Nutritional influences on bone metabolism : three studies in postmenopausal women
Eleven postmenopausal women made weighed food intakes and urine collections for one week, to determine influences on urinary calcium and deoxypyridinoline excretion. Urinary calcium was influenced by both dietary calcium and dietary fibre. Urinary deoxypyridinoline was increased in women consuming more dietary fibre. The influence of ketosis was examined in five postmenopausal women, who increased urinary hydrogen ion excretion, but had no consistent changes in urinary calcium or deoxypyridinoline excretion. Forty-six postmenopausal women, with body mass index greater than 27kg/m2, were randomised to diet XA (5010kJ, 89g protein, 110g carbohydrate, 17g dietary fibre daily) or diet XK (5010kJ, 62g protein, 186g carbohydrate, 28g dietary fibre daily) for six months later. Calcium intakes fell significantly in both groups and fibre intakes were significantly increased in XK dieters compared to XA. Throughout the year group XA had significantly greater weight loss than XK, at one year XA-6.5kg (SE 1.1) and XK-3.0kg (0.8), p < 0.05. No significant changes in deoxypyridinoline or osteocalcin were found for XA or XK during the six months of dieting. Sex hormone binding globulin and follicle stimulating hormone rose particularly in group XA, suggesting a decline in endogenous oestrogen levels. Bone mineral density changes were compared to 46 normal weight non-dieting controls. Sixteen XK dieters lost 20% of their excess body weight, but returned to their starting weight. Annual changes in lumbar spine bone mineral density, measured by dual energy X-ray absorptiometry, for this group were -4.8% (SE 0.9), controls -2.5% (0.5), 95% confidence interval of difference between groups -0.2 to -4.3%, p = 0.03. For group XA, the annual percentage change in lumbar spine bone mineral density was -3.3% (1.0), incorporating a correction factor for truncal thickness. This was not significantly different from the control group. No significant difference in changes of annual femoral neck bone mineral density was found between XA, XK and the control group.