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Bone Density: An Overview

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Our bones are essential to body mobility and support, yet they are often overlooked for maintaining physical fitness and health. 

While we can gauge muscle strength from how muscles are shaped on our bodies or how firm they feel, we cannot see nor touch our bones. 

So what makes bones strong? 

Bone density is the most common signifier of bone strength. Becoming familiar with bone density can help you learn how you can better take care of your bones and prevent bone loss as you age. 

Understanding Bone Tissue

There are 206 bones in the adult body, all that have different functions but share structural similarities. It is first important to discuss the basics of bone composition and function. 

Bone tissue is a type of connective tissue that makes up our bones. It is made up of four major components: 

  • Osteoblasts and osteocytes are cells that formulate bones. 
  • Osteoclasts are cells that aid in the repair and regeneration of bones.
  • Osteoids, made up of collagen and proteins, are organic components of bone tissue. 
  • Mineral salts are inorganic components of bone tissue that make bones hard and rigid. The main minerals found in bones are calcium and phosphorus. 

There are two major types of bone tissue: 

  1. Compact bone is the hard outer layer of bone tissue. 
  2. Cancellous bone is the soft inner layer of bone tissue. 

While compact bone tissue provides stretching and structure to our bones, cancellous tissue allows for the storage and movement of nutrients and minerals. 

What Is Bone Density?

Bone density, sometimes referred to as bone mineral density (BMD), is how thick or dense your bones are. Strong bones are dense, while weak bones lack density and are at a greater fracture risk. 

Bone tissue is made up of different components and minerals. While the organic components are very important to growth and repair, the inorganic mineral components are what give bones their shape and hardness. 

Bone density is measured by how tightly packed minerals are inside of bone tissue. 

Tightly packed molecules result in strong and rigid bones, while loosely packed ones result in weakness and excessive softness. 

Bone density affects both compact and cancellous bone tissue. Compact bone tissue that is not sturdy cannot provide protection or support for the body. 

While cancellous bone tissue is naturally softer than compact bone tissue, it requires a certain amount of strength and hardness to handle stress and pressure caused by the body. 

Bone Density Testing

But if we cannot see or touch our bones, how can we tell if they are dense or not? 

Bone density tests are used to evaluate bone density in individuals. They are not invasive procedures and are instead undergone by x-rays and scans of bones in the body. 

A bone density test measures how dense a bone is based on patterns of cells and minerals, and it can show what bones look like on the inside. When you go to the doctor’s office for a bone density test, you may be advised to wear comfortable clothing without zippers or buttons, which may interfere with the technology of certain scans like a CT scan.

Bone density scores are called T-scores. A T-score score of -1.0 or higher signifies normal bone density. Test results with scores of negative numbers between -1.0 and -2.5 and lower signify low bone density. A score of -2.5 and below may indicate osteoporosis.

Other types of testing, such as blood tests, can determine if an individual is deficient in any of the nutrients and minerals necessary for bone composition and strength. 

Symptoms and Causes of Low Bone Density

Low bone density has negative impacts on mobility and overall health. We recommend you speak to a doctor about testing for bone density if you experience any of the following symptoms: 

  • Back pain, especially in the vertebrae and spine
  • Bone fractures, like fractured hips or wrist
  • Loss of height over some time 
  • Worsening posture
  • Frequent fractures or bone injuries

Several different factors can cause low bone density. Here are some of the most common. 

Poor Diet and Under Eating

When individuals do not regularly consume essential nutrients or eat sufficient amounts of food, the body begins to use nutrients and minerals stored in the body to maintain function. 

Our bones are made up of minerals, but they are also where those minerals are stored. If the body begins to use the minerals in our bones, our bones lose density and become weak. Under-eating also leads to low body weight, which can further increase the risk of weak bones.

Substance Use

The use of certain substances, such as tobacco or alcohol, causes damage to our bodies and the depletion of essential vitamins and minerals. Substance use can contribute to liver disease and kidney disease even in healthy young adults and risk low bone mass.

The depletion of minerals in our bones, therefore, decreases their density. 

Aging

Part of the natural aging process is weakening our body tissues, which is why older adults are at an increased risk for osteoporosis, osteopenia, and rheumatoid arthritis. While bone density typically decreases with age, managing other risk factors, like hyperthyroidism or low body mass index, can help slow its degeneration. 

Medical Conditions

Low bone density can occur in individuals with certain illnesses, even if they are otherwise healthy and not at risk. Low bone density can occur due to diabetes, hyperparathyroidism, autoimmune disease, or kidney problems, among other ailments. 

How To Maintain Healthy Bone Density 

While low bone density can impact mobility and strength, there are many ways to maintain a healthy bone density. If you have a family history of osteoporosis, taking preventative steps is even more important for you.

The absolute best way to keep your bones healthy is by making sure you are consuming the essential minerals that form them. 

The two main minerals found in bones are phosphorus and calcium. 

Load up on them by eating: 

  • Milk and dairy products 
  • Non-dairy milk alternatives 
  • Green leafy vegetables 
  • Lean meat 
  • Beans, lentils, and nuts 

The body needs vitamin D to absorb calcium, so vitamin D intake is just as important. A great way to do this is by taking a vitamin D supplement, as diet alone may not provide sufficient amounts of the vitamin. 

Alongside a healthy diet, regular physical activity, like weight-bearing exercise, can build muscle, enhance mobility, and prevent bone stiffness. While exercise may not directly impact bone density, it can help promote overall health and wellbeing even with advancing age. 

Conclusion

Bone density describes the density of the minerals and other materials that make up strong and healthy bones, and our bone mineral density naturally decreases as we age. However, pre-existing conditions, family history of bone diseases, and substance use can contribute to low bone mineral density. 

If you suspect you have low bone density, talk to your doctor to see if X-rays, t-score, z-score tests, or a DEXA scan may be necessary to further investigate the issue. If your BMD result indicates low density, your doctor may recommend the use of steroids or corticosteroids.

To avoid decreased bone density, keep an eye on risk factors, such as substance use and pre-existing conditions. If you have a calcium deficiency, you may be at high risk for disease, and your healthcare provider may recommend calcium supplements to help support your musculoskeletal health.

In all cases, it is best to consult a physician for proper testing and treatment if you are experiencing symptoms. 

Sources: 

Bone Density | Bone Mineral Density | BMD | Medline Plus

Bone Density Scan | Medline Plus

Low Bone Density > Fact Sheets | Yale Medicine

Healthy Directions Staff Editor