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What Causes Degenerative Bone Disease?

Instructor: Amanda Robb
In this lesson we'll go over what degenerative bone disease is, and the process of normal bone remodeling. We'll then learn what the main causes of the disease are.

What Is Degenerative Bone Disease?

If you've been in an old house, you might notice that the floors are a little uneven. This is caused by an uneven foundation. Sometimes, chemicals in the ground can eat away at the concrete foundation that is beneath the house. This happens gradually over time from exposure to chemicals that occur naturally in the soil. The thick, stable concrete easily becomes weak in the presence of these chemicals and starts to wear away, becoming riddled with holes.

Concrete degradation
concrete degradation

You can think of your bones like this concrete foundation. Bones make up your skeletal system and provide structure for the body.

Human skeleton
human skeleton

Bones are normally hardened with calcium deposits, but as we age, the bone can break down, much like the concrete in our example. This is called degenerative bone disease, when our bones break down and become weak over time. The most common degenerative bone disease is osteoporosis. In this condition, the bones become weak and filled with holes, leading to easily broken bones and a lack of support for the body.

Diagram of bone loss in osteoporosis
osteoporosis

To fully understand how degenerative bone disease happens, we first need to understand how bone is created and broken down during our lifetime. This process is called bone remodeling.

Bone Remodeling

Our bones are living structures made of cells called osteocytes. Despite the rigid structure, bones are not static. Cells are born, die, and are replaced. Osteoclasts are bone cells that break down bone, which contain a lot of calcium. We need calcium for various processes in our body, and when calcium is scarce, osteoclasts break down bone to release it. The opposite process, building bone, is accomplished by osteoblasts.

Types of bone cells
bone cells

Causes of Degenerative Bone Disease

During childhood, our bone density increases and outpaces the destruction of bone. It is during this time that we build up dense bone that will serve us throughout our lives. After growth in childhood, bone destruction outpaces bone growth and we start to gradually lose bone mass. The more bone you build when you are young, the more you will have when you are older. Think of it like a savings account. If you stock up your bone bank when you are young, you'll have more bone in the future when you retire. This is a normal process, and everyone loses bone mass over time. However, in people with osteoporosis, bone loss happens more rapidly. There are several reasons this might occur.

Nutrition

Bones are built from calcium, which can be obtained from vitamins, or calcium rich foods like milk. Vitamin D is also needed for bone growth and can be found in fish like salmon, or eggs and milk. Vitamin D is also formed in the body with sun exposure. Proteins, another major component of bone, can be found in foods like fish, meat or beans. Since nutrition is such an important factor for bone growth, people with low calorie intake, such as patients with anorexia nervosa, are especially at risk for degenerative bone disease.

Salmon is a great source of protein and vitamin D to prevent bone loss
salmon steak

Impact Exercise

Perhaps you've heard the saying, 'if you don't use it, you lose it.' This is absolutely true for bone growth. Since your bones are needed to support your body they need to be used through impact exercise. Running, dancing or even walking at a quick pace outside can stimulate bone growth. Astronauts who spend extended periods of time in space live in a zero gravity environment with minimal impact. The result is a huge decrease in bone growth that can be up to ten times that of normal degenerative bone diseases.

A lack of impact exercise can contribute to degenerative bone disease
runners

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