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United States Department of Agriculture

Agricultural Research Service

Research Project: BONE METABOLISM IN OBESITY Title: Calcium homeostasis and bone metabolic responses to protein diets and energy restriction: a randomized control trial

Authors
item Cao, Jay
item Pasiakos, Stefan -
item Margolis, Lee -
item Whigham Grendell, Leah
item Mcclung, James -
item Young, Andrew -
item Combs, Gerald

Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 2012
Publication Date: April 9, 2013
Citation: Cao, J.J., Pasiakos, S.M., Margolis, L.M., Whigham Grendell, L.D., Mcclung, J.P., Young, A.Y., Combs, G.F. 2013. Calcium homeostasis and bone metabolic responses to high protein diets and energy restriction: a randomized control trial. Federation of American Societies for Experimental Biology Conference. 27:249.1.

Technical Abstract: Despite some beneficial effects on bone, high protein diets are conventionally considered a primary dietary risk factor for osteoporosis and bone fracture due to the acid load associated with protein catabolism. To test the hypothesis that high dietary protein diets do not negatively affect calcium homeostasis and bone turnover, 32 men and 7 women consumed diets providing protein at 0.8 (RDA), 1.6 (2X-RDA), or 2.4 (3X-RDA) g•kg-1•d-1for 31 days in a randomized-block design. Ten-day of weight maintenance (WM, days 1-10) preceded 21-day of energy deficit (ED, days 11-31), during which energy intake was restricted to 60% of daily requirements. Ca absorption (ratio of 44Ca:42Ca) and circulating indices of bone turnover and were determined during WM (day 8) and ED (day 29). Regardless of energy state, urinary pH was lower (P < 0.05) for 2X-RDA (6.28 ± 0.05) and 3X-RDA (6.23 ± 0.06) compared to RDA (6.54 ± 0.06), but urinary Ca excretion and absorption were not affected by dietary protein level or ED (P > 0.05). ED induced weight loss (3.2 ± 1.0 kg body mass, P < 0.05), and a 13% reduction in serum IGF-I (P < 0.01). Remaining markers of bone turnover, as well as bone mineral density and content were not affected by protein level and ED (P > 0.05). These data demonstrate that consuming high protein diets do not disrupt Ca homeostasis and skeletal integrity, whereas reductions in IGF-1 may suggest diminished bone formation during sustained ED. The study was supported by USDA ARS and USAMRMC.

Last Modified: 10/25/2014
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