All About Bones
Bones form a living framework that supports our muscles, organs and other tissue. They are complex, having several different layers. The outer layer, called the “periosteum”, is a thin but very strong membrane that surrounds and protects bones. It allows the passage of nutrients via blood vessels, and contains nerves that can sense pain. Within the periosteum reside the “osteoblasts” or cells that make new bone. Deeper down is a thicker, compact layer called “cortical” bone, the bone’s outer wall. This layer provides most of the bone’s mechanical strength. A combination of bone minerals (including calcium and phosphorous) provide hardness, while collagen fibres provide flexibility. Inside the compact bone is the more brittle and sponge-like, “cancellous” bone. This is the light and porous core of long bones. In the pores lives the bone marrow, the red blood cell “factory”. It is also a way to transport nutrients between the marrow and the bloodstream, via a network of blood vessels, housed in long channels within the cancellous bone. In long bones, these channels can run the entire length of the bone. Some nutrients are converted to tissue, like collagen, and others are stored for later use in body fat. Bones contain a combination of biochemicals, which require a delicate balance to maintain.
Bones for life – Who needs supplements?
Fetal Health – Bones form in utero, between 8 weeks gestation and the end of trimester 2. Throughout the entire pregnancy, bones continue increasing in size and maturing until birth. Nutrient demands for fetal bone development are consistently high during trimester 2 and 3 as the baby’s skeleton grows and fully forms.
Infants – As baby learns to use their limbs, head and neck, muscles begin to work and bone density increases, causing an increased nutrient demand. This demand persists during breastfeeding and early growth, for mother and child alike. Many nutrients are transferred from mother to baby through breast milk, so maintaining healthy levels during this time is of utmost importance.
Children – A great deal of bone development and growth occurs during childhood and bones need a constant supply of nutrients to cope with these demands. If your family’s diet is low in milk products or fish with edible bones, supplementation is advised for parents and children, to help support healthy bone growth and development
Adolescents – Bones experience a quick growth spurt at puberty and throughout the teenage years, expanding in size to accommodate growing bodies. Nutrient demand is high, especially in adolescents with inadequate diets.
Adults – 20 to 50 years – Throughout adulthood, continuous bone remodelling occurs. Bone building responds directly to physical activity, like manual labour and frequent or load-bearing exercise.
Pregnant women – Getting enough calcium throughout pregnancy is important for maternal support and fetal bone development. Calcium supplementation during pregnancy may prevent bone health issues from occurring later in life for mothers and their babies (1). Although recommendations by most health authorities are the same as those for non-pregnant adults, low calcium intake before, during and after pregnancy can have health consequences for Mum’s risk of osteoporosis in later years, and also for baby’s skeletal formation and development(2). In some regions, calcium intake is much lower due to minimal dairy in the cultural diet. People in these areas have a stronger need to supplement because calcium is not able to be replenished as easily through diet(2).
Breastfeeding women – Throughout breastfeeding and lactation there is a high calcium demand, as much of Mum’s calcium is transferred to baby through breast milk. These demands on maternal calcium may lead to temporary osteoporosis if not enough is available in the bloodstream, particularly where dietary intake is low(2). Likewise, other nutrients are important for both maternal and newborn health – in particular, vitamins D and K. Vitamin D is responsible for helping calcium absorption, where vitamin K is responsible for assisting with production of the proteins that make bones(3). Vitamin K1 supplementation at this time has been shown to improve bone health outcomes and is particularly important because of its ability to transfer from mother to child via breast milk(4).
Calcium needs in later life: 50 + – Bones begin to degenerate after 50, along with other organ systems, becoming less efficient at renewal. Studies have indicated that levels of calcium and vitamin D in our bloodstream decrease dramatically between 50 and 70 years (5). To prevent bone health complications, and reduce the risk of fractures due to falling, calcium & vitamin D supplementation may assist (6).
70+ – Seniors endure one of the most risk-prone times in life, where bones can weaken and fracture more easily than in younger people. Aging often brings reduced physical activity, decreased muscle coordination and lowered bone nutrient levels in blood serum, increasing the risk of bone damage. With reduced activity, bone begins to weaken, and nutrient supplementation is important to maintain its strength and integrity. Combined vitamin D and calcium supplementation for bone health in elderly people may help preserve skeletal integrity and prevent fractures if falls occur(1). Vitamin D may even reduce the risk of falling (7) by improving bone and muscle function(8).
- Flynn A. The role of dietary calcium in bone health. Proceedings of the Nutrition Society. 2003;62(04):851-8.
- Heringhausen J, Montgomery KS. Continuing Education Module—Maternal Calcium Intake and Metabolism During Pregnancy and Lactation. The Journal of perinatal education. 2005;14(1):52.
- Goldberg G. Nutrition and bone. Women’s Health Medicine. 2006;3(4):157-9.
- Greer FR, Marshall SP, Foley AL, Suttie JW. Improving the vitamin K status of breastfeeding infants with maternal vitamin K supplements. Pediatrics. 1997;99(1):88-92. Epub 1997/01/01.
- Nordin BEC, Need AG, Morris HA, O’Loughlin PD, Horowitz M. Effect of age on calcium absorption in postmenopausal women. The American journal of clinical nutrition. 2004;80(4):998-1002.
- Chapuy MC, Arlot ME, Duboeuf F, Brun J, Crouzet B, Arnaud S, et al. Vitamin D3 and calcium to prevent hip fractures in the elderly women. The New England journal of medicine. 1992;327(23):1637-42.
- Cameron ID, Gillespie LD, Robertson MC, Murray GR, Hill KD, Cumming RG, et al. Interventions for preventing falls in older people in care facilities and hospitals. The Cochrane database of systematic reviews. 2012;12:CD005465.
- Agergaard J, Trøstrup J, Uth J, Iversen JV, Boesen A, Andersen JL, et al. Does vitamin-D intake during resistance training improve the skeletal muscle hypertrophic and strength response in young and elderly men? – a randomized controlled trial. Nutrition & metabolism. 2015;12(1):1-14.
How do bones change?
In adulthood, our bones continuously undergo “remodelling”, a process during which they completely renew themselves with brand new cells. Metabolising the minerals that make up older bones (called “resorption”), they build new ones. Old bone is remodelled in the marrow, inside the cancellous bone.
Like the rest of our bodies, bones are not static and rebuild according to:
- Physical activity and load bearing exercise
- Age and stage of development
- Pregnancy and breastfeeding
- Dietary Nutrients
- Sun exposure
Nutrients we need
Nutritional requirements – Recommended Daily Intakes
“Substantial evidence shows that good maternal health and nutrition before and during pregnancy can have a positive effect on the long-term risk of non-communicable diseases in the next generation”(1)
Source: World Health Organisation (2) Vitamin & Mineral Requirements in Human Nutrition 2nd ed. National Health and Medical Research Council (NHMRC) – Australia (3) Nutrient reference values for Australia and New Zealand: Including recommended dietary intakes
- Hanson MA, Bardsley A, De-Regil LM, Moore SE, Oken E, Poston L, et al. The International Federation of Gynecology and Obstetrics (FIGO) recommendations on adolescent, preconception, and maternal nutrition: “Think Nutrition First”#. International Journal of Gynecology & Obstetrics. 2015;131, Supplement 4:S213-S53.
- Organization WH. Vitamin and mineral requirements in human nutrition. 1998.
- NHMRC. Nutrient reference values for Australia and New Zealand: Including recommended dietary intakes. In: Health Do, editor.: Commonwealth of Australia; 2006.