First recognized in the 1870's as a normal constituent of blood, copper is a trace mineral that plays an important role in our metabolism, largely because it allows many critical enzymes to function properly. Although copper is the third most abundant trace mineral in the body (behind iron and zinc), the total amount of copper in the body is only 75-100 milligrams, less than the amount of copper in a penny. Copper is present in every tissue of the body, but is stored primarily in the liver, so concentrations of the mineral are highest in that organ, with lesser amounts found in the brain, heart, kidney, and muscles.
What is the function of copper?
Copper is an essential component of many enzymes. Each of the copper-containing enzymes discussed below has a distinct function, indicating that copper plays a role in a wide range of physiological processes including iron utilization, elimination of free radicals, development of bone and connective tissue, and the production of the skin and hair pigment called melanin.
Approximately 90% of the copper in the blood is incorporated into a compound called ceruloplasmin, which is a transport protein responsible for carrying copper to tissues that need the mineral. In addition to its role as a transport protein, ceruloplasmin also acts as an enzyme, catalyzing the oxidation of minerals, most notably iron.
The oxidation of iron by ceruloplasmin is necessary for iron to be bound to its transport protein (called transferrin) so that it can be carried to tissues where it is needed. Because copper is necessary for the utilization of iron, iron deficiency anemias may be a symptom of copper deficiency.
Elimination of Free Radicals
Superoxide dismutase (SOD) is a copper-dependent enzyme that catalyzes the removal of superoxide radicals from the body. Superoxide radicals are generated during normal metabolism, as well as when white blood cells attack invading bacteria and viruses (a process called phagocytosis). If not eliminated quickly, superoxide radicals cause damage to cell membranes. When copper is not present in sufficient quantities, the activity of superoxide dismutase is diminished, and the damage to cell membranes caused by superoxide radicals is increased. When functioning in this enzyme, copper works together with the mineral zinc, and it is actually the ratio of copper to zinc, rather than the absolute amount of copper or zinc alone, that helps the enzyme function properly.
Development of Bone & Connective Tissue
Copper is also a component of lysyl oxidase, an enzyme that participates in the synthesis of collagen and elastin, two important structural proteins found in bone and connective tissue. Tyrosinase, a copper-containing enzyme, converts tyrosine to melanin, which is the pigment that gives hair and skin its color.
As a part of the enzymes cytochrome c oxidase, dopamine hydroxylase, and Factor IV, copper plays a role in energy production, the conversion of dopamine to norepinephrine and blood clotting, respectively. Copper is also important for the production of the thyroid hormone called thyroxine and is necessary for the synthesis of phospholipids found in myelin sheaths that cover and protect nerves.
What are deficiency symptoms for copper?
Because copper is involved in many functions of the body, copper deficiency produces an extensive range of symptoms. These symptoms include iron deficiency anemia, ruptured blood vessels, osteoporosis, joint problems, brain disturbances, elevated LDL cholesterol and reduced HDL cholesterol levels, increased susceptibility to infections due to poor immune function, loss of pigment in the hair and skin, weakness, fatigue, breathing difficulties, skin sores, poor thyroid function, and irregular heart beat.
Despite the fact that most Americans consume less than recommended amounts of copper in their diet, these symptoms of copper deficiency are relatively rare. However, certain medical conditions including chronic diarrhea, celiac sprue, and Crohn's disease result in decreased absorption of copper and may increase the risk of developing a copper deficiency. In addition, copper requires sufficient stomach acid for absorption, so if you consume antacids regularly you may increase your risk of developing a copper deficiency. Inadequate copper status is also observed in children with low protein intake and in infants fed only cow's milk without supplemental copper.
What health conditions require special emphasis on copper?
Copper may play a role in the prevention and/or treatment of the following health conditions:
- Heart Disease
- Hypothyroid disease
- Periodontal disease
- Rheumatoid arthritis
- Stomach ulcers
What foods provide copper?
Excllent sources of copper include raw cacao, dried apricots, lentils, asparagus, crimini mushrooms, turnip greens and blackstrap molasses.
Very good sources of copper include chard, spinach, sesame seeds, mustard greens, kale, shiitake mushrooms, and cashews.
Good sources of copper include eggplant, tomatoes, summer squash, winter squash, green peas, romaine lettuce, garlic, sunflower seeds, green beans, beets, fennel, olives, leeks, sweet potato, quinoa, buckwheat, barley, spelt, walnuts, pumpkin seeds, flaxseeds, peanuts, almonds, pineapple, raspberries, lentils, garbanzo beans, lima beans, kidney beans, ginger, and black pepper.
What are current public health recommendations for copper?
In 2000, the Institute of Medicine at the National Academy of Sciences established new recommendations for copper including Adequate Intake (AI) levels for infants up to one year old and Recommended Dietary Allowances (RDAs)for all people older than 1 year old. The recommendations are as follows:
- 0-6 months: 200 micrograms
- 7-12 months: 220 micrograms
- 1-3 years: 340 micrograms
- 4-8 years: 440 micrograms
- Boys 9-13 years: 700 micrograms
- Girls 9-13 years: 700 micrograms
- Boys 14-18 years: 890 micrograms
- Girls 14-18 years: 890 micrograms
- Men 19-70 years: 900 micrograms
- Women 19-70 years: 900 micrograms
- Men greater than 70 years: 900 micrograms
- Women greater than 70 years: 900 micrograms
- Pregnant women 14-50 years: 1000 micrograms
- Lactating women 14-50 years: 1300 micrograms
In 2000, the Institute of Medicine at the National Academy of Sciences established the following Tolerable Upper Intake Levels (ULs) for copper:
- 0-12 months: not possible to establish a TUL, sources of copper must be from food and formula only
- 1-3 years: 1000 micrograms
- 4-8 years: 1000 micrograms
- 9-13 years: 5000 micrograms
- 14-18 years: 8000 micrograms
- 19 years and older: 10,000 micrograms
- Pregnant women 14-18 years: 8000 micrograms
- Pregnant women 19 years and older: 10,000 micrograms
- Lactating women 14-18 years: 8000 micrograms
- Lactating women 19 years and older: 10,000 micrograms