To Eat or Not to Eat

Parents of Children with NDI Share Their Experiences
By Jody K. Vilschick

If we knew what would make our sons dig in, we would cook it and serve it. I’d probably cook up the family pet if I thought he’d eat it. And I’m tired of hearing, "Have you tried fried clams?"… or pickled green tomatoes, or whatever other dish that is suggested. "Trust me," I say to myself silently (because if I said it out loud I’d end up being rude). "If I thought Eli would eat it, I would have served it to him. That includes caviar and Godiva chocolates."

My son Eli has nephrogenic diabetes insipidus (NDI), and, like most other young boys with NDI, would rather drink water than eat.

Worry about sodium? Two-year-old Eli does’t eat enough food to worry about sodium. My philosophy is to take things one step at a time. Let’s get him eating, my husband and I have decided, then once the habit of eating is established we’ll worry about a low-sodium diet. Still, if there’s a choice between regular sodium and a low sodium product, we’ll choose the low-sodium option. Dr. Tom Watson, a pediatrician whose 8-year-old son also has NDI and was a poor eater, agrees with this approach. "Let them eat whatever they want," he says. "Get them eating, even if it’s potato chips, as long as they have complete access to water." However, many physicians knowledgeable in the issues surrounding NDI disagree, instead recommending a low-sodium diet from the get-go. Other parents have chosen to follow this approach, believing that it’s best not to start the sodium habit at all.

Although Eli’s case is a bit different—he is the only child of the four presented here who’s had a feeding tube throughout his infancy and into his toddler-hood—all the children share two things: NDI and they don’t eat well. The parents share their combined concern and frustration over their sons’ eating, or lack of it, mixed with just a bit of envy that parents of other children, children who don’t have NDI, can feed their children without a second thought, without appreciation for what a miracle it is to see your toddler chew up a single, tiny bite of pizza, and then look up and say, "more."

I’m not the only mother in the world whose day is made when her son chews a Cheerio or gnaws a raw carrot. There are others, like Kris Schwander, mother of 28-month-old Augi, who also see the wonder of chewing. "To me," Schwander says, "the best thing in the world is watching my son chew. Isn’t that silly?"

One of the hardest experiences I’ve endured is watching other children chow down. My friend Mary and I took our children on a picnic this past summer. Mary’s daughter Alison ate bread, cheese, crackers, a few bites of pasta salad, some chicken pieces, a large piece of banana, and chased everything down with some apple juice. Eli drank his water, and ate one Pepperidge Farm cheddar cheese fish cracker. This envy, this watching what other children of similar ages eat, is one of those shared experiences that only other parents of NDI children know. "I watched my niece (who is two months older than my son) eat a whole peanut butter and jelly sandwich the other day," says Schwander. "Augi just nibbled at his. It’s very hard to watch. Eating is such a simple thing that I had taken for granted."

Why don’t they eat? It seems little is scientifically known about lack of appetite. Our sons’ nutritionists, pediatricians, and nephrologists can’t seem to have any answers to explain why they’re not eating. "We don’t know why these children don’t have an appetite," says Darla Everly, a clinical nutritionist at the Children’s Hospital of Philadelphia. "But we’ve seen a large majority of these patients who don’t eat well." Darla Everly and Dr. Kevin Meyers, a pediatric nephrologist at the Children’s Hospital of Philadelphia, have extensive experience with young children who have NDI. "Most children with NDI have a lack of appetite in the first few years of life," says Meyers. Dr. Daniel Bichet, a member of DiF’s Scientific Advisory Committee and leading expert in NDI, concurs. "Usually young boys with NDI have feeding problems early on," says Bichet, who is a professor of medicine at the University of Montreal in Canada. "More so when they’ve suffered dehydration episodes." The happy news is that most children improve with age, according to Dr. Nine M. Knoers, who has 15 years’ experience working with people with NDI. "Many older children eat well and do have appetite, and their weight normalizes," she says.

There are a number of theories circulating about why young children with NDI tend not to eat well. "It is not clear why some children with NDI grow more slowly and seem to eat less than other children. One possibility is that their appetites are poor because their stomachs are so often filled with water," says Dr. Gary Robertson, the chair of DiF’s Scientific Advisory Committee, and professor of medicine at Northwestern University. This theory also has been suggested by Drs. Anginita F. Van Lieburg and Nine M. Knoers in an article published in the Journal of the American Society of Nephrology (10:1958-64, 1999). "That’s consistent with the fact that they usually start to eat and grow better when they are started on treatment that reduces their urine output and fluid intake," continues Robertson. "But it is inconsistent with the fact that children with untreated pituitary [neurogenic] DI often drink nearly as much water but seem to eat and grow more normally."

Yet another possibility is that "the genetic mutation that causes NDI also interferes with taste or appetite," says Robertson. "That seems unlikely also, since reducing urine output seems to improve eating and growth even though it should not correct the receptor defect caused by the mutation."

Gastroesophageal reflux, fairly common in children with NDI, might have something to do with it, in that these children learn as infants that some oral sensations are unpleasant, or even hurtful. But Meyers points out that "not all children with NDI have reflux."

And it seems equally unlikely that the bland diet NDI children are often put on discourages their eating. "Many children with NDI start to eat and grow more normally when they are started on effective treatment, which includes a low-salt diet," says Robertson. As Everly notes, "We are not born with a salt craving, it’s a learned taste."

Dr. Heinz Valtin, founding vice president of DiF and an emeritus professor at Dartmouth Medical School, notes that appetite or satiety receptors are located in the hypothalamus, as are, of course, the cells that produce the antidiuretic hormone (ADH, or vasopressin). "In NDI, these cells are hyperstimulated and vasopressin is overproduced," Valtin says. He wonders about possible spillover of nervous impulses within the hypothalamus or some feedback mechanism that would inhibit appetite. "Currently, much attention is focused on a protein called leptin, which seems to regulate eating behavior, possibly by combining with satiety receptors in the hypothalamus," states Valtin. He thinks that many theories about problems of eating in NDI could be tested by working with animal models of the various forms of diabetes insipidus.

Robertson concludes that none of the existing theories "adequately explains the fact of poor appetite and growth." Bottom line: this is worth studying, according to Everly. "Obviously their eating affects their growth and development," she says. "But we just don’t know if there’s any physical reason for it. And until we do, we can’t really be sure what approach to take to the problem."