Copper
Description
Copper is a versatile mineral found in large quantities in bone and muscle, respiratory pigments, brain, heart, and kidney tissues. Over 90% of the copper in blood plasma is found within the copper-carrying protein ceruloplasmin.
Copper is absorbed from the stomach and upper gut. The bulk of absorption occurs in the intestine, by means of the copper-binding protein metallothionein. Absorption is hindered by a large intake of vitamin C and zinc, as well as cadmium, molybdenum, and sulfate.
Copper is involved in the development and maintenance of cardiovascular and skeletal integrity, central nervous system structure and function, production of red blood cells, and hair keratinization. In conjunction with vitamin C, copper maintains the activity of enzymes involved in the synthesis of elastin and collagen.
The high estrogen levels of pregnancy and estrogen therapy result in a marked increase in both serum copper and ceruloplasmin concentrations. Copper is a factor in the efficient absorption of iron. Serum copper levels have been shown to rise during viral and microbial infections, rheumatoid arthritis, and myocardial infarction.
Copper excretion occurs primarily in the feces.
Method of Action
Copper assists in the formation of hemoglobin by facilitating iron absorption.
Copper is important for many body processes. It aids in the conversion of tyrosine into the pigment which colors hair, helps the body oxidize vitamin C, helps build nerve fibers, is necessary for the production of RNA, and is also involved in protein metabolism.
In the proximal part of the small intestine, copper is absorbed and taken up in the mucosal cells by the copper-binding protein metallothionein and carried in the portal blood system. In plasma it is bound to amino acids, especially histidine, and to serum albumin, and is taken to the liver.
In the liver, copper is bound by an alpha-globulin to form ceruloplasmin. Although ceruloplasmin contains about 95% of the plasma copper, it is not a copper-transport protein, but a copper-dependent ferroxidase, which helps oxidize iron in preparation for its absorption. Some unabsorbed dietary copper is excreted in the intestinal feces, but the major intestinal excretion route is by way of bile into the gastrointestinal tract. This biliary excretion route is the main control of copper balance in the body. Only traces of copper are excreted in the urine.
Due to urinary loss of ceruloplasmin, hypocupremia has been observed in nephrosis. Malabsorption diseases such as sprue can also cause low plasma levels because of interference with normal copper absorption.
Properties & Uses
Copper is useful in the treatment of anemia and edema, and in the treatment of kwashiorkor in children.
Consequence of Deficiency
Copper deficiency can have the effect of impairing iron absorption, possibly leading to iron deficiency. Characteristic of copper deficiencies is the decrease in the concentration of the copper-carrying protein ceruloplasmin. This resuts in a reduced efficiency of iron transportation from the intestine, liver, and various tissues to the blood plasma. Utilization of iron for hemoglobin synthesis is then impaired, and red blood cells with abnormally short life spans are produced.
Copper deficiencies can result in massive internal hemorrhages in major blood vessels due to the formation of abnormal collagen and elastin. For similar reasons, infants suffering from copper deficiency can develop fragile bones.
More severe symptoms of copper deficiencies include retarded growth, anemia, edema, and nervous irritability. Less severe symptoms include bone demineralization, chronic or recurrent diarrhea, hair depigmentation, and low white blood cell count. Substantial evidence has linked a lack of unbound copper to rheumatoid arthritis and several other inflammatory diseases. Menkes kinky hair syndrome, a sex-linked recessive defect that results in inhibited copper absorption, is characterized by slow growth, degeneration of brain tissue, and white, stubby hair.
Toxicity Factors
Copper toxicity is rare, since only a small amount is absorbed and stored; the greatest part is excreted. However, the possibility of copper toxicity occurs with Wilson's disease, a rare genetic disorder which results from abnormal copper metabolism, bringing about excess copper retention in the liver, brain, kidneys, and corneas.
Recommended Dietary Allowance
| age | RNI (mg) | |||
| infants/children | ||||
| 9-12 months | 0.3 | |||
| 1-3 years | 0.4 | |||
| 4-6 years | 0.6 | |||
| 7-10 years | 0.7 | |||
| males | ||||
| 11-14 years | 0.8 | |||
| 15-16 years | 1.0 | |||
| 17 years | - | |||
| 18+ years | 1.2 | |||
| females | ||||
| 11-14 years | 0.8 | |||
| 15-16 years | 1.0 | |||
| 17 years | - | |||
| 18+ years | 1.2 | |||
| pregnancy | - | |||
| lactation | 1.5 |
The average person ingests 2.5 to 5.0 milligrams of copper daily.
For over thirty years, Recommended Daily Amounts has existed in the United Kingdom. It has been used to measure the adequacy of an individual's diet. However, in 1991 the Committee on Medical Aspects of Food Policy (COMA) gave forth a whole new set of figures upon the request of the Department of Health's Chief Medical Officer. Reference Nutrient Intake (RNI) is one of these sets collectively known as "Dietary Reference Values." RNI is an amount of a nutrient that is enough for almost every individuals, even someone who has high needs for the nutrient. This level of intake is, therefore, considerably higher than what most people would need. If individuals are consuming the RNI of a nutrient they are most unlikely to be deficient in that nutrient.
Food Sources
| Beef kidney | Beef liver | |
| Brown rice | Cherries | |
| Green pea | Nuts | |
| Poultry | Prune | |
| Rice bran | Split peas | |
| White rice (enriched) | Wheat bran | |
| Whole wheat bread | Wild rice |
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