Henry C. Lukaski supervises the Applied Physiology Laboratory. A major research focus is determining the effects of graded intakes of trace elements (iron, copper and zinc) on physiologic responses to challenges of various stressors such as temperature and exercise. These studies, which began with women who were iron deficient and acutely exposed to cold air (62oF) while wearing a swim suit, indicated that certain hormones that regulate the body's ability to increase heat production were not present in adequate amounts. This resulted in an inability to maintain body temperature. More intensive studies with animals permit the study of the proteins in tissues and cells that control the production and utilization of temperature regulating hormones. Our work indicates a commonality with trace element deprived animals and failure to maintain body temperature the thyroid hormone and catecholamine systems.

We seek to determine if trace element intake influences or is influenced by physical activity. We have studied university athletes, determined nutritional status throughout training and related a variety of indices of mineral nutrition to performance measures during competition. We developed a model to predict swimming performance and successfully tested it in other swimmers. Iron, copper and magnesium were important nutritional predictors of physical performance. Each of these minerals plays a critical role in transforming energy in food into chemical energy for work.

More than 30% of Americans are overweight and over­fat. Studies of obese animals suggest that trace element metabolism is altered. We have conducted two studies to determine in obese women if trace element status is affected during controlled energy restriction and exercise. We found that copper and magnesium were lost in amounts exceeding intake during weight loss. This was paralleled with loss of bone. Whether increased dietary mineral intake will reduce the risk of bone loss remains to be determined.

The body's ability to absorb iron is improved when meat is present in a meal. We hypothesized that stearic acid, a fat found in beef, may be this factor. Studies in rats and dogs indicate that stearic acid and beef tallow increase the absorption and use of iron that is generally found in non­meat sources. These findings suggest that stearic acid, which does not increase serum cholesterol, may be a beneficial component of the diet which improves the iron status of humans.

Developed and validated the tetrapolar bioelectrical impedance method for assessing human body composition. Models for predicting fat-free mass based upon conductance measurements of the body were developed and cross-validated in adults. The error of estimating fat-free mass was within the limits of the reference method of assessing body composition. The predictive accuracy was better than that found by standard caliper procedures. Based on these results, this method is currently used in the National Health and Nutrition Examination Survey to determine the body composition of the U.S. population. Other studies resulted in the development and validation of models using impedance measurements to estimate total body water and extracellular water in healthy adults, to assess fluid changes in surgical patients, obese women undergoing weight loss, and women during pregnancy and lactation.
Provided the first evidence that dietary copper in amounts consumed by a majority of American adults raises blood pressure during low level work. Young women fed marginal dietary copper had markedly increased diastolic and systolic blood pressures during mild intensity exercise similar to lifting grocery bags or shoveling snow. This finding indicates that copper plays a key role in regulating blood pressure in humans.

Demonstrated that iron deficiency without overt anemia in humans is associated with impairments in energy metabolism. A reduced thermogenic response during acute cold exposure and a blunted rate of oxygen utilization during progressive exercise to exhaustion were observed in young women who were iron-deficient but not anemic by a combination of reduced iron intake, phlebotomy and menstruation. The inability to produce heat in the cold and the reduced rate of oxygen uptake during work were associated with an increase in anaerobic metabolism. Thus, iron-dependent factors other than oxygen-carrying capacity can influence body energy metabolism.

Demonstrated that dietary stearic acid promotes iron utilization. Studies of iron-deficient dogs revealed that 59Fe absorption and red blood cell regeneration were increased significantly after ingestion of stearic acid compared to that after safflower oil. Studies of intestinal mucosal kinetics in canines indicated that the mechanism behind these effects was an increased transfer of iron from the intestinal cell into the blood. Cells in culture, made iron-deficient by using a novel serum-free media, demonstrated increased iron uptake and translocation when incubated in media containing stearic and palmitic fatty acids as compared to safflower oil. These findings suggest that stearic acid may be the factor in meat that facilitates the utilization of non-heme iron.

Identified altered energy efficiency during moderate intensity work in women fed a low magnesium diet (150 mg/d). Postmenopausal women exhibited a 10% increase in oxygen utilization with an increase of 9 beats per minute during submaximal ergocycle exercise when they performed the same amount of work as when they consumed a diet adequate (350 mg/d) of magnesium. These findings indicate that adequate dietary magnesium is needed for optimal use of energy to perform daily activities.

Determined that women consuming diets low in magnesium, but similar to amounts ingested by many American women, had depleted muscle and red blood cell magnesium concentrations and lost magnesium from their bodies. This deficiency resulted in increased oxygen needs to perform low level exercise, which has been shown previously in competitive athletes. This finding provides the first confirmation of the new recommendation for dietary magnesium for women.

Determined a new role of zinc in support of energy use during exercise. Physically active men consuming diets low in zinc had significantly decreased activity of carbonic anhydrase that was associated with increased ventilation, reduced carbon dioxide exhalation and oxygen use during exercise. Studies in rats fed graded dietary zinc and exercise-trained confirmed these findings and showed for the first time that skeletal muscle carbonic anhydrase activity and protein were decreased with low dietary zinc. These observations provide novel evidence that zinc supports cardiorespiratory function during exercise in humans.