Call me Popeye (or maybe Popette?), because I’m absolutely obsessed with spinach. I eat it constantly, cooked and raw, in everything from nachos to pasta to salads to hummus. The other day, I tweeted about my deep, abiding love for the leafy green and one of my friends replied to my tweet, saying that eating large amounts of spinach can actually interfere with the body’s ability to absorb calcium. Wait, what? This was news to me, as I always thought spinach was hands-down one of the healthiest foods you could eat. Confused, I did a little research, hoping my love for my favorite vegetable wasn’t actually harming my health. I didn’t find much information, so I took my question to the experts. Here’s what they had to say about the science of spinach and calcium absorption.
Registered dietitian Mary Hartley explained that oxalate, a pesky little molecule that binds to the calcium in spinach, leaves only 10% of the essential mineral available for absorption:
Oxalate occurs naturally in many common plants, especially rhubarb and dark leafy greens such as spinach, chard, beet greens, and kale. It’s present in lesser amounts in other vegetables, fruits and nuts. Oxalate binds with calcium in the digestive tract to form an insoluble salt that cannot be absorbed. For instance, one would have to eat 15.5 cups of raw spinach to match the level of calcium absorbed from one cup of milk. Oxalates do not significantly impact calcium absorption except when levels are high. Still, it is important to remember that dark leafy greens are not an important source of calcium in the diet.
Uh oh. Bad news for vegans who rely on leafy greens as a large source of calcium.
Dr. Bess Stillman, integrative medicine consultant and practicing ER physician in New York City, told me more about spinach specifically, and its role in a healthy diet:
In addition to the vast array of cancer fighting anti-oxidants and flavanoids, research has shown that a compound called ”glycoglycerolipids,” found in the spinach leaf, can prevent damage and inflammation to the lining of the stomach—meaning a healthier digestive tract that’s better at absorbing the nutrients you need to feel energized and healthy. Spinach also is a fantastic source of iron, making it an especially important food for both vegetarians and women, who often need iron to help replace blood lost during their monthly periods.
Whew. No need to panic (or cut spinach out of your diet). Dr. Stillman comments that, “in the case of spinach, it’s all about how you eat it.” Here are her suggestions on how you can cook spinach so you can get the maximum nutritional benefits of the little green leaf:
- Cook It: Lightly cooking spinach will also breakdown the oxalic acid molecules without causing you to lose too many of the vital nutrients—try steaming, sauteeing or blanching, which also increases the amount of vitamin K available. Pour some extra virgin olive oil into a pan on low to medium head and sautee lightly until the leaves begin to wilt.
- Eat With Citrus Or Tomatoes: The Center for Disease Control and Prevention recommends eating spinach with citrus or tomatoes. These foods are high in vitamin C, which changes the form of iron in spinach to the easily absorbed kind you find in steak–but with much fewer calories or risks to your health. Vitamin C also blocks the oxalate from binding to calcium, encouraging further absorption. Try adding spinach to your pasta sauce, or make your BLT a bacon spinach tomato sandwich. Toss with orange muscat vinagrette and enjoy absorbing both the flavors and the nutrients you want.
- Buy Organic: Remember, spinach is one of the “dirty dozen” foods, which have high pesticide residue. To get the most out of spinach’s health benefits, buy organic.