Take our Continuing Professional Education course, "Micronutrients and Bone Health." SummaryOur bony skeleton provides support, protection, and mobility for the body and constitutes a major storage site for calcium and phosphorus. Bone health is intrinsically linked to calcium (and phosphorus) metabolism. Calcium concentrations in the blood must be maintained within a very narrow concentration range to preserve normal physiological functions (e.g., muscle contraction, nerve impulse conduction, constriction and relaxation of blood vessels). Because these functions are essential, the body will use calcium stored in bone to maintain normal blood calcium concentrations when calcium intake is inadequate. However, this is done at the expense of our skeleton. It is well established that malnutrition diminishes the ability of bone to grow, respond to mechanical forces, and act as a homeostatic buffer to regulate calcium concentration in body fluids. Therefore, to fulfill its functions, our skeleton relies on adequate supply of nutrients, in particular large amounts of calcium and phosphorus that must come from the diet. At a minimum, getting the recommended dietary allowances (RDA) for calcium and vitamin D is necessary to maximize bone development in children and young adults and limit bone loss later in life; whether intakes above the RDA for these micronutrients might reduce the risk of fracture in older adults is debated. There is little evidence to suggest that supplementation of other micronutrients with essential roles in bone health (fluoride; magnesium; and vitamins A, B, C, and K) at levels above current recommendations may be of further benefit. Striving to reduce phosphorus and sodium intakes while increasing intakes of potassium is likely to indirectly benefit bone health through improving overall health. Finally, physical activity is highly beneficial to bone health during development and throughout life. Overview of Bone BiologyBone functionsThe skeleton serves two major functions at the same time:
To fulfill its functions, bone tissue is constantly remodeled. Bone modeling and remodelingThe skeleton is an active tissue. Two bone-making processes are involved in the development, growth, and shaping of bones, as well as the continuous renewal of bone tissue throughout life:
The two main types of cells responsible for bone (re)modeling are osteoblasts and osteoclasts. Bone compositionBone tissue is a composite material:
The bone matrix is made of triple helices of collagen arranged into fibrils and assembled into large fibers. This constitutes the interior scaffolding of bone onto which bone mineral is deposited. Determinants of adult bone healthBone mass and architecture are determined by our genes but also significantly influenced by external factors:
Exercise and diet can significantly affect the ability to achieve one's genetically determined peak bone mass. High peak bone mass reduces the risk of osteoporosis and fracture later in life. Bones weaken when:
HIGHLIGHT: CALCIUM-REGULATING HORMONES AND BONE HEALTH Vitamin D deficiency, which impairs the intestinal absorption of calcium and phosphorus, can result in the formation of poorly mineralized bone.
Osteoporosis
Fracture
DEFINITIONS For references and more information, read the report of the Surgeon General on Bone Health and Osteoporosis (2004). Nutrition Research DEFINITIONS Protein-energy Malnutrition (PEM)What it isGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on Protein-energy malnutrition (PEM) in the in-depth article on Immunity.
Essential Polyunsaturated Fatty Acids (PUFAs)What they areGeneral
Bone-specific
What we know
DEFINITIONS
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CalciumWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information:
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FluorideWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on Fluoride in the in-depth article on Bone Health.
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MagnesiumWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information:
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PhosphorusWhat it doesGeneral
Bone-specific
What we know
HIGHLIGHT:
DEFINITIONS For references and more information:
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PotassiumWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on Potassium in the in-depth article on Bone Health.
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SodiumWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on Sodium in the in-depth article on Bone Health.
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Vitamin AWhat it doesGeneral
Bone-specific
What we know
HIGHLIGHT:
DEFINITIONS For references and more information:
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B VitaminsWhat they doGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on B Vitamins in the in-depth article on Bone Health.
Vitamin CWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on Vitamin C in the in-depth article on Bone Health.
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Vitamin DWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS HIGHLIGHT: RISK FACTORS FOR VITAMIN D DEFICIENCY
HIGHLIGHT: VITAMIN D IN FOOD
For references and more information:
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Vitamin KWhat it doesGeneral
Bone-specific
What we know
HIGHLIGHT:
DEFINITIONS For references and more information, see the section see the sections on Osteoporosis and Osteoarthritis in the article on vitamin K.
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Alcoholic BeveragesWhat they doGeneral
Bone-specific
What we know
HIGHLIGHT
For references and more information:
CoffeeWhat it doesGeneral
Bone-specific
What we know
DEFINITION Homeostasis - a state of balance For references and more information, see the section on Lifestyle factors in the in-depth article on Bone Health.
Physical ActivityWhat it doesGeneral
Bone-specific
What we know
HIGHLIGHT
DEFINITIONS For references and more information:
SmokingWhat it doesGeneral
Bone-specific
What we know
DEFINITIONS For references and more information, see the section on Lifestyle factors in the in-depth article on Bone Health.
The writing of this content was supported by a grant from Pfizer Inc. |