Diet, lifestyle and musculoskeletal health
With advancing age, the musculoskeletal system undergoes a number of physical and physiological changes. These changes may manifest as loss in bone mass, muscle strength and physical function, thus increasing susceptibility to falls, fractures, disability, and osteoporosis. Multiple factors contribute to musculoskeletal decline, including modifiable factors such as dietary intake, physical activity and other lifestyle related factors. More specifically, observational evidence suggests that increased fruit and vegetable consumption may be associated with improved musculoskeletal health. However, there is a lack of direct evidence to support this concept. Of the intervention studies undertaken to date, the results have generally been inconsistent with some demonstrating beneficial effects of fruit and vegetables on musculoskeletal health and others showing no effect. Furthermore, this specific hypothesis has not yet been fully tested in intervention studies involving free living older men and women. The overall aim of the thesis was therefore to examine the effects of increased FV consumption on musculoskeletal health among adults aged 65 years and above. In order for a fruit and vegetable intervention to ultimately be effective in public health terms, it is imperative to firstly understand the barriers associated with increased fruit and vegetable consumption. Chapter 3 of the thesis provides an overview of barriers to fruit and vegetable consumption in older adults. The findings suggest that in order to improve fruit and vegetable consumption in older adults, strategies need to predominantly focus on increasing knowledge, awareness and consumption of a broader range of fruit and vegetables, including fruit and vegetable products and dishes, in order to increase liking; increasing knowledge and awareness of current recommendations and the benefits of fruit and vegetables for health and well-being; raising awareness regarding current inadequate intakes of fruit and increasing motivation and willingness to change. The effect of participating in a fruit and vegetable intervention study (methods described below) on barriers to change was also investigated. Older adults reported a greater liking of FV after participating in the intervention regardless of group allocation. Participants in the intervention group (consuming 5 portions of fruit and vegetables/day) also reported greater ease of consumption and awareness at the end of the 16 week intervention. In order to examine the effect of increased fruit and vegetable consumption on clinically relevant measures of musculoskeletal health in older adults, a 16 week parallel group randomized controlled intervention study was undertaken. Eighty three healthy free living participants aged 65 - 85 years, habitually consuming less than 2 portions of fruit and vegetables per day, were randomised to either continue with their normal diet ( < 2 portions/day), or to consume at least 5 portions of fruit and vegetables per day for 16 weeks. Fruit and vegetables were delivered to all participants each week, free of charge. Compliance was assessed in two ways: by 7-day diet history and by measuring a panel of biochemical markers of nutrient status. Biochemical bone markers (osteocalcin and CTX) were measured in serum by ELISA. Barriers to fruit and vegetable consumption were assessed by questionnaire. Muscle strength was assessed by dynamometry, while lower extremity physical function was assessed using a Short Physical Performance Battery. Physical activity was measured by accelerometry and self-report questionnaire. Eighty two participants completed the intervention. Self reported intakes of fruit and vegetable increased significantly in both groups. This was also reflected with significantly larger increases in vitamin C, lutein, zeaxanthin, p-cryptoxanthin, lycopene and folate in the 5 portions/day group compared to the 2 portions/day group. Between group comparisons revealed no significant differences in change in bone marker status or physical function between the two intervention groups. However, there was a trend towards a greater change in grip strength in those consuming 5 portions per day compared to those consuming 2 portions per day. The thesis also explored cross-sectional associations between nutrient intake, physical activity and musculoskeletal health at baseline in the intervention study participants. Fruit and vegetable intake showed a significant inverse association with CTX after adjusting for confounding factors, although no association was evident with QC. Folate, vitamin B12, potassium and dietary fibre were also inversely associated with CTX. No consistent associations were evident between fruit and vegetable intake and grip strength, physical function or physical activity. In conclusion, increased fruit and vegetable consumption over a period of 16 weeks had no effect on bone marker status or physical function in healthy older adults, although barriers to fruit and vegetable consumption were reduced by participation in the study. Further larger intervention studies of longer duration are warranted in order to establish whether or not long term consumption of fruit and vegetables can have a beneficial effect on musculoskeletal health.
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