Occurrence in Nature
Oxalate occurs in many plants, where it is synthesized via the incomplete oxidation of carbohydrates.
Oxalate-rich plants include fat hen ("lamb's quarters"), sorrel, and several Oxalis species. The root and/or leaves of rhubarb and buckwheat are high in oxalic acid. Other edible plants that contain significant concentrations of oxalate include—in decreasing order—star fruit (carambola), black pepper, parsley, poppy seed, amaranth, spinach, chard, beets, cocoa, chocolate, most nuts, most berries, fishtail palms, New Zealand spinach (Tetragonia tetragonioides) and beans. Leaves of the tea plant (Camellia sinensis) 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.
| Common high-oxalate foods | ||
|---|---|---|
| Food Item | Serving |
Oxalate Content (mg) |
| Beet greens, cooked | 1/2 cup | 916 |
| Purslane, leaves, cooked | 1/2 cup | 910 |
| Rhubarb, stewed, no sugar | 1/2 cup | 860 |
| Spinach, cooked | 1/2 cup | 750 |
| Beets, cooked | 1/2 cup | 675 |
| Chard, Swiss, leaves cooked | 1/2 cup | 660 |
| Rhubarb, canned | 1/2 cup | 600 |
| Spinach, frozen | 1/2 cup | 600 |
| Beets, pickled | 1/2 cup | 500 |
| Poke Greens, cooked | 1/2 cup | 476 |
| Endive, raw | 20 long leaves | 273 |
| Cocoa, dry | 1/3 cup | 254 |
| Dandelion greens, cooked | 1/2 cup | 246 |
| Okra, cooked | 8 - 9 pods | 146 |
| Potatoes, sweet, cooked | 1/2 cup | 141 |
| Kale, cooked | 1/2 cup | 125 |
| Peanuts, raw | 1/3 cup (1-3/4 oz) | 113 |
| Turnip greens, cooked | 1/2 cup | 110 |
| Chocolate, unsweetened | 1 oz. | 91 |
| Parsnips, diced, cooked | 1/2 cup | 81 |
| Collard greens, cooked | 1/2 cup | 74 |
| Pecans, halves, raw | 1/3 cup (1-1/4 oz) | 74 |
| Tea, leaves (4 min. infusion) | 1 level tsp in 7 oz water | 72 |
| Cereal germ, toasted | 1/4 cup | 67 |
| Gooseberries | 1/2 cup | 66 |
| Potato, Idaho white, baked | 1 medium | 64 |
| Carrots, cooked | 1/2 cup | 45 |
| Apple, raw with skin | 1 medium | 41 |
| Brussel sprouts, cooked | 6 - 8 medium | 37 |
| Strawberries, raw | 1/2 cup | 35 |
| Celery, raw | 2 stalks | 34 |
| Milk chocolate bar | 1 bar (1.02 oz) | 34 |
| Raspberries, black, raw | 1/2 cup | 33 |
| Orange, edible portion | 1 medium | 24 |
| Green beans, cooked | 1/2 cup | 23 |
| Chives, raw, chopped | 1 tablespoon | 19 |
| Leeks, raw | 1/2 medium | 15 |
| Blackberries, raw | 1/2 cup | 13 |
| Concord grapes | 1/2 cup | 13 |
| Blueberries, raw | 1/2 cup | 11 |
| Currants, red | 1/2 cup | 11 |
| Apricots, raw | 2 medium | 10 |
| Raspberries, red, raw | 1/2 cup | 10 |
| Broccoli, cooked | 1 large stalk | 6 |
| Cranberry juice | 1/2 cup (4 oz) | 6 |
The "gritty mouth" feeling one experiences when drinking milk with a rhubarb dessert is caused by precipitation of calcium, abstracted from the casein in dairy products, as calcium oxalate.
Read more about this topic: Oxalate
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