Scientists once thought that the greater the oxalate level in a food, the more likely it was to increase the risk of forming a kidney stone. However, researchers have discovered that consumption of only certain oxalate-containing foods is likely to significantly increase urinary oxalate.
The foods reported by at least one group of researchers to cause a significant increase in urinary oxalate include:
- wheat bran
- tea (Not every study has found tea to significantly increase urinary oxalate.)
There remains no universal consensus on which oxalate-containg foods belong on this list. Nonetheless, there is a growing awareness that the important issue for people with a history of kidney stone formation is to avoid certain high-oxalate foods—those that are most responsible for increasing urinary levels of oxalate.
To avoid oxalate ask about ingredients at restaurants and others’ homes, and read food labels. The following list is not complete. Consult with a healthcare professional before making any significant changes to your diet.
These foods are high in oxalate (greater than 10 mg per serving):
- Beans in tomato sauce
- Black and red raspberries
- Coffee powder (Nescafe)
- Concord grapes
- Crackers made from soy flour
- Dandelion greens
- Fruit cake
- Fruit salad (canned)
- Green bell pepper
- Grits (white corn)
- Juices containing berries
- Lemon and lime peel
- Nuts (especially peanuts and pecans)
- Soy (see below)
- Summer squash
- Sweet potatoes
- Tomato soup
- Wheat germ
These foods are moderately high in oxalate (2–10 mg per serving):
- Bottled beer (12 oz [360 ml] limit/day)
- Chicken noodle soup (dried)
- Coffee (8 oz [240 ml])
- Cola beverage (12 oz [360 ml] limit per day)
- Lima beans
- Orange juice (4 oz [120 ml)
- Peas (canned)
- Pepper (greater than 1 tsp [2 grams] per day)
- Soy products (most)
- Sponge cake
- Tomato juice (4 oz [120 ml)
These foods are low in oxalate (0–2 mg per serving); eat as desired:
- Apple juice
- Beef (lean)
- Bing cherries
- Brussels sprouts
- Green grapes
- Lamb (lean)
- Lemonade or limeaid (without peel)
- Pork (lean)
- Peas (fresh)
- Salad dressing
- White bread
Research indicates that soybeans and soy-based foods, a staple in the diets of many health-conscious consumers, may promote kidney stones in those prone to the painful condition. The researchers measured nearly a dozen varieties of soybeans for oxalate, a compound that can bind with calcium in the kidney to form kidney stones.
They also tested 13 types of soy-based foods, finding enough oxalate in each to potentially cause problems for people with a history of kidney stones, according to Linda Massey, Ph.D., at Washington State University in Spokane.
The amount of oxalate in the commercial products easily eclipsed the American Dietetic Association’s 10 milligram-per-serving recommendation for patients with kidney stones, with some foods reaching up to 50 times higher than the suggested limit, she noted.
“Under these guidelines, no soybean or soy-[based] food tested could be recommended for consumption by patients with a personal history of kidney stones,” she said.
No one had previously examined soy foods for oxalate, thus the researchers are the first to identify oxalate in store-bought products like tofu, soy cheese and soy drinks. Other foods, such as spinach and rhubarb, also contain significant oxalate levels, but are not as widely consumed for their presumed health benefits, Massey said.
During their testing, the researchers found the highest oxalate levels in textured soy protein, which contains up to 638 milligrams of oxalate per 85-gram serving. Soy cheese had the lowest oxalate content, at 16 milligrams per serving. Spinach, measured during previous research, has approximately 543 milligrams per one-cup (2 oz. fresh) serving. [Journal of Agricultural and Food Chemistry September 2001]
Oxalate Avoidance can help with the following
The most common type of stone contains calcium in combination with either oxalate or phosphate. These chemicals are part of a person’s normal diet and make up important parts of the body, such as bones and muscles. Oxalate avoidance / reduction in the diet can help prevent subsequent stone formation in those who tend to form calcium oxalate stones.
Reducing the amount of oxalate in your diet may be helpful. Things to avoid include tea, spinach, beer, berry juices, baked beans in tomato sauce, peanuts, peanut butter creams, pecans, soybean curd, concord grapes. In addition, do not take more than 250mg of Vitamin C per day as it may contribute to oxalate formation. Restrict or limit milk or dairy products to reduce the amount of calcium oxalate in the body. Calcium citrate may prescribed to neutralize high blood or urine levels of oxalate.
|Likely to help|
A stone (concretion) in the kidney. If the stone is large enough to block the tube (ureter) and stop the flow of urine from the kidney, it must be removed by surgery or other methods. Also called Renal Calculus. Symptoms usually begin with intense waves of pain as a stone moves in the urinary tract. Typically, a person feels a sharp, cramping pain in the back and side in the area of the kidney or in the lower abdomen. Sometimes nausea and vomiting occur. Later, pain may spread to the groin. The pain may continue if the stone is too large to pass; blood may appear in the urine and there may be the need to urinate more often or a burning sensation during urination. If fever and chills accompany any of these symptoms, an infection may be present and a doctor should be seen immediately.
(mg): 1/1,000 of a gram by weight.
Ounce. Approximately 28 grams.
(tsp) Equivalent to 5cc (5ml).
(gm): A metric unit of weight, there being approximately 28 grams in one ounce.
The body's most abundant mineral. Its primary function is to help build and maintain bones and teeth. Calcium is also important to heart health, nerves, muscles and skin. Calcium helps control blood acid-alkaline balance, plays a role in cell division, muscle growth and iron utilization, activates certain enzymes, and helps transport nutrients through cell membranes. Calcium also forms a cellular cement called ground substance that helps hold cells and tissues together.
A measure of an environment's acidity or alkalinity. The more acidic the solution, the lower the pH. For example, a pH of 1 is very acidic; a pH of 7 is neutral; a pH of 14 is very alkaline.
Compounds composed of hydrogen, oxygen, and nitrogen present in the body and in foods that form complex combinations of amino acids. Protein is essential for life and is used for growth and repair. Foods that supply the body with protein include animal products, grains, legumes, and vegetables. Proteins from animal sources contain the essential amino acids. Proteins are changed to amino acids in the body.