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In Defense of Oxalic Acid

Moderate OxalateContent:
- barley, cooked
- corn bread
- corn tortilla
- cornmeal
- cornstarch
- flour, white or wheat
- oatmeal
- rice, brown
- unsalted saltine or soda crackers
- spaghetti in tomato sauce
- sponge cake
High Oxalate Content:
- Fig Newtons
- fruit cake
- graham crackers
- grits, white corn
- kamut
- marmalade
- soybean crackers
- wheat germ
Low Oxalate Content:
- acorn squash
- alfalfa sprouts
- cabbage
- cauliflower
- peas, frozen and fresh
- peppers, red
- radishes
- turnips, roots
- zucchini
- squash
Moderate Oxalate Content:
- asparagus
- artichokes
- brussels sprouts
- broccoli
- carrots
- corn
- cucumbers, peeled
- kohlrabi
- lettuce
- lima beans
- mushrooms
- onions
- potatoes, white
- peas, canned
- snow peas
- tomato, fresh
- tomato sauce
High Oxalate Content:
- beans (green, wax, dried)
- beets (tops, roots, greens)
- celery
- chives
- collards
- dandelion
- eggplant
- escarole
- kale
- leeks*
- mustard greens
- okra*
- parsley
- parsnips
- peppers, green
- pokeweed*
- rutabagas
- sorrel
- spinach*
- summer squash
- sweet potatoes*
- Swiss chard*
- tomato soup
- vegetable soup
- watercress
- yams
Low Oxalate Content:
- any not listed
Moderate Oxalate Content:
- basil, fresh
- malt, powder
- pepper
High Oxalate Content:
- cinnamon, ground
- parsley, raw
- pepper, more than 1 tsp/day
- ginger
- soy sauce

The word "Oxalic" formed from the Latin "oxalis", which referred to plants with leaves similar to clover. A plant such as wood sorrel - belonging to Genus Oxalis.

In the early 17th Century via Latin to Greek "wood sorrel," from oxus "sour" or "oxygen", because of the taste of its leaves.

It was believed in the late 18th century (France) that oxygen (literally meaning "acid-former" formed from the Greek oxus "sharp, sour") was a basic component of acids.

In 1776, Oxalic acid was prepared synthetically for the first time by Scheele.

Oxalic acid (IUPAC name: ethanedioic acid, formula H2C2O4) is a dicarboxylic acid with structure (HOOC)-(COOH). Because of the joining of two carboxyl groups, this is one of the strongest organic acids. It is also a reducing agent. The anions of oxalic acid as well as its salts and esters are known as oxalates.

Biological Hazards:
Oxalic acid and oxalates are mild nephrotoxic acids that are abundantly present in many plants, most notably fat hen (lamb's quarters), rhubarb and sorrel. Oxalic acid irritates the lining of the gut when consumed, and can prove fatal in large doses. The LD50 for pure oxalic acid is predicted to be about 378 mg/kg body weight, or about 22 g for a 60 kg human. Oxalic acid can also be present in the body due to the consumption of another toxin, ethylene glycol (generally known as automobile antifreeze), because over time, the body metabolizes ethylene glycol partially into oxalic acid. Estimated fatal dose is 5 to 15 grams.

Bodily oxalic acid may also be synthesized via the metabolism of either glyoxylic acid or unused ascorbic acid (vitamin C), which is a serious health consideration for long term megadosers of vitamin C supplements. 80% of kidney stones are formed from calcium oxalate. Some Aspergillus species produce oxalic acid, which reacts with blood or tissue calcium to precipitate calcium oxalate. There is some preliminary evidence that the administration of probiotics can affect oxalic acid excretion rates (and presumably oxalic acid levels as well.)

Action of Poisoning:
Oxalic acid also combines with metals such as calcium, iron, sodium, magnesium, and potassium in the body to form oxalate crystals which precipitate and irritate the gut and kidneys. The calcium oxalate preciptate (better known as kidney stones) obstruct the kidney tubules. Because it binds vital nutrients such as calcium, long-term consumption of foods high in oxalic acid can lead to nutrient deficiencies.

Healthy individuals can safely consume such foods in moderation, but those with kidney disorders, gout, rheumatoid arthritis, or certain forms of chronic vulvar pain (vulvodynia) are typically advised to avoid foods high in oxalic acid or oxalates. Conversely, calcium supplements taken along with foods high in oxalic acid can cause oxalic acid to precipitate in the gut and drastically reduce the levels of oxalate absorbed by the body (by 97% in some cases.)

Symptoms of poisoning are weakness, burning in the mouth, death from cardiovascular collapse; on the respiratory system - difficulty breathing; on the eyes, ears, nose, and throat - burning in the throat; one the gastrointestinal system - abdominal pain, nausea, vomiting, diarrhea; and on the nervous system - Convulsions, coma.

Oxalic Acid Containing Foods:
The root and leaves of rhubarb contain dangerously high concentrations of oxalic acid.

Foods that are edible, but still contain significant concentrations of oxalic acid include - in decreasing order - buckwheat, star fruit (carambola), black pepper, parsley, poppy seed, rhubarb stalks, amaranth, spinach, chard, beets, cocoa, chocolate, most nuts, most berries, and beans. The gritty feel one gets in the mouth when drinking milk with rhubarb desserts is caused by precipitation of calcium oxalate. Thus even dilute amounts of oxalic acid can readily "crack" the casein found in various dairy products.

Leaves of the tea plant (Camellia sinensis) are known to contain among the greatest measured concentrations of oxalic acid relative to other plants. However the infusion beverage typically contains only low to moderate amounts of oxalic acid per serving, due to the small mass of leaves used for brewing.

Research is being done on methods to safely reduce oxalate in food.

Plants Containing OXALIC ACID (Dr. Duke's Phytochemical and Ethnobotanical Databases)

In household chemical products such as Bar Keeper's Friend, some bleaches, and rustproofing treatments.
In wood restorers where the acid dissolves away a layer of dry surface wood to expose fresh material underneath.
As a mordant in dyeing processes.
Vaporized oxalic acid is used by some beekeepers as an insecticide against the parasitic Varroa mite.

Tests for Oxalic Acid:
Titration with potassium permanganate can reveal the presence of oxalic acid (as the acid is only a weak reductant, and needs an oxidant as strong as permanganate in order to react). However, this test will confuse ascorbate and oxalic acid, as will most test based on reducing power: the solution is to run a second test for strong reductants using, for example, iodine.

Preparation and Manufacture:
Oxalic acid can be conveniently prepared in the laboratory by oxidizing sucrose using nitric acid as the oxidizer and a small amount of vanadium pentoxide as a catalyst. On a large scale, sodium oxalate is manufactured by absorbing carbon monoxide under pressure in hot sodium hydroxide.

What Should We Consider:

The human body can synthesizes oxalic acid from ascorbic acid (Vitamin C). It also may combine with calcium, iron, sodium, magnesium, or potassium to form less soluble salts known as oxalates.

Since oxalic acid binds with important nutrients, making them inaccessible to the body, regular consumption of large amounts of food high in oxalic acid over a period of weeks to months may result in nutrient deficiencies, most notably of calcium.

Oxalic acid is a strong acid, and is irritating to tissue all by itself. Extremely high doses are fatal. Oxalates, on the other hand, form tiny little insoluble crystals with sharp edges, which are also irritating to tissue. So, high levels of oxalic acid/oxalates in the diet lead to irritation of the digestive system, and particularly of the stomach and kidneys. They may also contribute to the formation of kidney stones (the most common form of kidney stone is composed of calcium oxalate).

Hard water (which contains calcium and magnesium) will tie up much of the oxalate consumed in the diet within the gastrointestinal tract, thereby decreasing oxalate absorption.

Calcium carbonate (precipitated chalk) is used to remove excess acid from juices. It is used extensively to remove oxalic acid from Rhubarb juice.

What About Rhubarb?
All parts of the rhubarb plant contains oxalates, but anthraquinone glycosides is also contained in the plant. It is possible that the combination of both compounds are the problem.

So-How much rhubarb do you have to ingest to induce poisoning?

If you weight about 145 pounds, it will take about 25 grams of pure oxalic acid required to cause death. In essense-you will have to eat about 11 pounds of it. These numbers are relative, and it would take a lot less to become ill.

Drink plenty of fluids. Drink more than 8 cups of fluid every day. Your urine should be as clear as water. If it isn't, drink more fluids.

To help prevent oxalate stones from forming, limit oxalates to 40 to 50 mg per day.


Low Oxalate Content:
                              Moderate Oxalate Content:                       High Oxalate Content:
Apple juice                                                 Coffee(limit to 8 oz/day)                                Any juice made from high oxalate fruits
Beer-bottled or canned                                Cola(limit to 12 oz/day)                                 Beer, draft
Cider                                                         Cranberry juice                                             Chocolate, plain
Distilled alcohol                                          Grape juice                                                  Chocolate milk
Ginger Ale                                                 Orange juice                                                 Cocoa
Grapefruit juice                                           Orangeade                                                   Coffee Powder (instant)
Lemon juice                                                                                                                  Ovaltine
Lemonade/limeade                                                                                                        Tea, brewed
(made without peel)
Lime juice
Milk(skim, 2%, whole)
Orange soda
Root Beer
Tea, instant


Milk (skim, 2%, whole)                                None                                                            Chocolate milk
yogurt with allowed fruit


Beef, lamb, pork                                         Beef kidney                                                    None
Eggs                                                         Liver

Meat Substitutes, Beans, Nuts, and Seeds:

Eggs                                                         Garbanzo beans canned                               Almonds, cashews, peanuts, pecans and
Lentils                                                       Lima beans                                                  walnuts
Water Chesnuts                                         Split peas, cooked                                       Baked beans canned in tomato sauce
                                                                                                                                   Green beans, waxed and dried
                                                                                                                                   Peanut butter
                                                                                                                                   Sesame and sunflower seeds
                                                                                                                                   Tofu (soybean curd)
Fats and Oils:

All                                                             None                                                           None


Apples, peeled                                           Apples with skin                                           Blackberries
Avocado                                                    Apricots                                                       Black raspberries*
Bananas                                                    Black currants                                              Blueberries
Cantaloupe                                                Cranberries,dried                                           Red Currants
Casaba                                                     Grapefruit                                                     Dewberries
Cherries, bing                                            Oranges                                                       Figs, dried
Coconut                                                    Peaches                                                       Grapes, purple
Cranberries, canned                                   Pears                                                           Gooseberries
Grapes, green                                            Pineapple                                                     Kiwi
Honeydew                                                 Plums                                                           Lemon Peel*
Mangoes                                                   Prunes                                                         Lime Peel*
Nectarines                                                                                                                    Orange Peel
Papaya                                                                                                                         Red Raspberries
Raisins                                                                                                                         Rhubarb
Watermelon                                                                                                                  Strawberries

Bread and Starches:

Breakfast cereals
Noodles, egg or macaroni
Rice, white or wild



So, it would seem that the key to preventing problems is a diet that is varied. Moderation In All Things.

At least 75 percent of kidney stones are composed of calcium combined with phosphate or oxalic acid. Medical experts believe that these stones result from an accumulation of unused calcium, and lack of exercise is generally thought to be a factor.

A study conducted in 1973 showed that cranberries help prevent stones in some people by reducing the excessive amounts of calcium commonly found in the urinary tract.

There is some scientific evidence that this may also be true of rose hips, which have traditionally been used to ease various urinary tract infections. Since the calcium-phosphate stones are most common in alkaline urine, cranberries and other herbs that acidify urine also help prevent stones.

Many years ago, an enzyme (an oxidase) that breaks down oxalic acid into CO2 and H2O2 was discovered and found to be naturally present in spinach leaves. However, nitrate, which can also be present because of the use of common nitrate-based fertilizers, inactivates the enzyme.

In the controlled-environment agricultural technique, done by Corinne Johnson-Rutzke of Cornell Research Foundation, Inc., for Kennedy Space Center , one cuts off the supply of nitrate and keeps the spinach plants cool while providing sufficient oxygen. This technique allows the enzyme to naturally break down oxalate. The result is that the oxalate content is reduced by 2/3 in one week.

Oxalic acid is even needed by our body for many functions (including peristalsis), and plays an important role in colon health, so much so that when it is not gotten through the diet, the body synthesizes it from ascorbic acid.

When you cook the spinach the heat crystalizes, destroying it, the acid particles making them salt atoms, then the crystalized particles you obtain called oxalate bind with other salts such as calcium and potassium and they become stones. The calcium becomes unavailable and stones are therefore created. Therefore,,it's not the oxalic acid that bind with other minerals making them bio-unavailable, but oxalates that are only formed when heat destroy and then crystalize the acid particles.

According to the book "Fresh Vegetable and Fruit Juices" by Dr. Walker (1936 --BTW, his reference to organic means raw food):

"Organic oxalic acid is one of the important elements needed to maintain the tone of, and to stimulate peristalsis. . .

If the important organs comprising the alimentary and eliminative departments of our system, or any parts of them, are moribund or dead, the efficiency of their function is impaired, to say the least. This condition can result only from a lack or deficiency of live atoms in the food nourishing the cells and tissues concerned. Live food means that food which contains live organic atoms and enzymes found only in our raw foods. . . .

It is very vital to stress this matter in regard to oxalic acid. When the food is raw, whether whole or in the form of juice, every atom in such food is vital ORGANIC and is replete with enzymes. Therefore, the oxalic acid in our raw vegetables and their juices is organic, and as such is not only beneficial but essential for the physiological functions of the body. ...

The oxalic acid in cooked and processed foods, however, is definitely dead, or INORGANIC, and as such is both pernicious and destructive. Oxalic acid readily combines with calcium. If these are both organic, {meaning raw} the result is a beneficial constructive combination, as the former helps the digestive assimilation of the latter, at the same time stimulating the peristaltic functions in the body. ....

When the oxalic acid has become INORGANIC by cooking or processing the foods that contain it, then this acid forms an interlocking compound with the calcium even combining with the calcium in other foods eaten during the same meal, destroying the nourishing value of both."

In 1997, a research division of a healthcare provider conducted a double-blind study with a group of 64 patients who had a history of renal calculi to determine if potassium/magnesium citrate would prevent the recurrent formation of calcium oxalate kidney stones (Ettinger et al. 1997).

The patients were given 42 mEq (milliequivalent) potassium, 21 mEq magnesium, and 63 mEq citrate or a placebo daily for 3 years. New renal calculi formed in 63.6% of patients receiving the placebo. However, patients receiving the potassium/magnesium citrate protocol presented with 12.9% recurrent renal calculi. Ettinger et al. (1997) concluded that "potassium/magnesium citrate effectively prevents recurrent calcium oxalate stones, and this treatment given for up to 3 years reduces risk of recurrence by 85%."

Contrary to what was considered to be "common sense" thinking in the past, two major studies have shown that calcium should not be reduced for patients with a history of kidney stones (Takei 1998; Williams 2001). It was originally thought that patients with a history of renal calculi should limit their intake of calcium.

In fact, current recommendations from the National Institutes of Health published on their Web site continue to call for calcium-restricted diets. Such dietary changes also affect the alkali and pH of the body by calling for the restriction of foods such as apples, beets, parsley, broccoli, spinach, and pineapples. However, newer findings contradict these dietary restrictions and offer scientific evidence that uncombined intestinal oxalic acid is the real culprit for calcium oxalate kidney stones (Ohgitani 2000).

Harvard researchers studied nearly 92,000 nurses over a period of 12 years to determine the relationship between calcium intake and the occurrence of renal calculi . The conclusion of this massive study was that those nurses who consumed diets that were higher in calcium were at lower risk for kidney stones.

Another study conducted in South Africa found that "mineral water containing calcium and magnesium deserves to be considered as a possible therapeutic or prophylactic agent in calcium oxalate kidney stone disease" (Rodgers 1997). French mineral water containing calcium (202 ppm) and magnesium (36 ppm) was selected as the delivery method. Twenty subjects of each sex who had previously formed calcium oxalate renal calculi and 20 healthy volunteers of each sex participated in the study. Each subject provided 24-hour urine collection samples each day during the study. The mineral water was ingested over a 3-day period. Then the participants switched to tap water. The cycle was repeated at least twice by each subject. The male stone formers received the most benefit, showing nine risk factors that were favorably affected by the mineral water containing calcium and magnesium (Rogers 1997).

In considering the literature below, it would seem that by themselves to have very little impact. However, if we build on the information some interesting conclusions can be made or assumed.

In the Book "Oxalic acid in Biology and Medicine" by A. Hodgkinson, it is stated that:

"The decomposition of solutions of oxalic acid by y-radiation has been made the basis of a method for measuring radiation dosage, in the sterilization of food and medical products (Holm and Sehested). The absorbed dose is determined from the decrease in oxalic acid concentration which occurs during irradiation". .....

"A mean value of 288mcg of anhydrous oxalic acid/100ml was reported for normal human blood" (Pernet and Pernet). ....

And then add the information that oxalic acid is high in foods reported to be great cancer fighters, like carrots, spinach, beets, nuts, and, hundreds of other foods and beverages.

Also The National Institute of Environmental Health and Sciences and The U.S. Department of Energy published a booklet called "Questions and Answers About E- M- F, Electric and Magnetic Fields Associated with the Use of Electric Power", which links epidemiological studies with cancer.

"When oxalic acid is in our blood; in foods & beverages we eat and drink, and testimonials confirm oxalic acid kills cancer cells, virus, bacteria, and decalcifies the material in plaque in arteries; and is in the blood of all warm blooded mammals".

Radiation is given as a "just in case" and the number, time and power of each treatment will determine how completely oxalic acid in the blood is decomposed.

The decomposition of the oxalic acid in the blood by radiation may so weaken the immune system so that one cannot fight off any viral or bacterial disease.

Therefore it is understandable that many cancer patients die from cancer related to viral pneumonia.

There are many questions that are left unanswered that cover the effects and sources of E-M-F as well as a discussion of the history of Oxalic Acid, and Cancer diets.

Here is an abstract (patent) where oxalic acid is used for a health benefit:

US6133318: Oxalic acid or oxalate compositions and methods for bacterial, viral, and other diseases or conditions.

What is claimed is:

1. A bactericidal composition for treating infectious or pathogenic bacterial diseases or conditions in warm blooded animals sensitive to treatment comprising: a bactericidal composition including an effective amount of at least one therapeutically effective bactericidal form of at least one of oxalic acid and oxalate and at least one of a carrier and diluent for said at least one of oxalic acid and oxalate, wherein said effective amount is less than a lethal dosage of oxalic acid and wherein said bactericidal composition is adapted to be administered to warm blooded animals on a periodic basis in less than a lethal dosage.

And let's not forget that oxalic acid is a chemical in Chocolate!!


Kidney stone disease by Coe FL, Evan A, Worcester E, on NIH website

Aspects of oxalosis associated with aspergillosis in pathology specimens by Pabuccuoglu U. on NIH website

Use of a probiotic to decrease enteric hyperoxaluria by Lieske JC, Goldfarb DS, De Simone C, Regnier C. on NIH website

Gastrointestinal oxalic acid absorption in calcium-treated rats by Morozumi M, Hossain RZ, Yamakawa KI, Hokama S, Nishijima S, Oshiro Y, Uchida A, Sugaya K, Ogawa Y. on NIH website

Milk and calcium prevent gastrointestinal absorption and urinary excretion of oxalate in rats by Hossain RZ, Ogawa Y, Morozumi M, Hokama S, Sugaya K. on NIH website

Biodegradation of oxalic acid from spinach using cereal radicles by Betsche T, Fretzdorff B. on NIH website

Back to Eden by Jethro Kloss

Boning Up by Lynn Grieger

Fresh Vegetable and Fruit Juices by Dr. Walker 1936

Go Light on Oxalic Acid, by Mary Schrick, N.D.

Growth Conditions To Reduce Oxalic Acid Content of Spinach -John F. Kennedy Space Center, Florida

King's American Dispensatory, Acidum Oxalicum-Oxalic Acid by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D., 1898.

Low Oxalate Diet (Information for Patients), University of Pittsburgh Medical Center

Oxalic acid in Biology and Medicine"by A. Hodgkinson

Practical Organic Chemistry by Julius B. Cohen, 1930 ed. preparation #42

Questions and Answers About E- M- F, Electric and Magnetic Fields Associated with the Use of Electric Power, published by The National Institute of Environmental Health and Sciences and The U.S. Department of Energy

The Rhubarb Compendium from http://www.rhubarbinfo.com/

U.S. Patent 1602802

U.S. Patent: 6133318: Oxalic acid or oxalate compositions and methods for bacterial, viral, and other diseases or conditions.

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