating, Diet, & Nutrition for Kidney Stones. National Institute of Diabetes and Digestive and Kidney Diseases. National Institutes of Health.|