The Role of Vitamin K, Vitamin D and Calcium on Bone Health across the Lifespan - Term Paper Example

Discuss the Role of Vitamin K, Vitamin D and Calcium on Bone Health across the Lifespan and Review the Evidence that Supplementation with Vitamin D and Calcium can Help Prevent Bone Fractures among Older People Living in Residential Care. Introduction: Bones make up the skeletal system of the body and are am essential part of several aspects of the human body and its activities. Bones provide structural support to the body, assist in transportation, give protection to the vital organs and are the storehouse of calcium in the body. Though we may feel that our bones remain the same during life, in reality there is a constant process of breaking down of old bone and replacement with new strong bone throughout life. In this manner the strength and vitality of the bones are maintained. However, this process varies in significant manner during advanced age, which may have a negative impact on the strength of the bone and its ability to satisfactorily perform its essential functions. With the increase in life spans being experienced around the world and particularly in the developed world maintaining healthy bones has become more important, so that the elderly segments of population can continue their active phase of life, without risks of damage of fractures to bones impeding the quality of their lives. This has led to increasing interest in the interaction between nutrition and bone growth and development and the nutrients that are significant in prevention of deficiencies, with particular emphasis on optimising peak bone mass and making the risk for osteoporosis minimal (Prentice, et al, 2006). Bone Structure and Changes throughout Life: Bones are made up of hard living tissue, which are in the form of hard matrix consisting of calcium salts deposited around protein fibres. The protein fibres are made up of collagen and provide the bones with their strength and elasticity, while it is the mineral deposits that make the bones rigid. Bones may be divided into the outer bone and the inner bone. The outer bone layer is called the periostem and it makes up eighty percent of the mass of a bone and provides rigidity to the bone. The trabecular bone is the inner bone, the structure of which looks like a honeycomb, due to the spongy mesh-like bone that it consists of to provide strength to the bone. It makes up twenty percent of the mass of the bone. Within the cavity of the bone, bone marrow is found, which is responsible for the production of red blood cells. Bones are in different shape and length based on the functions that they perform in the skeletal system. osteoclasts and osteoblasts play an important role in the development and maintenance of bone known as remodelling (Bridwell, 2008). Starting from infancy and right through adolescence there is a predominant bone formation activity that goes along with the growth and development of the human body. It is during the adolescent stages that bone development peaks, which is demonstrated through the almost doubling of skeletal mass at the end of adolescence (Saggese, Baroncelli & Bertelloni, 2002). According to Rauch 2007, the increase in bone mass that occurs by the growing bones comes from changes in the outer dimensions of the bones and from the net addition of tissue that takes place in the inner bone surfaces. Hence any consideration of increase in bone mass has to take into account the bone accrual that occurs at the trabecular or inner bone surfaces and the periosteal or inner bone surfaces. Bones get bigger through the addition on the outside surfaces and get denser through additions in the inner surfaces. Two different processes are involved in the growth of bone, one which increases length and the other which increases width. Bones just do not increase in length alone, but in width too. Increase in length occurs through the growth plate, while the periostem is responsible for the increase in width. The process of increase in length and the increase in width is a well coordinated process, for if the bone were to merely increase in length, it would become unstable and prone to breaking. The processes involved in this coordination are still not clear, but an essential factor to the functions of the bone to take up mechanical loads (Rauch, 2007). During the developmental stages trabecular bone becomes thicker as a result of bone remodelling with a positive balance. In the process of remodelling osteoclasts remove worn out bone cells, while osteoblasts deposit new bone cells, which is closely linked over time and space. The balance is positive when more new bone is deposited in relation to the removal of old bone. Bone accrual on periosteal surfaces that is responsible for the bone size is a critical element in the determination of bone strength during the entire period of life. In what is termed as bone modelling periosteal osteoblasts continue to deposit new bone over an extended period of life, without having to contend with the removal of bone old bone by the osteoclasts. Subsequent to the growth period of an individual there are limited and slow changes to the size of the bone. It is this factor that makes the bone growth in size during the developmental period and important factor in the determination of bone strength throughout the life of an individual (Rauch, 2007). The peak bone mass in an individual is attained between the age of twenty-five and thirty and at this stage the vertebral body, which is the load bearing part of the vertebral body is capable of withstanding a load of one thousand kilograms or more, because of the special architecture that it endows it with great strength in comparison to its low bone mass. Peak bone mass in the case of men is 25% -30% higher in men than in women, because the size of bones in men are larger than in women, though the bone density remains the same. Several factors impinge on peak bone mass, which include genetic factors, physical activity and nutrition. As one ages there is reduction in trabecular bone mass due to a negative balance in the remodelling process through greater removal of bone material and less deposit of new bone material. Thus from the age of twenty-five to thirty onwards there is a continual loss of bone mass, which starts from the central part of the ventral body and progresses upwards and downwards. In addition there are changes in the cross section area of the bone that results from periosteal bone formation and osteophyte formation. Osteophytes are a part of the aging process and are normally observed from the age of fifty onwards. Osteophytes cause addition of bone to the periosteal surface. The problem with this bone addition is that though it adds bone mass it does not increase bone strength or bone quality. The sum total of the these changes that occur from the age of twenty-five to thirty onwards is the load bearing capacity of the vertebral body drops to about 150-250 kilograms in elderly individuals. These are normal to the ageing process, but when they become pronounced they add to the fragility of the bones in the elderly (Mosekilde, 2000). There is another significant factor in the changes that occur in bones and they are gender related. There is already the element of larger bone mass due to the larger bone size with the same density as in women at the peak of bone development. In addition males show a greater tendency for age-related compensatory increase in bone size that is not seen in women. Women with osteoporosis show very small vertebral bodies and hence have a very low load bearing capacity. Furthermore, after menopause there is a tendency in women for disconnection of the horizontal trabecular struts, which leads to more exaggerated deterioration of the network and onto decrease in strength of the bone (Mosekilde, 2000). Nutrition in Maintaining Bone Health: An adequate intake of several different nutrients is essential to the growth and development of bones. Studies into the impact of intake of proper nutrients for bone growth and development show that there is the requirement for intake of these nutrients above the normally advised dietary intake to prevent deficiencies, with regard to maintaining optimum bone mass and reducing the risk for osteoporosis. Evidence from these studies also show that peak bone mass and the potential risk for osteoporosis is influenced by the availability of these nutrients at different stages of life that include as a foetus, in infancy and childhood and in childhood. However, there have been constraints in the ability currently to clearly provide reference values for these nutrients using with bone health as the criterion. Hence currently there is no definite indication on the type of diet required for proper bone growth and development. However there are guidelines that suggest that intake of these nutrients early stages of life be as close to the guidelines provided for adults, indulge in physical activity, maintain a healthy body weight, restrict salt intake and consume plenty of fruit and vegetables (Prentice, et al, 2006). Among the several nutrients calcium is a key nutrient for maintaining bone health at all stages of life. There is a threshold level for the intake of calcium. This threshold level of calcium is calculated such that the skeletal accumulation is a function of the intake in the case of intake below this threshold level and remains constant irrespective of the level of increase in the intake of calcium above the threshold level. At intake levels of calcium below this threshold level, younger individuals will not be capable of reaching the genetically predetermined peak bone mass and in the case of older individuals there will be loss of bone tissue faster than it can be replaced or is normal at that age, leading to osteoporosis. Calcium intake at the threshold levels is thus essential for bone health during the stages of growth and development and also as a preventive measure against excessive bone loss with advance in age (Illich & Matkovich, 1997). The issue of exceeding the threshold levels for calcium is controversial, with support coming in the form of it being useful in preventing osteoporosis in those segments of population at high risk for osteoporosis, while others claim that no extra benefits are gained from excess intake of calcium. There are other problems associated with increasing the recommended daily intake of calcium, as excess intake of calcium could hinder the absorption of other essential minerals like iron and changes in agricultural policies and fortification of food stuffs to provide for the increased intake of calcium (Prentice, 2002). The World Health Organization (WHO) points out based on evidence that intake of calcium and vitamin D should be sufficient to maintain bone health and reduce the incidence of osteoporosis. In addition WHO, while recognizing the need for setting country specific levels for recommended dietary allowance for calcium, has set its recommendation for daily intake of calcium at 400-500 mg/day in countries which demonstrate a high bone fracture rate (WHO, 2003). In the United Kingdom the Reference Nutrient Intake (RNI) is 700 mg/day and the Lower Reference Nutrient Intake is 400 mg/d (Food Standards Agency, 2004). Vitamin D is also known as the ‘sunshine vitamin’ as it is obtained by the endogenous synthesis of cholecalciferol (D3), in the skin through the action of ultraviolet rays. It is also obtained from diet in the form of cholecalciferol from animal sources and ergocalciferol (D2) from plant sources. The dependence on dietary sources increases when there is deficient like in the temperate regions. For example in the United Kingdom the ultraviolet of appropriate sunlight are only available from April to October, raising the dependence on dietary sources (Prentice, 2002). Macdonald, et al, 2008, maintain that the role of vitamin D in maintaining bone health is controversial, though its role in rickets has been establishment. Studies that have tried to establish the role of dietary vitamin D in maintaining bone health have found conflicting results that have led to the controversy. However, it is quite likely that a daily intake of 800 IU of vitamin D for people living in the higher latitudes would be beneficial in reducing bone turn over and bone loss (MacDonald, et al, 2008). The WHO recommendation on dietary intake of vitamin D is restricted to countries with high fracture rates, where it advices increase the daily intake of vitamin D and in the countries with limited exposure to sunlight, in which case it recommends a daily intake of 400 IU of vitamin D (WHO, 2003). In the United Kingdom there are no government guidelines on the daily requirement of vitamin D in healthy individuals below the age of sixty-five. The elderly over sixty-five and those segment of population are advised a daily intake of 400 IU by the government (MacDonald, et al, 2008). Vitamin K is made up of a group of related compounds consisting of the natural forms phylloquinone (K1) and menaquinone (K2) and the synthetic phytonadione. Vitamin K is essentially got from leafy vegetables. Vitamin K is believed to have a role to play in bone health, as the undercarboxylated serum osteocalcin has been associated with lower bone density and fractures. Vitamin K plays a key role in the carboxylation of osteocalcin. Some studies have shown that vitamin K may have role in bone health, but this has yet to be established (Adams & Pepping, 2005). As a result there are no recommendations on daily intake from WHO, or from the U.K. government. Prentice, 2004, points out that with the exception of calcium and vitamin D there is hardly any evidence of that the dietary intake of other minerals and vitamins in maintaining bone health and reducing osteoporosis. The nutritional advice for maintaining bone health has been summed by Prentice, et al, 2006, p.348, as “to consume a Ca intake close to the reference nutrient intake, optimise vitamin D status through adequate summer sunshine exposure (and diet supplementation where appropriate), be physically active, have a body weight in the healthy range, restrict salt intake and consume plenty of fruit and vegetables”. Literary References Adams, J. & Pepping, J. 2005, ‘Vitamin K in the Treatment and Prevention of Osteoporosis and Arterial Calcification’, American Journal of Health-System Pharmacy, vol.62, n.15, pp.1574-1581. Bridwell, K. 2008, ‘Basic Bone Structure’, spineuniverse [Online] Available at: http://www.spineuniverse.com/displayarticle.php/article1224.html (Accessed April 27, 2008). Food Standards Agency. 2004, ‘The National Diet & Nutrition Survey: adults aged 19 to 64 years(Survey carried out in Great Britain on behalf of the Food Standards Agency and the Departments of Health by the Office for National Statistics and Medical Research Council Human Nutrition Research)’, Vol. 5 [Online] Available at: http://www.food.gov.uk/multimedia/pdfs/ndns5full.pdf Illich, Z. J. & Matkovich, V. 1997, ‘OSTEOPOROSIS: ITS PEDIATRIC CAUSES AND PREVENTION OPPORTUNITIES’, Preventive Care Update, vol.4, no.1, pp. 15-20. MacDonald, M. H., Mavroedi, A., Barr, J. R., Black, J. A. Fraser, D. W. & Reid, M. D. 2008, ‘Vitamin D status in postmenopausal women living in higher in the UK in relation to bone health, overweight, sunlight exposure and dietary vitamin D’, Bone, vol.42, pp.996-1003. Prentice, A. 2002, ‘What are the Dietary Requirements for Calcium and Vitamin D?’ Calcified Tissue International, vol.70, pp.83-88. Prentice, A. 2004, ‘Diet, nutrition and the prevention of osteoporosis’, Public health nutrition, vol.7, no.1A, pp.227-243. Prentice, A., Schoenmakers, !., Laskey, M. A., de Bono, S., Ginty, F. & Goldberg, G. R. 2006, ‘Nutrition and bone growth and development’, The Proceedings of the Nutrition Society, vol.65, no.4, pp.348-360. Rauch, F. 2007, ‘Bone Accrual in Children: Adding Substance to Surfaces’, Pediatrics, vol.119, no. March Supplement, pp. S137-S140. Mosekilde, L. 2000, ‘Age-related changes in bone mass, structure, and strength – effects of loading, Zeitschrift fur Rheumtologie, vol.59, no.Suppl.1, pp. S1-S9. Saggese, G., Baroncelli, I. G., & Bertelloni, S. 2002, ‘Puberty and Bone Development’, Best Practice & Research Clinical Endocrinology and Metabolism, vol.16, no.1, pp.53-64. WHO. 2003, ‘Diet, nutrition and the prevention of chronic diseases, Report of the joint WHO/FAO expert consultation, WHO Technical Report Series, No. 916 (TRS 916)’ [Online] Available at: http://libdoc.who.int/trs/WHO_TRS_916.pdf (Accessed April 27, 2008). Read More