"Copper proteins have diverse roles in biological electron transport and oxygen transportation, processes that exploit the easy interconversion of Cu(I) and Cu(II). The biological role for copper commenced with the appearance of oxygen in earth's atmosphere."

"Claims that copper supplements are effective in the treatment of arthritis or skin conditions have not been proven. Use of copper supplements to cause vomiting has caused death and should be avoided."

"DRI Tables"

"Recommended Dietary Allowances (RDA) - The daily dietary intake level of a nutrient considered sufficient by the Food and Nutrition Board to meet the requirements of 97.5% of healthy individuals in each life-stage and sex group. It is calculated based on the EAR and is usually approximately 20% higher than the EAR. ... Tolerable upper intake levels (UL) - To caution against excessive intake of nutrients (like vitamin A) that can be harmful in large amounts. This is the highest level of daily consumption that current data have shown to cause no side effects in humans when used indefinitely without medical supervision."