Copper is essential to life. Plants growing in soil containing too little copper fail to thrive. Animals that graze on plants that have too little copper, or laboratory animals fed diets restricted in copper become ill and may die, usually of damage to the heart and blood vessels. Copper's importance to human health is obvious from the severe health consequences in malnourished infants supported only on cows' milk (which is low in copper); in patients receiving intravenous feeding with copper inadvertently omitted; and in people who have a hereditary inability to absorb and metabolize copper. Fortunately, such severe deficiency is rare among people because we eat a varied diet. But some researchers and health professionals hold that mild copper deficiency is common and may contribute to diseases of aging, such as coronary heart disease.
Why do we need copper? At least twenty enzymes contain copper, and at least ten of those depend on copper to function. Because these enzymes occur in most tissues, the biochemical defects of copper deficiency are widespread. They affect functions of the cardiovascular, nervous and immune systems, as well as the lung, thyroid, pancreas and kidney.
The cardiovascular system -- heart, blood and blood vessels -- seems to be particularly vulnerable to copper deficiency. In studies in my laboratory and those of other researchers, many aspects of the function of the heart and circulation have been adversely affected by copper deficiency. For instance copper-deficient diets alter the heart's electrical rhythm and this impairs the heart's ability to pump blood. Further, studies with laboratory animals indicate that hearts don't contract as strongly during copper deficiency, further reducing their pumping ability. Also, recent studies indicate that copper deficiency reduces the ability of the heart to use energy, which may contribute to reduced heart function.
Blood vessels don't dilate as well in laboratory animals that lack copper. This altered blood vessel control, in addition to interfering with appropriate distribution of blood throughout the body, may contribute to the high blood pressure observed in copper-deficient animals and humans.
Other cardiovascular functions are also affected by dietary copper deficiency. Copper-deficient animals and humans have fewer red blood cells (anemia), which reduces the delivery of oxygen to their tissues. Studies with laboratory animals also show that blood clotting is impaired by copper deficiency. This leads not only to increased bleeding following injury, but, once clots form, to reduced ability to dissolve those clots. And finally, copper-deficient blood vessels tend to leak excessive fluid into injured tissues, thus exaggerating swelling.
The Food and Nutrition Board of the National Research Council estimates adults need between 1.5 and 3.0 mg of copper daily. But, despite the strong evidence of copper's essentiality, the Board has not established a specific Recommended Dietary Allowance (RDA). That's because it's difficult to assess the harmful effects of low copper intakes in people without risks to their health. One of the challenges of nutrition researchers at the Grand Forks Human Nutrition Research Center is to devise creative ways of assessing people's copper status and the possible serious outcomes of copper deficiency in humans without danger to them.
Should the above consequences of copper deficiency alarm you, rest assured that if you eat a balanced diet that includes foods high in copper -- such as liver, legumes, shellfish, meats, nuts, seeds and whole grains -- you will avoid any such consequences and may reap benefits into old age.