Phytase supplementation increases bone mineral density, lean body mass and voluntary physical activity in rats fed a low-zinc diet

Scrimgeour, Angus G.; Marchitelli, Louis J.; Whicker, Jered S.; Song, Yang; Ho, Emily; Young, Andrew J.

doi:10.1016/j.jnutbio.2009.03.015

« Previous Next »The Journal of Nutritional Biochemistry
Volume 21, Issue 7 , Pages 653-658, July 2010

Phytase supplementation increases bone mineral density, lean body mass and voluntary physical activity in rats fed a low-zinc diet☆

Angus G. Scrimgeour
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
- Corresponding author. Tel.: +1 508 233 5155; fax: +1 508 233 4869.
Louis J. Marchitelli
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
Jered S. Whicker
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
Yang Song
- Department of Nutrition and Exercise Sciences, Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA
Emily Ho
- Department of Nutrition and Exercise Sciences, Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA
Andrew J. Young
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
- The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Army or the Department of Defense.

Received 5 September 2008; received in revised form 27 February 2009; accepted 23 March 2009. published online 03 July 2009.

Abstract

Phytic acid forms insoluble complexes with nutritionally essential minerals, including zinc (Zn). Animal studies show that addition of microbial phytase (P) to low-Zn diets improves Zn status and bone strength. The present study determined the effects of phytase supplementation on bone mineral density (BMD), body composition and voluntary running activity of male rats fed a high phytic acid, low-Zn diet. In a factorial design, rats were assigned to ZnLO (5 mg/kg diet), ZnLO+P (ZnLO diet with 1500 U phytase/kg) or ZnAD (30 mg/kg diet) groups and were divided into voluntary exercise (EX) or sedentary (SED) groups, for 9 weeks. SED rats were significantly heavier from the second week, and no catch-up growth occurred in EX rats. Feed intakes were not different between groups throughout the study. ZnLO animals had decreased food efficiency ratios compared to both phytase-supplemented (ZnLO+P) and Zn-adequate (ZnAD) animals (P<.01 compared to ZnLO). The ZnLO+P and ZnAD rats ran 56–75 km more total distance than ZnLO rats (P<.05), with the ZnLO+P rats running more kilometers per week than the ZnLO rats by Week 6. In vivo DEXA analyses indicate that rats fed phytase-supplemented diets had higher lean body mass (LBM) than those fed ZnLO diets; and that rats fed the Zn-adequate diets had the highest LBM. Body fat (%) was significantly lower in EX rats and was both Zn- and phytase insensitive. Rats fed phytase-supplemented diets had higher bone mineral content (BMC), bone area (BA) and BMD than rats fed ZnLO diets; and in rats fed ZnAD diets these indices were the highest. The dietary effects on BMC, BA and BMD were independent of activity level.

We conclude that consuming supplemental dietary phytase or dietary Zn additively enhances Zn status to increase BMD, LBM and voluntary physical activity in rats fed a low-Zn diet. While the findings confirm that bone health is vulnerable to disruption by moderate Zn deficiency in rats, this new data suggests that if dietary Zn is limiting, supplemental phytase may have beneficial effects on LBM and performance activity.

Keywords: Zinc, Phytase, Bone mineral density, Exercise