By W. Thomas Johnson
Proper nutrition during pregnancy cannot be overstated because it provides building blocks for the developing fetus, fulfills maternal energy requirements, and increases energy reserves needed for lactation. Recommendations for good prenatal nutrition traditionally have addressed weight gain and nutrient intake during pregnancy. Although calorie requirements increase during pregnancy, a woman's body adapts to the increase in requirements and becomes more efficient. This means that only a small increase of about 300 calories a day is needed to meet energy requirements.
But the requirements for vitamins and minerals also increase during pregnancy and the increase in vitamin and mineral requirements is more difficult to meet through changes in dietary intake than by simply consuming more calories. As a result, vitamin and mineral supplements are often used as a component of prenatal care.
Copper is one of several minerals whose requirements are increased during pregnancy and lactation. The Food and Nutrition Board of the Institutes of Medicine of the National Academies of Science has established recommended dietary allowances, or RDA's, for a large number of nutrients. The RDA for a nutrient is defined as the average dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97-98%) healthy individuals in a particular life stage and gender group. For copper, the RDA for women who are 19 years-old or older is 0.9 milligram per day. During pregnancy the RDA for copper increases to 1 milligram per day and increases further to 1.3 milligrams per day during lactation. Although these are relatively small amounts of daily copper, results from surveys of food intakes indicate that average copper intakes in 14 to 30 year-old women range from 0.44 to 0.76 milligrams per day. These surveys also indicate that up to 75% of pregnant women and 90% of lactating women may have dietary copper intakes below the RDA for copper. These findings suggest that the nutrient requirements for copper are not always met by dietary intake in women of reproductive age and during pregnancy and lactation.
The importance of vitamins and minerals during pregnancy is often reflected in outcomes for the infant. For instance, it is well-recognized that folate deficiency during pregnancy can lead to certain types of birth defects in the brain and spinal cord. Although the outcomes for infants that result from copper deficiency during pregnancy are not as clear, its importance during pregnancy is reflected in several animal species where a variety of neurological defects occur in the offspring of copper-deficient mothers. Recent work at the Grand Forks Human Nutrition Research Center indicates that long-lasting heart defects also may occur in the offspring of rats who had low dietary copper intakes during pregnancy and lactation.
The cells in the heart contain mitochondria which are responsible for supplying the energy required for cellular function. One of the components in the mitochondrial energy generating mechanism is a copper-dependent enzyme called cytochrome c oxidase. My research showed that the activity of this enzyme was reduced in the hearts of apparently normal, healthy rat pups whose mothers ate diets that were low in copper during pregnancy and lactation. Surprisingly, the reduction in the activity of cytochrome c oxidase in the hearts of these offspring was very persistent and could not be fully restored even after supplementing their diet with adequate copper for 9 months. Furthermore, mitochondria isolated from the hearts of the 9-month old offspring of the copper-deficient mothers produced more oxygen radicals, which are highly reactive forms of oxygen, than normal.
Our findings indicate that low copper intakes by pregnant and lactating rats have irreversible consequences on mitochondrial function and oxygen radical production in the hearts of their offspring. Although further research is needed to understand how the changes in mitochondrial function and oxygen radical production affect heart function and susceptibility to disease, an expanding body of evidence from several laboratories has shown these changes contribute to several common degenerative diseases, including some forms of heart disease.
Although it is difficult to extend research findings from laboratory animals to humans, my research suggests that adequate copper nutrition during pregnancy and lactation is an important consideration for women that may help reduce the risk for their children of developing heart disease during adulthood. As mentioned above, women of reproductive age in general may have daily copper intakes below the RDA and should try to incorporate more foods that are good sources of copper into their diets. These foods include shellfish such as shrimp, crab and lobster, whole-grain foods, beans, lentils and mushrooms. Also, because copper requirements increase during pregnancy and lactation, women should follow the advice of their health care provider if vitamin and mineral supplements are recommended as part of prenatal care.