What causes bone mass to decrease? A comprehensive guide

Over 54 million Americans are at risk for osteoporosis or low bone mass, a condition where bone tissue deteriorates. Understanding what causes bone mass to decrease is the first step toward proactive health management and reducing your risk of fractures. This guide provides a detailed look into the factors influencing bone health.

Quick Summary

Bone mass can decrease due to an imbalance in the natural remodeling cycle, where old bone is reabsorbed faster than new bone is created. This process is influenced by factors like age, hormonal shifts, nutritional deficiencies, and lifestyle choices, which can lead to osteopenia and osteoporosis.

Key Points

• Age and Remodeling: After age 30, the rate of bone breakdown naturally exceeds formation, leading to a gradual decrease in bone mass over time.

• Hormonal Shifts: The decline in estrogen during menopause is a primary driver of rapid bone loss in women, while lower testosterone levels affect men as they age.

• Nutritional Needs: Inadequate intake of calcium and vitamin D is a major cause of decreased bone mass, as these nutrients are essential for building and maintaining strong bones.

• Lifestyle Impact: Sedentary behavior, smoking, and excessive alcohol consumption significantly accelerate bone loss and weaken the skeletal structure.

• Medication and Medical Conditions: Certain medications, such as corticosteroids, and chronic diseases, like kidney or liver issues, can negatively affect bone metabolism and increase the risk of osteoporosis.

The natural process of bone remodeling and aging

Bone is a living tissue that is in a constant state of renewal, a process known as remodeling. This involves two types of cells: osteoclasts, which break down and reabsorb old bone tissue, and osteoblasts, which create new bone. During childhood and young adulthood, new bone is formed faster than old bone is broken down, leading to an increase in bone mass. Most people achieve their peak bone mass around age 30.

After age 30, the balance of this process begins to shift, with bone resorption gradually outpacing bone formation. While some age-related bone loss is normal, several factors can accelerate this process, leading to a significant decrease in bone mass and increasing the risk of osteoporosis.

Hormonal influences on bone density

Hormones are powerful chemical messengers that play a critical role in regulating bone health. Fluctuations or deficiencies in certain hormones can profoundly impact the bone remodeling cycle.

Menopause and estrogen decline

For women, the sharp decline in estrogen levels during menopause is a major cause of accelerated bone loss. Estrogen has a protective effect on bones, helping to inhibit osteoclast activity. With less estrogen, osteoclasts become more active, breaking down bone more quickly than osteoblasts can rebuild it. In the first few years after menopause, women can lose bone mass rapidly. This is why women, especially white and Asian women over 50, are at a significantly higher risk of developing osteoporosis than men.

Testosterone in men

While less dramatic than the changes during female menopause, men also experience a gradual decline in testosterone as they age. Testosterone plays a role in maintaining bone density, and a significant drop can contribute to bone loss. This effect is particularly noticeable in men over 70.

Other hormonal factors

• Thyroid hormones: An overactive thyroid gland (hyperthyroidism) can lead to increased bone loss by speeding up the bone remodeling process.
• Parathyroid hormone: Produced by the parathyroid glands, this hormone regulates calcium levels. An overactive parathyroid gland can cause excessive calcium to be pulled from the bones, weakening them.
• Cortisol: Chronically high levels of cortisol, the stress hormone, can interfere with the bone-building process.

Nutritional deficiencies that affect bone health

A lifelong diet low in certain key nutrients can prevent the body from building and maintaining a healthy bone bank, leaving bones more susceptible to decrease in mass over time.

Critical nutrients for bone health

• Calcium: The primary mineral component of bones, calcium is essential for strength. When dietary calcium is insufficient, the body draws it from the bones to maintain blood calcium levels, which are critical for nerve and muscle function.
• Vitamin D: This vitamin is crucial for the body's ability to absorb calcium from food. Without enough vitamin D, even a calcium-rich diet won't be enough to support bone health.
• Protein: Adequate protein is necessary for the bone matrix, the framework upon which minerals are deposited. Both low and excessively high protein intake can negatively impact bone density.
• Other micronutrients: Magnesium, vitamin K, and potassium also play roles in bone metabolism and mineralization.

Lifestyle factors and bone mass

Your daily habits and level of activity have a major impact on your skeletal strength. Bone is dynamic and responds to mechanical stress. Engaging in weight-bearing exercise helps stimulate osteoblast activity, strengthening bones.

Factors that decrease bone density

• Sedentary lifestyle: Lack of physical activity leads to weakened bones. People who spend a lot of time sitting or are bedridden are at a higher risk of bone loss.
• Tobacco use: Smoking has been consistently linked to lower bone density and a higher risk of fractures. The exact mechanism isn't fully clear, but it is believed to harm bones and interfere with hormone production.
• Excessive alcohol consumption: Regular heavy drinking (more than two drinks a day for men, one for women) can interfere with calcium absorption and vitamin D production, contributing to bone loss.
• Low body weight: Being underweight or having a very small body frame provides less mechanical stress on bones, resulting in lower bone mass. Eating disorders can also lead to malnutrition and hormonal imbalances that harm bones.

Medical conditions and medications

Several chronic illnesses and commonly prescribed medications can increase the risk of developing low bone mass.

Underlying medical conditions

• Chronic kidney or liver disease: These conditions can interfere with calcium and vitamin D metabolism.
• Inflammatory bowel disease and Celiac disease: These can affect nutrient absorption in the gut, leading to deficiencies of bone-building nutrients.
• Rheumatoid arthritis: Chronic inflammation associated with this autoimmune disease can contribute to bone loss.
• Diabetes: Type 1 diabetes and long-term insulin use have been associated with lower bone mineral density.

Medications that affect bone density

Long-term use of certain drugs can suppress bone formation or increase bone resorption. It is important to discuss these risks with your doctor.

• Corticosteroids: Drugs like prednisone, often used to treat conditions like asthma and arthritis, significantly interfere with the bone-rebuilding process.
• Proton pump inhibitors (PPIs): Used to reduce stomach acid, long-term use of PPIs like omeprazole may affect calcium absorption.
• Anticonvulsants: Some medications used for seizures, such as phenytoin, can interfere with vitamin D metabolism.
• Hormone-blocking therapies: Treatments for certain cancers that reduce estrogen or testosterone levels can lead to rapid bone loss.

Genetic and ethnic factors

While age and lifestyle play a large role, genetic predisposition is a significant factor in bone mass. Heredity accounts for 50-85% of the variance in peak bone mass. A family history of osteoporosis, particularly a parent with a hip fracture, increases your risk. Ethnicity also plays a role, with white and Asian individuals generally having a higher risk of osteoporosis. However, all ethnicities are susceptible, and other risk factors should not be ignored.

Comparison of risk factors

Risk Factor Category	Examples	Impact on Bone Mass
Aging	Post-30 bone turnover shift, slower new bone formation.	Universal, gradual decline.
Hormonal	Menopause (low estrogen), low testosterone, high cortisol, thyroid issues.	Significant, can cause rapid or steady decline.
Nutritional	Low intake of calcium, vitamin D, protein; eating disorders.	Inhibits bone formation and mineral density.
Lifestyle	Sedentary lifestyle, smoking, excessive alcohol, low body weight.	Accelerates bone loss by suppressing formation and increasing resorption.
Medical	Chronic kidney/liver disease, RA, celiac disease, some cancers.	Interferes with nutrient absorption, metabolism, and increases inflammation.
Medication	Long-term use of corticosteroids, PPIs, some anticonvulsants.	Direct and indirect effects on bone remodeling.
Genetic	Family history, ethnicity (e.g., Caucasian/Asian).	Predisposition, higher risk for lower peak bone mass.

How to protect and strengthen your bones

Preventing or slowing the decrease of bone mass is an active process that involves lifestyle and dietary changes, alongside medical guidance.

1. Consume a calcium-rich diet: Include dairy products, leafy green vegetables, tofu, and fortified foods. Adults 51-70 should aim for 1,000-1,200 mg of calcium daily.
2. Get sufficient vitamin D: Expose your skin to sunlight for a few minutes daily, or consume fatty fish and fortified milk. Supplements may be necessary.
3. Incorporate weight-bearing exercise: Activities like walking, jogging, dancing, and weightlifting help stimulate bone formation and improve bone density. Balance exercises like tai chi can reduce fall risk.
4. Quit smoking and moderate alcohol: These habits significantly weaken bones and increase fracture risk.
5. Talk to your doctor: Especially if you have a family history or are on medications known to affect bone density, your doctor can recommend screenings like a DEXA scan and discuss preventative strategies or treatments.

Conclusion

Decreased bone mass is a complex issue influenced by a multitude of factors, not just aging. Understanding the roles of hormones, nutrition, and lifestyle provides a powerful foundation for taking control of your bone health. By adopting a proactive approach that includes a nutrient-rich diet, regular weight-bearing exercise, and open communication with your healthcare provider, you can significantly reduce your risk of developing osteoporosis and improve your quality of life as you age. For more information on preventative care, visit the National Institutes of Health website.

Frequently Asked Questions

At what age does bone mass typically begin to decrease?

Bone mass generally begins to decrease after you reach your peak bone density, which typically occurs around age 30. After this point, the natural process of bone turnover shifts, and resorption starts to outpace formation.

Can low body weight contribute to bone mass decrease?

Yes, people with a low body mass index (BMI) or small frame size are at a higher risk of developing low bone mass. This is because they have less bone to lose as they age compared to individuals with larger frames.

Are men also at risk for bone mass decrease?

Yes, men are also at risk. While less common than in women, men experience bone loss as they age, especially after 70. This can be influenced by declining testosterone levels and other lifestyle or medical factors.

What is the difference between osteopenia and osteoporosis?

Osteopenia is a condition where bone density is lower than normal but not yet low enough to be classified as osteoporosis. Osteoporosis involves significantly reduced bone mass and weakened bone architecture, leading to a much higher risk of fractures.

Can exercise help prevent a decrease in bone mass?

Yes, regular weight-bearing exercise is one of the most effective ways to prevent bone mass decrease. Activities like walking, running, and weightlifting put stress on bones, stimulating the bone-building cells and increasing density.

Do dietary supplements help in preventing bone mass decrease?

Supplements can help, but they are most effective when combined with a balanced diet. Calcium and vitamin D supplements are often recommended to ensure adequate intake, especially for those with low dietary consumption or absorption issues. Always consult a healthcare provider before starting new supplements.

How do I know if my bone mass is decreasing?

Decreased bone mass is often a 'silent' condition with no obvious symptoms until a fracture occurs. The best way to know is through a bone mineral density test, or DEXA scan. It is recommended for women over 65 and men over 70, or earlier for individuals with specific risk factors.