Dear GreenSmoothieGirl: Some people think you should lightly cook your spinach and other greens before eating them. Is it safe to eat them raw?
Answer: This is an excerpt from Ch. 1 of my e-book, 12 Steps to Whole Foods. It is both safe and good to eat spinach raw, which I have done every day for 15 years. Cooking, by any method, kills 100% of the greens’ enzymes.
A popular and growing theory and opinion among those interested in nutrition is that greens (especially spinach) are high in oxalates and should be avoided because oxalates cause kidney stones or gallbladder problems, since oxalates may interfere with absorption of calcium from the body. Another popular opinion is that cooking spinach renders the oxalates harmless.
In fact, a review of the peer-reviewed research reveals that the ability of oxalates to lower calcium absorption is small and does not outweigh the ability of those foods to contribute significant calcium to the diet, since spinach is rich in calcium. A few rare health conditions require oxalate restriction: absorptive hypercalciuria type II, enteric hyperoxaluria, and primary hyperoxaluria. These are not the more common condition wherein kidney stones are formed. The research is not clear that restricting foods such as spinach helps prevent stones in those who have previously had them. Many researchers believe that dietary restriction cannot reduce risk of stone formation. In fact, some foods that were assumed to increase stone formation because of oxalate content (like black tea) have appeared in more recent research to have a preventative effect.
Further, cooking has a small impact (about 10 percent) on the oxalate content of foods, with no statistically significant lowering of oxalates following blanching or boiling of greens. It appears that the nutritional advantages of eating raw greens continue to far outweigh any benefit of cooking them.
Two other classes of nutritional compounds, purines and goitrogens, are found in some leafy greens such as spinach. Eating “excessive” amounts of spinach or cruciferous vegetables (broccoli and cauliflower, for instance) containing these compounds can be a problem for people who suffer with gout, kidney stones, or low thyroid hormone production. These chemical compounds are also found in peanuts, strawberries, soy products, and other foods as well. Lightly steaming these foods may help, as well. However, the literature seems to support that a few weekly servings of these foods is a good idea for almost everyone.