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United States Department of Agriculture

Agricultural Research Service

Title: Long-Term High Copper Intake: Effects on Copper Absorption, Retention, and Homeostasis in Men

Authors
item Turnlund, Judith
item Keyes, William
item Kim, Soon Kyung - SOONCHUNHYANG UNIV. NUTR.
item Domek, Joseph

Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2004
Publication Date: November 23, 2004
Citation: Turnlund, J.R., Keyes, W.R., Kim, S., Domek, J.M. 2004. Long-term high copper intake: effects on copper absorption, retention, and homeostasis in men. American Journal of Clinical Nutrition, 81:822-828.

Interpretive Summary: Numerous studies have examined the effect of low and adequate intakes of copper on absorption and retention, but little information is available on the regulation of absorption and retention of copper when intake is high. We conducted a study to determine the effects of long-term high copper intake on copper absorption, retention and homeostasis. Nine men were confined to a metabolic research unit (MRU) for 18 d and were fed a 3-d rotating menu containing an average of 1.6 mg Cu/d. They continued the study under free-living conditions for 129 d, supplementing their usual diets with 7 mg Cu/d. They then returned to the MRU for 18 d and consumed the same diet as during the first period, except that copper intake was 7.8 mg/d. The stable isotope 63Cu was fed to three of the subjects and infused into the other 6 on day 7 of each MRU period and complete urine and stool collections were made throughout the study. Total copper and 63Cu were determined by inductively coupled plasma-mass spectrometry (ICP-MS). Copper absorption, excretion and retention were calculated based on dietary, urinary, and fecal copper and 63Cu. When comparing the high copper intake to the usual intake: fractional copper absorption was significantly lower, but the amount absorbed was significantly higher; excretion of the infused 63Cu was significantly faster; and total retention was significantly higher. Homeostatic regulation of copper absorption and retention helped to minimize the amount of copper retained with high copper intake, but was not sufficient to prevent retention of over 0.6 mg Cu/d. The study demonstrated that the homeostatic mechanisms controlling copper retention in humans are not sufficient to prevent accumulation of copper when intake is high. There were few changes in indices of copper status, but changes in several functional parameters suggest that antioxidant defense and immune function may have been adversely affected by the level of dietary copper. It is possible that these effects are related to the accumulation of copper during the high copper intake and this should be considered in setting the upper safe level of copper intake.

Technical Abstract: Background: Numerous studies have examined the effect of low and adequate intakes of copper on absorption and retention, but little information is available on the regulation of absorption and retention of copper when intake is high. Objective: A study was conducted in men to determine the effects of long-term high copper intake on copper absorption, retention and homeostasis. Design: Nine men were confined to a metabolic research unit (MRU) for 18 d and were fed a 3-d rotating menu containing an average of 1.6 mg Cu/d. They continued the study under free-living conditions for 129 d, supplementing their usual diets with 7 mg Cu/d. They then returned to the MRU for 18 d and consumed the same diet as during the first period, except that copper intake was 7.8 mg/d. The stable isotope 63Cu was fed to three of the subjects and infused into the other 6 on day 7 of each MRU period and complete urine and stool collections were made throughout the study. Total copper and 63Cu were determined by inductively coupled plasma-mass spectrometry (ICP-MS). Copper absorption, excretion and retention were calculated based on dietary, urinary, and fecal copper and 63Cu. Results: Results were as follows when comparing the high copper intake to the usual intake: fractional copper absorption was significantly lower, but the amount absorbed was significantly higher; excretion of the infused 63Cu was significantly faster; and total retention was significantly higher. Conclusions: Homeostatic regulation of copper absorption and retention helped to minimize the amount of copper retained with high copper intake, but was not sufficient to prevent retention of over 0.6 mg Cu/d.

Last Modified: 9/10/2014
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