Bone Health

Most people don’t consciously think about bone health.  It may come to mind when an elderly family member or friend has been diagnosed with osteoporosis, a disease that causes bones to become weak and brittle and likely to fracture from a minor fall.  In reality, bone health, which refers to the amount and quality of bone, starts in childhood.  Bone mineral content increases 40-fold from birth till adulthood and about 40%-60% of all adult bone mass is accrued during the adolescent years.

Individuals who obtain a higher peak bone mass in youth will be better protected against fractures and osteoporosis later in life.  Peak bone mass remains relatively stable from age 20 up to age 50, after which bone mass begins to decrease.  Bone health in an adult reflects everything that has happened to that individual from the womb through adolescence.

Healthy, strong bones are crucial for maintaining a strong and active lifestyle as we age.  

The role that bones play in the body.

The bony skeleton is a remarkable organ.  It provides the framework that supports the body and gives it shape.   Bones support body structure and anchor muscles for movement and mobility.  Bones enclose and protect vital organs, such as the skull shielding the brain, the rib cage protecting the heart and the lungs, and the vertebrae protecting the spinal cord.  Bones also have a reservoir function by storing essential minerals such as calcium and phosphorus and supplying them to cells and organs in the body when dietary sources are inadequate.  In this respect the maintenance of a constant level of calcium in the blood, as well as providing an adequate supply of calcium and phosphorus to cells, is critical to the functioning of nerves, muscles, and all body organs.  Bone marrow is found inside many bones and is where red blood cells, white blood cells, platelets, and bone cells are made. 

How bones work:

Bone is a composite material, which consists of crystals of minerals bound to protein, to provide both strength and resilience to allow bones to absorb impact without breaking.  Were bone made only of minerals, it would be more brittle and break easily, and if bone were made only of protein, it would be soft and bend easily.

The mineral content is bound in an orderly manner to a matrix that is largely made up of a single protein, collagen, which is made by bone cells.  Other proteins in bone can help to further strengthen the collagen matrix and to regulate its ability to bind mineral.

Most bones are hollow structures to provide the body with a frame that is light and strong.  The outer dense shell of bone is called cortical bone, which makes up about three-quarters of the skeletal mass.  Inside the cortical outer shell is a fine network of connecting plates and rods, called trabecular bone, that makes up the remaining 25% of skeletal mass.  These rods and plates are aligned in a pattern that provides maximum strength without being too bulky.

The cortical outer shell provides strength, and sites for attachment of tendons and muscles.  The inner trabecular network provides a large bone surface for mineral exchange, as well as helping to maintain skeletal strength and integrity.

During childhood and adolescence, bones are sculpted by a process called modeling, which allows individual bones to grow in size.  Modeling allows for the formation of new bone at one site and the removal of old bone from another site within the same bone.  Modeling is the process by which the skeleton forms and grows to its adult size.  The size and shape of the skeleton follow a genetic programme.

Once the skeleton is adult size, it regenerates about every 10 years.  This regenerative process is called remodeling and removes old pieces of bone and replaces them with new, fresh bone tissue.  Remodeling keeps the bone and its cells healthy and strong.  In young, healthy adults, the amount of bone removed and replaced is about equal and is called balanced bone remodeling.  The remodeling process continues throughout life but can shift out of balance with aging and result in loss of bone structure and strength in the elderly.

The remodeling process does not change the shape of the bone but can repair damage to the skeleton such as small cracks or deformities due to cell damage caused by stresses to the bone.  Remodeling also prevents the accumulation of too much old bone, which can become brittle.  Remodeling also plays an important role in the function of the skeleton as a reservoir for calcium and phosphorus. The process of breaking down bone during remodeling is called resorption and can supply calcium and phosphorus when there is a deficiency in the diet.

The removal and replacement of bone during the remodeling cycle takes place in a carefully orchestrated sequence.  However, due to differences in their genes, some individuals may have strong bones and others weak bones.  Genetics may account for up to 70% of variance in bone mass between individuals.

Peak bone mass is defined as the amount of boney tissue reached at skeletal maturity during the second decade of life.  At peak height velocity, when adolescents have reached 90% of their adult stature, the age of peak bone mass lags behind, as adolescents have by then only obtained 57% of their total body bone mineral content.  Interestingly, this explains the increased rate of fractures, such as forearm fractures, amongst adolescents during this period.

Bone cells are able to respond rapidly to their environment as increased bone stress through weightbearing exercises can strengthen bone structure, while lack of bone stress such as extended bed rest or weightlessness in space can rapidly weaken bone.

Maintaining bone health.

Genes and the environment both contribute to bone health.  Genes largely determine the size and shape of the skeleton and errors in gene signaling can result in birth defects.  Environmental factors such as diet and physical activity are critically important to bone health throughout life.

Bone health ingredients: Ingredients for healthy bone include calcium, vitamin D, vitamin C, vitamin K, boron, silicon, and magnesium.  Calcium is a mineral that is necessary for building and maintaining strong bones.  Vitamin D produces osteocalcin that aids in bone absorption of calcium.  Vitamin C helps to form collagen and impacts its ability to make bone.  Vitamin K helps to enable calcium binding.  Boron extends the half-life of vitamin D and estrogen.  Silicon attracts calcium.  Magnesium assists in forming bone.

Adequate nutrition: Bone health depends on a steady stream of nutrients.  Calcium is the primary mineral needed for strong bones. A diet rich in calcium, vitamin C and the abovementioned vitamins and minerals are essential to build and maintain strong bones.  Excessive caffeine and salt in the diet may cause the body to lose calcium.

Regular exercise: Staying active and following a regular exercise routine are important to maintain heathy bones.  Weight-bearing exercises such as brisk walking, jogging, and even dancing, as well as strength-training exercise such as lifting weights or using resistance bands help build and maintain bone density.  Be active every day.

Healthy lifestyle habits: Both smoking and excessive alcohol consumption can negatively impact bone density.  Nicotine inhibits bone-forming cells and smokers have a higher risk of fractures.  Heavy alcohol use interferes with the body’s ability to absorb calcium and other nutrients necessary for bone health, resulting in reduced bone mass.  It may also increase the risk of falls and broken bones.

Healthy weight: Being overweight can put extra stress on bones and joints, while being underweight raises the risk of bone loss and fractures.

Fall prevention: It is crucial for older adults with weakened bones to take steps to prevent falls, such as removing home hazards and doing exercises to improve balance.

Regular screenings: Bone mineral density tests can determine bone strength, which is particularly relevant for older adults and individuals with risk factors for osteoporosis.

Balance hormones: Maintaining hormone balance is important for bone health, particularly post-menopausal women.  The most important regulating hormones regarding bone health are three calcium regulating hormones. 

• Parathyroid hormone (PTH) maintains the level of calcium and stimulates the absorption and formation of bone. 
• Calcitriol is the hormone derived from vitamin D and its most important function is to stimulate the intestine to absorb enough calcium and phosphorus and in this way supply minerals for the skeleton. 
• Calcitonin can block bone breakdown and also plays an important role in early life to maintain bone development and normal blood calcium levels.   
• The sex hormones such as the female hormone estrogen and the male hormone testosterone both have effects on bone in men and women.  Estrogen acts to inhibit bone breakdown at all stages in life and the marked decrease in estrogen at menopause is associated with rapid bone loss.  Testosterone is important for skeletal growth as it directly affects bone and also stimulates muscle growth and thus increasing bone formation.  Testosterone is also a source of estrogen, as it is converted into estrogen in fat cells. 
• Growth hormone from the pituitary gland is also an important regulator of skeletal growth.  The growth hormone and another hormone called insulin-like growth factor-1 stimulate both the bone-resorbing and bone-forming cells, resulting in an increase in bone mass. 
• Thyroid hormones increase the energy production of all body cells.  In bone cells they increase the rates of both bone formation and resorption. 
• Cortisol is an important regulator of metabolism and the body’s ability to respond to stress and injury.  Small amounts are needed for normal bone development, but large amounts can block bone growth.  

Medication: Certain medications such as steroids and some cancer treatments may result in bone loss over time.  Some other types of medications taken for a long time may also damage bones, such as hormone medicines used to treat breast cancer and prostate cancer; medicines to treat thyroid disease; medicines used to prevent seizures; selective serotonin reuptake inhibitors; and proton pump inhibitors, amongst others.

Conclusion

Bone mass attained early in life is an important determinant of lifelong skeletal health.  As we age, various factors such as genetics, nutrition, exercise, and hormonal loss can affect the health of our bones.  Our genes are a given, but we can control our nutrition and activity level.  You are never too old or too young to actively take care of your bone health.

References:

Bone health: Tips to keep your bones healthy.  Published 11 September 2025.  Mayo Clinic.  USA. (www.mayoclinic.org)

Bone health basics.  Published online and reviewed February 2024.  OrthoInfo.  American Academy of Orthopedic Surgeons.  (www.orthoinfo.aaos.org)

Why bone health matters.  Published 10 October 2024.  BUSAMED Hospital Group.  South Africa.  (www.busamed.co.za)

Bone health and osteoporosis: A report by the Surgeon General.  USA.  National Centre for Biotechnology Information.  US National Library for Medicine. National Institutes of Health.  USA.  (www.ncbi.nlm.nih.gov)

Understanding the importance of peak bone mass.  Published May 2024 in Journal of the Pediatric Orthopedic Society of North America.  Vol 7.  Science Direct.  (www.sciencedirect.com)

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