The Effects of a Two-Year Randomized, Controlled Trial of Whey Protein Supplementation on Bone Structure, IGF-1, and Urinary Calcium Excretion in Older Postmenopausal Women

J Bone Miner Res. 2011 Sep;26(9):2298-306. doi: 10.1002/jbmr.429.

Abstract

The effects of dietary protein on bone structure and metabolism have been controversial, with evidence for and against beneficial effects. Because no long-term randomized, controlled studies have been performed, a two-year study of protein supplementation in 219 healthy ambulant women aged 70 to 80 years was undertaken. Participants were randomized to either a high-protein drink containing 30 g of whey protein (n = 109) or a placebo drink identical in energy content, appearance, and taste containing 2.1 g of protein (n = 110). Both drinks provided 600 mg of calcium. Dual-energy X-ray absorptiometric (DXA) hip areal bone mineral density (aBMD), 24-hour urinary calcium excretion, and serum insulin-like growth factor 1 (IGF-1) were measured at baseline and at 1 and 2 years. Quantitative computed tomographic (QCT) hip volumetric bone mineral density (vBMD) and a femoral neck engineering strength analysis were undertaken at baseline and at 2 years. Baseline average protein intake was 1.1 g/kg of body weight per day. There was a significant decrease in hip DXA aBMD and QCT vBMD over 2 years with no between-group differences. Femoral neck strength was unchanged in either group over time. The 24-hour urinary calcium excretion increased significantly from baseline in both groups at 1 year but returned to baseline in the placebo group at 2 years, at which time the protein group had a marginally higher value. Compared with the placebo group, the protein group had significantly higher serum IGF-1 level at 1 and 2 years (7.3% to 8.0%, p < .05). Our study showed that in protein-replete healthy ambulant women, 30 g of extra protein increased IGF-1 but did not have beneficial or deleterious effects on bone mass or strength. The effect of protein supplementation in populations with low dietary protein intake requires urgent attention.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Bone Density / drug effects
  • Bone and Bones / anatomy & histology*
  • Bone and Bones / drug effects*
  • Calcium / urine*
  • Diet
  • Dietary Supplements* / adverse effects
  • Energy Metabolism / drug effects
  • Female
  • Femur Neck / diagnostic imaging
  • Femur Neck / drug effects
  • Femur Neck / physiology
  • Food
  • Hip / diagnostic imaging
  • Hip / physiology
  • Humans
  • Insulin-Like Growth Factor I / metabolism*
  • Milk Proteins / administration & dosage
  • Milk Proteins / adverse effects
  • Milk Proteins / pharmacology*
  • Postmenopause / drug effects*
  • Postmenopause / urine
  • Tomography, X-Ray Computed
  • Whey Proteins

Substances

  • Milk Proteins
  • Whey Proteins
  • Insulin-Like Growth Factor I
  • Calcium