Brain Rules for Baby (Updated and Expanded). John Medina
should pay attention to these cravings? Is the baby telegraphing its nutritional needs? The answer is no. There is some evidence that iron deficiencies can be consciously detected, but the data are thin. Mostly it’s a matter of how a person uses food in her daily life. An anxious person who is comforted by the chemicals in chocolate might grow to crave chocolate whenever she feels stressed—and a woman will feel stressed a lot during pregnancy. (This craving for chocolate reflects a learned response, not a biological need, though I think my wife would disagree.) We actually don’t know why a pregnant woman’s random cravings occur.
That doesn’t mean the body doesn’t have nutritional needs, of course. The pregnant woman is a ship with two passengers but only one galley, and we’re looking to stock this kitchen with the right ingredients for brain growth. An infant’s body needs 45 different nutrients for healthy growth. A whopping 38 of these are critically involved in the development of the nervous system. You can look on the back of most pregnancy-formulated vitamin supplements to see the list. We can look to our evolutionary history for some guidance on what to eat to get these nutrients. Since we know something of the climate in which we developed for millions of years—one that supported ever-increasing brain girth—we can speculate about the type of foods that helped it along.
Caveman cuisine
An old movie called Quest for Fire opens with our ancestors seated by a fire, munching on a variety of foods. Large insects buzz about the flames. All of a sudden, one of our relatives shoots out his arm, clumsily grabbing an insect out of thin air. He stuffs it into his mouth, munches heartily, and continues staring into the fire. His colleagues later dig around the soil for tuberous vegetables and scrounge for fruit in nearby trees. Welcome to the world of Pleistocene haute cuisine. Researchers believe that for hundreds of thousands of years, our daily diet consisted mostly of grasses, fruits, vegetables, small mammals, and insects. Occasionally we might fell a mammoth, so we would gorge on red meat for two or three consecutive days before the kill spoiled. Once or twice a year we might run into a beehive and get sugar, but even then only as unlinked glucose and fructose. Some biologists think we are susceptible to cavities now because sugar was not a regular part of our evolutionary experience, and we never developed a defense against it. Eating this way today (well, except for the insects) is called in some circles the paleo diet.
So it’s a bit boring. And familiar. Eating a balanced meal, with a heavy emphasis on fruits and vegetables, is probably still the best advice for pregnant women. For the non-vegetarians in the crowd, a source of iron in the form of red meat is appropriate. Iron is necessary for proper brain development and normal functioning even in adults, vegetarian or not.
Miracle drugs
There is a lot of mythological thinking out there about what you should and should not eat—not just during pregnancy but your whole life long. I had an honors student at the University of Washington, the thoughtful type of kid who has to sit on his hands not to answer a question. One day he came up to me after class, breathless. He was taking an entrance exam for medical school and had just found out about a “miracle” drug. “It’s a neurotonic!” he exclaimed. “It improves your memory. It’ll make you think better. Should I take it?” He thrust in front of my face an advertisement for ginkgo root. Derived from the ginkgo tree, ginkgo biloba has been advertised for decades as a brain booster, improving memory in both young and old, even treating Alzheimer’s. These claims are testable. A number of researchers began to study gingko as they would any promising pharmaceutical. Sorry, I told the student. Ginkgo biloba does not improve cognition of any kind in healthy adults—not memory, not visual-spatial construction, not language or psychomotor speed or executive function. “What about old people?” my student asked. Nope. It doesn’t prevent or slow down Alzheimer’s, dementia, or even normal age-related cognitive decline. Other botanicals, like St. John’s wort (purported to treat depression) show similar impotence. My student left, crestfallen. “The best thing you could do is get a good night’s sleep!” I hollered after him.
Why is it that these nutrition myths can fool even bright kids like my student? First, nutrition research is really, really hard to do, and it is shockingly underfunded. The types of long-term, rigorous, randomized trials needed to establish the effects of food often go undone. Second, most foods we consume are very complex at the molecular level; wines, for example, can have more than 300 ingredients. It is often tough to discern what part of a food product is actually giving the benefit or doing the harm.
The way our bodies handle food is even more complex. We don’t all metabolize food exactly the same way. Some people can suck calories out of a piece of paper; some people wouldn’t gain weight if they inhaled milkshakes. Some people use peanut butter as their primary source of protein; others will die of an allergic reaction if they smell it on an airplane. To the eternal frustration of just about every researcher in the field, no single diet is going to work the same way for all people, and that’s because of this extraordinary individuality. This is especially true if you’re pregnant.
Neurons need omega-3s
So you can see why only two supplements thus far have enough data behind them to support an influence on brain development in utero. One is the folic acid taken around conception. The other: omega-3 fatty acids. Omega-3s are a critical component of the membranes that make up a neuron; without it, neurons don’t function very well. Humans have a hard time making omega-3s, so we have to outsource the materials to get them into our nerves. Eating fish, especially oily ones, is a good way to do it. Those of us who don’t get enough omega-3s, studies show, are at much greater risk for dyslexia, attention-deficit disorders, depression, bipolar disorder, even schizophrenia. Most of us get enough of the fatty acids in our regular diet, so it’s generally not a problem. But the data underscore a central fact: The brain needs omega-3 fatty acids for its neurons to function properly. Apparently, the Three Stooges knew this decades ago! (Larry: “You know, fish is great brain food.” Moe: “You know, you should fish for a whale.”)
If a moderate amount of omega-3s keeps you from being mentally disabled, does a whale-sized helping of it increase brain power, especially for the baby? Here the evidence is decidedly mixed, but a few studies indicate the question warrants further research. One Harvard study looked at 135 infants and the eating habits of their mothers during pregnancy. The researchers determined that mothers who ate more fish starting in the second trimester had smarter babies than those who didn’t. By smarter, I mean that the babies performed better on cognitive tests that measure memory, recognition, and attention at six months post-birth. The effects weren’t large, but they existed. As a result, researchers recommend that pregnant women eat at least 12 ounces of fish per week. What about the mercury in fish, which can hurt cognition? It appears that the benefits outweigh the harm. Researchers recommend that pregnant women eat those 12 ounces from sources possessing less concentrated mercury (salmon, cod, haddock, sardines, and canned light tuna) as opposed to longer-lived predatory fish (swordfish, mackerel, and albacore tuna).
My belly is evidence that I know how tough it is to eat properly, whether you are trying to control how much to eat, what to eat, or both. There’s Goldilocks again: You need enough, but not too much, of the right types of food. And the third factor usually doesn’t help.
3. Avoid too much stress
It was not a good idea to be in Quebec and pregnant around January 4, 1998. For more than 80 hours, freezing rain and drizzle fell relentlessly across eastern Canada—immediately followed by a steep drop in surface temperature. This meteorological one-two punch turned eastern Canada into ice hell. Under the weight of the freeze, more than a thousand towering metal power-line structures toppled like dominoes. Tunnels collapsed. Thirty people died. A state of emergency soon was declared; the army was called up. Even so, thousands of residents were without power for weeks, in freezing temperatures. If you were pregnant and could not get to a hospital for your regular checkups—God forbid if you went into labor—you were stressed out of your mind. And so, it turned out, was your infant. The effects of that storm could be seen on the children’s brains years later.
How do we know that? A group of researchers decided to study the effects of this natural disaster on babies in the womb—then follow the children as they grew older and entered the school system. The result was scary. By the time