You Can’t Identify Abnormal If You Don’t Know What's Normal

June 19, 2012


Although I am a physician who takes care of infants who are often critically ill, much of my research at the USDA/ARS Children’s Nutrition Research Center involves evaluating healthy infants and children. This may seem odd. Who cares about how healthy children are growing??? Feed ‘em (but don’t overdo it) and they’ll grow sounds like a good plan! So, it may not be easy to see why a physician specializing in caring for the sickest of babies focuses much of his research on healthy ones.

Yet, thoroughly understanding “normal” and “healthy” growth is absolutely essential to taking care of sick children, especially the nearly 20% (over 14 million children!) with special health care needs.

Let’s consider a baby who is born with a major heart problem such as hypoplastic left heart syndrome. This condition requires multiple cardiac surgeries over a period of years. Before and after our incredible cardiovascular surgeons begin the surgical intervention process in the early weeks of life, a nutritional plan needs to be developed so that the baby can grow and be ready for the next surgery and the ultimate goal of a functional, happy childhood.

Now, we have many factors to consider in determining the right nutritional advice and plan for this baby and his family. On the one hand we know that children with heart and lung problems may need extra calories due to their illness and extra work that is done by their heart and lungs. However, it isn’t always that simple. Many babies with chronic health conditions are less active than healthy babies which may decrease the amount of calories they need over time. Some babies with chronic illnesses may even become overweight, adding more stress to the heart and lungs. Furthermore, their heart or lung diseases may limit the amount of liquid (milk or formula) they can drink without overburdening them.

Frequently one critical barrier to growth in children with chronic illnesses is their appetite. They may just not be able to eat enough, or tire out before finishing a feeding. We work closely with experts in feeding, including occupational therapists and lactation consultants to solve these problems and determine the best approach to feeding each child on an individual basis.

Now, how does this relate to research on healthy children? Well, to provide the best advice for a baby with a problem like hypoplastic left heart syndrome, we need to really understand normal growth and its components. Breast milk is a perfect food for healthy babies, but infants who are not healthy may need both breast milk along with added protein or minerals to make up for their difficulty in tolerating a full volume of feedings or to ensure good growth. If we don’t understand the range of usual requirements for these nutrients in a healthy baby, we can’t determine how much to provide in these special circumstances.

Instead of just focusing on weight gain, we need to be certain that a child is growing muscle, brain and bone as they would if they did not have a chronic illness. Sometimes this isn’t possible, but we’d like to come close and understand where we need to work on “catching up” when it becomes possible. We need to make sure they are receiving and absorbing micronutrients such as iron, zinc and calcium needed for bone and body growth. For example, not enough zinc in the diet can cause poor growth and diminish the appetite of children. On the other hand, too much zinc in the diet can compete with other minerals like iron so that not enough of the other nutrients are absorbed. This can lead to anemia and poorer developmental outcomes. It’s not always simple to balance these needs, especially in a situation in which food intake is limited or nutrient absorption is abnormal.

I have focused my research at the USDA/ARS Children’s Nutrition Research Center on evaluating dietary minerals, their absorption, their effects on growth in healthy children and at times, doing comparison studies with groups of children with chronic illnesses. We study the best forms of minerals to optimize absorption, how these minerals are tolerated, and what happens when the diet is low in minerals, vitamins or energy. Armed with these data, scientists and physicians can work together with our dietitians to plan diets, discuss options with families, and help children with chronic illnesses not just survive, but thrive.

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