Basic Background Information About Bones

Bones give us our shape and structure and separate the animal kingdom into "haves" and "have nots." Scientific research has revealed much about bones, but there is still much to learn. We still do not fully understand why bones weaken as they age.

Bones are made of collagen fibrils hardened with coatings of little mineral plates made mostly of calcium. Bones also contain a small portion of sticky organic material, a combination of mostly proteins and sugars, which glues the mineralized collagen fibrils together. Calcium is the most abundant mineral in the body and in bone. The health of both the mineral and organic components of bones determines their strength. Calcium is also important for the function of blood, nerves, and muscles.

If your body doesn't get the calcium it needs from food, it leeches calcium from your bones, which is one reason why it's important to eat foods rich in calcium, such as dairy products (especially yogurt) and green vegetables. (Kelp, parsley, kale, and broccoli are particularly high in calcium.)

If children have healthy eating habits, it definitely pays off later. Research shows that bone mass peaks around age 30 for most people, but during teenage years -- particularly between the ages of 11-15 -- nearly half of all bone mass is formed, and a great deal before then. If people have rich calcium diets when they're children, it helps their bodies prepare for the gradual loss of bone that inevitably begins after age 30. Healthy eating and exercising habits reduce the bone loss rate.

Vitamin D is crucial for the body's absorption of calcium. Vitamin D is found in foods like fish and green vegetables or by basking in the sun for about five minutes daily. Children who don't spend enough time outdoors can develop rickets, a deforming disease in which bones don't grow properly because the children cannot absorb the calcium in their food.

Exercise is also extremely important in building bone. Weight-bearing exercise, or resistance, like walking, running, climbing stairs, dancing, gymnastics, and lifting weights, increases bone mass in childhood and slows down bone loss after 30.

Cells make new bone, while other cells eat away old bone. Weight-bearing exercise helps make new bone with nice, fresh organic molecules that are more fracture resistant.

Clearly, bone is a complex material -- minerals, collagen and other organic substances all work together to make it strong.

So, what goes wrong with bone as we age?

Bone weakening is a key area Dr. Paul Hansma and his research team at the University of California, Santa Barbara are studying.

All components of bone change as we age. Some degrade and some increase, but the overall result is that the bone is weaker than it was when a person was 30. Dr. Hansma's group has shown that the proteins and sugars in bone are like a glue that keeps the hard collagen fibrils (coated with mineral) stuck to each other. They think that as people get older, this glue becomes less effective -- perhaps less sticky -- or maybe there is less of it.

Several years ago, after studying the abalone shell, they realized that there might be a glue in bone. The composition of a typical abalone shell is 3% sticky organic material paired with 97% mineral. The mineral is crystalline calcium carbonate, not a particularly sturdy or strong material. But the abalone shell is nearly 3,000 times more fracture resistant fracture resistant than crystalline calcium carbonate!

A closer look at the abalone shell reveals the key to the shell's fracture resistance. Abalone shell adhesives, adhesives, or glue made of the organic material, are found between mineral plates. This protein-based glue is so strong that it holds on even when the plates are pulled apart. Its molecules are bunched into springy bonds so that they can absorb energy when the shell is battered, by stretching and then springing back to their regular shape. The result is that abalone shell is amazingly resistant to fracture, and so is bone, partially because such a strong glue holds its parts together.

The contribution of the glue in bone to its strength is an exciting new area of study. Another exciting aspect is researching why some people form stronger bones than others. Current and future research might help us understand exactly how bones age, so that we may prevent their getting weaker, and maybe help them become stronger.

Mimicking what nature does best can help us develop new materials for aerospace research and long-duration space exploration. We can imitate nature by understanding how nature makes strong materials, such as bones and abalone shell, and use that knowledge to help us develop very tough new materials that can also heal themselves in space. The glues in abalone shell and bone are self-healing because of their springy molecular structure.

The lessons learned from Dr. Hansma's group could also further our understanding of how to slow down bone aging. Such knowledge may help us keep astronauts healthier on long trips to other planets. The conditions in space may accelerate bone aging, and the more we understand about how bones age, the better our chance to prevent it.