Copper: Reference and Dietary Sources

Abstract

In this article, we describe:

  • the major purposes of this specific nutrient in the human body, 
  • its experimentally confirmed health uses, 
  • conventional ways to estimate nutrient status,
  • nutrient’s toxicities and deficiencies,
  • experimentally confirmed and approved levels of the nutrient intake for different demographics,
  • dietary sources of the nutrient.

Introduction

Copper, an essential mineral, is naturally present in some foods. It is a cofactor for several enzymes (known as “cuproenzymes”) involved in energy production, iron metabolism, neuropeptide activation, connective tissue synthesis, and neurotransmitter synthesis. One abundant cuproenzyme is ceruloplasmin (CP), which plays a role in iron metabolism and carries more than 95% of the total copper in healthy human plasmaCopper is also involved in many physiologic processes, such as angiogenesis; neurohormone homeostasis; and regulation of gene expression, brain development, pigmentation, and immune system functioning. In addition, defense against oxidative damage depends mainly on the copper-containing superoxide dismutases.

A wide variety of plant and animal foods contain copper, and the average human diet provides approximately 1,400 mcg/day for men and 1,100 mcg/day for women that is primarily absorbed in the upper small intestine [1,2,7-9]. Almost two-thirds of the body’s copper is located in the skeleton and muscle [1,3].

Only small amounts of copper are typically stored in the body, and the average adult has a total body content of 50–120 mg copper. Most copper is excreted in bile, and a small amount is excreted in urine. Total fecal losses of copper of biliary origin and nonabsorbed dietary copper are about 1 mg/day. Copper levels in the body are homeostatically maintained by copper absorption from the intestine and copper release by the liver into bile to provide protection from copper deficiency and toxicity.

Human studies typically measure copper and cuproenzyme activity in plasma and blood cells because individuals with known copper deficiency often have low blood levels of copper and CP. However, plasma CP and copper levels can be influenced by other factors, such as estrogen status, pregnancy, infection, inflammation, and some cancers. Normal serum concentrations are 10–25 mcmol/L (63.5–158.9 mcg/dL) for copper and 180–400 mg/L for CP.

Copper deficiency is uncommon in humans. Based on studies in animals and humans, the effects of copper deficiency include anemia, hypopigmentation, hypercholesterolemia, connective tissue disorders, osteoporosis and other bone defects, abnormal lipid metabolism, ataxia, and increased risk of infection.

The following groups are most likely to have inadequate copper status: People with Celiac Disease; People with Menkes Disease; People Taking High Doses of Zinc Supplements.

Copper deficiency leads to changes in blood lipid levels, a risk factor for atherosclerotic CVD. Animal studies have shown that copper deficiency is associated with cardiac abnormalities, possibly because of the resulting decreases in the activity of several cardiac cuproenzymes. Some experts also believe that dietary copper deficiency plays a role in the etiology and pathophysiology of Alzheimer’s disease, the leading cause of dementia, because of several reports of low copper levels and low activity of copper-dependent enzymes in the brains of people with the disease.

In turn, copper toxicity is rare in healthy individuals who do not have a hereditary copper homeostasis defect. However, copper toxicity has been reported in people who consume water containing high levels of copper as a result of stagnant water in copper-containing pipes and fixtures as well as copper alloys in water distribution systems and household plumbing that allow copper to leach into water. People with Wilson’s disease, a rare, autosomal recessive disease, have a high risk of copper toxicity.

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Recommended Dietary Allowances (RDAs) for Copper

AgeMaleFemalePregnancyLactation
Birth to 6 months*200 mcg200 mcg
7–12 months*200 mcg200 mcg
1–3 years340 mcg340 mcg
4–8 years440 mcg440 mcg
9–13 years700 mcg700 mcg
14–18 years890 mcg890 mcg1,000 mcg1,000 mcg
19+ years900 mcg900 mcg1,300 mcg1,300 mcg

*Adequate Intake (AI)

Dietary Sources of Copper

The richest dietary copper sources include shellfish, seeds and nuts, organ meats, wheat-bran cereals, whole-grain products, and chocolate. The absorption of copper is strongly influenced by the amount of copper in the diet; bioavailability ranges from 75% of dietary copper when the diet contains only 400 mcg/day to 12% when the diet contains 7.5 mg/day.

Tap water and other beverages can also be sources of copper, although the amount of copper in these liquids varies by source (ranging from 0.0005 mg/L to 1 mg/L).

Selected Food Sources of Copper

FoodMilligrams
(mcg) per
serving
Percent
DV*
Pan-fried bee liver, 3 ounces12,4001,378
Cooked eastern oysters, wild-caught, 3 ounces4,850539
1,500168
Baking chocolate, unsweetened, 1 ounce938104
Cooked potatoes with skin, 1 medium67575
Shiitake mushrooms, cut and cooked, ½ cup65072
Cashew nuts, dry roasted, 1 ounce62970
Dungeness crab, cooked, 3 ounces62469
Sunflower seed kernels, toasted, ¼ cup61568
Simmered Turkey giblets, 3 ounces58865
Dark chocolate, 70%-85% cacao solids, 1 ounce50156
Raw firm tofu, ½ cup47653
Chickpeas, ½ cup28932
Cooked millet, 1 cup28031
Cooked Atlantic salmon, 3 ounces27330
Whole wheat pasta, cooked, 1 cup (not packed)26329
Raw avocado, ½ cup21924
Figs, dried, ½ cup21424
Cooked spinach, ½ cup15717
Cooked asparagus, ½ cup14917
Sesame seeds, ¼ cup14716
Ground turkey, broiled, 3 ounces12814
Cream of Wheat cereal, , cooked with water, 1 cup10412
Raw tomatoes, ½ cup536
Plain Greek yogurt, 7-ounce container425
Milk, 1 cup273
Raw apples with skin, ½ cup slices172
  • *DV = Daily Value.
  • The DV for copper used for the values in the table above is 0.9 mg (900 mcg) for adults and children age 4 years and older.
  • Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.

References

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