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Ask Tufts Experts June 2012 Issue

Q: Is it true that you don’t get much nutrition from eating raw spinach, because its nutrients are bound to something called oxalates?

Answer :  Lingxia Sun, a dietetic intern at Tufts’ Frances Stern Nutrition Center, replies: “This is a ‘no’ and ‘yes’ answer. Spinach is endowed with a lot of nutrients and plant compounds, so that answer is no, it is not true about not getting ‘much nutrition.’ Yes, however, oxalates interfere with the body’s ability to absorb the calcium that is found in spinach. Oxalates are naturally occurring molecules in the organic acid family. In addition to spinach, many other foods contain oxalates, such asalmonds, sesame seeds, beets, rhubarb, cashew nuts and chocolate.

“Oxalates can bind to metal ions, especially calcium, which forms a compound called calcium oxalate. This binding process interferes with the body’s absorption of calcium. Although spinach is high in calcium (245 milligrams in 1 cup of cooked spinach), calcium absorption is hindered because of the oxalates. Raw spinach still contains other healthful nutrients, such as lutein, vitamin C, vitamin K and folate.

“Boiling is often suggested to reduce oxalates contained in spinach; however, the actual reduction is small, only about 5% to 20%. Spinach contains other nutrients that can be affected by heat and water, such as vitamin C and folate; these will be significantly reduced by boiling as well.

“Individuals who have a history of kidney stones may have already been questioned about their intake of spinach and other foods that contain oxalates. For most people, however, the non-oxalate nutritional benefits of spinach, raw or cooked, make it a healthy choice.”

For more on spinach, see this issue’s Special Report.

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