What is oxalate?
Oxalate is the salt of oxalic acid, a natural constituent of many plants. In the body it binds calcium to form calcium oxalate, the main component of most kidney stones. Turmeric root and plain powder contain relatively much of it, purified extracts hardly any.
Oxalate explained simply
Oxalate (oxalic acid) occurs naturally in many plants, such as spinach, rhubarb, chard, nuts, cocoa, tea and also turmeric. The body also makes it as a by-product of metabolism. In the gut, oxalate binds calcium; part of it is then excreted in stool, while another part enters the blood and is excreted through the kidneys.
For most people this is unproblematic. In some people, however, calcium oxalate can form in the urine and grow into crystals and kidney stones. Calcium oxalate is the main component of most kidney stones.
Oxalate and turmeric
Turmeric root and plain turmeric powder contain relatively much oxalate. If you eat larger amounts of powder daily, for example several grams in a smoothie, your oxalate intake rises noticeably. If you are prone to kidney stones, that is a risk you should discuss with your doctor.
An extract is a different matter: during manufacturing the curcuminoids are separated from the root while fibres and accompanying compounds stay behind. A purified, standardised extract therefore usually contains hardly any oxalate. That is an advantage over spice powder where kidney stones are a concern. Whether a specific product is really low in oxalate can only be judged from the manufacturer's information and test values.
Oxalate intake by form of turmeric
Qualitative classification.
| Form | Oxalate content | Note |
|---|---|---|
| Form Fresh root | Oxalate content Relatively high | Note As a food in normal amounts usually unproblematic |
| Form Spice powder | Oxalate content Relatively high | Note Larger daily amounts raise intake noticeably |
| Form Purified extract | Oxalate content Usually hardly any | Note Accompanying compounds of the root are removed |
What else matters for kidney stones
Oxalate is only one factor. Adequate fluid intake, calcium intake (calcium in the gut binds oxalate and so reduces its absorption), body weight and individual metabolic factors also matter. People with a history of kidney stones should clarify dietary questions with medical advice rather than avoid foods across the board.
Frequently asked questions about oxalate
Which foods contain a lot of oxalate?
Particularly rich are spinach, rhubarb, chard, beetroot, many nuts, cocoa and black tea. Turmeric powder is also among the spices with relatively much oxalate.
Do I have to avoid foods high in oxalate?
For most people, no. Those prone to kidney stones often receive individual advice, for example to drink enough and to eat oxalate together with calcium-containing foods so that it is bound in the gut.
How much oxalate is in a turmeric capsule?
That depends on the product. For a purified extract the content is usually very low. Only the manufacturer can give you a binding figure for its product.
If you have had kidney stones before or have a kidney condition, talk to your doctor before taking turmeric or curcumin supplements. This entry is not medical advice.
