The likes of lettuce, kale, spinach, avocados, and broccoli supply vitamin K, which might fight off hip fracture when consumed in adequate amounts.
A study of 72,327 female nurses over a 10-year period A\found that women who ate lettuce at least once a day were less than half as likely to break a hip than those who ate lettuce no more than once a week. Researchers credited vitamin K for these promising results.
According to bone researcher Diane Feskanich, Sc.D., little-known vitamin K promotes the chemical conversion of a specific bone protein known as osteocalcin. Once this transaction has occurred, osteocalcin can do its job of strengthening bone tissue. In other research, people who took vitamin K supplements lost less calcium in their urine and showed better one mineral density than people who didn't take vitamin K. Still other research links low concentrations of vitamin K to low bone mineral density and bone fractures.
No one knows exactly how much vitamin K it takes to keep bones healthy and strong, but it could be much more than the Recommended Dietary Allowance of 65 micro-grams for women and 80 micro-grams for men (which are set to stave off blood clotting, not to strengthen bone). Dr. Feskanich's own study suggests that women may need 109 micro-grams a day or more to fend off fractures.
The good news is that it's not too hard to get your K if you eat salad, because it's plentiful in leaf lettuce, endive, watercress, and spinach. If you don't like greens alone, add cooked dark greens such as kale or spinach to soups, stews, omelettes, and frittatas. A mere half-cup of cooked cabbage, spinach, kale, or collard greens is more than enough to meet the 109 micro-gram level. Brussels sprouts, broccoli, soybean oil, and whole eggs also supply you with vitamin K.
One caveat: If you take the prescription medication warfarin (Coumadin), ask your doctor before increasing vitamin K. The two work against each other.
—Diane Feskanich, Sc.D., is a researcher and instructor at Harvard Medical School in Boston.
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