字幕列表 影片播放 列印英文字幕 Your skeleton has the difficult task of being strong and hard enough to hold your whole body up, but bendy and shock-absorbing enough not to break upon minor impact. So when something goes wrong in the bone-forming process, your bones can get weaker and the results can be shattering. Under a microscope, healthy bone looks like a honeycomb. It's a matrix of flexible collagen protein with harder minerals, calcium and phosphate, laid down on top—so it naturally has little gaps in it. But if something interrupts the formation of healthy bone, those gaps get bigger, like in osteoporosis, which literally means 'porous bone'. My name is Dr. Suneela Vegunta. I am one of the women's health providers here at the Mayo Clinic in Arizona. I have been here at the Mayo Clinic in Arizona for almost nine years now. We see patients with a lot of women's health problems, and osteoporosis is a very common women's health problem. Your bones are a living, dynamic tissue, constantly regenerating themselves to stay healthy. This is called bone remodeling, and occurs throughout our entire lives—in fact, about every ten years, your entire skeleton has been replaced with new, healthy bone … Thanks to specialized cells. One is the bone chewing cell, which is called the osteoclast, which chews up the bone, and it chews up the old bone. As the old bone is being chewed up and being absorbed, the new bone is being formed by a different type of cell called osteoblast. So this process is usually coupled. They go hand-in-hand. A few essential ingredients are necessary to keep this bone-forming process in balance, mainly calcium. Your whole body relies on calcium in some form or another, so if you're not consuming enough of it, your body will cannibalize the calcium it needs...from your bones. So let's say that they are low blood calcium levels, and calcium is essential for muscle metabolism. So heart being a muscle, the heart is essentially muscle, in order to stabilize the calcium levels, the calcium can be pulled from the bone. So if there's not enough calcium or adequate amount of calcium, the bone formation process can be hampered or impaired. And that impairment is what can lead to osteoporosis. Now, while calcium is definitely an essential ingredient, other key ingredients are just as important. So not only just calcium, you know, there are other things that actually affect bone density nutrition-wise, like vitamin D. Vitamin D is essential for absorption of calcium and phosphate in the gut. And all kinds of things can impair your body's absorption of calcium: too much protein, too much salt, too much caffeine, or too much acid in your diet can all block the absorption of calcium for use in building healthy bones. So can habits that are bad for your body in many ways, like smoking. It impairs the osteoblastic activity, whereas the bone chewing part or the osteoclastic activity continues, so they can actually cause the uncoupling that we were talking about. So avoiding all of those things and following healthy life habits will be very helpful. But bone loss can occur because of factors beyond our control as well. Like aging, and what hormones we have less of as we age. So an osteoporotic bone, if you look at a normal bone which has normal bone density, the trabeculae or the holes between the matrix, are much smaller compared to an osteoporotic bone where there's less matrix and the pores are much bigger, making it very fragile and easy to fracture. And here's the thing: until your bone fractures when it shouldn't, you don't know that you have osteoporosis. There are absolutely no symptoms for osteoporosis. So the first symptom of an osteoporosis can be a fracture. These are called fragility fractures. So a woman can actually fall from a standing height or even, you know, not even no trauma, just spontaneous fractures. That's why screening is very important in high-risk women to diagnose if they have osteoporosis and to intervene in a timely fashion. Because when it comes to bone loss...sex matters. Just to reiterate, sex steroids are very helpful for bone formation, especially estrogen in women, is helpful for bone formation and even absorption of calcium from the gut. Women typically have lower bone density and muscle mass than men to begin with—that's just one of the ways sexual dimorphism expresses itself in our species. That, plus the sex hormone component, means that women, especially as they age, are more prone to osteoporosis and fragile bones in a way that most men are not. Around menopause, the estrogen levels are very low and it's a state called hypoestrogenism, where there's very low estrogen in the system. So that low estrogen by itself can actually cause some deleterious effects on the bone. But we can do ourselves a huge favor when we're young by building our bone density up as much as we can, while we can. The peak bone density is reached around ages 25 to 35, so we reach our peak bone mass by that time. So our health habits during this phase of our life actually affects how much peak bone density we reach. While we can and should build up our bone density in that peak bone-building phase, all hope is not lost if we want to take action later in life. So I have seen in my practice many patients improving their bone density with just purely lifestyle modifications. Vitamin D and C supplements, avoidance of smoking and excessive alcohol, are all great ideas for building bone mass while young and keeping your bones healthy later in life. And maybe ... try to avoid going to space if you can help it. You know, exercise is very essential for bone building, bone formation, because exercise and especially weight-bearing and muscle-strengthening exercises, they actually stimulate the osteoblastic activity where there's more bone forming. You can actually see that in people who travel to space like astronauts where there is no weight bearing. When they come back and reach Earth, they actually lost 30% of their bone density because there's no weight bearing in space. So that tells us that weight bearing is very essential for bone building and bone formation.