ARS | Publication request: ALTERED METABOLIC RESPONSES DURING EXERCISE IN MEN FED DIETS LOW IN ZINC

Submitted to: Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: April 17, 1999
Publication Date: N/A

Technical Abstract: The role played by micronutrients such as zinc (Zn) in promoting physiological function during exercise is not well defined. Although some Zn-containing enzymes are postulated to participate in the regulation of energy expenditure (EE), there are limited data on the effect of dietary Zn restriction on metabolic responses during exercise. Dietary Zn may impact physiological function during exercise by influencing a Zn- containing enzyme, carbonic anhydrase (CA) in red blood cells (RBC). Twelve vigorous men, aged 21-28 yr, were randomly assigned to consume diets that consisted of conventional foods, fed on a 3-d rotating menu, and were low (3 mg/d; ZD) and adequate (18 mg/d; ZA) for 9-wk periods with a 6-wk washout period in a double-blind cross-over study. Peak work capacity was determined by using a graded exercise protocol with a cycle ergometer at the start and end of each dietary period. Dietary Zn did not affect hemoglobin or RBC count. Serum Zn decreased (13.9+/-0.5 vs 11.2+/- 0.5umol/L; p<0.01) and Zn retention declined (1.43+/-0.48 vs 0.23+/-0.28 mg/d; p<0.05) with ZD. Peak oxygen uptake (3.11+/-0.11vs 3.41+/-0.12 L/min), peak carbon dioxide output (3.41+/-0.13 vs 3.99+/-0.09 L/min) and respiratory exchange ratio (1.09+/-0.01 vs 1.18+/-0.02) were decreased (p<0.01) in ZD. Total CA (1779+/-63 vs 1964+/-56 U/mL), CA-I (623+/-56 vs 678+/-36 U/mL) and CA-II (1126+/-42 vs 1266+/-38 U/mL) activities decreased (p<0.05) with ZD. The ventilatory equivalents for oxygen (42.1+/-2.2 vs 37.5+/-1.5) and carbon dioxide (40.9+/-1.9 vs 35.4+/-1.4) were increased (p<0.05) with ZD. These findings indicate that low dietary Zn is associated with significant decreases in RBC CA activity and results in impaired gas exchange and energy production during peak exercise.