December 15, 2009
Of the approximately 100 members of my class at Yale School of Medicine, every single graduate—100%—were eating solid food.
With that admittedly anecdotal experience, I have reassured many parents that at some unpredictable point between 4 months of age and medical school, their baby will—I virtually guarantee it—eat solid food.
Jamie, barely 4 months, used to sleep 6 or even 8 hours at night last month. But as the weeks went by, he was awakening more often. His parents said that he’d get a good nursing at about 10pm and then he’d be out for about 3-4 hours. Then when he awoke, he’d nurse again, out for 2 hours. Then 1 hour intervals through the rest of the night. The nursing was sometimes 15 minutes, sometimes 30. What was happening?
Unlike The Human Pacifier, this 4-month old appeared to want to eat. He wasn’t looking for reassurance or comfort during the night, he was really nursing. There’s a behavioral aspect to frequent awakenings, that can become a problem as babies get older. (I hasten to add that there’s no crying baby who doesn’t need attention and care. Maybe there’s a sleep problem or a behavioral issue, but the approach to this should never include ignoring the baby, even if it does include a measured response.)
There’s no way to untangle the comfort provided by nursing with mommy in the middle of the night from the baby’s hunger. Or is there? In the 3-part Human Pacifier series [part 1, part 2, part 3], the baby was waking up to nurse for a minute or two, sometimes less. He’d go to sleep right away after just a moment or two of snuggling with mom. But Jamie’s mom didn’t have it any easier. She, too, was getting up nearly through the night. This baby was nursing pretty much to the capacity of the mother’s production.
Here’s what’s going on. The baby is full when he’s going to sleep. That’s why he has his longest sleep immediately after that last big feeding. He was about 2 pounds less a month ago—that’s a big proportion of his body weight. At the time, it was enough to keep him nearly through the night. Now, it’s enough for 3 hours, maybe 4. Then he wakes up hungry. Nursing for 15 to 30 minutes is enough to take the edge off his hunger, and get him back to sleep. It’s not enough to fill him. The less-than-enough feeding may take the edge off, but it’s not enough to last long. So this second feeding doesn’t last as long as the first. He wakes up and mom does her best. But 2 hours later, he doesn’t get the same amount he got after giving mom a 4-hour break. Her manufacturing apparatus just isn’t set up for just-in-time inventory management. He’ll get just enough to take the edge off again, but this time wakes up in an hour. This is much less time than the factory needs to meet demand. So from this feeding until morning, both baby and mother are locked in lactational Reaganomics—a trickle-down model of infant feeding.
So there’s a couple of logical approaches, with both possibly rooted in an econometric, perhaps even game theory perspective on infant rearing. Isn’t this the approach most parenting authorities take?
First, we can decrease demand to match supply. It’s hard to see Superman taking valuable time from his busy schedule and presumably many other commitments to fly really fast around the planet backwards and so turn back time to when the baby would stay full through the night. There’s some ambiguity about how Superman ages, since he progressed from baby to newspaperman quickly but hasn’t changed much since the 1950’s. I mention this because he’s going to have to accomplish this same task every month forever if we’re really intent about restraining the baby’s growing demand.
So, like true Reaganomics devotees, we need to focus on the supply side. Here, there is a fork in the road. There are many ways to try to increase milk supply. This is a reasonable way to go, for a while. Babies, however, can be relentless in their ever-increasing demands. Will they never learn? The other fork bypasses this captive supply chain and outsources the inventory management. This baby was ready for solid food.
Human milk is really easy to digest. There isn’t much else that goes through a baby’s stomach faster. Solids get digested much slower, so they keep the baby full a lot longer. For the record, the calorie content of solids is typically much less than breast milk or formula—so I don’t rush to start solids in babies who are having problems gaining weight. Not every baby takes to solids right away, but the level of stress this induces occasionally confounds me. I think of my fellow graduates and can’t think of a single one, not one, who wasn’t eating solid food. I can’t authoritatively say that this was true at other medical schools, of course.