NUTRISPEAK by Vesanto Melina
Among greens that are outstanding sources of calcium, kale has been hitting the headlines as a superstar. Not only is it an excellent source of calcium – the mineral is readily available to the body – it is an excellent source of carotenoids, which are converted to vitamins A, C and K. It also provides a source of iron.
The calcium in many greens (kale, collards, broccoli, okra and Oriental greens, such as bok choy, turnip and mustard greens) has a relatively high bioavailability. As shown in the table, the percentage of calcium absorbed from calcium-set tofu and cow’s milk is similar (between 31 to 32 percent). In contrast, the calcium in greens such as broccoli and kale is absorbed almost twice as efficiently.
Many common beans, almonds and sesame seeds have lower bioavailability (around 20 percent) and sweet potatoes, which contain moderate amounts of oxalates, are in the same range. Although spinach, beet greens, Swiss chard and rhubarb contain calcium, they are also high in oxalates, allowing little of the calcium that is present to be absorbed. Thus they cannot be counted on as calcium sources.
Fractional absorption of calcium from various foods *
Bok choy, ½ cup - 53.8%
Broccoli, ½ cup - 61.3%
Chinese cabbage flower leaves,
½ cup - 39.6%
Chinese mustard greens, ½ cup - 40.2%
Kale, ½ cup - 49.3%
Fruit punch with calcium citrate malate, ¾ cup - 52.0%
White beans, 1 cup - 21.8%
Pinto beans, 1 cup - 26.7%
Tofu with calcium, ½ cup - 31.0%
Sweet potatoes, ½ cup - 22.2%
Spinach, ½ cup - 5.1%
Rhubarb, ½ cup - 8.54%
Cow’s milk, ½ cup - 32.1%
*From The Weaver Group, Purdue University
Now that we know that kale is so good for us, what do we do with those big green leaves? If you are adding them to a salad, prepare them by removing the centre rib and chopping them matchstick thin. You might also choose to steam kale and explore the seasoning possibilities. Around the world, people have developed delicious ways to season greens, at the same time supporting their lifelong bone health.
• 8 cups kale
(about 8 ounces when purchased) • 3 cloves garlic, minced
• 1 tbsp olive oil
• 1 tsp cumin
• 2 tsp paprika
• ½ cup fresh parsley or cilantro, chopped (optional)
• 1 lemon or 1 tbsp lemon juice
• Salt and ground pepper, to taste.
Wash greens well. Fold kale leaves in half; with a knife, remove the tough centre ribs and discard. Chop remaining greens. Heat the oil in a large saucepan or frying pan with a lid. Add garlic, cumin, paprika and parsley (if using) and cook for about one minute stirring well to make an aromatic seasoning mix. Add greens and mix well. Lower heat and simmer for five minutes or until tender. If using lemon slices, serve the kale hot with fresh lemon slices. If using lemon juice, squeeze lemon juice liberally over the greens. Makes 1-1/2 cups (2-3 servings).
Vesanto Melina is a registered dietitian and co-author of nutrition classics. For more information about protein and nutrients, see Becoming Vegetarian, Raising Vegetarian Children, Becoming Vegan and the Food Allergy Survival Guide. She is based in Langley, BC, and regularly consults for people who wish to improve their health or who are in dietary transition.