The Low-Down on Osteoporosis

What We Know and What We Don't
by National Institute of Health

It's in our cereals, our orange juice, our bread. Manufacturers are adding calcium to all sorts of foods and beverages. That's because increasing the amount of calcium you consume daily can decrease your chances of fracturing a bone due to osteoporosis. Ten million people in the United States already have osteoporosis and 18 million more have low bone mass (osteopenia) and are at increased risk for developing osteoporosis.

The bones of a person with osteoporosis have become thin and fragile and are more likely to fracture. In the U.S., osteoporosis is responsible for more than 1.5 million fractures annually, 700,000 of them in the vertebrae of the spine and 300,000 in hips, at an estimated cost of more than $14 billion each year. Other common fractures occur in wrists, forearms, feet and toes.

And according to Dr. Joan McGowan, director of the Musculoskeletal Diseases Branch of NIH's National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the number of fractures in the U.S. is expected to increase in the next 40 years due to the increase in the average age of our population.

Many myths have sprung up about osteoporosis and its fractures that aren't based on solid science. While scientists don't yet have all the answers about the best ways to diagnose, treat or prevent osteoporosis, NIH, led by NIAMS, is conducting and supporting research to help find those answers. Here's what we know now about some of those myths.

Myth: Our bones don't change after we have finished growing.

We reach our peak bone mass around age 30 but our bones are changing constantly throughout our lives. This process - known as remodeling - involves two major types of bone cells: osteoclasts, which break down old or worn bone and thus create bone cavities, and osteoblasts, which fill in the cavities. If the amount of new bone equals the amount being dissolved, your bones stay strong. But several things can shift the balance so that bones become weaker and more brittle.

Myth: We know all the risk factors for osteoporosis.

"We don't have a complete set of risk factors that describe a person who is at very high risk for fracture," says Dr. McGowan. One of the biggest risk factors, she points out, is age. "Forty to fifty percent of women over 50 will have an osteoporotic fracture sometime in their life," she says. "As you age, your bones become less dense and weaker due to an increased rate of bone loss - the osteoclasts are breaking down more bone than the osteoblasts are filling in. Younger people ice skate or ski and, without severe trauma when they fall, they don't break any bones. We get older, do the same activities and fall, and we do suffer a fracture."

We also know that being a woman makes a big difference, too. Women have an increase in the rate of bone loss during the first three to five years after menopause. After that, it continues at a slower but steady rate. NIH is now funding several studies to learn more about how and why bones become fragile and fracture.

Myth: A DXA scan can predict whether or not you will have a fracture.

A DXA scan, a special type of x-ray exam, is used to measure the bone mineral density (BMD) of the spine or hip. BMD is used as a common indicator of bone health. But BMD is just one component of bone strength and is not the perfect marker for gauging a person's risk of fracture.

"There is a lot more about the quality of bone that isn't captured by DXA," says Dr. McGowan. "Yet DXA is as good at predicting fracture as blood pressure measurement is at predicting stroke and better than cholesterol numbers at predicting heart disease. However, just because you have normal blood pressure doesn't mean that you won't have a stroke, or just because you have normal cholesterol levels doesn't mean that you are protected from having a heart attack. There are many different risk factors involved for those diseases and the same is true for osteoporosis and for fractures."

NIH-funded investigators are now working to develop ways to measure bone strength and quality that, coupled with some simple risk factors like age and previous fractures, could more accurately predict a person's fracture risk.

Myth: You can't get all the calcium you need from food.

On the contrary, Dr. McGowan says it is best to get your daily amounts of calcium from food whenever possible. "You won't have to worry about getting enough calcium, vitamin D and vitamin K," she explains, "if you eat a balanced diet of fruits, vegetables - especially leafy green ones - grains, protein, and low-fat dairy products." And with so many calcium-fortified products on the market, it's getting easier all the time to get all the calcium you need from food.

If you can't get enough calcium from your diet, you may need a calcium supplement. They come in different forms, such as calcium carbonate and calcium citrate. Dr. McGowan says there is no significant difference among the various forms. So if one type seems to disagree with you, switch to another. Check your supplement's label to ensure that your calcium supplement meets USP standards. (USP, or the U.S. Pharmacopeia, is an organization that helps ensure consumers receive quality medicines by setting standards that drug manufacturers must meet.)

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.