Osteoporos Int (2007) 18:1661–1667 DOI 10.1007/s00198-007-0422-0
ORIGINAL ARTICLE
Dietary protein intake and bone mineral content in adolescents—The Copenhagen Cohort Study A. Z. Budek & C. Hoppe & H. Ingstrup & K. F. Michaelsen & S. Bügel & C. Mølgaard
Received: 28 March 2007 / Accepted: 13 June 2007 / Published online: 17 July 2007 # International Osteoporosis Foundation and National Osteoporosis Foundation 2007
Abstract Summary Data indicate that various protein sources may exhibit a differential effect on bone metabolism. We investigated associations of milk and meat protein intake with bone mineral content (BMC) in adolescents. Milk, but not meat, protein intake was positively associated with sizeadjusted BMC. Milk-derived protein may be beneficial for bone mineralization. Introduction Milk and meat protein intake has been reported to exhibit a differential effect on serum insulin-like growth factor-I (IGF-I). IGF-I plays a key role in bone metabolism. Therefore, we investigated associations of different protein sources with BMC and bone area (BA) in adolescents. Methods This was a cross-sectional study of 17-year-old girls (n=63) and boys (n=46) participating in the second follow-up of The Copenhagen Cohort Study. We measured dietary intake (7-day food record), BMC and BA (dualenergy X-ray absorptiometry), serum markers for bone turnover and serum IGF-I (immunoassays). Results The mean total protein intake (∼1.2 g/kg) was modestly higher than that recommended. Total and milk (∼0.3 g/kg) protein intake, but not meat protein intake (∼0.4 g/kg), was positively associated with size-adjusted BMC (P≤0.05). The positive association between milk protein intake and size-adjusted BMC remained significant after correction for energy, calcium, and physical activity (P≤0.01) and did not seem to be mediated via current
A. Z. Budek (*) : C. Hoppe : H. Ingstrup : K. F. Michaelsen : S. Bügel : C. Mølgaard Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg, Denmark e-mail:
[email protected]
serum IGF-I. None of the analyzed protein sources was significantly associated with size-adjusted BA. Conclusions Our results suggest that some components of milk protein may promote bone mineralization. Further studies are needed to elucidate this phenomenon. Keywords BMC . Diet . Growth . Meat protein . Milk protein
Introduction Osteoporosis is a disease characterized by decreased bone mass and deterioration of bone tissue [1]. It is estimated to cause 9 million fractures worldwide per year [2]. The risk for osteoporosis later in life can be reduced by the maximization of peak bone mass during growth, partly by optimizing lifestyle factors, including nutrition [1]. Although an adequate intake of dietary protein is important for bone metabolism [3], its bone promoting effect during growth remains under debate [4–8]. In two observational studies, total protein intake was positively associated with size-adjusted bone mineral content (BMC) in 8-year-old children (P
