By Tom Johnson
Most everyone knows that a diet composed of fruits, vegetables, whole grain foods, low-fat dairy products, fish, poultry and lean meats is important for having a healthy heart. The importance of regular physical activity, about 30 minutes of moderate activity most days of the week, also is recognized as part of a healthy heart lifestyle.
Although many people modify their lifestyles to include both a healthy diet and physical activity, heart disease remains the No. 1 killer of Americans and burdens this country with an economic toll amounting to hundreds of billions of dollars every year.
It has been recognized for a long time that diets that are deficient in copper produce heart enlargement and other forms of heart disease in laboratory animals. However, copper often is overlooked as an important nutrient when considering diets that promote cardiovascular health in humans.
In a study conducted more than years ago, several of the two dozen people who ate a diet supplying 1 milligram of copper per day experienced irregular heartbeats. That's more than the current Recommended Dietary Allowance for copper, which is 0.9 milligrams for adults who are older than 19 years. Agricultural Research Service findings provide science-based data to experts who establish and update the RDAs.
Although the irregular heartbeat in these people was not considered serious, it serves as an example showing the importance of copper for normal heart function. Another indication of the relationship between copper and heart disease comes from the finding that copper concentrations in diseased hearts often are lower than the concentrations found in healthy hearts.
A recent study performed by scientists in the Grand Forks Human Nutrition Research Center in collaboration with the University of Louisville, Ky., showed that dietary copper may be beneficial even when the heart already is diseased.
In this study, the aorta, a major artery leading from the heart, was partially constricted by surgery in laboratory mice. The constriction increased the workload on the heart by causing it to beat against a higher pressure. The increased workload caused heart enlargement four weeks after surgery and caused heart failure eight weeks after surgery. Examination of the hearts under a microscope showed that the increased workload caused extensive structural damage in the heart cells. All of these mice were on a diet that provided the recommended amount of copper for the eight-week duration of the experiment.
Another group of mice that had identical surgery began eating a diet containing slightly more than three times the recommended amount of copper, four weeks after their surgery. These mice continued eating the high copper diet for the remaining four weeks of the experiment. Unlike the other group of mice that ate the recommended amount of copper, the mice eating the high-copper diet did not experience heart failure eight weeks after their surgery. Instead, their hearts no longer were enlarged and the structural damage to the heart cells was greatly reduced.
Other findings from this experiment showed that the high copper diet might have reversed the heart enlargement and damage caused by work overload by increasing the number of capillaries supplying blood to the heart.
Although more research is required to completely understand how copper protected the overworked hearts in the mice, the practical message from this study is that heart disease may increase the dietary requirement for copper.
The finding that increased dietary copper intake reversed heart enlargement in mice provides hope that copper may be a useful weapon in combating some forms of heart disease.
However, it is not possible to predict if humans with enlarged hearts would benefit in the same way from an increase in dietary copper as the mice in this experiment. For one thing, the surgical procedure used on the mice provided a severe, sustained pressure overload on the heart that caused enlargement and heart failure in a matter of weeks.
In humans, heart enlargement occurs for a variety of reasons and may not respond to copper in the same fashion as heart enlargement occurring in mice under carefully controlled experimental conditions. In addition, the availability of copper in experimental diets fed to mice is constant, and this is not true in the variety of whole foods eaten by humans.
The RDA for a nutrient is the average dietary intake that is sufficient to provide the nutrient requirement for nearly all (97 percent to 98 percent) healthy individuals in a particular life stage or gender group.
Although foods in a typical American diet vary considerably in the amount of copper, foods that are high in copper content such as shrimp, lobster, crab, whole grains, nuts, seeds, beans, lentils and mushrooms can be added to help people consume enough copper to achieve, or slightly exceed, the RDA.
Adding copper-rich foods may be particularly important for women. Diet surveys indicate that about 10 percent to 25 percent of women have copper intakes lower than the RDA.
So, for people trying to make lifestyle changes to include a heart-healthy diet, adding servings of foods that are good sources of copper is a good idea. The copper content of many foods in addition to the foods listed above can be obtained online from the USDA National Nutrient Database for Standard Reference.