Changes in dietary zinc and copper affect zinc-status indicators of postmenopausal women, notably, extracellular superoxide dismutase and amyloid precursor proteins.
BACKGROUND
Zinc is an essential trace element for human health and well-being; however, methods currently available for the assessment of zinc status in humans are unsatisfactory.


OBJECTIVE
The objective was to critically evaluate the use of various indicators of zinc status in humans in a controlled metabolic ward study.


METHODS
Indicators of zinc status were measured in 25 healthy postmenopausal women aged 64.9 +/- 6.7 y. After a 10-d equilibration period, volunteers consumed a diet with either a low (1 mg/d; n = 12) or a high (3 mg/d; n = 13) copper content based on a total energy content of 8.4 MJ. They received the same amount of copper throughout the study. Both groups were fed the basal diet (3 mg Zn/d) with no zinc supplement for one 90-d period, and the diet supplemented with 50 mg Zn/d for another 90-d period.


RESULTS
Zinc supplementation significantly increased (P < 0.0001) extracellular but not erythrocyte superoxide dismutase activity. This increase was more apparent when subjects were fed the low-copper diet. Zinc supplementation in combination with the low-copper diet significantly decreased (P < 0.01) amyloid precursor protein expression in platelets. Other indicators of zinc status that were significantly elevated after zinc supplementation were as follows: plasma zinc and free thyroxine concentrations and mononuclear 5'-nucleotidase activity.


CONCLUSIONS
The measurement of serum extracellular superoxide dismutase activity may be useful as a marker for the functional assessment of zinc status in humans.
Davis
C D
CD
US Department of Agriculture, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. cdavis@gfhnrc.ars.usda.gov
Milne
D B
DB
Nielsen
F H
FH
D015720:5'-Nucleotidase / Q000097:blood; D000368:Aged; D016564:Amyloid beta-Protein Precursor / Q000097:blood / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism; D003300:Copper / Q000008:administration & dosage*; D004032:Diet; D019587:Dietary Supplements; D002149:Energy Intake; D004912:Erythrocytes / Q000201:enzymology; D005110:Extracellular Space / Q000201:enzymology; D005260:Female; D006801:Humans; D008875:Middle Aged; D009752:Nutritional Status; D017698:Postmenopause; D013482:Superoxide Dismutase / Q000097:blood / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood; D015032:Zinc / Q000008:administration & dosage* / Q000097:blood
D016564:Amyloid beta-Protein Precursor; D003300:Copper; D013482:Superoxide Dismutase; D015720:5'-Nucleotidase; D015032:Zinc; D013974:Thyroxine