Eat your fruits and vegetables”: These days, good health relies on this mantra, which also extends to ensuring bone health and preventing osteoporosis later in life. In China, where women consume half as much calcium as American women, rates of osteoporosis are uncommonly low. They also eat less animal protein than their Western counterparts.
American women with diets high in animal protein had three times the rate of bone loss and nearly four times the rate of hip fractures as women with diets higher in vegetable protein, according to a study from the Bone Density Clinic at the University of California San Francisco Medical Center at Mount Zion. Deborah Sellmeyer, director of the clinic, analyzed data of osteoporotic fractures from more than 100 women, aged sixty-five to eighty.
When consumed, all proteins release acids, which must be buffered by the body and excreted by the kidneys, she says. With age, even healthy individuals lose some of their ability to excrete these acids. Bones, containing bases and minerals, step in to pick up the slack and, in the process, calcium is lost in urine. Protein-rich animal foods are highly acidic; vegetables may contain acids but also have bases to neutralize those acids.
A similar study from the Harvard School of Public Health found that a high consumption of animal protein was associated with an increased risk of forearm fracture, but no association was found for vegetable protein. Sellmeyer suggests not eliminating high-protein foods, keys to a healthy diet but, rather, finding more balance in your diet by eating protein with a higher intake of fruits and vegetables, which are acid buffers.
Bone expert Robert Heaney of the Osteoporosis Research Center at Creighton School of Medicine, stresses the importance of protein to ensure bone health. “Although it’s true that all protein increases the loss of calcium through the kidneys,” he says, “with adequate calcium intake you can offset calcium loss and build bone with protein.”
You need adequate protein intake to build bone, he says, and not just in childhood, because bone is 50 percent protein by volume. “It wouldn’t make any sense to build bone without it. But clearly, it’s good to get lots of fruits and vegetables in your diet every day.”
Not so definitive is whether substantial animal protein intake negatively affects bone density, how the body compensates, and what the long-term affects are. Many studies have shown conflicting reports on the protein-calcium connection, says Heaney.
What both researchers do agree on, however, is to eat a balanced diet including protein, with lots of fruits and vegetables, and to obtain calcium from a variety of sources, including green leafy vegetables, milk, and calcium-fortified foods such as orange juice and tofu.
When comparing absorption rates of different calcium-rich foods, the calcium in greens such as collards and kale is most efficiently absorbed by the body, followed closely by milk and lastly soy milk, says Heaney. Additionally, one cup of skim milk and one cup of collard greens each contain 300 mg of calcium, respectively, and one cup of nonfat yogurt has 294 mg of calcium, compared to one cup of spinach, containing 278 mg of calcium. The doctors’ advice? Get calcium from varied sources to reach the recommended 800 to 1,000 mg a day.
- Sardines (375 mg of calcium per half-cup)
- Yogurt (About 300 mg per cup)
- Collard greens (300 mg per cup)
- Calcium-fortified juice or milk substitute (300 mg per cup)
- Nonfat milk (300 mg per cup)
- Cheddar cheese (205 mg per cup)
- Garbanzo beans (200 mg per cup)
- Spinach (278 mg per cup)
- Broccoli (136 mg per cup)
- Cooked beans (100 mg per cup)
- Carrots (100 mg per cup)