I know people think it’s poor form to research from an open-source place like Wikipedia, that anyone can edit. While I understand that Wikipedia’s many editors have a bias in favor of mainstream medicine, and against alternative health, that is also the bias in the larger overall society in which we live. Remember, 70% of people have taken at least one pharmaceutical in the last year. Wikipedia also has more complete research than is easily found elsewhere, and articles are often well-sourced these days.
“Various factors influence copper absorption. For example, copper absorption is enhanced by ingestion of animal protein, citrate, and phosphate. Copper salts, including copper gluconate, copper acetate, or copper sulfate, are more easily absorbed than copper oxides. Elevated levels of dietary zinc, as well as cadmium, high intakes of phytate and simple sugars (fructose, sucrose) inhibit dietary absorption of copper. Furthermore, low levels of dietary copper inhibit iron absorption.”
How can low copper inhibit iron? Copper is needed to create ceruloplasmin, which transports both copper and iron.
Side note. Too little copper is bad for iron. Some copper is necessary for iron. Too much copper can block iron. It appears that mineral interaction effects are not “either/or”, but rather, are more likely to be shaped like bell curves.
Wiki implicitly confirms, there is a lack of studies on copper between 500 mg and 10 mg. And, inadvertently implies that toxic effects start above 500 mg for a 100-kilo man.
“Toxic>5.0 mg/kg body weightGastrointestinal metallothionein induced (possible differing effects of acute and chronic exposure) 100 μg/kg body weight… (10 mg for a 100-kilo man) Plateau of absorption maintained; homeostatic mechanisms regulate absorption of copper”
Even more interesting, they imply that deficiency starts at 850 mcg for a 100-kilo man, which is so very close to the 900 mcg RDA.
“Deficient…8.5 μg/kg bodyweight…Negative copper balance”
I note further that these levels would all change in the presence of copper-depleting substances. Copper deficiency was seen in a woman taking 100 mg of zinc, even at 2 mg copper, which means that 2 mg copper can also be a “deficiency level”.
“The EPA lists no evidence for human cancer incidence connected with copper”
https://en.wikipedia.org/wiki/Category:Copper_enzymes –when I started editing, there were 21. Now, 32. I added 11.
One of the reasons why we know what copper does in the body is by looking at copper enzymes. We know, in part, many of the things the enzymes do. And we know that the enzymes are generally more active, and sometimes there are more of the enzymes if there is enough copper to make them.
Amine oxidase (copper-containing)
Cytochrome c oxidase
Nitrite reductase (NO-forming)
It has been estimated that over half of proteins in the body contain copper!