China Bone Health Popular Science Guide

Bone health runs through a person's life and is a very important theme in life from birth to old age. From the healthy development of bones in childhood, to the maintenance of ideal peak bone mass in youth and middle age, to the popularization of protective measures to prevent falls and fractures in the elderly, everyone needs to understand and master it.

Bone health issues pose a serious threat to public health, not only because of its high incidence, but also because it is closely related to aging. Osteoporosis is considered the most common and challenging bone disease in bone health, and with the aging of the population in my country, it has gradually become a health problem that threatens the whole society. However, the current popular science knowledge related to bone health has problems such as uneven quality and even misleading content. Therefore, the formulation of standardized popular science guidelines for bone health is of great significance.

At present, there is no standardized bone health popular science guide at home and abroad. Therefore, the Science Popularization Branch of the Chinese Medical Association, in conjunction with the Medical Science Popularization Research Institute of Fudan University, the Orthopedic Committee of the Science Popularization Branch of the Chinese Medical Doctor Association, and the Editorial Board of the Chinese Medical Association's "Healthy World" organized relevant experts to conduct extensive research and solicit opinions, sort out the scientific content related to bone health, identify key issues related to bone health, including primary prevention, secondary prevention, and bone health-related rehabilitation, and write guidelines to guide the popularization of bone health knowledge among the public, hoping to improve the public's bone health status, improve national health literacy, and provide practical suggestions for the prevention of bone health problems among the public.

Understanding Bones

1. Basic knowledge

Bones are important organs of the human body. Their structures include periosteum, bone and bone marrow. Periosteum contains abundant nerves and blood vessels, and bone includes compact bone and spongy bone, as shown in Figure 1. Human bones are living organs that can grow and develop. They are also very special: they have the ability to repair, regenerate and reshape. A normal adult has 206 bones, some long and some short, with different shapes, which play an important role in human life.

Figure 1 Schematic diagram of bone structure

(1 ) Supporting function. Bones support the human body and are very strong. The middle part of the femur is even harder than granite of the same volume. The spine, which is often likened to the spiritual support of the human body, is the axial skeleton of the body - the spine.

( 2 ) Protective function. Bones also serve as shelters for important internal organs of the human body. For example, the skull protects the brain tissue, and the thorax composed of the spine, ribs and sternum protects the heart and lungs. If the bones lose their protection, even the slightest external blow will cause fatal damage to these internal organs.

( 3 ) Movement function. Human body movement is the joint movement of bones under the coordination of ligaments, tendons and muscles. Bones act as levers, tendons and muscles provide power for movement, and ligaments maintain the stability of joints. The combination of the three allows movement to be completed.

(4) Hematopoietic function. Bones are also very important hematopoietic organs in the human body. The bone marrow cavity and cancellous bone of bones contain bone marrow, among which red bone marrow has a strong hematopoietic function. A large part of the blood needed by the human body is produced by it. Therefore, many blood system diseases are often related to bone marrow lesions.

(5) Metabolic function. Bones are rich in nutrients such as calcium, phosphorus, organic matter, and inorganic matter. For example, about 99% of the body's calcium and 87% of the body's phosphorus are stored in bones in the form of calcium salts and phosphates. When other organs need it, the body issues orders through hormone secretion, allowing the bones, the "storage depot", to release the corresponding elements to meet the body's needs.

2. Growth and Development

The growth and development of human bones achieves a dynamic balance through bone formation and bone loss. It is constantly constructed and shaped, and changes quietly at different ages.

(1) Before the age of 20. Childhood and adolescence are critical periods for bone growth and development. From birth to two years old is the period of fastest height change. The height at the age of two is about half of the adult height. After that, the height grows slowly until the puberty period, which is 10 to 14 years old for girls and 12 to 16 years old for boys. After puberty, sexual maturity occurs and the length of bones basically stops increasing. Bone formation in children and adolescents is greater than bone resorption, and bone mass continues to increase. More than 90% of the bone mass of adults is accumulated before the end of puberty. Ensuring adequate sleep, adequate nutrition and active physical exercise during this stage will help adolescents grow taller.

(2) 20 to 40 years old. This stage is the peak period of human bone growth and development. Bone formation and bone resorption reach a positive balance. Sunlight, exercise, and calcium supplementation are very important. They can achieve a higher and more ideal peak bone mass and reduce the occurrence of osteoporosis in the elderly.

(3) 40 to 60 years old. With age, bone absorption is greater than bone formation, bone mass is in a negative balance, and bone loss begins. Normal bone tissue is like a honeycomb, with many small cavities in the middle, and the skeleton structure in the middle is very strong. When people get older, some of the cavities in the trabeculae in the middle become larger, while the supporting skeleton trabeculae structure in the middle becomes thinner, making fractures more likely to occur. This is osteoporosis, as shown in Figure 2. Especially after menopause, women will suffer from osteoporosis when they lose bone mass rapidly, and the risk of fracture increases accordingly. Men generally begin to lose bone mass after the age of 50, leading to osteoporosis, and the risk of fracture increases significantly. Therefore, after the age of 40, in addition to continuing to pay attention to bone health and developing good living habits, it is very important to have regular physical examinations to understand the health of your bones.

Figure 2 Schematic diagram of bone loss and osteoporosis

(4) After age 60. As bone loss accelerates, the prevalence of osteoporosis in people over 60 years old in my country has increased significantly, especially in women.

3. Alarms from bone disease

As an important organ of the human body, bones are always playing their role silently, but problems may also occur. If the following alarms are issued, it means that the bones are sick and you need to go to the hospital for treatment in time.

(1) Pain. Since bones and muscles are inseparable, and there are a large number of nerves distributed on the muscles closely connected to them, pain will occur when bones are damaged due to various reasons. The pain can be dull or intense, and can be intermittent or continuous. In addition, some chronic bone diseases such as bone tumors and osteoporosis are often ignored because the disease lasts for a long time and the pain is not severe in the early stage.

(2) Shortening of height. The epiphyses of the human body usually close around the age of 20 to 24, and height generally stops growing after that. After middle age, due to spinal aging, intervertebral disc degeneration and narrowing of intervertebral spaces, the height of most people will decrease slightly, but rarely by more than 3 cm. If the height decreases by more than 3 cm, you should be alert to the possibility of osteoporosis.

(3) Easy to fracture. Bones are very hard organs in the human body and can withstand great stress to maintain normal function. However, if a fracture occurs with very little stress, the cause may be bone disease, such as osteoporosis or bone tumors.

(4) Lumps and deformities. During the development of the human skeleton, the bones on both sides grow symmetrically with the spine as the central axis. If you find obvious lumps or deformities in the bones of the limbs or trunk on both sides in your daily life, this indicates that there may be a bone disease.

Bone examination

1. Imaging examination

When patients have bone problems and go to the hospital for treatment, they are often asked by doctors to take imaging tests, which is what we often call "taking a film". The information provided by imaging tests is very important for doctors to make clinical judgments to determine whether there are bone diseases such as traumatic fractures, inflammation or tumors. Among them, X-rays, CT and magnetic resonance imaging (MRI) are the most common imaging tests.

(1) X-ray is a low-cost basic imaging examination. Doctors can find obvious bone problems such as fractures, bone hyperplasia, and deformities. Dual-energy X-ray bone density measurement is also the current "gold standard" for diagnosing osteoporosis, and it is also the main means of evaluating the efficacy of anti-osteoporosis drugs. Judging the stability of the spine through special posture radiographs of the spine in hyperextension and hyperflexion is also a feature of X-ray examination. However, since X-ray images are two-dimensional planes with limited clarity, accurate diagnosis of lesions in many parts of the body requires further examination with the help of CT or MRI. X-ray examinations have a certain amount of radiation, and pregnant women should try to avoid this examination.

(2) CT, or computer tomography, can be simply understood as taking multiple X-rays of the patient at multiple angles at the same time, and then processing them with a computer to form a clearer picture. With the help of CT, doctors can diagnose fractures and bone diseases more accurately. Three-dimensional CT has incomparable advantages in judging whether the lesion is calcified, fractures involving joints, and metal internal fixation. Because CT takes multiple X-rays at the same time, its radiation is also higher than that of X-ray examinations, and pregnant women need to avoid it. The price is also more expensive than X-ray examinations.

(3) MRI is magnetic resonance imaging. It mainly looks at soft tissue lesions and is the most commonly used imaging examination for the brain and spinal cord. It can clearly distinguish nerves, ligaments, cartilage and other tissues. It is widely used in orthopedics for the diagnosis of spinal cord neuropathy, bone tumors, ligament and cartilage injuries. MRI is not as clear as CT in resolving cortical bone tissue, but is worse than X-ray or CT in resolving details of cancellous bone, but the cost is much higher. Its advantage is that it does not cause radiation to the human body, and pregnant women can usually undergo this examination. However, it should be noted that MRI examination is not recommended for women within 3 months of pregnancy. In addition, patients with metal implants in their bodies need to inform their doctors in advance, including metal dentures, pacemakers, IUDs, bone plates and screws, etc., which contain metal. They need to adjust the machine parameters or use a low magnetic field before they can undergo MRI examinations.

Taking a patient with cervical spondylosis as an example, the following will introduce the respective characteristics of X-ray, CT and MRI in disease diagnosis, see Figure 3.

Figure 3 The difference between X-ray, CT and MRI examinations in disease diagnosis 3A: Lateral cervical X-ray shows cervical vertebral curvature deformity and vertebral bone hyperplasia 3B: Sagittal cervical MRI, red arrows indicate C4/5 intervertebral disc herniation and obvious spinal cord compression 3C: Cross-section of cervical CT, red arrows indicate calcification of the posterior longitudinal ligament behind the intervertebral disc 3D: Cross-section of cervical MRI, red arrows indicate intervertebral disc herniation and spinal cord compression, but it is impossible to determine whether calcification exists

Therefore, X-ray, CT and MRI examinations have different focuses and cannot replace each other at present. Doctors will prescribe all three examinations at the same time when necessary.

In addition, there are color ultrasound and radionuclide imaging, such as emission computed tomography (ECT), positron emission tomography-computed tomography (PET-CT), positron emission computed tomography-magnetic resonance imaging (PET-MRI), and other imaging examination methods, which can help doctors diagnose diseases such as bone tissue, surrounding muscle and ligament lesions, and bone tumors.

2. Blood test

In addition to imaging examinations, doctors will also conduct corresponding blood tests according to the patient's condition to assist in diagnosis and treatment. If the human leukocyte antigen B27 (HLA-B27) in the blood is positive, the patient is very likely to suffer from ankylosing spondylitis; and abnormal alkaline phosphatase in the blood may also be caused by osteosarcoma; increased calcium ions in the blood may be related to bone destruction caused by metastatic bone tumors, while decreased calcium ions indicate that it is related to diseases such as rickets; and the detection of bone metabolism indicators has important reference value for the selection of anti-osteoporosis drugs and the judgment of efficacy.

3. Other examinations

In fact, when a patient goes to the hospital for treatment, the doctor may first conduct some simple physical examinations such as "sight, touch, movement, and measurement" to gain a preliminary understanding of the condition. The doctor can then prescribe an imaging examination based on the interview and physical examination.

Bone health

1. Nutritional supplements

Bones are like the four beams and eight pillars of a house. If you want them to be strong, you need adequate nutrition. Calcium is the cornerstone of strong bones, and vitamin D and vitamin K2 are the two golden partners for calcium supplementation.

Adequate calcium intake is very important for obtaining ideal peak bone mass, alleviating bone loss, improving bone mineralization and maintaining bone health. The recommended daily calcium intake for young and middle-aged Chinese residents is 800 mg (elemental calcium), and the recommended daily calcium intake for middle-aged and elderly people over 50 years old, people in the middle and late stages of pregnancy and lactation is 1,000 to 1,200 mg, see Table 1. The following principles should be followed when supplementing calcium.

(1) Dietary supplements are a priority. Foods rich in calcium include dairy products such as milk, cheese, and yogurt. It is recommended that each person consume more than 300 ml of liquid milk per day. Green vegetables, but fresh vegetables contain oxalic acid, which will affect calcium absorption and increase the risk of kidney stones. It is recommended to blanch them before cooking. Soybeans and soy products such as dried tofu and old tofu are rich in calcium, but the calcium content of soy milk is low, about only 1/10 of that of milk. Nuts and seafood such as dried shrimps and seaweed are also rich in calcium.

(2) When calcium intake from food is insufficient, you can choose appropriate calcium tablets for additional supplementation under the guidance of a doctor or nutritionist. Nutritional surveys show that Chinese residents consume about 400 mg of elemental calcium per day, so they still need to supplement about 500 to 600 mg of elemental calcium.

(3) It is recommended to take calcium tablets with meals. Gastric acid helps the absorption and utilization of calcium. Taking calcium tablets with meals can also reduce the risk of kidney stones.

(4) Calcium should be supplemented in small doses over several times to facilitate intestinal absorption. It is recommended to drink plenty of water while supplementing calcium.

Vitamin D is the "engine" of calcium, which can increase the active absorption of intestinal calcium, promote bone mineralization, maintain muscle strength, improve balance and reduce the risk of falling. The main source of vitamin D is sunlight. 7-dehydrocholesterol in the skin can be converted into vitamin D after exposure to ultraviolet rays in sunlight. It is recommended to expose the skin to sunlight as much as possible from 11 am to 3 pm, without glass windows or sunscreen, for 15 to 30 minutes (the specific time depends on local sunshine time, latitude and season, etc.), at least twice a week. The content of vitamin D in food is relatively low, mainly found in marine fish, animal liver, egg yolk, cod liver oil, etc. The level of 25-hydroxyvitamin D in the blood can be tested to determine whether the body has sufficient vitamin D: the ideal level of serum 25-hydroxyvitamin D is 30 ng/ml, 20 to 30 ng/ml is vitamin D deficiency, and less than 20 ng/ml is vitamin D deficiency. If you cannot get enough vitamin D from daily sunlight and diet, you can take additional oral supplements: it is recommended that healthy infants, children, adolescents, middle-aged people, and pregnant women take 400 IU/day of vitamin D, and people over 50 years old take 600 IU/day. Whether it is vitamin D2 or vitamin D, supplements can equivalently increase the serum 25-hydroxyvitamin D level in the body.

Vitamin K2 is a calcium "navigator". It can help "bring calcium into the bones" through calcium absorbed from the intestines into the blood, activate osteocalcin, an important factor in the bones, deposit calcium on the bones, and reduce the deposition of calcium ions on the blood vessel walls. In the diet, vitamin K2 is mainly found in some fermented foods such as natto, cheese, etc., as well as egg yolks and lean meat. In addition, vitamin K, which is present in large quantities in green vegetable leaves, can also be converted into vitamin K2 with the help of intestinal bacteria.

Protein is the "rebar" that supports the skeletal building. About 30% of bones are collagen, which plays an important role in maintaining bone toughness, preventing fractures, maintaining bone metabolism and growth and repair. In addition, protein is also the main source of muscle, which can prevent sarcopenia and reduce the risk of frailty and falls in the elderly. The so-called "flesh and bones are connected", bone and muscle health affect each other, and both are inseparable from sufficient protein. It is recommended that each person consume 0.8-1.0 g/kg of protein per day, which can be increased to 1.2-1.5 g/kg for elderly people with acute and chronic diseases. Increase the intake of high-quality protein, such as eggs, milk, fish, shrimp, chicken, duck, cattle, sheep, pork, etc., as well as soy protein. Of course, overeating should also be avoided, and excessive protein intake will also accelerate calcium loss.

Other nutrients such as magnesium ions also play an important role in maintaining calcium balance; zinc can promote bone formation; glucosamine plays a certain role in repairing and maintaining cartilage growth; OMEGA-3 (ie Ω-3, ω-3), called "Omega 3" in Chinese, has anti-inflammatory effects and has a certain protective effect on the knee joint.

2. Exercise properly

Bone health is inseparable from exercise. Exercise can directly stimulate bone metabolism, maintain bone mass, increase muscle strength and balance, and reduce the risk of falls and fractures. What are some exercises that are good for bones?

(1) Resistance exercise. For young and middle-aged people, you can choose pull-ups, barbell shoulder raises, push-ups, etc., 2 to 3 times a week. It is not advisable to do high-load resistance exercise for the same group of muscles for two consecutive days. For middle-aged and elderly people, you can choose static wall squats, standing push-ups, heel raises, sit-up training, etc.

(2) Aerobic exercise. Young and middle-aged people can choose running, dancing, skipping rope, aerobics, dumbbell exercises, etc. The elderly can choose brisk walking, jogging, square dancing, and stepping on the spot, etc. 3 to 5 times a week, 20 to 30 minutes each time.

(3) Balance exercises, such as Tai Chi, Ba Duan Jin, standing on one leg, walking in a circle in the shape of an "8", pendulum training, etc.

(4) Posture training, such as chest expansion exercises, Pilates, stretching exercises, plank support, etc.

(5) Local exercise. For example, quadriceps isometric contraction training and straight leg raising training can increase the strength of the quadriceps to protect the knee joint. Five-point support and cervical and lumbar spine aerobics can increase the stability of the spine, improve the physiological curvature of the vertebrae, and prevent cervical and lumbar spine diseases, as shown in Figure 4.

Figure 4 Lumbar spine aerobics diagram 4A, 4B: Flying Swallow exercise

In daily life and work, the following precautions are also important for protecting bones.

(1) Avoid bad eating habits, such as smoking, long-term heavy drinking, eating too much salty food, drinking strong tea or too much coffee, carbonated drinks, etc.

(2) Avoid bad postures, such as sitting or standing for a long time, working at a desk for a long time, looking down at the phone for a long time, squatting on the floor to do housework, sitting on the sofa, crossing your legs, etc. Sitting for a long time means sitting still for a total of 6 hours or more a day, so it is recommended that you should get up and move around if you sit still for more than 45 minutes.

(3) Avoid sports injuries. Warm up before exercise to avoid sudden force that may cause injuries to bones, ligaments, tendons and muscles. During exercise, especially strenuous exercise, you can wear appropriate protective gear. Avoid excessive weight-bearing and strength training. It is recommended to exercise scientifically under the guidance of professionals and rehabilitation doctors, and do it step by step and within your ability. Relaxation and stretching after exercise will help recovery and reduce sports injuries. The elderly should avoid high-impact movements (jumping from high places), excessive rotation (turning the waist), sit-ups and other movements. If there is obvious pain or discomfort during exercise, stop immediately and seek medical attention.

Source: Health World Magazine