We see it everywhere: spinach is a superfood. “Healthy” sections of menus are often headed up by delicious spinach salads. And it’s true! Spinach is packed with beneficial nutrients: potassium, which can help lower blood pressure, lutein and zeaxanthin (for eye health – guard against macular degeneration and cataracts, as well as improving cognition), vitamin K for bone health, vitamin A for glowingly healthy skin, and anti-oxidants like kaempferol (reducing cancer risk) and quercetin (warding off infection and inflammation). It even contains compounds like MGDG and SQDG, which have been found to slow cancer growth. And to top it off, spinach is loaded with healthy fiber. BUT, like most superlatives, it has a dark side: oxalic acid (also called oxalates – there is a chemical difference, but for our purposes, these terms will be used interchangeably). Oxalic acid binds with calcium, and when leaving the body, can form kidney stones. It also inhibits the absorption of minerals, like calcium and the iron that spinach was famed for in times gone by (though the non-heme iron in spinach is very difficult for the body to absorb anyway, but that’s another topic).* I am not saying Spinach is bad – it’s great, and is the key ingredients in many, many of my healthiest recipes! But what can we do about its dark side?
- BOIL IT! Oxalic acid can be destroyed (or at least diminished) by steaming or boiling. Boiling spinach is the most effective way to reduce its oxalic acid content. But sadly, this will also diminish other nutrients like vitamin C and the B vitamins, so, don’t overdo it! A minute should be plenty!
- Substitute Kale. While Spinach is high in oxalates, Kale is low. (For those in greater danger of kidney stones, other substitutions can also be made easily for other high-oxalate foods…. Raspberries are high, blueberries and blackberries are both low. Almonds are high, but walnuts and cashews are low. Navy beans are high, but Kidney beans are low. Dates are high oxalate, but Figs are low. Spinach is high, but Kale is much lower)
- HYDRATE! OK, that’s kind of cheating. Hydration does not reduce oxalic acid. But, when our bodies are well hydrated, urine passes more easily, and the risk of kidney stones is greatly reduced, making oxalic acid less of an issue.
So munch away on Superfood Spinach – your cells with thank you – but first reduce the villainous oxalates, at least sometimes. Limited amounts of raw spinach can still be beneficial. Like most dietary issues – moderation is key!
- Note – as with any health topic, research is ongoing, and opinions vary as to the relative safety of oxalic acid / oxalates in diet. Those with a history of kidney stones should consult a doctor regarding their particular health situation. For most of us, moderate amounts of raw spinach are generally regarded as safe.