Most of us need more calcium in our diets, especially as we age. In fact, according to the National Osteoporosis Foundation, one in two women and one in eight men over the age of 50 suffer from osteoporosis, a porous and brittle bone condition resulting in back pain and fracture-prone bones. This occurs because our bodies rob calcium from our bones to use it for other essential and more immediate needs, such as proper nerve function and blood pressure control.
The remedy is to consume enough calcium in your diet so your body never has to turn to your bones as a source. Most adults need about 1,000 mg of calcium per day. After age 50, 1,200 to 1,500 mg per day are recommended.
Dark green, antioxidant-rich vegetables are also among the best sources of dietary calcium. Richest in calcium are collard greens (357 mg per cooked cup). Turnip greens are close behind (249 mg). Kale (179 mg), okra (176 mg), bok choy (158 mg), and broccoli (94 mg) are runners-up.
An important virtue of these vegetable sources of calcium is that our bodies can actually utilize 50 to 70 percent of the calcium. By comparison, the calcium in milk (302 mg per cup) is only 30 percent absorbable. In other words, a cup of cooked collard greens contains more than 2-1/2 times the usable calcium than in a cup of milk.
A few calcium-rich vegetables, such as spinach, rhubarb, Swiss chard, and beet greens, are also high in oxalic acid. As nutritious as these vegetables are, the calcium they contain is of no benefit because the oxalic acid renders the calcium unavailable. But only the calcium in that specific vegetable is affected. Calcium in other foods, even consumed at the same meal, remains available.
For more information, contact Osteoporosis and Related Bone Diseases, National Resource Center, 1150 17th St. NW, Suite 500, Washington, DC 20036.
Lynn Grieger is a registered dietitian who lives in Arlington, Vermont.
Photography by Suzanne DeJohn/National Gardening Association.
Article published on June 23, 2008.