Copper
Copper is essential in all higher plants and animals. Copper is carried mostly
in the bloodstream on a plasma protein called ceruloplasmin. When copper is
first absorbed in the gut it is transported to the liver bound to albumin.
Copper is found in a variety of enzymes, including the copper centers of
cytochrome c oxidase and the enzyme superoxide dismutase (containing copper and
zinc), and is the central metal in the oxygen-carrying pigment hemocyanin.
The blood of the horseshoe crab, Limulus polyphemus, uses copper rather than iron
for oxygen transport.
It is believed that zinc and copper compete for absorption in the digestive
tract so that a diet that is excessive in one of these minerals may result in a
deficiency in the other. The RDA for copper in normal healthy adults is 0.9
mg/day.
All copper compounds, unless otherwise known, should be treated as if they were
toxic. Thirty grams of copper sulfate is potentially lethal in humans. The
suggested safe level of copper in drinking water for humans varies depending on
the source, but tends to be in the region of 1.5 to 2 mg/L. The Daily Recommended Intake (DRI) Tolerable Upper
Intake Level for adults of dietary copper from all sources is 10 mg/day.
In toxicity, copper can inhibit the enzyme dihydrophil hydratase, an enzyme
involved in haemopoiesis (formation of blood cells).
An inherited condition called Wilson's disease causes the body to retain copper,
since it is not excreted by the liver into the bile. This disease, if untreated,
can lead to brain and liver damage.
In addition, studies have found that people with mental illnesses such as schizophrenia had heightened levels of copper in
their systems. However it is unknown at this stage whether the copper
contributes to the mental illness, whether the body attempts to store more
copper in response to the illness, or whether the high levels of copper are the
result of the mental illness.
