Effects of dietary improvement on bone metabolism in elderly underweight women with osteoporosis: a randomised controlled trial.

Malnutrition in elderly people contributes to osteoporosis and fracture. The aim of the study was to investigate the effects of nutritional improvement on bone metabolism in elderly community-dwelling women. A 12-month randomized controlled trial of 71 ambulant women aged > or =70 years with BMI < or =21 kg/m(2 )and osteoporosis at the hip was undertaken. They received either calcium (1 g) and vitamin D (800 units of cholecalciferol) only (group 1: n=35) or calcium/vitamin D and one or two cartons of a nutritional supplement drink which provided 300 Kcal, 12 g protein, 11.6 g fat and 36.8 g carbohydrate per carton (group 2: n=36). Body composition and bone mineral density (BMD) were assessed at baseline and 12 months. Biochemical markers of bone turnover were measured at baseline and at 1, 3, 6, 9 and 12 months. Group 2 gained significantly more weight [mean (SD) group 1: 0.15 (2.45), group 2:2.66 (2.8) kg P<0.001] and fat mass [group 1: -0.26 (1.8), group 2:1.9 (1.7) kg P<0.001]. BMD at the spine, femoral neck and total hip did not change significantly, although there was a positive trend at the total hip in group 2 [group 1: -0.5 (5.2), group 2:1.25 (3.3)%, P=0.13]. In a subgroup analysis, irrespective of their treatment group, there was a significant difference in changes in BMD at the lumbar spine and total hip in those who lost body weight (A) compared to those who had maintained or increased their weight (B), [mean (SD) % change in BMD lumbar spine; A: -1.64 (3.75), B: 0.96 (2.75) P=0.013, total hip A: -2.09 (6.0), B: 1.04 (3.3), P=0.05)] A significant reduction in serum CTX, a marker of bone resorption, was seen in group 2 [% decrease at 3 months, group 1: 1 (8.7), Group 2: 32 (5.8), P<0.01]. Serum osteoprotegerin (OPG) increased significantly in group 2 with a maximal increase (27%) observed at 6 ( P<0.01) and 9 months ( P<0.05). A small increase in bone-specific alkaline phosphatase was seen at 12 months in group 2 [% increase group 1:5 (5), group 2: 17 (6), P=0.05]. Serum osteocalcin increased at 12 months in group 2 ( P=0.01). Dietary improvement in elderly women with low BMI is associated with a reduction in bone resorption with a small but "net" positive effect on bone formation.