Excretion of Zinc and Copper Increases in Men during 3 Weeks of Bed Rest, with or without Artificial Gravity

Abstract

Zinc and copper have many physiologic functions and little or no functional storage capability, so persistent losses of either element present health concerns, especially during extended-duration space missions. We evaluated the effects of short-term bed rest (BR), a spaceflight analog, on copper and zinc metabolism to better understand the role of these nutrients in human adaptation to (simulated) spaceflight. We also investigated the effect of artificial gravity on copper and zinc homeostasis. Zinc and copper balances were studied in 15 men [mean ± SD age: 29 ± 3 y; body mass index (in kg/m): 26.4 ± 2.2] before, during, and after 21 d of head-down tilt BR, during which 8 of the participants were subjected to artificial gravity (AG) by centrifugation for 1 h/d. Control subjects were transferred onto the centrifuge but were not exposed to centrifugation. The study was conducted in a metabolic ward; all urine and feces were collected. Data were analyzed by 2-factor repeated-measures ANOVA. Urinary zinc excretion values for control and AG groups were 33% and 14%, respectively, higher during BR than before BR, and fecal zinc excretion values for control and AG groups were 36% and 19%, respectively, higher during BR, resulting in 67% and 82% lower net zinc balances for controls and AG, respectively (both < 0.01), despite lower nutrient intake during BR. Fecal copper values for control and AG groups were 40% and 33%, respectively, higher during BR than before BR ( 0.01 for both). Urinary copper did not change during BR, but a 19% increase was observed after compared with before BR in the AG group ( 0.05). The increased fecal excretion of copper and zinc by men during BR suggests that their absorption of these minerals from the diet was reduced, secondary to the release of minerals from bone and muscle. These findings highlight the importance of determining dietary requirements for astronauts on space missions and ensuring provision and intake of all nutrients.

Copper deficiency may be a leading cause of ischaemic heart disease

“…87 Copper excretion increases during bedrest. 88 Kidney disease, coeliac disease and bariatric surgery all increase the requirement for copper. 89–91 The prevalence of these conditions in the population is high, and copper deficiency may masquerade as other conditions, such as myelodysplastic syndrome, and go unrecognised.…”

Gender Differences in Zinc and Copper Excretion in Response to Co-Exposure to Low Environmental Concentrations of Cadmium and Lead

“…Likewise, Cu excretion was notably higher in Japanese women with itai-itai disease, compared with women in a control group, but Zn excretion was not increased by Cd exposure in either group [26]. In a study that examined another form of stress as artificially low gravity, simultaneous increases in Zn and Cu excretion were observed in men [34]. In an experimental study, high urinary Cu excretion seen in Wilson's disease, a genetic disorder resulting in excessive hepatic Cu accumulation, was a mechanism to remove Cu through upregulation of a 2kDa small copper carrier (SCC) that transports Cu to kidneys [35].…”

Effect of intermittent fasting during acrylamide exposure on blood copper, zinc and lead levels in rats

“…8 weeks of acupuncture treatment was shown to increase iron absorption compared to control group (27). In another study, 3 weeks of bed rest increased Zn and Cu excretion (28). Therefore it can be suggested that acrylamide may interfere with mechanisms other than diet and altered Zn, Cu and Pb absorption and excretion.…”