Low bone density (i.e., reduced bone mass or osteoporosis) is a significant manifestation of bone health issues, which may be caused by various factors and involve multiple aspects such as physiology, nutrition, lifestyle, diseases, and medications. The following is a detailed classification of common causes:
I. Physiological factors
After the age of 35, bone mass begins to gradually decrease. After menopause, the level of estrogen in women drops sharply, bone resorption accelerates, and the decline in bone density becomes more obvious.
The elderly are prone to osteoporosis due to the slowed bone metabolism and reduced osteoblast activity.
The bone density of women, especially postmenopausal women, is lower than that of men because the protective effect of estrogen on bones is weakened.
Those with a family history of osteoporosis or fractures have a significantly increased risk of developing the disease.
Some genetic variations (such as the vitamin D receptor gene and the collagen gene) may affect bone metabolism.
Ⅱ. Nutritional Factors
Calcium intake is insufficient. Calcium is the main component of bones. Long-term calcium deficiency in the diet (such as vegetarians and those with lactose intolerance) can lead to a reduction in bone mass.
Vitamin D deficiency: Vitamin D promotes calcium absorption. When there is a deficiency (such as insufficient sunlight exposure, dark skin, or the elderly), it can indirectly lead to a decrease in bone density.
Insufficient nutrients such as protein, magnesium and zinc: protein is a component of bone matrix, and magnesium and zinc are involved in the activity of bone metabolic enzymes. A deficiency of both may affect bone health.
Excessive dieting or malnutrition, long-term low-calorie diets, anorexia or digestive and absorptive disorders (such as celiac disease) can lead to nutrient deficiencies.
Ⅲ. Lifestyle factors
Lack of exercise, prolonged sitting or long-term bed rest can reduce bone stress stimulation, leading to bone resorption exceeding bone formation.
Smoking and heavy drinking: Smoking inhibits the activity of osteoblasts and accelerates bone loss. Alcohol interferes with calcium absorption and affects vitamin D metabolism.
Excessive caffeine and carbonated beverages may increase the excretion of calcium in urine. Phosphates in carbonated beverages may interfere with calcium absorption (subject to other factors).
Excessive sodium intake in a high-salt diet can increase the excretion of calcium in urine, which may affect bone density in the long term.
Ⅳ. Disease factors
Hyperthyroidism, an endocrine disorder: Excessive thyroid hormones accelerate bone turnover, leading to bone loss.
Hyperparathyroidism: Excessive parathyroid hormone directly stimulates the activity of osteoclasts.
Diabetes: Long-term high blood sugar may affect bone metabolism and increase the risk of fractures.
Hypogonadism: such as early-onset ovarian insufficiency and hypotestosterone syndrome.
Digestive system diseases such as inflammatory bowel disease (like Crohn’s disease), celiac disease, and post-gastrectomy can affect nutrient absorption.
Chronic kidney disease leads to disorders in vitamin D hydroxylation and calcium and phosphorus metabolism.
Rheumatic immune diseases such as rheumatoid arthritis and systemic lupus erythematosus require long-term use of glucocorticoids to directly inhibit bone formation.
Blood system diseases such as multiple myeloma and leukemia damage bone tissue, leading to a decrease in bone density.
V. Drug factors
Long-term use of glucocorticoids (such as in the treatment of asthma and autoimmune diseases) is the most common cause of secondary osteoporosis.
Antiepileptic drugs such as phenytoin sodium and carbamazepine may accelerate the metabolism of vitamin D and reduce blood calcium.
Anticoagulant heparin (especially when used for a long time) may inhibit bone formation.
Proton pump inhibitors inhibit gastric acid secretion for a long time and affect calcium absorption.
Some chemotherapy drugs (such as methotrexate) may interfere with bone metabolism.
Ⅵ. Other factors
People with a body mass index (BMI) of less than 18.5 who are underweight usually have lower bone density due to reduced bone load.
During multiple pregnancies and lactation, the development of the fetus and the calcium demand during lactation increase. If not supplemented in time, it may affect the bone density of the mother.
Long-term immobilization, such as prolonged bed rest after a fracture, leads to accelerated bone resorption.
How to improve bone density?
Diet: Ensure the intake of calcium (1000-1200mg per day) and vitamin D (800-1000IU per day), and consume more dairy products, dark green vegetables and fish.
Exercise: Weight-bearing exercises (such as walking, running and strength training) can stimulate bone formation.
Sunbathing: 15 to 30 minutes of sunlight exposure every day promotes the synthesis of vitamin D.
Avoid risk factors: Quit smoking, limit alcohol intake, and reduce caffeine and salt intake.
Regular check-ups: It is recommended to undergo bone density testing after the age of 40 for early detection and intervention.
If there are disease or drug factors, the treatment plan should be adjusted under the guidance of a doctor, and changes in bone density should be closely monitored.
Post time: Jul-16-2025