The impact of diet and lifestyle on bone health in the elderly : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Nutritional Science at Massey University

Abstract

Osteoporosis is a multi-factorial disorder in which nutrition and lifestyle play an important role. There were two main reasons for doing this study. The purpose of the first part of the study was to determine the prevalence of nutritional and lifestyle factors related to bone health in a group of senior citizens from the Manawatu who were over the age of 70 years. This was followed by an intervention trial in which the purpose was to assess the impact of a single serve of a high-calcium milk on bone resorption using two ingestion strategies. Calcium, magnesium and zinc intakes were below currently recommended levels in many of the study participants. Some of the participants and particularly those in rest homes received very little sunlight exposure and low dietary vitamin D. Participants spent an average of around 3.5 hours/day in physical activity. Weight-bearing activities such as walking, gardening and certain sports were common in this group. Institutionalised women were most compromised by nutrition and lifestyle. Dietary supplementation may therefore benefit many in this group. Of the 52 participants in the diet and lifestyle study, a group of 28 women and 14 men volunteered to take part in an intervention trial, which was approved by the Massey University Human Ethics Committee. The mean calcium intake of trial participants was only 70% of the current US recommended adequate intake (AI). Each person consumed a supplementary serve of 250mls of high calcium milk (640mg Ca), every evening for two weeks. Half consumed a whole dose one hour before bedtime (single serve group), whilst the rest consumed the milk in three divided doses of 80mls every hour before bedtime (divided dose group). Free deoxypyridinoline (Dpd), a biochemical marker of bone resorption, was measured in urine that was collected overnight on two consecutive days before and after two weeks of milk intervention. In the single serve group Dpd was 4.15 ± 1.99 at the start and 3.94 ± 2.15 mmol/mmol creatinine after two weeks (NS). In the divided dose group Dpd was 4.25 ± 2.21 at the start and 4.79 ± 2.27 mmol/mmol creatinine after two weeks (NS). In conclusion, a supplementary serve of milk in this group of elderly people did not produce significant changes in urinary Dpd, whether the milk was consumed as the whole amount or in divided doses.