When I was an astronaut I got to experience the fun of being weightless—imagine being able to do twenty-four mid-air somersaults in a row, float across the room with a gentle push, or lift a refrigerator with one hand!

But weightlessness also carries some risks. For example, astronauts lose bone rapidly while they're in space. That's because their bones aren't stressed while they're weightless. This wasn't a problem for me on my 7-10 day space shuttle flights, but it is an issue for the astronauts who spend months on the International Space Station. Those astronauts don't have a problem while they're in space—after all, they don't need their bones while they're weightless—but it's something to be aware of when they return to Earth. As you might expect, bone density is closely monitored in astronauts who spend a long time in space. Fortunately, they gradually regain bone once they get their feet back on terra firma.

Astronauts aren't the only ones who lose bone. In fact, bone loss is one of the most pressing health issues for women today. But the issue that is so closely monitored in astronauts is often overlooked by the Earthbound public. It's easy to see why: bone loss is silent and invisible. It can sneak up on you without you knowing there's a problem—and that's what makes it insidious.

When I left NASA to join the faculty at University of California-San Diego, my UCSD colleague Dr. Diane Schneider became my primary care physician. She was a well-known bone researcher, and since I was a former astronaut we began talking about bone loss. That was many years ago, and she's still helping me understand and navigate the subject.

In this book, Dr. Schneider provides essential information for women and men of all ages. Preteens and teens build a foundation that must last a lifetime; older women must understand their options and take steps to avoid or minimize bone loss. Perhaps most important, she emphasizes the value of women educating themselves on the topic. In this case, knowledge really is power. There are many things that women and men can and should do, throughout their lives, to build and maintain strong, healthy bones.

It's important for the future of space travel for NASA to understand bone loss in weightlessness and to ensure that astronauts maintain healthy bones. It's just as important for women and men to understand this critical health issue and how to develop bone healthy habits.

—Sally Ride, PhD
Astronaut and CEO, Sally Ride Science
Professor of Physics, Emeritus, UCSD