bone health
given that physical activity in chil- dren per se has potential benefits for bone health. Not all exercise influences bone health according to Kohrt et al (57). Falk et al (58) suggest that adoles- cents and children who participate in high impact activities including; gymnastics, jumping and plyomet- rics, which include tuck jumping, have been shown to have en- hanced bone mineral density.
Nutrition and bone health in adults
There is evidence to suggest that the diet of the UK adult population has improved significantly over the past 15 years (59). Nevertheless, research has shown that women in particular should pay close attention to their diet and lifestyle in order to promote their optimal bone mineral density (60). Sex hormone status clearly affects bone either directly or indirectly and a longer oestrogen exposure appears to be a major de- terminant of postmenopausal BMD (61). The menopause is associated with a natural decline in oestrogen that increases visceral fat mass, de- creases bone mass density, muscle mass, and strength (62). The meno- pause is associated with a decrease in lean body mass and redistribution of fat particularly in the trunk region (63). Increased central body fat in woman has been shown to have a significant negative impact on bone mineral density increasing the risk of osteoporosis (64). Phytoestrogens, which are weakly-oestrogenic compounds present in plants, deserve particular mention because emerging data support the suggestion that they may prevent bone loss associated with the menopause (65). How- ever the results of studies which have examined the effects of soy derived products including the plant oestrogens on bone health in post menopausal woman have given rise to equivocal results (66). A recent meta analysis (67) of the randomised controlled trials which have examined the effects of soya isoflavone extract supplements on bone mineral density in meno- pausal woman has found that these supplements may increase lumbar spine BMD. Despite these positive results further research is required in order to establish the effects of plant oestrogens on both the magnitude of effect on spine BMD and on the effect of BMD in the hip.
NHDmag.com June '10 - issue 55
(More on phytoestrogens in the April issue of NHD pg 14.)
It is also important to note that despite males not going through a physical menopause, this group do experience age-related accelera- tion of bone loss, placing them at risk of developing osteoporosis (68). There is some evidence albeit weak that the consumption of products containing isoflavones may be ben- eficial in males (66).
The British Nutrition Foundation (BNF) (69) proposes that the UK diet should provide more than enough of most nutrients and should there- fore be sufficient to meet most adult health needs. However, Wynne et al (49) suggest that the current Wester- nised diet generates a high amount of acid which can be detrimental to bone health. Furthermore, data from the Diet and Nutrition Survey (50) has identified that 15 percent of adult males and females be- tween the ages of 19-64 years have significantly low plasma levels of vitamin D which is cause for con- cern given that there is an associa- tion between the levels of vitamin D and bone mineral density in adults (70). Vitamin D can be obtained from dairy foods, oily fish such as sardines, eggs liver and margarine. It is also thought that half an hour’s exposure to winter sunshine on the hands and face is enough to enable Caucasian adults to make sufficient vitamin D (71). In order to prevent osteoporosis it is also recommended that both males and females aged between 19-64 years should aim to have an intake of 700 micrograms of calcium per day (59). This can be achieved through eating at least three portions of dairy foods which contain a high amount of calcium everyday (72). Vitamin K contributes significantly in adult bone health probably through its role as a co-factor in the carboxylation of osteocalcin (73). Whilst this is an interesting theory, it is important to note that although data from systematic reviews and meta-analysis of randomised con- trolled trials (RCTs) have concluded that vitamin K is effective in prevent- ing fractures, the effect of vitamin K on the skeleton remains a matter of controversy (74).
Adults and exercise
Adults require at least 30 minutes of moderate intensity exercise at least five days of the week (54), but
the type of exercise undertaken should have a different physiological focus as age progresses (75). Con- tinuous high intensity weight-loading physical activity is deemed as necessary to preserve bone mineral density in woman as they progress through the lifespan (76). Guada- lupe-Grau et al (77) argue that it is not clear which training method is superior for bone stimulation in adults of all genders and has also suggested that exercises involving high impact, even a relatively small amount, may appear to be the most efficient for enhancing bone mass, but are not the case in postmeno- pausal women.
Nutrition and the elderly
Many older people and their doctors still see osteoporosis as part of the natural course of ageing in- stead of as a preventable treatable disorder (78). The adverse effects of ageing on the skeleton are well known with age-related changes, for example oxidative stress being one of the fundamental mecha- nisms involved in the decline of bone mass and strength (79). There is abundant data to suggest that good nutrition is an important factor in the prevention and treatment of chronic diseases such as osteopo- rosis (80). To this end, it is important that elderly people are encouraged to eat small, nutritionally dense meals and regular healthy snacks in order to achieve their optimum nutritional status (81) which in turn will assist to maximise bone health.
Unfortunately, there is evidence to suggest that elderly individuals are not achieving their optimal nutritional status given that 19 percent of men aged 75 years and over and 21 percent of woman aged 75 years and over are de- scribed as obese (1). Obesity in older adults has been shown to have adverse effects on bone density. There is a growing body of evidence which proposes that a significant number of individuals aged 65 years and over are either at risk of, or have been diagnosed with malnutrition (British Association for Enteral and Parenteral Nutrition - BAPEN) (82). Research has shown that older people with hip fractures are often malnourished and have poor food intake at the time of fracture (83). One of the major nutrients found to be lacking in the diet of some
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