The theory: This essential fatty acid, which occurs naturally in breast milk, is believed to provide both visual and cognitive benefits to infants -- especially preemies, who need to catch up with their peers -- as they develop. It's been added to many formulas, along with a sister fatty acid, ARA, in recent years.
The evidence: A flurry of new research is proving that "the positive effects of DHA go way beyond the period when babies are actually consuming it," says Connye Kuratko, Ph.D., a dietitian who researched DHA at Texas Tech University. One study showed that the higher the level of DHA in breast milk, the better newborns perform on a neonatal behavior scale at 9 days of age. Another study found that 2-year-olds who received higher levels of DHA as infants could concentrate and stay on task better than their peers. And yet another found that 4-year-olds had higher IQ scores if their moms took DHA supplements during pregnancy and while breastfeeding.
The conclusion: Expectant and breastfeeding moms should take DHA supplements, in the form of a capsule or nutrition bars, along with eating about 12 ounces of low-mercury fish a week (for guidelines, type "mercury" in the search bar on fda.gov