Building Bones That Last a Lifetime

FROM THE LECTURE SERIES: How We Move: The Gross Anatomy of Motion

By Elizabeth A. MurrayMount St. Joseph University

We need a steady supply and consistent level of calcium in our blood for various functions, like muscle contraction and nerve impulse conduction. If we don’t take in enough dietary calcium to offset our body’s daily needs, then more calcium is taken from our bones than what we can replace through our diet. When this happens, bones steadily lose their mineral content.

Highlighted leg bones while walking on the pavement
Exercise helps in getting blood levels high. (Image: wavebreakmedia/Shutterstock)

Strengthening Bones When You’re Young

While we can limit or slow bone loss to some degree with weight-bearing exercise and a good diet, a certain amount of bone loss is inevitable, especially since the ability to build new bone starts a steady decline past around age 40. Sadly, we continue to take calcium out to support physiological needs, but we lose the ability to replace it in bone, like we could when we were younger.

The time to build a strong skeleton, then—strong enough to last a lifetime—is when we’re young. So, what can be done when you’re young to keep blood calcium at levels that won’t lead to a loss of bone minerals when you’re older? 

The best thing to do is to have a good diet, and supplement with calcium tablets or calcium-fortified foods and drinks. That, plus exercise, will help keep your blood levels high enough to prevent the body’s physiological needs from taking it out of your bones.

Remember, since we naturally lose the ability to build bone as we age, we can only hope to maintain our bone calcium levels through a calcium-rich diet and weight-bearing exercise. In addition to talking about what’s good for bones, there are factors and habits that can negatively impact bone strength, and even accelerate bone loss. These include smoking, excessive alcohol consumption, poor diet, and a sedentary lifestyle.

This article comes directly from content in the video series How We Move: The Gross Anatomy of MotionWatch it now, on Wondrium.

Skeletal Demineralization Is Inevitable

Not to be a downer here, but even without any of those negative factors, at some point, bone mineral loss is inevitable. Women, in particular, have accelerated bone loss after they hit menopause, which on a worldwide average happens at about age 50.

Illustration of four stages of bone demineralization
Though it can be significantly slowed down, given enough time, the skeleton’s demineralization will happen one way or other. (Image: Crevis/Shutterstock)

This postmenopausal bone loss is because the female hormone, estrogen, has protective effects that keep bone strong, but estrogen is no longer produced after menopause. At that point, women begin to lose bone minerals at an increased rate, compared to before menopause, or when compared to men of the same age. 

Given that women can spend about a third of their lives in a postmenopausal state, osteoporosis is a global health concern for females. Men also have bone loss, and by about age 65 or 70, their rates of skeletal demineralization are about the same as in women, leading to osteoporosis. Since women started their bone loss sooner, however, they are at greater risk of more advanced osteoporosis.

And when bone is demineralized by osteoporosis, someone’s own body weight can be enough to cause a fracture. This is called a pathological fracture, because the bone was already weakened by another condition, as opposed to a fracture caused by trauma. When bones are that weak, they have difficulty healing, especially if the blood supply to the bone is disrupted by the fracture.

How Are Bones So Unique in Structure?

Bone spongy structure close-up
The flexibility and resilience of bones is a unique feature that exists thanks to both the mineral part and the collagen fibers. (Image: eranicle/Shutterstock)

A bone has widely scattered living cells that are surrounded by and embedded within a connective tissue matrix. For the most part, the cells produce this matrix bed, and then they lie in it. The matrix is mostly composed of a variety of calcium phosphate salts, collectively called hydroxyapatite. 

These minerals are crystallized around strands of the protein collagen. Depending on age and health, the overall chemical breakdown of bone is generally about 50% inorganic minerals, around 25% organic compounds, mostly the collagen, and about 25% water—much of which is inside the bone cells.

A good analogy is that the makeup of bone is similar to fiberglass. Bone’s collagen fibers, like the fibers in fiberglass, give it some flexibility and resiliency. You may not think of a bone as being flexible, but it definitely bends before it breaks. It really takes a lot of force to break healthy bones. 

The mineral part of the matrix, on the other hand, gives bone its strength—just like the glass in fiberglass—but it’s brittle. It’s this combination of the flexible collagen and strong minerals that give bone its remarkable properties.

Common Questions about Building Bones That Last a Lifetime

Q: How can one stop skeletal demineralization?

Skeletal demineralization cannot be stopped but it can be slowed down significantly. Most of the work has to be done when one is young so the bones can be strengthened to stand the test of time. The best option is to have a healthy diet that’s supplemented with calcium supplements along with exercising.

Q: Why do women have accelerated bone loss after they hit menopause?

The female hormone named estrogen protects the bones from losing minerals, but after menopause, that hormone is no longer produced and the protection the bones previously had is now lost, which is why bone loss in women is accelerated.

Q: What are some of the remarkable properties of bones?

Bones are both somewhat flexible and resilient. They’re very hard to break and though they don’t look flexible, they bend before breaking. The strength of the bone comes from the mineral part of the matrix. The flexibility comes from the collagen fibers in the bone.

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