Leslie M. Klevay
In an article I published a few years ago, I suggested that nutrients without Recommended Dietary Allowances (RDAs) tend to be ignored by people who plan diets and do research. Copper was among those ignored nutrients . . . until recently.
In a sense, copper has been promoted because it now has RDA status along with zinc. The National Academy of Sciences’ Institute of Medicine recently issued new dietary reference intakes--which include RDAs--for copper and other trace elements. Research and staff members at Grand Forks Human Nutrition Research Center, particularly Dr. James Penland who was a member of the expert panel on micronutrients, contributed critical information toward the new recommendations.
The Academy’s panel thinks there is sufficient, quantitative information available to permit a good estimate of copper requirements and of the consequences for not satisfying the requirements. In contrast, calcium no longer has an RDA indicating that recent changes in nutritional perspectives and newer research makes the definition of requirements for this element less certain.
The copper RDA for adults is 0.9 mg daily. A slightly higher amount is recommended during pregnancy, and 1.3 mg daily is recommended for mothers who breast feed. Several collaborators and I have pooled data on the chemical analyses of 849 diets collected in the U.S., Belgium, Canada and the United Kingdom. Approximately one fourth of these diets contain less than the RDA for adults and nearly half of them contain less than 1.3 mg daily.
Evidence indicates that chronic low-copper intake can increase risk of heart attacks and osteoporosis. Research that relates a low-copper intake to heart disease has been increasing over the last quarter century.
The association between low-copper status and human bone disease generally is less extensive, although I recently found numerous older articles in pediatric journals describing osteoporosis in children deficient in copper. Whether or not these observations are related to the osteoporosis in late middle-age remains to be seen, but two recent experiments show that copper supplements for women improved bone density. The first study was done in San Diego; a supplement of calcium plus trace minerals (including copper) produced improvement compared to no treatment. Copper probably was the main active ingredient because a later study done in Belfast, Northern Ireland, showed that a copper supplement retarded bone loss.
It is easy to find a diet that fails to meet these dietary references intakes. For instance, a tuna fish salad made with lettuce, mayonnaise and salad oil is very low in copper. The recipe can be improved by adding high-copper foods such as soy or other legumes, mushrooms and sunflower or other seeds. Other good sources of copper include some ready-to-eat cereals, chocolate, nuts, peanut butter, liver and oysters.
The panel also defined the tolerable upper intake for adults as 10 mg daily and suggested that it is quite unlikely that people will reach even half this level even if dietary supplements of copper and small amounts of copper in drinking water are included.
I hope that neglect of copper will fade with the new recommendations. In any event, many of us probably will benefit from eating foods high in copper more frequently.