My intellectual journey began in the far reaches of northern Quebec, in a smattering of small villages on the frigid coast of Hudson Bay. No roads connect the villages to each other or to southern Canada, so when Joseph Jacobson, Ph.D., of Michigan’s Wayne State University and his intrepid crew of researchers first arrived 12 years ago, they flew in on small propeller planes from Montreal. Jacobson studies the Inuit, and he does so for just about the same reason cardiovascular disease researchers have been interested in other northern communities for years: their diet. “The Inuit eat a lot of fish,” says Jacobson from his Detroit office. “Arctic char, a type of salmon, is very big in their diet. And it’s all very rich in DHA.”
DHA, or docosahexaenoic acid, a long-chain polyunsaturated fatty acid in the omega-3 family that’s found in fish and their roe (particularly fattier types like salmon and sardines) is the magic nutrient du jour. I have seen literally hundreds of studies investigating its power to prevent cardiovascular disease. Now the focus has turned to the brain: dozens of studies report that mother animals deprived of DHA have offspring with memory, sensory and visual problems, and that supplementing them with DHA improves their performance on learning, memory and problem-solving tasks. This makes intuitive sense: DHA forms the backbone of much of the brain cells’ membranes.
Jacobson wanted to see whether higher DHA levels, both in the womb and after birth, could have the same positive effect on human infants. So working with midwives in the three largest Hudson Bay villages, his team collected umbilical cord blood from 109 newborns. They analyzed the DHA concentration in their cord blood (a good measure of how much DHA the mother consumed during her last few months of pregnancy), and then tested how well the infants performed on tests throughout their first year. He found that at 6 months and 11 months, infants whose cord blood had the highest concentrations of DHA performed better on a number of different tests—such as recognizing faces—than those with lower levels. “The mother’s intake during the third trimester, when the brain’s neurons and synapses are developing at a very rapid rate, is most important. When we focused on that period, we found the most evidence of beneficial effects,” he says.
My mother certainly didn’t eat salmon while pregnant with me, so that could be my problem, but it’s doubtful: my memory problems only emerged recently. Luckily for my son, my OB/GYN is on top of the literature: when she found out that I couldn’t stomach salmon or other fatty fish, she recommended taking a DHA supplement during my third trimester. (Pregnant mothers are advised to get 300 milligrams per day—the equivalent of about three to four 3-ounce servings of salmon a week.)
Apparently, much of the rest of the country isn’t too fond of fatty fish either. “Most populations, and this is particularly true in the U.S. and southern Canada, are not getting nearly the amount of DHA that humans got prehistorically,” says Jacobson, who like many in his field believes that before the agricultural revolution, fish played a much more prominent role in our diets. “In our original environment, we were getting a lot of DHA,” he comments, “then we switched over to a more grain-based diet.”
Compounding the problem, adds Jacobson, is that our diets are rich in another type of fatty acid: arachidonic acid (AA), an omega-6 polyunsaturated fatty acid found in animal fats and formed in the body when we consume linoleic acid from vegetable oils in foods. There’s nothing inherently bad about AA—it’s important for normal growth. But Jacobson and others believe that our prehistoric ancestors evolved to eat a more balanced ratio of omega-6 to omega-3 fatty acids. Today, few people eat enough fish to achieve this balance; the ratio is currently about 10:1 in the U.S. Since AA competes with DHA for space in the membrane and affects other functions in the brain, some experts suggest an abundance of AA is less optimal for cognitive development in babies (and may be associated with early cognitive decline in older adults—more on that later).
Unless they stick to the “eat fish at least twice a week” dietary guideline, it’s hard for most Americans to meet DHA recommendations without supplements. This is why many infant formulas are now fortified with DHA (breast milk can be a great source of DHA, if the mom eats fish or takes supplements herself). Jacobson hints that supplementing formula, however, could be a case of too little too late—in his Inuit study he saw no beneficial effect of breast milk that contained high levels of DHA on the cognitive performance in infancy, although there could still be some beneficial effects on cognitive function in childhood. In the majority of studies that have demonstrated beneficial effects from DHA-enhanced infant formula, he notes, “most of the effects have been limited to preterm babies”—e.g., those who missed getting their full in utero complement of the nutrient. Does this mean that the typically DHA-poor American diet places infants at risk? Jacobson is quick to assure me there is no reason to assume that it does. “You don’t want to oversell the problem, but our data suggest that greater quantities of prenatal DHA intake could be beneficial.”